June 14, 2021

Phoenix Could See One Of Its Hottest Streaks On Record As Extreme Heat Builds Across West


A significant heat wave will build across much of the western United States this week, bringing record-threatening temperatures to a region that could stand a break from the relentless warmth and dryness. Excessive heat warnings in place for communities like Phoenix, Arizona, which could be on the cusp of one of their hottest stretches ever recorded. 

The Setup

Source: Tropical Tidbits

A steep upper-level ridge will build over the western United States and Canada, allowing strong high pressure to dominate the region's weather through next week. Air sinks beneath a ridge, warming up and drying out as it falls toward the surface. This pattern will allow the hot summer sun to push afternoon temperatures toward the top of the records, especially in the Southwest. 

The ridge will grow strongest by mid-week—potentially leading to triple-digit high temperatures as far north as the Canadian Prairies—before beginning to weaken later in the week.

The animation above (from Tropical Tidbits) shows the upper-level ridge on the Monday morning run of the GFS model. The map depicts the 500 millibar level of the atmosphere, which is usually around 20,000 to 25,000 feet above sea level, giving us a great view of the ridge over the west.

The Heat


Beginning on Monday, forecasters expect the high temperature in Phoenix, Arizona, to push 115°F and hit or exceed that mark every day through Friday. Triple-digit readings are likely in and around Las Vegas, Nevada, during the same period, while the interior suburbs of Los Angeles and San Diego could push 100°F for several days during the first half of next week. Highs could peak near 110°F in California's Central Valley toward the end of the week. Record-breaking heat will even stretch as far north as Utah and western Colorado.


An excessive heat warning is already in effect for a significant portion of the Southwest for the next week, while a slate of heat alerts will progressively cover more communities across the western United States in the coming days.

It's a "dry heat," of course, but that doesn't matter much when temperatures are this darn hot. The low temperature in Phoenix will sit close to 90°F for a couple of days this week. When it's in the upper 110s during the day and near 90 at night, you're not cooling off that much!

The heat index tells you what the outdoor temperature feels like to your body when you factor in the humidity. (Humid air prevents sweat from evaporating, which limits your ability to cool off efficiently.) If it's 90°F with a heat index of 105°F, the heat is hitting your body as hard as an actual air temperature of 105°F even though it's much cooler.

The actual air temperature in much of the west is going to be hotter than the highest heat index you'll ever encounter in the southeast or central states.

This is a brutal, uncompromising heat that's tough for anyone to handle. The healthiest, most summer-hardy person is liable to fall out if they're not careful in these temperatures. This is going to be an awful stretch of weather for anyone who can't get relief from the elements, especially folks who are low-income, elderly, work outdoors, or those who live with illnesses that make heat tough to handle.

The Records


Extreme heat itself isn't rare in the Southwest. Phoenix, Arizona, has recorded a high temperature of 115°F at least once in 15 of the last 16 years, while temperatures of 110°F or greater are a yearly occurrence in Las Vegas, Nevada. 

What is unusual, however, is the timing and duration of this heat wave. It's early in the season for such hot temperatures in the Southwest. Phoenix doesn't typically record its first 115°F reading until the first week of July, while the end of June marks the average first appearance of a high temperature of 110°F in Las Vegas.

The duration is also what's really going to take a toll. Phoenix's longest streak of days with a high temperature at or above 115°F was 4 days. The NWS's current forecast calls for five days of afternoons hitting that mark, every day from Monday through Friday, which would make this the hottest stretch the city's recorded in living memory in terms of afternoon highs.

The Drought


Extreme heat baking areas experiencing an extreme drought is terrible news for folks who live in fire-prone areas. Last week's update of the U.S. Drought Monitor found that week-over-week drought conditions stayed the same or worsened west of the Rockies, and that's probably going to be the story over the next few months as hot temperatures and little rain exacerbate damage to the parched land.

The combination of widespread drought and persistent above-average temperatures has experts terribly worried about this year's wildfire season in the western states. Fire activity is already above-average for this point in the year and the region still has a long, hot stretch to get through before hoping for beneficial rainfall from the Southwest's midsummer monsoon and California's wet season in the fall.


