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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I graduated from the University of South Alabama in 2014 with a degree in political science and a minor in meteorology. I contribute to The Weather Network as a digital writer, and I've written for Forbes, the Washington Post's Capital Weather Gang, Popular Science, Mental Floss, and Gawker's The Vane. My latest book, The Skies Above, is now available. My first book, The Extreme Weather Survival Manual, arrived in October 2015.