March 25, 2021

A High-Risk Tornado Outbreak Is Likely In The Southeast On Thursday


A severe weather outbreak is likely across the southeastern United States on Thursday as a powerful low-pressure system moves through the region. This is another rare "high risk" day for the southeast, covering many of the same areas as last week. Forecasters at the Storm Prediction Center don't issue high risks lightly, signaling their confidence in the potential for a tornado outbreak (in their own words) as well as widespread damaging wind gusts and hail the size of golf balls or larger. 


A high risk is a full 5 out of 5 on the categorical scale measuring the threat for severe weather. The scale-topping risk area covers a big swath of the southeastern United States. The high risk covers northeastern Mississippi, northwestern Alabama, and a portion of southern Tennessee, including the communities of Florence and Decatur in Alabama and Tupelo and Columbus in Mississippi.  

A moderate risk, which is still a significant 4 out of 5 on the categorical scale, covers a much wider area that includes northern Mississippi, northern Alabama, and most of western and central Tennessee. This moderate risk includes the cities of Tuscaloosa, Birmingham, and Huntsville in Alabama; Columbus, Starkville, and Jackson in Mississippi; and Nashville, Memphis, and Jackson in Tennessee.

Strong to severe thunderstorms are possible outside of the bullseye, so to speak, with folks from Galveston to Cleveland at risk of seeing some severe thunderstorms on Thursday.

Don't just focus on the high risk area. There's a threat for significant, long-lived tornadoes in and around the enhanced risk (orange), moderate risk (red), and high risk (magenta) areas. The categories only convey the confidence in storms and coverage of storms expected in that particular region. You're not out of the woods if the red or magenta shading on the map is a few dozen miles away from where you live. In fact, it means you need to pay closer attention specifically because the greatest threat is so close to you.

Scale-topping high risk days are rare because it's the closest tool meteorologists have to sounding the alarm for a dangerous severe weather outbreak. High risks are reserved for setups that could produce significant tornado outbreaks or extensive wind damage from derechos. Environmental conditions appear favorable for strong, long-lived tornadoes with this outbreak. The experts at the Storm Prediction Center are trying to focus residents' full attention toward the sky on Thursday.

The Threat


The impending severe weather threat comes to us courtesy of a strong low-pressure system over the southern Plains that'll move toward the Midwest during the day on Thursday. Strong southerly winds to the south and east of the low will drag plenty of unstable air over the southeastern states. Powerful wind shear through the atmosphere will allow thunderstorms to develop rotating updrafts, turning into supercells capable of supporting strong tornadoes, damaging winds, and large hail. Forecasters expect the tornado threat—the greatest combination of instability and wind shear—to peak across the moderate and high risk areas late in the afternoon and evening hours on Thursday. 

The map above shows the Storm Prediction Center's tornado probability forecast for Thursday. The graphic shows the potential for at least one tornado within 25 miles of any point within the shaded areas. Remember that we're talking about tornadoes and not rain showers here—a 5 percent risk is enough to warrant concern, so it's pretty darn serious when you get up to 15 percent and 30 percent. The black hatching covers the areas where supercells could support strong, long-track tornadoes.

A weather model graphic showing intense low-level winds, providing the wind shear thunderstorms will need to spin and potentially produce tornadoes. SOURCE: Tropical Tidbits

Severe thunderstorms will likely begin across the southern end of the risk areas during the late morning or early afternoon hours on Thursday, spreading northward across the region through the afternoon. It's important to pay attention through the whole day and not to assume that the threat is over after one round of ugly storms moves through.

Caveats

No two severe weather outbreaks are ever alike. There's a strong urge to compare big severe weather days in the southeast to April 27, 2011, the benchmark day that saw hundreds of deadly tornadoes across more than a dozen states. It's really hard for all the ingredients to come together to create a historic day like that. It's not all that hard, on the other hand, for a single tornado to cause a significant amount of harm and destruction.

Last week's tornado outbreak lacked the photogenic, monstrous tornadoes that they make documentaries about on cable television. The lack of big tornadoes doesn't mean that the outbreak was a "bust." In fact, the state of Alabama recorded 25 tornadoes from the March 17th severe weather event, making it the state's sixth-most prolific tornado outbreak on record. Only five other tornado outbreaks on record saw more tornadoes touch down than what happened last week. It was a stroke of luck and a messaging success that there were no major injuries or deaths.