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June 6, 2021

Intense Heat Wave Shatters Records In Rarely-Roasted Parts Of U.S. And Canada


An intense heat wave that's swept over the United States and Canada over the last week will hear its last hurrah in New England and the Canadian Maritimes on Monday before temperatures cool down to a more manageable level. The heat set impressive temperature records from California to Manitoba, generating more heat than some communities have seen in a generation.

A strong upper-level ridge formed over the eastern Pacific early last week, bringing unseasonably hot temperatures to the West Coast. The high temperature in Sacramento, California, reached 105°F on Monday, May 31, the second-earliest instance of such a hot reading in the state capital. (The earliest temperature of 105°F or hotter in Sacramento occurred on May 28, 1984.)

Temperatures didn't get any cooler as the ridge crested the Rocky Mountains. The pattern allowed high temperatures to break the century mark as far north as Manitoba, which saw some of its hottest readings in decades.

Friday, June 4, saw a scorching high temperature of 106°F in North Dakota's capital of Bismarck, while Grand Forks, North Dakota, saw its first triple-digit reading since 1989. High heat continued moving east with the ridge, with temperatures well into the 90s across parts of Maine and eastern Canada.


It's not easy to get this much heat this early in the season. A strong upper-level ridge allowed the heat to crank as the feature crossed the United States and Canada. Weather conditions beneath an upper-level ridge are usually calm and warmer-than-normal because ridges foster sinking air, which heats up and dries out as it descends toward the surface. Southerly winds reinforced the warmth.

The powerful upper-level ridge had assistance from the drought plaguing the northern Plains and Canadian Prairies. The latest update of the U.S. Drought Monitor found extreme to exceptional drought covering much of the northern U.S. and south-central Canada.

Soil moisture and vibrant vegetation both add humidity to the air, which typically helps to modulate temperatures in agricultural communities during the heat of the summer. (Think about how humid it gets in places like Iowa and Illinois when the corn is in season.) Lacking that additional moisture, temperatures were able to climb far higher than normal, breaking longstanding records in many locations.


It'll be another hot day on Monday with high temperatures approaching the upper 90s in parts of New England and eastern Canada. The NWS's forecast on Sunday night called for a high of 98°F in Manchester, New Hampshire, on Monday afternoon, while highs could top out in the 90s on Prince Edward Island, where a heat warning is in effect. Temperatures will return closer to normal as the week wears on.


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June 3, 2021

It's Hurricane Season. (Again.) Here's What To Expect Heading Into The Summer Months.


Well...here we are. Even though the de facto beginning of the Atlantic hurricane season came on May 15, and we’ve seen our first named storm already, this week is still the official start of the season on paper. Forecasters expect above-average activity in the Atlantic Ocean this year. While we probably won’t come close to matching last year’s all-time record of 30 named storms, even one storm is bad news if it hits land.

The Forecasts

An average Atlantic hurricane season produces 14 named storms, about half of which become hurricanes and a few of those strengthen into major hurricanes. This 30-year average includes both hyperactive years (2005 and 2020) and relatively quiet years (2014 and 2015) alike.

Forecasters (see CSU and NOAA for examples) generally expect an above-average hurricane season this year. These forecasts are based on a variety of trends in long-range models, including water temperatures in the eastern Pacific, water temperatures in the Atlantic, and other factors like overall wind and pressure patterns.

One annoying feature of these long-range forecasts is that they predict a specific number of storms. Ignore the numbers. There’s not much anyone can do to alter their hurricane preparedness based on whether we’re expecting 14 named storms or 17 named storms. Even one storm poses a grave threat to safety and property if it approaches land.

The Niño

El Niño and La Niña get huge billing at the beginning of a hurricane season. There’s lots of talk about it, but little talk about why it’s important.

It seems counterintuitive, but water temperatures in the eastern Pacific matter for storms over in the Atlantic because of the El Niño-Southern Oscillation (ENSO), which produces El Niño and La Niña events. El Niño describes warmer-than-normal waters in the eastern Pacific, while those same waters are colder-than-normal during a La Niña.

