February 17, 2024

How an incredible band of snow developed over the Northeast on Saturday

One of the most impressive bands of snow we've seen in a long time developed over a narrow swath of the Northeast overnight Friday into early Saturday, creating an intense snowfall gradient over very short distances.

A fast-moving low-pressure system tracked out of the Midwest toward the East Coast through the day Friday, producing heavy snow along its path from St. Louis to New York City.

A radar snapshot from around 1:30 a.m on February 17, 2024 (RadarOmega)

This wasn't an ordinary clipper system, though. While weak systems like this tend drop a few inches of snow before moving on their way, we saw a dramatic band of snow develop on the northern side of the low.

The band left behind enhanced snowfall totals from Indiana to New York, reaching its peak intensity over portions of Pennsylvania and New Jersey. 

A tremendous gradient sliced through Allentown, Pennsylvania, with folks on the south side of town witnessing 13" of snow while neighborhoods north of town saw just 3" of snow. Farther east, observers measured 10" of snow in Brooklyn, while only 2" of snow fell in Central Park just a dozen miles to the north.

Even more impressive is that parts of New Jersey saw snowfall rates of 5" per hour at the peak of the snowfall. This kind of convective banding is something more like what you'd see off the Great Lakes rather than eastern Pennsylvania and northern New Jersey. Instead of lake-warmed air fueling intense bands of snow, we saw intense frontogenesis along the northern side of the low.

Frontogenesis in the mid-levels of the atmosphere early Saturday morning. (NOAA/SPC)

Frontogenesis occurs when an airmass on the move collides with another airmass nearby. This interaction creates a stretching motion through the atmosphere. Winds slowing down and fanning out leaves a 'void' in the atmosphere that air has to rush upward to fill, a rising motion that creates a convective band of very heavy snowfall.

We often see this process during classic nor'easters when a shield of very heavy snow develops on the northwestern side of the storm. But it's not limited to nor'easters—conditions were just right for this relatively weak system to generate the intense dynamics needed to drop a tremendous amount of snow across a narrow stretch of real estate.

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February 11, 2024

From 60s to Snow: The Northeast's Nor'easter's Set To Hit Hard Tuesday

It's been a long wait, but we've finally got a classic nor'easter brewing for the eastern half of the United States.

A foot of snow is likely to fall on Tuesday where temperatures climbed up into 60°F on Saturday. While this one isn't going to bring the blockbuster I-95 snows that weather enthusiasts gush about for the rest of their lives, this will be an impactful storm for a full one-third of the country.

We've got one heck of an upper-level low scooping through the southern half of the U.S. on Sunday and Monday. This feature, along with a ripping-fast jet stream, will help develop and strengthen a robust low-pressure system at the surface over the next few days. 

A model image depicting the upper-level pattern early Monday morning. (PolarWx/Tomer Burg)

Ample moisture streaming into the storm from the Gulf of Mexico will provide plenty of juice to fuel thunderstorms, heavy rains, and eventually heavy snowfall once the storm rolls into the Northeast late Monday into early Tuesday.

Severe weather risk

We're already feeling the start of this robust storm across the south where heavy rain and severe thunderstorms are ongoing from Texas to Mississippi.

The Storm Prediction Center issued an enhanced risk for severe weather on Sunday—a 3 out of 5 on the scale—stretching from the Houston metro area east into central Mississippi, with a broader risk for severe weather radiating out to cover the northern Gulf Coast up toward Birmingham and Atlanta.

The main risk we'll see with any thunderstorms that develop on Sunday will be damaging wind gusts of 60+ mph and hail the size of quarters or larger. A few tornadoes are possible, as well, especially in and around the enhanced risk area.

A risk for tornadoes on Super Bowl Sunday is a pretty nerve-wracking prospect for broadcast meteorologists in the region. It's likely that some CBS affiliates will have to cut into game-day programming for live coverage of tornado warnings.

Local television news stations are required to cover tornado warnings. It's a public service they're compelled to fulfill in exchange for holding a federal broadcast license. Getting the word out that deadly severe weather is imminent is more important than any show or sporting event, angry viewers and hateful comments be damned.

The risk for severe weather will push east into the day Monday, with a threat for damaging wind gusts spreading over most of the southeast as our low-pressure system continues strengthening as it tracks into the Mid-Atlantic.