There are plenty of modes of failure for a bigtime severe weather outbreak. Those rare and memorable events are rare and memorable for a reason. Early-morning rain and storms could limit instability available for more storms later on in the day. Sloppy storm modes—storms forming as clusters or lines instead of individual supercells—could limit the tornado threat. Lots of storms forming in the same area could interfere with one another, preventing any one storm from taking root and living up to its full potential. 

But we can't count on any of that happening. The environment is primed for significant, long-track tornadoes across Mississippi, Alabama, and Tennessee on Thursday. That's what residents should prepare for. It's trite, but it really does "only take one." Even if the whole day is just a rainy slopfest, one storm could break out and create a huge mess. 

Safety

(I shamelessly copied and pasted this section from my post last week. Don't tell anyone.)

The best way to prepare for severe weather is to have a way to receive warnings the moment they're issued. No matter where you live, even if you're reading this from some chilly town up in New England, take a second to check your phone and make sure that emergency alerts are activated for tornado warnings.

These are push notifications that pop up and screech at you if you're within a tornado warning issued by the National Weather Service. They only pop up if your location (really, the nearest cell phone tower's location) is within the warning polygon drawn on a map by an NWS forecaster. This means won't get notified for storms on the other side of the county unless they're headed your way in the next few minutes.

Remember that the goal of tornado safety is to protect yourself from flying debris. That's why they urge you to get to the lowest floor and in an interior room, putting as many walls between you and the outside as possible. It doesn't stop there, though. Wear a helmet if you have one. Even a simple bicycle helmet can help protect your head from flying debris. Also, wear jeans and closed-toe shoes in case you have to walk through debris. I've slept in my jeans and socks before in case I had to jump out of bed for a tornado warning. It's uncomfortable, but it's worth it.

(1140AM: Corrected the fourth-to-last paragraph where I mistakenly said "Wednesday" instead of "Thursday." Sorry about that.)


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March 19, 2021

The 2021 Hurricane Season Effectively Starts On May 15 And Ditches The Greek Alphabet


Big changes are coming to the 2021 Atlantic hurricane season. After an active couple of years, meteorologists are (to their great credit) making some quick and necessary changes to make it easier to keep track of future storms, including unofficially moving the start date for the hurricane season and ditching the use of the Greek alphabet as a fallback. Here's a rundown of the changes you can expect to see beginning this season.

Hurricane Season (Effectively) Moves To May 15th


Beginning this year, the National Hurricane Center (NHC) will initiate their twice-daily tropical weather outlooks beginning on May 15. These outlooks normally don't start until the first day of hurricane season on June 1, but we've seen the year's first named storm develop before that date every year since 2015. This change effectively moves the beginning of hurricane season to May 15th without actually adjusting the start date...yet.

Back in February, the World Meteorological Organization (WMO), the United Nations' agency tasked with maintaining global meteorology standards, wrote a recommendation that the NHC should consider moving the start of the Atlantic hurricane season from June 1 to May 15—a proposal this humble blog made two years ago. We've seen the Atlantic's first named storm develop before the beginning of the season every year since 2015.

By moving regular tropical weather outlooks from June 1 to May 15, the NHC is effectively moving the start date of the Atlantic hurricane season without officially moving the date up a few weeks. It's a wink and a nod that doesn't make a big splash.

Atlantic hurricane season currently runs from June 1 to November 30. These dates are based on when conditions are most likely to allow tropical cyclones to develop and the fact that almost all storms on record formed between those two dates. Since 2003, we've seen 14 named storms form before the official beginning of the season, with each of the last six hurricane seasons recording a named storm in April or May. (2016 also saw an oddball hurricane in January.) Last year, which was the most active hurricane season on record, saw its first two storms form during the final weeks of May.

Many of these preseason storms formed close to land. Tropical Storm Arthur and Tropical Storm Bertha both brought nasty weather to the Carolinas in May 2020. Topical Storm Alberto made landfall in Florida in May 2018. Tropical Storm Bonnie hit South Carolina in May 2016. Even though these preseason storms were relatively weak, they prompted tropical storm warnings and forced coastal residents to go through the motions a few weeks before the season officially began.

Meteorology is a conservative field. I don't mean politically conservative—it's conservative in its habits. Traditions must be followed. Entrenched meteorologists don't like change. Big changes, when they're allowed, usually move at a glacial pace and lots of professionals bristle at the thought of change at all because we do things the way they've always been done, and that's that.

Resistance to change is deep. Heck, even big changes to a snowfall or hurricane forecast are done in increments. And now, after six straight years of storms forming before the start of hurricane season, there's momentum toward changing our artificial timeline that nature doesn't quite follow. It's admirable that the NHC and WMO are receptive to change and reacted to previous seasons by implementing new practices so quickly.