These temperature anomalies can affect weather patterns over the region, which in turn influences the potential for tropical development over the Atlantic Ocean. El Niño events often lead to destructive wind shear flowing over the Atlantic that nips developing tropical cyclones in the bud, while La Niña events can suppress wind shear and remove a major obstacle to tropical development in the Atlantic.

The latest projection from the Climate Prediction Center calls for ENSO-neutral conditions to persist through the summer months, with water temperatures right around normal for this time of year and neither El Niño nor La Niña present. The Atlantic tends to see healthy tropical development during ENSO-neutral conditions, so that factors into the forecasts.

The NHC


The National Hurricane Center’s website should be one of your first visits in the morning if you live anywhere near the coast. (Let’s be honest...if you’re reading this, it probably already is. Good on you.)

Hurricanes.gov is responsible for providing information about tropical cyclones in the Atlantic, the eastern Pacific, and the central Pacific basins, which covers everyone from Hawaii to Portugal.

The agency issues daily tropical weather outlooks at 2:00 AM/PM and 8:00 AM/PM Eastern every day between May 15 and November 30. Tropical weather outlooks cover potential tropical development over the next five days, with the option for more additional updates as needed. These should be required reading during the summer and fall months.

Once the NHC initiates advisories (forecasts) on a storm, forecasters will release new advisories at 5:00 AM/PM and 11:00 AM/PM Eastern for the duration of the system. If there are any watches or warnings in effect for land, they’ll issue intermediate advisories in between full advisories, giving us updates on the storm every three hours. (All times are an hour earlier once we set the clocks back in the fall.)

Each full advisory offers plenty of written and graphical information about storms, including:
  • A three-day and five-day forecast map for the storm’s path and intensity
  • Watches and warnings for land near the storm’s path
  • The current extent of tropical storm force/hurricane force winds
  • The estimated and likely arrival times of tropical storm/hurricane force winds
  • Wind speed probabilities for locations along the storm’s predicted path
  • Storm surge forecasts for coastal areas in the United States

The Cone


The single most important product to understand is the cone of uncertainty.

The cone of uncertainty is the historical margin of error in the National Hurricane Center’s forecast track. The center of the storm stays within the cone of uncertainty about 66 percent of the time, which means it tracks outside of the cone the remaining one-third of the time.

It’s so important to understand the cone of uncertainty because it gives us a clue of where the storm could travel based on errors made in past hurricane forecasts. Forecasters calculate the extent of the cone using forecast errors from the previous five years, so 2021’s forecast errors include the 2016-2020 hurricane seasons.

The cone is actually a radius drawn around each of the eight timesteps in the forecast period—12 hours, 24 hours, 36 hours, 48 hours, 60 hours, 72 hours, 96 hours, and 120 hours.

The error is smaller at 12 hours than it is at 48 hours, and the error smaller at 48 hours than it is at 120 hours. This year, the error at 12 hours is 31 miles while the error at 120 hours is 230 miles. All of these circles get smoothed out and joined together so they create one cone that’s narrow at the beginning of the forecast and large at the end of the forecast, visualizing the potential for error in the track forecast.

Even though the cone looks pudgy on some forecasts and super narrow in others, the margin of error always remains the same throughout the season. The shape of the cone depends on the speed and shape of the forecast track. A slower forward speed or a curvy track will result in a shorter and thicker cone because the error circles around each timestep overlap with one another.

Some forecasts are easier to nail than others. Last year’s Hurricane Laura is a great example of a storm that falls on both ends of the spectrum. The storm’s forecast track was tough to pin down early in its existence when it was weak and there were lots of factors pushing and pulling on the storm, but the NHC's forecast came within a few miles of its landfall point in southwestern Louisiana within more than three days before the category four hurricane moved ashore.

The Names


Names are the most important non-issue when it comes to a tropical storm or hurricane. The system of naming hurricanes is occasionally cumbersome or controversial, especially when an unnamed tropical disturbance causes major flooding but it’s still too disorganized to earn a name. 