Sharp cutoff in heavy snowfall totals

After the severe weather wanes, attention turns to the threat for disruptive snows across the Northeast.

This is going to be an all-or-nothing ordeal for many folks from northern Pennsylvania east toward coastal New England. The Weather Prediction Center's Winter Storm Severity Index (WSSI) shows "major impacts" are likely across eastern Massachusetts, centered around the Boston area, as a result of the very heavy snowfall expected on Tuesday.

Heavy snow will spread over much of Pennsylvania early Tuesday morning as our storm pushes into the region. We'll see snow steadily push east through the morning hours Tuesday as the low-pressure system intensifies and tracks toward the coast. 

This will be a daytime storm for the region, with very heavy snowfall rates and gusty winds plastering northern Pennsylvania through southern Maine into the evening commute before the snow eventually tapers off through the evening and overnight hours.

A very sharp cutoff in precipitation on the north side of the storm, combined with a sharp changeover to rain near the center of the low, will produce a swath of heavy snowfall that rapidly tapers to a dusting to the north and south.

Double-digit snowfall totals are likely for portions of northeastern Pennsylvania, upstate New York, northern Connecticut, and just about all of Massachusetts. This is likely going to cause traffic jams across the area, especially if people head to work and school in the morning and then try to head home after the snow begins. 

Slight changes in the track of the storm can have huge implications on snowfall totals with a cutoff this sharp. A nudge of five or ten miles to the north or south will drag those hefty snowfall totals right along with it.

If the current forecasts hold up, this is likely going to be Boston's largest snowstorm in two years. The city's last big-time snowstorm was 23.9" on January 29, 2022. The city's only measured 21.6" of snow in total across all of the storms they've seen in the past two winters combined.

[Satellite image via NOAA]

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February 3, 2024

Flooding risk as atmospheric river fuels rainy, windy storm sweeping into California

A series of systems rolling through the eastern Pacific will wash ashore in California over the next couple of days, fueling a spell of foul weather across the state. 

Heavy rains are likely up and down the coast, with southern California facing the greatest risk for flooding and landslides. Prolific mountain snows are likely across higher elevations throughout the Sierra. Gusty winds are likely across the state early into the workweek, which may lead to tree damage and power outages.

A quick look at the pattern across the country this weekend almost looks like an image you'd see in the El Niño chapter of a meteorology textbook. A strong jet stream draped across the entire southern half of the U.S. is exactly what you'd expect to see during an El Niño winter.

A model image of the jet stream on Saturday afternoon. (Tropical Tidbits)

An upper-level trough digging into the West Coast will drive the active weather over the next couple of days. The most impactful conditions will arrive courtesy of a low-pressure system hitting the coast late Saturday through Sunday, though heavy rains will continue Monday and Tuesday across the southern half of the state.

Powerful southwesterly winds hauling tail into the California coast is dragging a plume of tropical moisture straight from Hawaii. This ribbon of elevated moisture—called an atmospheric river—will fuel the drenching rains we'll see across California over the next few days. Atmospheric rivers provide a vast reserve of moisture for storms to tap into to create excessive rainfall rates.

A model animation showing the atmospheric river moving into California through Tuesday, Feb. 6. (PolarWx/Tomer Burg)

Rain is already starting to come ashore in California on Saturday afternoon, and we'll see the rain increase in coverage and intensity through the overnight hours and into the day Sunday.

We'll see the rain slacken a bit for the northern half of the state as this initial system moves east. However, the heart of the atmospheric river will continue streaming over southern California through at least Tuesday, providing ample opportunity for bouts of heavy rain to continue throughout the area.

The Weather Prediction Center's latest forecast calls for 3-5 inches of rain for just about the entire California coast from San Diego all the way up to near Eureka. It's going to be a soggy couple of days for San Diego, Los Angeles, and San Francisco.

Higher terrain will enhance rainfall totals up and down the coast—especially along the Transverse Ranges, where 5-7 inches of rain is in the forecast with the potential for some areas to see locally higher rainfall totals.

Folks in the Central Valley will benefit (or suffer, depending on your point of view) from the rain shadow effect, with less than an inch of rain over the next week for communities like Bakersfield and Fresno.