That's why this next change is even more impressive.

The Greek Alphabet Is Gone


Beginning with the 2021 hurricane season in both the Atlantic and eastern Pacific basins, forecasters will no longer rely on the Greek alphabet to name storms once the official list of names is exhausted. The WMO determined that using Greek letters as a backup was confusing, distracting, and bad practice since some of these surplus storms might need to be retired.

Hurricane names are a big deal. They're not all that important when you consider that the storm's hazards should be the sole focus, but we're human. Humans are obsessed with process stories. Hurricane names are important for tracking and communications, and they're culturally significant for the affected areas. 

Tropical cyclone names in the Atlantic basin come from a predetermined list of 21 names that are in alphabetical order (excluding Q, U, X, Y, and Z) and alternate between masculine and feminine. There are six different lists of names. Each list is used every six years, so 2020's list of names will be used again in 2026, and 2021's list of names was last used in 2015.

Since there are only 21 names for a season, we run into a problem if we see 22 or more named storms in one year. We've only dealt with that twice—for the first time in 2005 and again in 2020. The fallback for exhausting the official list of names was to begin using the Greek alphabet to name the 22nd storm and any storms that formed thereafter.

Names are retired when a storm causes so much death or destruction that it would insensitive and confusing to continue using that name again. Andrew, Dennis, Katrina, and Sandy are all some of the dozens of names that were retired. This is also why we don't use Q, U, X, Y, or Z—there simply aren't enough common names to use as replacements.

But what happens when a storm named after a Greek letter needs to be retired? The official line going into that unprecedented back-half of the 2020 hurricane season is you can't retire a Greek letter and a letter used to name a particularly bad storm would continue being used in the future if needed. We dove nine letters deep into the Greek alphabet in 2020, and the final two storms—Hurricane Eta and Hurricane Iota—slammed into Nicaragua as a category four and a category five, respectively.

Given the destruction those two storms caused, the WMO decided that using Greek letters as a fallback wasn't tenable, so they developed two supplemental lists that'll be used as a backup in case we see another season like 2005 or 2020.

The supplemental lists will only be used if the official list of names is exhausted, and any of the included names can easily be retired and replaced if necessary. We'll probably go many years without ever having to think about these lists again. (Oh, and if this system was in place for the 2020 season, we would've gone up to Isla on the new list.)


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March 17, 2021

A Rare "High Risk" Severe Weather Outbreak Is Expected In The Southeast On Wednesday


A significant severe weather outbreak will unfold across the southeastern United States on Wednesday and Thursday, bringing the potential for strong, long-lived tornadoes, as well as many instances of large hail and widespread damaging wind gusts. Wednesday is a rare "high risk" day in the Storm Prediction Center's severe weather outlook, highlighting the seriousness of the threat posed by storms in the southeast. If you live anywhere between Texas and Virginia, make sure you have a way to receive severe weather warnings over the next few days.

The Risk


The Storm Prediction Center's update early Wednesday morning paints a rare high risk for severe thunderstorms—a full 5 out of 5 on the categorical scale measuring severe weather risk—across portions of northern Louisiana, north-central Mississippi, and western Alabama. Forecasters at the SPC don't issue high risks lightly. This is an "alarm bells ringing" moment for folks in the south, the kind of severe weather potential that's keeping meteorologists and weather enthusiasts awake tonight with nervous stomachs.

Don't just focus on the high risk area. Moderate risk (4 out of 5) and enhanced risk (3 out of 5) zones extend outward to cover a significant portion of the southeast, each denoting a significant risk for severe weather in their own right. "Moderate" is a bit of a misnomer when it comes to these categorical outlooks. A moderate risk is a 4 out of 5 on the scale measuring severe weather risk. That's a pretty big deal, and it covers a pretty big area!

To highlight the area of concern on Wednesday, here's a look at the tornado risk during the afternoon and evening hours:


These probabilities may seem a little low, but a 2 percent chance means there's a 2 percent chance of seeing a tornado within 25 miles of any location in the highlighted area. That's not nothing you consider we're talking about a tornado. Meteorologists grow concerned when the tornado risk reaches 5 percent, and it's a serious weather day when the probabilities grow to 10 percent or higher in the SPC's outlook.

The shaded hatching indicates the risk for strong, long-lived tornadoes, the type that can stay on the ground for many dozens of miles before finally lifting. The environment is primed for an extremely dangerous severe weather event.