This year’s list of names was last used in 2015. The World Meteorological Organization retired the names Erika and Joaquin after that season due to the damage caused by those storms, replacing them with Elsa and Julian on this year's list.


Names became a big deal last year because the Atlantic hurricane season produced so many storms that we exhausted the official list of 21 names, requiring the use of the Greek alphabet to name the final nine storms. The resulting confusion and need to retire two of the names (Eta and Iota) forced the WMO to ditch using the Greek alphabet as a fallback.

Beginning this year, in the unlikely event that this or any future season exhausts its list of names, we have supplementary name lists for both the Atlantic and eastern Pacific basins ready to serve as a fallback. These names should cause less confusion going forward and they’re easier to replace if needed.

The Prep

Hurricanes don’t really sneak up on us anymore. If there’s a bad storm heading for land, we usually get a couple of days to prepare before it arrives. That gives folks in harm’s way plenty of time to hit all the checkmarks on the to-do list, like filling up the gas tank and getting ready to leave if told to do so.

You have to wait until the storm is on its way to do the disruptive last-minute prep. There’s plenty you can do now to make things easier if and when the time comes to take action.

Keep a reserve of non-perishable food on hand in case the power goes out. This isn’t just helpful for hurricanes, but it's useful for any summertime storm that could knock out the power. It’s easy to forget how much we rely on electricity for food until the electricity turns off. Stuff like canned foods, Pop Tarts, and fruit cups are easy to store, fine to eat cold, and they have a long shelf life.

Make sure you have batteries and flashlights. The flashlight feature on cell phones is fine in a pinch, but it’s not there to get you through a power outage. That bright light kills your cell phone battery in a hurry. Have a couple of real flashlights (and battery refills) on hand so you don’t have to worry about draining your phone’s juice or burning unsafe candles during a lengthy outage.

Speaking of cell phones, invest in one (or more) cell phone battery charging packs. They’re relatively cheap nowadays and they’re good for a couple of recharges before the charging pack itself has to be recharged.


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May 25, 2021

Let's Talk About Tonight's Made-Up-Clickbait-Name Moon


Did you hear about the moon tonight? The moon is a wonderful sight every night, but sometimes it gives us a real treat. Tonight's moon has been dubbed—and I typed this in the most passive, judgmental way possible—the "Super Flower Blood Moon," which, to my great disappointment, is not the name of Elon Musk's second child, but rather some hyped-up amalgam news editors decided to use to lure people into clicking on posts they would otherwise scroll by.

Bloggers and news outlets have a strange relationship with astronomy. An interesting event can't just be a lunar eclipse or a noteworthy alignment of the planets. We have to come up with flashy names to sell the story to people who might not care.

One great example is last year's "Christmas Star." Remember that? Saturn and Jupiter passed very close to one another in our night sky late last December, appearing to the naked eye like a bright star suddenly appeared near the horizon.

The conjunction of the two planets quickly earned its nickname, and many popular news articles and social media pages illustrated the upcoming event with Christian-themed art that featured a prominent twinkling cross in the night sky. Many (many, many, many...) people came to expect a giant cross to appear in the sky as a result of this coverage, finding only disappointment when they saw a bright star on the southern horizon after sunset. 

It's strange how things take on a life of their own. It's obvious why the polar vortex became a sensation in 2014—it froze a critical mass of America's journalists and it's a great term that hardly anyone had heard before. But the moon falls victim to this strange phenomenon more than anything else outside of our atmosphere through a combination of longstanding lore and a need for traffic. 

That brings us to the "Super Flower Blood Moon," which should earn someone a marketing award. Whew.

Let's break down the name bit by painful bit:

Super

The moon's orbit isn't perfectly centered on Earth. The moon is about 224,000 miles away from Earth at its closest point, called the perigee, and about 251,000 miles away at its farthest point, called the apogee.

Occasionally, the full moon will occur during perigee or apogee. A full moon during perigee is known as a "super moon" because it appears a little bit bigger in the sky compared to other full moons. (A full moon at apogee is a "micro moon.") The embiggening of a super moon is barely perceptible unless you're good at photography.