As usual, a glut of torrential rain heading for California is a recipe for widespread flash flooding and landslides. The greatest risk for flooding exists across southern California.

The usual safety spiel is extra important this time around: Never attempt to drive across a flooded roadway. It's impossible to tell how deep the water is until it's too late, and California's rugged terrain makes it more likely that the road is washed-out beneath the water. 

Precipitation will fall as heavy snow across the Sierra above 3,000 feet. Freezing levels will rise to 4,000 to 6,000 feet as mild air flows inland with the surge of subtropical moisture. Several feet of snow and whiteout conditions are likely in areas expecting all snow, which will force some road closures through the mountains as the heavy, blowing snow will be extremely difficult or downright impossible.

Widespread gusty winds are likely as this initial storm rolls across the state Saturday night through Sunday. High wind warnings and wind advisories are in place for most of California. Gusts of 40+ mph are possible in areas under a wind advisory, while gusts of 60+ mph are expected for communities under high wind warnings.

The combination of strong winds and heavy rainfall will lead to a risk for tree damage and power outages. Avoid rooms where trees or tree limbs may fall through the walls or roof during high winds, and try not to park beneath trees if you can help it.

[Satellite image courtesy of NOAA]

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January 21, 2024

Why do adults act so darn weird about wishing for snow?

Snow upends our lives in memorable and sometimes bizarre ways. A hint of wintry weather in the forecast wakes up our inner kids more than any other conditions.

Snowmen, sledding, shoveling, crunchy footsteps amid the silent nights. Every bit of it stirs a sense of nostalgia for those of us who grew up with classic winter weather. It's not just filler or background scenery—snow is a tangible event. It's weather with a purpose.

But some folks take that internal awakening to a childish extreme, lashing out in absurd and even obscene ways when their hopes and dreams of snow are dashed.

If you've ever seen the comment thread on any meteorologist's post about snow, you know exactly what I'm talking about. Fully grown adults aggressively rooting for snow, as if their combative comments and arguing can manifest a big, hearty storm into existence. 

"You're only calling for a dusting? Did you see this morning's run of this weather model? I bet you didn't even look at that. This has SURPRISE written all over it."

"This trough is moving a lot slower than predicted—this is going to be the BIG ONE and you can take that to the bank!"

Every post wishing for snow gets pushback from someone who has (sometimes pretty valid) reasons for wishing that the snow doesn't happen. Frothing arguments begin between "IT MUST SNOW" and "NEVER AGAIN." And the weirdness gets even worse during and after the storm.

"I never said take it to the bank. It should've been snowing by now and it's not. TOTAL BUST. Winter's dead. Try again next year."

"This is total crap. How did the snow break around us? You said it was going to hit!"

"You said 2-4 inches and we only got 2 inches at my house. They still pay you?"

It's...so strange the way entire adults with families and careers seemingly morph into feral trolls whenever there's a potential snowfall on the horizon. 

Enjoying a good snowstorm and rooting for snow is one thing. Acting like a grownup brat whose entire mental well-being is wrapped up in a blanket of snow is not healthy, not normal, and incredibly off-putting.

What on earth is all that about, anyway?

Untangling the web of threads to figure out why people act the way they do on the internet is an impossibly large task. There are plenty of clues that help reveal why snow is a particular flash point above all the top-level chaos in the world that rightly deserves a bit of outrage.

Latent 'Snow Day Trauma'

My long-running theory about this bizarre phenomenon is that missing a snowstorm rips away the unhealed scab of childhood disappointment.

It's the 80s or 90s, you're a kid watching The Weather Channel, and you see a snow icon pop up in the extended forecast. Could it snow? Is it possible? You check the weather every day and see that little snow icon get heavier and closer. Meteorologists start talking about the forecast with promising jargon—system, accumulations, Arctic blast...it all seems like it's really happening.

The night before a potential winter storm is electric. It's cold and the air just smells like snow. Anticipation is through the roof. They said some stuff on the news about "mixing" and "track," but you heard snow and your parents got chips and bread from the store. It seems like a foregone conclusion that tomorrow will be a snow day, the unscheduled holiday that almost every kid dreams about.