The Setup

Source: NOAA/WPC
A budding low-pressure system over western Texas and Oklahoma will set the stage for the active weather coming up. The low will strengthen as it heads toward the Mid-South during the day on Wednesday. Warm, humid air will race northward from the Gulf of Mexico, providing the instability necessary for thunderstorms to thrive once they bubble up.

Meanwhile, a few thousand feet above the surface, winds will be tearing along out of the west and southwest. The sharp change in the speed and direction of the wind with height will allow thunderstorm updrafts to begin rotating, creating supercell thunderstorms. The rotating updraft in a supercell makes those storms strong and durable, capable of surviving for many hours while they produce large hail, damaging winds, and tornadoes.

The Threat

This won't be a clean severe weather outbreak where one line of storms moves through and it's over. There will be multiple rounds of storms throughout the day and evening hours, and each round will carry its own predominant hazards.

As these events usually go during a classic springtime outbreak in the southeast, the day will start with discrete thunderstorms in the afternoon that could easily develop into supercells capable of producing tornadoes and large hail. Later on in the evening and overnight hours, a squall line will develop ahead of the cold front and pose one final risk for severe weather, with damaging straight-line wind gusts and quick tornadoes the main threat.

These thunderstorms will move quickly. It won't be uncommon for a single thunderstorm to move 45+ MPH, which reduces your reaction time if you find yourself in the path of a storm. That's why it's so important to stay tuned to the weather and get warnings as soon as they're issued.

Many of the storms will occur after sunset on Wednesday, which packs the one-two punch of catching people while they're sleeping and making it hard to spot tornadoes before they arrive. Tornado chasing and tornado gawking in the southeast is a terrible idea to begin with because there are so many trees and tornadoes here are usually obscured by heavy rain. I used to live in Mobile. I know the impulse to look outside to see if you can see the tornado. Don't do that. A tornado warning means that someone already spotted the rotation or the tornado for you. Trust them and do what you need to do to get to safety.


Oh, and don't fret about comparisons to past outbreaks. It's really hard to get all the ingredients to come together just right to create a historic tornado outbreak like we saw in 2011. Every tornado threat is dangerous in its own right, so take every storm and every warning seriously.

Thursday


The threat doesn't end on Wednesday night. Another hallmark of major southeast severe weather outbreaks is that they continue the following day in Georgia and the Carolinas. A moderate risk for severe weather is in place for much of Georgia, South Carolina, and North Carolina in anticipation of strong tornadoes, widespread damaging winds, and large hail during the day on Thursday. It's rare for the SPC to issue a moderate risk for this area so far in advance, so this is also a big deal. Pay attention.

How To Prepare

The best way to prepare for severe weather is to have a way to receive warnings the moment they're issued. No matter where you live, even if you're reading this from some chilly town up in New England, take a second to check your phone and make sure that emergency alerts are activated for tornado warnings.

These are push notifications that pop up and screech at you if you're within a tornado warning issued by the National Weather Service. They only pop up if your location (really, the nearest cell phone tower's location) is within the warning polygon drawn on a map by an NWS forecaster. This means won't get notified for storms on the other side of the county unless they're headed your way in the next few minutes.

Remember that the goal of tornado safety is to protect yourself from flying debris. That's why they urge you to get to the lowest floor and in an interior room, putting as many walls between you and the outside as possible. It doesn't stop there, though. Wear a helmet if you have one. Even a simple bicycle helmet can help protect your head from flying debris. Also, wear jeans and closed-toe shoes in case you have to walk through debris. I've slept in my jeans and socks before in case I had to jump out of bed for a tornado warning. It's uncomfortable, but it's worth it.

*I apologize for any typos or strange errors in the text. I am my own editor, it's the middle of the night, and I haven't slept in six years.

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March 12, 2021

A Big Late-Season Snowstorm Will Blanket The Front Range This Weekend


A big-time snowstorm is on the way for the Front Range this weekend. Some communities will wind up measuring snow in feet, which is pretty rare for lower elevations during the heart of winter let alone the middle of March. The heaviest snow will fall in Colorado and Wyoming. The snow will be heavy and wet, leading to a greater-than-normal chance for power outages and tree damage across the affected areas.

A big upper-level low rolling over the southwestern United States tonight will feed the development of a low-pressure system along the leeward side of the Rocky Mountains on Friday night and into Saturday. The system will ramp-up in a hurry, quickly producing heavy rain and snow on the northern and western side of the system.