Flower

We've always had names for different full moons depending on the month or season. There's the Harvest Moon, the Wolf Moon, and the occasional Blue Moon when two full moons occur during the same month. A full moon during the month of May is called a Flower Moon, because flowers bloom in May. (Clever, right?)

Blood

Lunar eclipses are sometimes called "blood moons" due to the rusty red appearance of the moon's surface at the peak of a total lunar eclipse. Even though the moon is covered by Earth's shadow, light still passes through Earth's atmosphere and reaches the lunar surface. All the gasses and pollutants in our atmosphere scatter out the shorter wavelengths like blue and green, leaving only dark red light to escape our grasp and reach the moon. 

The term's popularity is relatively new, and it's largely due to evangelical pastors (such as John Hagee) using the phrase in relation to their prophecies about the end times.

Moon

Because it's the moon.

Source: NASA

If you're lucky enough to spot tonight's lunar eclipse—which is most visible in the Pacific region and the western half of the United States—please get out there early on Wednesday morning and enjoy the sight. It's really wonderful to catch a full lunar eclipse in all its glory. Astronomy is awesome. Our atmosphere is awesome. We don't need to gussy them up with ridiculous terms to get people interested in the skies above. (Speaking of which...I can't wait to share what I've been working on for the past five months!)

Correction: A commenter who's much smarter than I am pointed out I was wrong to say "the moon's orbit around Earth isn't perfectly circular." The Moon's orbit is not perfectly centered on Earth, accounting for the difference in distances between apogee and perigee. I corrected and apologize for making a mistake while mocking people who make mistakes.

[Top Image: Me (Not me me. Taken by me. I am not the moon.)]


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May 22, 2021

Ana Forms Near Bermuda; Hurricane Season Starts Before June For Seventh Year In A Row


Subtropical Storm Ana formed north of Bermuda on Saturday morning, kicking off the 2021 Atlantic hurricane season more than a week before the season's "official" start date of June 1—again. This is the seventh Atlantic hurricane season in a row that began early. Ana will remain far out to sea, posing little more than a nuisance to shipping interests and a source for rough seas around Bermuda and parts of the U.S. East Coast.

A low-pressure system meandering in the western Atlantic Ocean took advantage of a brief window where conditions allowed the system to develop into a subtropical storm.

It's a cute li'l storm on satellite imagery today. The storm has a delightfully swirly appearance and even a clear eye-like feature right at the center of circulation. Ana is conspicuously devoid of much thunderstorm activity, which is common for subtropical storms.


Forecasters expect Subtropical Storm Ana to remain far from land and dissipate in a couple of days. The Bermuda Weather Service dropped their tropical storm watch this morning because the storm's winds should stay away from the island.

Rip currents are the only effect this storm will have on land. Some beaches in places like North Carolina are on high alert for these fast-moving currents that can pull swimmers out to sea. A rip current forms between waves that hit the beach head-on, forcing this water to drain away from the beach straight out rather than on an angle. Remember, if you're ever caught in a rip current, don't panic—rip currents pull you out, not under. Swim parallel to the shore until the current releases you, or tread water and calmly signal for help if possible.

Like most early-season systems, Ana didn't originate in the tropics and it's not a fully tropical cyclone. "Cyclone" is the catch-all term for any low-pressure system, regardless of strength or location. A subtropical cyclone is a low-pressure system that has some characteristics of both a tropical cyclone and an extratropical cyclone, or the common type of low-pressure system that brings us most of our active weather.

Subtropical storms aren't purely tropical because air temperatures aren't warm all throughout the system and they don't derive all of their energy from the ocean. Tropical cyclones are powered by thunderstorms around the center of the storm, while subtropical cyclones get at least some of their energy from upper-level winds. Despite their differences, subtropical cyclones are close enough to tropical cyclones in composition and impacts that they warrant full tracking and forecasts from the National Hurricane Center.