You wake up at 4:30 the next morning and rush to the window to see the concrete shimmering beneath a cold, steady rain. It sets off a meteorological version of the stages of grief—this can't be happening, those jerks said it would snow, maybe it'll change over soon, aww man, I'm gonna have to go to school today.

Every kid who grew up in snowy parts of the country—especially somewhere like the I-95 corridor along the East Coast—is well acquainted with the high hopes of a snow day crashing to the ground with the brutal track of an unfulfilled storm. Dry air, warm temperatures, and an unfavorable track can seal the demise of a potential snowstorm before it ever had a chance.

Graduating snatches some of the fun out of snowstorms

The first snowstorm after you graduate high school doesn't hit quite the same. You've had a solid 13+ years of training for this. It's routine at this point. Excitement grows at the prospect of snow and crescendos the night before the looming storm. 

And when you wake up the next morning, that first snowy morning after earning your degree, you look out the window and it really did snow. Sure, the roads are covered and the schools are closed. But what good does it do you now that you're an adult?

Joyful snow-filled days spent with loved ones are memories we can cherish forever. Even as adults we can build snowmen, go sledding, goof around shoveling, and soak in those crunchy footsteps amid the silent night.

The anticipation for all that admittedly still falls a little flat, though, without that childlike yearning for a responsibility-free day off from life.

I grew up just a few miles from I-95 in northern Virginia. There were plenty of mornings as a kid I'd stare out the window on the verge of tears when a snow day I'd hoped for washed away with a cold, unexpected rain. I understand that feeling and I know firsthand how hard it is to shake that disappointment of snow that never falls even long after reaching adulthood.

But when you read these comment threads and see shouting matches erupt over the track of a snowstorm or a few degrees worth of difference between this weather model and that one, taking a step back really clarifies what's going on.

Those angry snow-shouters, in that moment, aren't themselves—they're the kid they were a few decades ago, shouting at the clouds to call off school tomorrow.

Loss of snow days may (sadly) solve the issue

What hasn't helped matters recently is the fact that the I-95 corridor, that same area so often teased by the thin line between epic snows and depressing rain, just this month ended a historic two-year snow drought. The lead-up to those drought-busting snows was almost deafening on social media. Any hint that the snow might turn into a near-miss would've gone as well as lighting a match in a sawmill.

The combativeness is only amplified by the fact that everyone is more ready to fight over everything these days. People have always been on edge. Throw political instability and a life-upending pandemic into the mix and...phew.

I'm not sure we'll ever be able to get past it. Policing emotions never ends well for anyone involved. But I do think this effect will wane with time as school districts gradually—and unfortunately—begin to phase out the entire idea of "snow days." 

The onset of COVID hastened the shift to virtual learning. Now that the infrastructure is in place for teachers to teach remotely and for kids to never know a moment's separation from their schoolwork, many school districts are ditching unscheduled days off in favor of "virtual learning days" instead.

Snow-covered roads? No problem! Put that sled down and hit the books, kid. You've got to log on to class in 30 minutes.

I could write another thousand-word rant on why that's tragic and we desperately need to let kids be kids. But on this one bizarre issue—adults flipping out over snow like they're kids who didn't study for tomorrow's test—the ultimate loss of snow days might even out the disproportionate emotions surrounding snow.

If kids aren't getting snow days at all, their parents might be less likely to feel like they're missing out by proxy. And as those kids grow up, they won't know what it's like to watch hopes of a snow day dashed by a busted forecast...since they'll rarely have hope of a free day off.

[Stock images courtesy of Unsplash]

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January 7, 2024

Significant early-week storm to bring flooding rains, widespread strong winds

A long-anticipated and high-impact storm is finally developing over the southern Rockies on Sunday as an impressive trough in the jet stream swoops over the United States. That trough (shown in the model image above) will fuel a powerful low-pressure system that'll roll from Texas toward the Great Lakes through the middle of the week. 

This storm is going to be a doozy for just about the entire eastern half of the country beginning Monday and lasting through Wednesday. Flooding rains, heavy snow, severe thunderstorms, and widespread gusty winds are all likely over the next couple of days. Expect airport delays and cancellations, tough road conditions in areas expecting snow, and disruptive flooding—especially across the Northeast.