Forecasters are expecting impressive snowfall totals from the system, largely as a result of the low's strength, its slow forward movement, and enhanced moisture pumping into the system from the south. Heavy snow will begin on Saturday and will last through Sunday night or Monday morning in most areas.

Friday night's forecast from the National Weather Service showed more than a foot of snow falling in metro Denver, nearly two feet of snow in Boulder and Fort Collins, and more than two feet of snow in Cheyenne, Wyoming. Higher elevations up in the mountains could see many feet of snow by the time the skies clear out, blowing out my the high end of my color scale on the map above.

That's a whole lot of snow for this region. March is typically Denver's snowiest month, accounting for about 20 percent of the city's average annual total. The all-time record for a March snowstorm in Denver was 31.8" during a storm in late March of 2003, followed by a foot-and-a-half of snow in March 1983. This storm probably won't break any monthly or all-time records, but it's going to be a memorable one if forecasts hold true, especially north of the city closer to Boulder and Fort Collins.

Snow isn't the only issue. It's going to get very windy. Wind gusts could easily exceed 40 MPH in places. Blizzard warnings are in place for southeastern Wyoming in anticipation of gusty winds and heavy snow leading to whiteout conditions during the height of the storm.

The combination of wet snow and gusty winds could lead to widespread power outages and tree damage. We've all pretty much got a handle on how to get through a power outage—and it's probably too late to run to the store and prepare for one. Just remain mindful of large trees and tree limbs that loom close to your home or vehicle. If you have a rickety tree limb that could fall through a wall or roof, it's best to avoid those rooms at all costs. Most serious injuries that result from storms like this are through car accidents on icy roads or trees falling into homes.


If you follow anyone tangentially interested in storm chasing, chances are you've heard all about the severe weather potential in Texas and Oklahoma on Saturday. The southern end of this snowstorm will have plenty of lift, instability, and wind shear for thunderstorms to develop and quickly turn severe.

The Storm Prediction Center issued an enhanced risk for severe weather across eastern parts of the Texas Panhandle, including a decent chance of tornadoes that could be strong or long-lived. This is the first "big" threat of the year across traditional chasing grounds, so there's more buzz online about the threat than there are residents in the at-risk areas.


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March 2, 2021

Today's Accidental Tornado Warning Is Exactly Why Officials Test Emergency Alerts So Often


Millions of people received a seemingly real tornado warning on their phones Tuesday morning during annual statewide tornado drills in Kansas and Missouri. The push alerts made no mention of the fact that it was a drill, causing widespread confusion on an otherwise clear and sunny day. The giant flub highlights exactly why officials test these emergency alerts in the first place.

The errant warning coincided with statewide tornado drills, a day devoted to making sure everyone and everything is prepared to handle the threat for tornadoes during the impending peak of severe weather season. Alerts issued during drills are clearly marked as drills so they don't freak people out.


The National Weather Service office in Wichita, Kansas, posted a screenshot on Twitter proving that the agency handled the test correctly on their end, reporting later in the day "that new software implemented last week mistakenly allowed the test to go out as an actual warning."

Incidents like Tuesday's accidental false alarm are exactly why local, state, and national agencies test these systems on a routine basis. With so many different points of failure possible between the alert's issuance and your screens, these systems need to be tested frequently to make sure they work. After all, if the system fails, you might not see a message about a tornado warning or any other dangers they can warn us about.

A Wireless Emergency Alert I received on my phone for a tornado warning on October 11, 2018.

These systems are surprisingly complex. The iconic screeches and pops that make the EAS so recognizable on television and radio are actually coded messages that are similar in purpose to the sound of a dial-up modem. Specially designed devices at television stations and cable providers listen for the sound of the EAS and interpret the message embedded within to know what kind of alert was issued and which communities need to see the alert.

Wireless alerts sent to smartphones are decidedly less entertaining—it's all computerized, and the recognizable screeching sound you hear is just an audio file on your device—but there are still multiple steps and multiple potential points of failure between the point of issuance and your screen.


While the greatest concern is the system failing altogether, we've seen plenty of incidents like today where a test accidentally reaches the public as if it was a real alert.

Back in 2018, an employee at the Hawaii Emergency Management Agency improperly ran a drill that resulted in an erroneous "BALLISTIC MISSILE THREAT INBOUND TO HAWAII" message popping up on every smartphone in the state. The message was particularly stress-inducing due to the boiling tensions between the U.S. and North Korea at the time.

An employee in Connecticut's emergency management office entered the wrong code into the system ahead of a statewide test of the Emergency Alert System in February 2005, sending out an emergency alert on television and radio that told everyone to evacuate the state.