This is the seventh hurricane season in a row where we saw the first named storm of the season form before June 1. This trend far surpasses the previous streak of three consecutive early-starting hurricane seasons in 2007, 2008, and 2009. It's a clear and undeniable trend—probably the mixed result of both a changing climate and better detection methods—and it's prompted the experts to ponder moving that climatological start date from June 1 to May 15.

The World Meteorological Organization wrote a recommendation a few months ago asking the National Hurricane Center to consider moving the official start of the season in light of all May storms we've seen in recent years. The NHC met them halfway for now, beginning their regular tropical forecasts on May 15 while continuing to call June 1 the beginning of the season. It's likely that they'll consider officially moving the start date in the years to come.

[Satellite Image: NOAA]


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May 18, 2021

More Significant Flash Flooding Is Possible Across The South Through Thursday


Thunderstorms will pose a significant threat for flash flooding across parts of Texas and Louisiana over the next couple of days, with the threat for more than half a foot of rain possible in some communities this evening through Thursday. Stubborn thunderstorms already produced destructive flooding across Louisiana on Monday evening, and some of those same areas could see even more heavy rain to come.


Flash flood watches cover a significant portion of the southern United States this evening, including a huge chunk of Texas, most of Louisiana, and parts of Oklahoma, Arkansas, and Mississippi.

The greatest threat for widespread flash flooding appears to exist in Texas and Louisiana, where the Weather Prediction Center issued a moderate risk for excessive rainfall for Tuesday, Wednesday, and Thursday. The WPC mentioned on Tuesday that they might upgrade parts of Texas to a high risk for flash flooding on Wednesday—these high risks are reserved for days when forecasters are confident that excessive rainfall could lead to significant flash flooding (and it usually does).

The agency's latest rainfall forecast calls for five or more inches of rain across a huge portion of eastern Texas, with isolated pockets of extreme rainfall totals that could lead to major flooding problems in vulnerable areas. This includes the cities (and suburbs) of Houston, San Antonio, Austin, Dallas, and Corpus Christi. 


We've already seen significant flash flooding over the past 24 hours in Louisiana, where persistent thunderstorms led to flash flood emergencies around Lake Charles and Baton Rouge. Local officials had to conduct water rescues to save residents trapped by waters that rose too fast to escape. The flooding in Lake Charles is especially gut-wrenching given that the community was hit so hard by category four Hurricane Laura in August 2020 and again by Hurricane Delta two months later.

The region is at risk of excessive rainfall because of a slow-moving upper-level trough that's meandering over the southern Rockies. This is the same trough that brought a tease of rain to California over the weekend and led to so many photogenic supercells on the Plains.

Southerly winds flowing between the trough to the west and a building ridge of high pressure to the east will pump humid air northward from the Gulf of Mexico. Any thunderstorms that form in this soupy airmass will have a deep reserve of moisture to tap into, and these heavy storms can linger over the same areas for hours without much in the way of prevailing winds to steer them along. 

The northern and western Gulf Coast is exceptionally vulnerable to flash flooding during high-intensity rainfall events like this. Low, flat, and soggy terrain makes drainage a challenge even during a routine summertime thunderstorm. The combination of persistent high rainfall rates, poor drainage, and communities spreading ever farther into flood-prone areas all leads to fairly routine flash flood emergencies these days. The increasing frequency of heavy rain events (likely influenced by a changing climate) makes matters worse.


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May 14, 2021

A Wet And Stormy Pattern Will Drench The Plains Through Next Week


Bouts of heavy rain and a low-grade threat for severe thunderstorms will cover the southern and central Plains through next week. Some areas in Texas and Oklahoma could see more than five inches of rain from the upcoming stormy pattern, which could cause flooding issues if storms persist over the same areas.

Much of the United States has enjoyed a pretty subdued weather pattern compared to how things usually go in May, which is great for storm-weary areas and a little much for those whose gardens could use a break from the cold weather. This past Thursday, Charlotte, North Carolina, saw one of its latest sub-40°F low temperatures on record this late into the season. That's an impressive chill!