The Setup

This is about as classic as it gets for a disruptive winter storm across a huge swath of the U.S. and Canada. A powerful trough swinging over the Rockies this weekend will give rise to a fast-strengthening low-pressure system over Texas late Sunday into Monday.

A model image showing above- or below-average moisture in the atmosphere through Wednesday evening. Green colors show higher-than-normal moisture drawn north by the storm. (Tropical Tidbits)

Our budding storm will track from Texas toward the Great Lakes over the next couple of days, reaching its peak strength on Tuesday and Wednesday as it taps into very strong upper-level winds throughout the region.

Conditions will vary greatly depending on which side of the storm you land on. The storm will carry a vast reserve of tropical moisture streaming in from the Gulf of Mexico, which will fuel heavy snow on the cold side of the system and impressive rains where warmer conditions prevail.

Strong Winds

Gusty winds are a given with any robust low-pressure system that covers a solid half of the country. This system will churn up the atmosphere in abundance through the middle of the week, allowing for widespread gusty winds along its path.
A model animation showing the probability of 40+ mph wind gusts between Monday and Wednesday. (Tomer Burg/PolarWx)

Wind advisories and high wind warnings are likely from the Gulf Coast all the way toward the Great Lakes and New England over the next few days as this storm revs up. 

The model image above (from Tomer Burg's incredible website PolarWx) shows the probability of 40+ mph wind gusts between Monday evening and Wednesday evening. Warmer colors indicate greater odds of gusty winds that could bring down trees and power lines, especially where soils are loosened by recent and ongoing heavy rains.

Falling trees are the greatest threat for injury during any wind event. Take note of trees or tree limbs that hang over your home or vehicle, taking care to stay away from those rooms and areas while gusty winds are blowing. 

Flooding Rains

Most of the East Coast will wind up on the warm side of this system. Tuesday should feel like a spring day across much of the east as temperatures and humidity levels climb toward something you'd expect in early April rather than early January.

A surge of moisture and the sheer amount of lift generated by this storm will combine to produce several inches of rain from Florida to Maine. Some of that precipitation will initially fall as snow in higher elevations and toward the Canadian border, but the vast majority of the east's precipitation will be liquid rain.

Standing water on roads and rising waterways will be a concern throughout the area, but the greatest risk for flooding will develop across areas of the Northeast that saw a thump of accumulating snow this weekend. Heavy rain falling on snowpack is bad news all around.

Snow prevents the runoff from readily absorbing into the ground. The risk for roof collapses will increase amid the weight of water-laden snow. Storm drains clogged by mounds of snow will enhance street and parking lot flooding, and water pooling against foundations could lead to water intrusion into homes and businesses.

Severe Thunderstorms

Strong wind shear, unstable air, and plenty of moisture will fuel a risk for severe thunderstorms along the northern Gulf Coast on Monday and throughout Florida and the southeastern coast on Tuesday.

The greatest threat with these storms will be damaging wind gusts, but a few tornadoes are likely, and there's a non-zero chance that a tornado or two could be on the stronger side—especially if any individual thunderstorms can engage with the wind shear present over the region.

Even though it's a yearly tradition, so to speak, winter severe weather threats are dangerous because many folks don't expect to duck from a tornado early January. If you're under the threat for severe weather this week, check your cell phone and make sure emergency alerts are switched on for tornado warnings.

Heavy Snow

Folks on the colder northern side of the storm will see plenty of snow through the middle of the week. The swath of heavy snow will be relatively narrow, making these totals dependent on the precise track of the storm as it swings through the region.

Right now, the National Weather Service has a swath of shovelable snow from Kansas into northern Michigan, with more than 6 inches of snow likely throughout northern Missouri, eastern Iowa, northwestern Illinois, and southern Wisconsin. Gusty winds will make travel difficult during bouts of heavy snowfall. 

Conditions for everyone affected by this storm will improve rapidly late Tuesday into Wednesday as the storm hustles into Eastern Canada. We'll have a little while to catch our breaths before another formidable storm develops and threatens many of the same areas Friday into next weekend.

[Top image shows the big trough sparking our storm, via the SPC]

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January 2, 2024

Uncertainty isn't a bad thing, and other info you need about the East Coast winter storm

A winter storm is possible across a wide chunk of the eastern U.S. this weekend as a strong storm developing in the southeast sweeps up the coast toward New England.