NORAD accidentally sent out a live code used to authenticate a real emergency message during a scheduled test in February 1971, causing at least one station—WOWO-FM in Fort Wayne, Indiana—to suspend programming and operate as if the Emergency Broadcast System had been activated for a national emergency. Audio of the false alarm is well-preserved on YouTube as the announcer stalled for time while the station sought more information.

[Top ImageStormless skies over the Midwest on March 2, 2021/NOAA]


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February 28, 2021

A Flash Freeze Will Chill New England on Monday Night And Tuesday


A brief but deep freeze will descend over New England on Monday night and bring the region a downright impressive temperature drop for this late in the season. Temperatures will swing more than 40°F between Monday afternoon's high and Monday night's low across parts of interior New England, with communities near the international border waking up to subzero lows on Tuesday morning.


A low-pressure system moving toward the Great Lakes today—part of the same pattern responsible for all the rain and thunderstorms down south this weekend—will strengthen as it heads into Ontario and Quebec on Sunday night and Monday. Winds wrapping around the low will pull bitterly cold Arctic air over New England as the cold front passes through on Monday evening. Temperatures will quickly fall behind the cold front, plunging into the teens and single digits across interior New England.

The greatest threat from this cold weather is a flash freeze, which occurs when standing water quickly freezes as temperatures drop. It's already raining, or will rain soon, across many of the areas expecting subfreezing temperatures on Monday night and Tuesday. The rapid temperature drop will set in before water on roadways and sidewalks has a chance to evaporate in the wind. 


The Weather Prediction Center's new-ish Winter Storm Severity Index highlights that parts of the region are at risk for minor to moderate impacts from a flash freeze. Travel on Monday night and Tuesday morning will be very dangerous in these areas due to the widespread potential for black ice. There are probably going to be a few accidents across the region as a result of the slick roads.

The sudden freeze on Monday night is the most pressing concern in the region from this week's weather. Tuesday should be the coldest day of the week. Temperatures will rebound a bit on Wednesday before falling back into "chilly for this time of year" territory through next weekend. 


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February 14, 2021

Snow, Ice, And Bitter Cold: This Is A Storm The South Will Talk About For Decades


The winter storm moving over the southern United States has all the hallmarks of one of those storms that people talk about for decades. The system will bring significant amounts of snow and ice to areas that don't typically see this kind of wintry weather, and the cold air that follows the storm is on a level the region hasn't seen in more than 30 years.

Meteorologists spent Sunday ogling at the National Weather Service's map of watches, advisories, and warnings across the country:
Source: NWS

That huge swath of pink is a winter storm warning. It covers the entire states of Texas, Oklahoma, and Arkansas, along with most of Louisiana and Mississippi, and continues on into the Northeast. The criteria for a winter storm warning changes from one office to the next based on what a region is used to during a typical winter. Any amount of snow and ice warrants a winter storm warning in parts of Texas, while it takes many inches of snow to trigger the same alert up north. 

It takes lots of things going juuust right for such an intense winter weather event to stretch so far south. The cold air is rooted in the infamous polar vortex. I explained the process more in-depth last week, but a disruption in the polar vortex circulation over the Arctic allowed a piece of the vortex to break off and sit over the Upper Midwest. This disruption allowed cold air to flow straight out of the Arctic and park itself over the central United States for a couple of weeks.

Meanwhile, an upper-level trough moving out of the Rockies led to the development of a low-pressure system over the southern Plains. Conditions are deteriorating across Texas tonight as the low organizes and snow, sleet, and freezing rain fill in. The low will strengthen and move northeast over the next 48 hours, bringing plenty of wintry precipitation from the Gulf Coast to interior New England.


Here's the National Weather Service's snowfall forecast through Wednesday evening. Widespread totals of 6-12" are possible from northern Texas to northern Maine and just about everywhere in between. Forecasters expect the greatest totals in central Oklahoma and central Arkansas, where some communities could wind up with more than a foot of snow by the end of the storm.

Freezing rain will fall closer to the track of the low. A significant ice storm is possible in Louisiana, Mississippi, Tennessee, and along the Appalachians. Down south, this could be the worst ice storm in memory for many folks.
Source: NWS

Everywhere shaded red on the map above could see more than one-quarter of an inch of ice accretion. Some areas could see one-half to three-quarters of an inch of ice, which will cause significant damage.