As the upper-level trough that brought the eastern states their late-season coolness moves out into the Atlantic, temperatures will climb closer to average and spring-like humidity will begin to slowly fill out across the country.

This weekend will see a "split" jet stream, with one branch arching into northern Canada while the other swoops south into Mexico, leaving most of the United States with relatively calm conditions aloft. This calmness will allow smaller, more subtle features dictate the weather.


Decent instability over the Plains should allow showers and thunderstorms to develop across the region over the next couple of days. The Storm Prediction Center paints a marginal to slight (1-2 out of 5) risk for severe weather over pretty much the same areas each day through Sunday, with Cheyenne, Denver, Amarillo, and much of Kansas at risk for thunderstorms that could produce damaging winds, large hail, and a couple of tornadoes.

An upper-level trough will move over the West Coast this weekend, prompting the risk for thunderstorms in California on Saturday and Sunday. Thunder and heavy rain are even possible in some spots high in the Sierras. 

That trough will kick off a low-pressure system on the eastern side of the Rockies on Monday and Tuesday, laying the groundwork for heavy rain to fall in earnest over the southern Plains. Tuesday through Thursday looks to be the best bet for folks in northern Texas and southern Oklahoma to see several inches of rain. Some communities could see flash flooding if the rain falls too quickly.

It's worth pointing this out any time there's a risk for flash flooding—please remember that you can't tell how deep the water is until it's too late. Water is deceiving and drivers are notoriously bad at underestimating the depth of floodwaters covering the road ahead of them. Plan out alternate routes ahead of time so you know multiple ways to get around if one road is cut off by high waters.

(This post was originally published at 8:30 PM EDT on May 14, 2021. A technical glitch on Google's part removed the post from the site for a day before it was restored.)


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April 29, 2021

Strong Winds Will Blow Across The Mid-Atlantic And Northeast On Friday


Who doesn't love a good windstorm? (Most people, it turns out.) High winds are likely on Friday as a cold front pushes across the East Coast, prompting wind alerts from the southern Appalachians to northern New England. Some communities could see wind gusts of 50-60 MPH on Friday afternoon and evening, which could be enough to bring down trees and cause power outages.

A low-pressure system over New England will move east over the Atlantic Ocean overnight Thursday into Friday. A center of high pressure will build in over the Great Lakes behind the front, and the strong pressure gradient between the high over the lakes and the low over the ocean will lead to blustery conditions across the region.

Modeled winds at the 850 mb level of the atmosphere on Friday evening. SOURCE: Tropical Tidbits

Winds in the lower levels of the atmosphere (around 5,000 feet or so) will crank up as they blow over the Northeast and Mid-Atlantic on Friday afternoon. Daytime heating causes the atmosphere to overturn as warm air rises and cool air descends to take its place. This churning motion—called "mixing"—can nudge some of those fast winds down to the surface, leading to the potential for strong wind gusts that could down trees and power lines.

A high wind warning is in place for parts of the Mid-Atlantic covering Delaware, much of New Jersey, central Maryland, and southeastern Pennsylvania, including Baltimore, Wilmington, and Philadelphia. These areas could see wind gusts as high as 60 MPH when the winds peak late on Friday. Wind advisories are in effect for the potential for 40-50 MPH wind gusts from New England on down the spine of the Appalachians.

Flights to, from, or over the Mid-Atlantic and Northeast could experience severe turbulence at times thanks to the strong winds, a point worth keeping in the back of your mind if you're flying somewhere on Friday.


Dry air behind the front will lead to an increased fire risk for some areas. The Storm Prediction Center's fire weather outlook issued on Thursday afternoon paints an elevated risk for fire weather conditions in parts of eastern North Carolina and Virginia, but local NWS offices issued fire weather watches for a much wider area that extends west to include upstate South Carolina and the Piedmont in North Carolina and Virginia. (The SPC fire weather outlook will update again in the very early morning hours on Friday.)

Gusty winds (and the associated wildfire risk) will wane overnight Friday into Saturday as the low pulls away from the Canadian Maritimes and the pressure gradient weakens. 


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