There's a great deal of uncertainty right now given that we're about four days away from the storm. Combine those lingering questions with the fact we haven't dealt with a winter storm here in almost two years (really!) and it's a recipe for confusion and viral misinformation.

Here's what you should know—and what we don't know—about the possible winter storm this weekend.

It's been a long time since the big cities have seen snow

A huge swath of the I-95 corridor has gone nearly two years without a significant snowfall.

New York's Central Park hasn't recorded at least one inch of snow in a single day since February 14, 2022, a historic streak of 688 days without enough snow to sweep or plow in a city that averages somewhere around 30 inches of snow in a typical winter.

This blew away Central Park's previous snow-free streak by something like double the old record, which is super impressive given their weather observations go all the way back to 1869.

It's the same sad tale farther down 95, where it's been about 700 days since we've seen an inch of snow in Philly, Baltimore, Washington, and even farther south toward Richmond and Greensboro.

We haven't had to deal with a true winter storm threat around these parts since early 2022. Many of these streaks may threaten to end by Saturday.

Necessary ingredients are coming together

You need to get lucky to have a decent winter storm along the eastern seaboard, especially if you're along the coast or south of Philly. The setup for an East Coast winter storm requires four basic ingredients:

  • A robust low-pressure system
  • Ample moisture across the storm
  • Ample cold air along the storm's track
  • The correct track to put you on the cold side of the storm
The failure of any of those factors can spell disaster for kids and kids at heart turning their pajamas inside out in the hopes of waking up to a blanket of frozen memories.

If the storm is weak, it could fizzle out. Lack of moisture could 'dry slot' you into very little to no precipitation. A battle of temperatures can lead to ice or boring rain.  And the precise track of any East Coast winter storm is make-or-break given the population density and unique geographic and atmospheric setup of the region.

"We don't know" reveals a mind at work

This storm is four days away. It's too soon to know specifics about who will get what, and how much of it you'll get.

Nuance and uncertainty aren't bad words, nor do they signal a lack of experience and expertise, nor are they hallmarks of laziness.

One of the major factors behind those hair-on-fire MASSIVE BLIZZARD COMING, LIKE AND SHARE! posts going viral on Facebook and Twitter and TikTok is that they fill the information void created by uncertainty. Fake confidence is more comforting than pondering the odds of different scenarios playing out.

Winter storms are particularly maddening because there are so many potential points of failure and it only takes a tiny shift in temperature or track to change snow to rain, rain to ice, or a promise of something shriveling up into a big ol' bust.

Forecasters along the East Coast from Atlanta to Bangor have to consider more than just the overall pattern when they're predicting a winter storm.

Terrain varies widely over short distances. Interstate 95 from Virginia to New York roughly runs along the fall line, the rapid elevation shift from the rolling hills of the Piedmont to the lowlands. Temperatures along the fall line often teeter around the freezing mark as cold continental air bucks against the ocean-warmed air to the east.
An example of cold air damming from November 2023.

This is why the tens of millions of people who live in cities dotting this major artery often struggle with the trickiest forecast. Will the storm bring rain, freezing rain, sleet, snow, or a shifting mix of all four?

That elevation change doesn't even factor in the cold air damming that often occurs along the Appalachian foothills, subjecting central Virginia—and central North Carolina in particular—to frequent threats for freezing rain and ice. 

Weather models aren't infallible

Weather models struggle with those issues, too. Meteorologists use computer guidance to craft their forecasts. No model is 100 percent correct. If you ever see someone posting raw snowfall totals from one weather model and passing it off as a forecast, it's an invitation to get your weather information somewhere else.
An animation showing weather model uncertainty over the course of a single day. (Tropical Tidbits)

These models all have their strengths and flaws, and it takes a knowledgeable forecaster to blend those strengths together and use their personal expertise to make a prediction.

The animation above shows raw output from the last five runs of the GFS model for 7:00 p.m. on Saturday, January 6. The model runs four times per day, so that's roughly a day's worth of GFS model prowess.

See how much the storm itself shifts around the Mid-Atlantic from one run to the next, not to mention how the precipitation types can wildly differ? That's the uncertainty! Confidence grows the closer we get to the storm, as models and forecasters both get a better handle on the situation and likely outcome. We're still four days out from the storm, which is why there's so much uncertainty.