One thing to keep in mind is that there really isn't much infrastructure in this part of the country to deal with significant amounts of snow and ice. This isn't a situation like North Carolina falling apart when it snows. We see snow and ice frequently enough that it's a shame we can't handle it better than we do.

This is all the way down south. They don't have many snow plows or salt/sand/brine trucks to go around. Most people don't have snow shovels at home or ice scrapers in their cars. You're lucky if you just happen to have sand or rock salt on hand. The region doesn't see winter weather enough to justify spending the money to have an infrastructure in place to deal with it. 

As if the snow and the ice isn't bad enough, tonight's cold is only going to get colder. This winter storm will drag the Midwest's frigid air all the way to the Gulf of Mexico, allowing temperatures to plummet on Monday and Tuesday.

Here are the National Weather Service's high and low temperature forecasts for Monday, Tuesday, and Wednesday:


Bitterly cold air will surge as far as northern Mexico, with low temperatures in the single digits approaching the suburbs of San Antonio. It hasn't been this cold across these regions since December 23, 1989, when it hit -2°F in Fort Worth, 0°F in Waco, 8°F in San Antonio, and a comfy 14°F in Houston. 

Between the snow, the freezing rain, and the surge in demand due to the frigid temperatures, the region will probably experience a tremendous number of power outages this week. Some communities will probably go without power for a week or longer in extreme cases. Trees in places like Louisiana and Mississippi aren't accustomed to the weight of ice on their branches and limbs. It won't take much ice—maybe not even one-quarter of an inch—to bring down limbs and cause trees to snap in half. 
I took this photo just a few minutes after a tree snapped and knocked out the power for 28 hours.

Don't take the threat for prolonged power outages lightly. If you follow me on Twitter, you probably saw that we were without power for 28 hours in my town near Greensboro, North Carolina, after about a third of an inch of ice overnight Friday into Saturday. I try to stay as prepared as I preach when it comes to having the supplies needed to get through an extended outage and it was still tough to get enough battery power and warmth to make it through more than 24 hours in the dark.

It's probably a little too late to get ready now, but if you're in a position where you still have time to prepare, make sure you've got enough batteries, flashlights, water, and non-perishable, ready-to-eat food to get through several days without power. Bottled water (or containers filled with water) are a mainstay on preparedness lists because municipal water treatment plants can lose power as well, potentially hampering their ability to treat or pump water out to you. (It's no joke. My town is under a boil water advisory for two days!)

Oh, and one more thing—if you live in an area expecting ice, stay away from parts of the house where trees and limbs could fall into the roof or walls. It's something people don't really think about until it's too late. Trees are heavy and houses are comparatively weak. Lots of injuries and deaths during ice storms are caused by trees falling into homes.


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February 11, 2021

We're Coming Up On This Winter's Roughest Stretch Of Cold And Snow


The next five days will see the roughest stretch of winter weather the United States has seen in quite a few years. Bitter cold will grip the center of the country while snow and ice fall on the Pacific Northwest, the southern Plains, and the Mid-Atlantic. The southern Plains could see some hefty snowfall next week if the forecasts pan out.

First thing's first, though, since I've seen (and experienced) some confusion about this. Winter storms aren't named in the United States. There's no such thing as Winter Storm Quavo/Boppo/Filbert or whatever you've hear on television or social media. The Weather Channel unilaterally names winter storms for the purposes of its coverage. The system is deeply flawed for many reasons, not the least of which is the fact that it doesn't work when hardly anyone else recognizes the names. Since the names are arbitrary, the DAMWeather Winter Storm Naming And Hot Wing Quality Assurance Committee voted 1-0 to name all of this year's winter storms Skittlebip.

There are plenty of Winters Storm Skittlebip rolling across the country this week. So many areas are at risk of disruptive snow and ice (and bitter cold) that it's best to break the threat down into three sectors: Pacific Northwest, the southern Plains, and the Mid-Atlantic. 

Since my computer has a case of the Mondays on this rainy Thursday afternoon, I'm not able to make a map of the National Weather Service's snowfall forecasts today. The snowfall graphic I usually compile and upload (like this) combines all 100+ snow forecasts issued by individual NWS forecast offices.


Given the issues I've had today, above is a hastily thrown together and ridiculously busy map highlighting the threats over the next couple of days.

This map combines the Weather Prediction Center's 50th percentile forecasts for snow and ice through Sunday evening. Some areas will see higher or lower snow and freezing rain totals than what's shown above, but this gives you a good rough idea of who could see significant snows or ice accretion from freezing rain over the next three days.