This week's setup

The pattern we're in this week is very reminiscent of the classic El Niño wintertime pattern you'd see in a textbook or explainer article.

Winters during a strong El Niño tend to see a powerful subtropical jet stream snaking over the southern United States, which gives rise to frequent low-pressure systems that blossom over the Deep South before roaring up the eastern seaboard.
A snapshot of the GFS model on Tuesday morning, showing what the jet stream might look like on Saturday afternoon. (Tropical Tidbits)

Well...we've got that for sure. This type of a pattern is great for areas mired in drought, but it also provides a spark of hope for winter-weather lovers if those systems coincide with shoves of cold air diving down from Canada.

Winds will strengthen in the jet stream as a steep trough sweeps over the Rockies later this week, giving rise to a formidable low-pressure system over the northern Gulf of Mexico that'll likely track up the length of the eastern states heading into the weekend.

Those powerful winds in the jet stream will force air to rise in abundance, allowing a low-pressure system to develop over the northern Gulf Coast and begin roughly paralleling the Appalachians late Friday until it exits New England late Sunday.

We'll very likely have a weekend storm. (Check.)

That storm will have plenty of moisture to work with. (Check.)

Now, we've just got the cold air and the track of the storm to worry about. (Uh oh.)

The ultimate track of the storm makes all the difference

If the storm tracks a little too far west and a little too close to the mountains, it'll help drag milder air inland and keep communities along and east of I-95 rain for most or all of the storm.

A storm tracking just offshore puts this megalopolis in the perfect spot for cold air to arrive alongside the heaviest precipitation, which can lead to a decent blanket of snow.

A track right up the middle, though, leaves little margin for error—a few miles makes all the difference between precipitation types and amounts.
The likelihood of at least "minor" winter weather impacts between 7 a.m. Saturday and 7 p.m. Sunday, according to the Weather Prediction Center.

And right now, four days out from this storm, it's too soon to tell with confident precision where this storm will track.

Unfortunately, current trends seem to bring the storm up the middle of the Mid-Atlantic, threading that swampy needle between the Appalachians and the Atlantic in a way that brings huge changes over tiny distances.

Forecasters have high confidence that the Appalachians, much of Pennsylvania, and a swath of lower New England are in for shovelable snows late Friday night through Sunday evening as the system moves south to north. The bulk of the system would likely affect the most folks between Saturday morning and Sunday morning.

It looks like it'll be exceptionally close for the I-95 megalopolis, but the potential is there for D.C., Baltimore, Philly, and New York to end their yearslong snowless streaks. Farther south toward me in central North Carolina, cold air damming will likely rear its ugly head, making ice more likely than snow before the changeover to rain through the day Saturday.

This is a storm worth watching, as every news writer in the western hemisphere likes to say. It could prove disruptive to road and air travel over the weekend, especially from Pennsylvania northeast through Maine.

But there's still lots of uncertainty surrounding the precise details of this impending storm. We'll have clearer and more confident answers tomorrow, and sharper details still by Thursday. It's tempting to seek out the loudest voices promising all the answers. Hard as it is to find them these days, it's best to stick with the level-headed folks willing to level with you and say "we don't know yet."

[Top image showing colorful weather-models-as-art created using WSV3]

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December 16, 2023

Weekend deja vu as second powerful East Coast storm hits Sunday and Monday

Didn't we go through this last weekend?

A(nother) powerful storm developing near Florida will roll up the length of the East Coast beginning Saturday night and lasting into Monday, producing a large swath of heavy rains and very strong winds.

The worst conditions will occur at the coast where communities—especially the N.C. Outer Banks—may experience significant storm surge flooding.

Our storm is developing today in the eastern Gulf of Mexico as a steep trough digs over the eastern U.S. This low will strengthen in a hurry as it taps into strong upper-level winds and parallels the southeastern coast.

We'll see the storm move from Florida through Georgia and into the Carolinas on Sunday, bringing widespread heavy rains and very strong winds. Gusts of 50+ mph are likely at the coast, with gusts of 30-40+ mph reaching inland all the way to the mountains.

The low-pressure system will quickly track into the Northeast by Sunday night, heading into Atlantic Canada by Monday.

A deep plume of tropical moisture sourced from the Caribbean will draw into the system as it revs up, allowing for torrential downpours along its path. Widespread rainfall totals of 2-3 inches are likely from Florida to Maine, with locally higher totals possible. This could easily lead to flash flooding in some areas.

In addition to the potential for bad coastal flooding, the combination of strong, persistent winds and heavy rainfall will lead to a risk for power outages along the storm's track. There's also a high chance that we'll deal with flying Santas over the next couple of days. Secure or bring inside all of your outdoor Christmas decorations. Inflatables are notorious for getting loose in high winds. Any decorations or furniture that tumbles down the road could cause injuries, damage, or even car crashes.

This is an...unusual...storm in that we're not really expecting any snow—at least not initially. Temperatures are too warm for anyone on the East Coast to see frozen precipitation as the storm swings through the region. It is the middle of December. That isn't normal. (But nothing really is anymore.)

Cold air wrapping in behind the system will allow for lake-effect snow to develop across the Great Lakes, so a dose of snow in the usual areas is likely to begin the week. This cold air will reach all the way to the coast in northwest flow behind the storm, making for a pretty chilly Tuesday before temperatures turn mild again as the week wears on.

[Top image via Tropical Tidbits, showing modeled surface winds on Sunday evening.]

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December 9, 2023

East Coast in for a pressure washing as a powerful storm arrives Sunday

A feisty low-pressure system is gearing up to bring plenty of disruptive weather to the East Coast over the next couple of days. Widespread heavy rain could lead to flooding along the I-95 megalopolis while the storm produces snow near the Great Lakes and severe storms across the southeast.

Sunday/Monday's storm is part of a dynamic pattern that's gradually making its way across the eastern half of the country. A cold front extending off a low-pressure system moving through the Great Lakes is responsible for most of the active weather we're seeing on Saturday. A new storm will develop along this front on Sunday, becoming the dominant system that'll bring all the headaches to end the weekend.

Sharp wind shear through the atmosphere combined with a cold front running into a pool of warm, moist air is a recipe for severe thunderstorms. An expansive severe risk covers a chunk of the southern U.S. on Saturday, mainly focused on the lower Mississippi Valley east into Alabama and Tennessee.

Any severe thunderstorms that bubble up on Saturday could produce damaging winds, hail, and a few tornadoes. We already saw a couple of tornadoes touch down in north-central Tennessee early Saturday afternoon.

We'll see that storm threat shift east on Sunday as the cold front heads toward the Atlantic coast. Severe thunderstorms are possible from the D.C./Baltimore region down the I-95/I-85 corridor toward southeastern Alabama and the northern half of Florida. The main risk with Sunday's storms would be damaging wind gusts, but a few tornadoes are possible, especially in parts of eastern Virginia and North Carolina.

Farther north, this developing storm's main threats will be drenching rains, heavy snow, and blustery conditions.

Flood watches span the I-95 corridor from D.C. to Portland as forecasters anticipate several inches of rain falling through the day Sunday. Lots of rain falling in short order can overwhelm waterways and drainage systems, leading to pooling and possible street flooding.

It's not going to be a gentle downpour, either. Widespread wind gusts of 20-30+ mph will accompany the storm as it chugs through interior New England on Sunday. Much stronger winds are likely for coastal communities across the northeast, where a period of 50-60+ mph wind gusts will be possible into Monday.

Winds this strong combined with wet soils could lead to fallen trees and power lines. Make sure your holiday decorations are tied down or brought inside, as well. Those things will take flight in a hurry once the gusty winds start, and it could be dangerous if they blow into the road.

Cold air flooding in behind the system will allow for widespread snow across the Northeast interior and down the spine of the Appalachians. The heaviest totals are likely near the Canadian border, where higher elevations in New York and Vermont could see more than a foot of fresh snow by Monday.

If you have plans to travel late Sunday or early Monday, it's worth keeping in mind that some models are struggling a bit with the potential changeover from rain to snow across parts of Pennsylvania, the Mid-Atlantic, and even down into the North Carolina Piedmont.

Plan ahead for the potential for a burst of snow during the last few hours of precipitation overnight Sunday into Monday, with possible accumulation if temperatures are cold enough.

[Top model image generated using WSV3]

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