Pacific Northwest

Source: NWS Seattle

There's a pretty good chance of snow and ice along the I-5 corridor in Washington and Oregon through Saturday. If everything stays on track according to the forecast, the region is looking at a disruptive snowstorm over the next couple of days.

Seattle averages about 5 inches of snow in a normal winter, while Portland typically sees about 7 inches of snow each year. But those snowstorms aren't a sure thing each year—Seattle received hardly any snow last season, but saw 20 inches of snow the previous winter.

Through this weekend, Seattle could wind up with up to half a foot of snow by the time the storm is over, with higher amounts at higher elevations. Covered roads, cancelled flights, and delayed trains will make it difficult to get around the region for a couple of days. 

Farther south along the interstate, southwestern Washington and northwestern Oregon will see a mixture of both snow and freezing rain. It's going to be a mess. Here's NWS Portland's helpful graphics highlighting the threat for wintry precipitation over the next couple of days.

Snow:

Source: NWS Portland

And the threat for ice from freezing rain:

Source: NWS Portland

The greatest ice accretion is possible in the mountains between Tillamook and Portland, where one-quarter of an inch of ice or more could bring down tree limbs and power lines. Freezing rain is possible in the Portland metro area as well, which is expected to see a couple of inches of snow right now. Any ice mixed in with snow makes it even more difficult to deal with.

Freezing rain is an ugly threat. It only takes a tiny amount of freezing rain to leave a glaze of ice on exposed surfaces, making it nearly impossible to drive safely—or even walk down the driveway. The threat of heavy snow and freezing rain in such heavily forested areas heightens the concern. If you live in an area expecting freezing rain, make sure you stay away from rooms in your house where large trees or tree limbs could fall through the roof or walls if they snap under the weight of the snow or ice.

Extreme Cold & Southern Plains Snow


Last week's cold didn't just stick around—it's getting worse. The heart of the much-maligned polar vortex will dip over the Upper Midwest early next week, sending subfreezing temperatures dipping as far south as the Gulf of Mexico. Tuesday looks like it's going to be the coldest day for the most people.

Low temperatures on Tuesday morning will dip below zero in northern Texas, with single digits likely in the Dallas-Fort Worth area. Lows in the teens are possible as far south as Houston and San Antonio. Temperatures this cold diving this deep into the southern Plains will easily break daily record lows. Some areas could come within a few degrees of their all-time record low temperatures.

The all-time lowest temperature on record in Dallas is -1°F at KDFW in December 1989 and 0°F at KDAL in January 1940. The all-time record low in Houston was 5°F at KHOU and 7°F at KIAH, both also set during those two cold snaps in 1940 and 1989. While it seems unlikely these two cities will see all-time lows, one of their top-ten coldest mornings on record is certainly possible.

It's going to be even colder up north, with subzero temperatures firmly gripping Oklahoma and temperatures in the double-digits below zero the norm from Kansas northward. Folks on the northern Plains and Upper Midwest just can't catch a break from this stretch of cold weather. Minneapolis has recorded highs in the single digits and lows below zero every day since last Saturday. It'll get even worse, with forecasts showing the city dipping below zero this evening and likely not seeing readings above zero again until early next week. 

Wind chill values will come in even colder than the actual air temperature. The wind chill is what it feels like to exposed skin when you factor in the cold air and gusty winds. Higher winds efficiently presses cold air right up against exposed skin, which allows frostbite and hypothermia to set in faster when it's windy than when it's calm. It doesn't take very long for the cold air to take its toll when wind chills fall below zero.

If everything goes according to forecast, a developing winter storm will meet that cold air over the southern Plains and bring the region a hefty dose of snow and ice. It's still too early to talk about specifics, but the potential is there for a high-end and disruptive amount of snow and ice from freezing rain beginning on Sunday and lasting through Monday. Winter storm watches are already in effect in central Oklahoma and northern Texas to make people well aware of the event. 

Mid-Atlantic

Source: NWS EDD

The ongoing slog of rain moving across the Mid-Atlantic will pose problems in the overnight hours on Friday morning and Saturday morning as temperatures close in on the freezing mark. Lots of areas will hover right around 32°F, leaving some areas with ice-glazed roads and other areas just wet. This kind of borderline setup can lead to serious traffic accidents.

Greater ice accumulations are possible from the Piedmont Triad to the southern D.C. suburbs during a steady period of freezing rain on Saturday. Winter storm watches are in effect for parts of northern Virginia, with more alerts possible farther southwest as we get closer to the event. Some areas could see one-quarter of an inch of ice or more, which makes tree damage and power outages possible.


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