It’s true: We’re tracking another snow threat, but it’s a foggy one

It may snow again next week.  But let’s not read too much into those 6 words.

Snow next week is qualified by “may”, to say nothing about amounts.

We can confidently predict there will be much colder than normal air in the region early to mid-week – and that disturbed weather will be in the vicinity.  It’s an open question whether this disturbed weather takes the form of a major storm hitting us head on or grazing us,  or whether  just a little front brushes us with flurries and/or rain showers.

“Models continue to highlight the Tuesday-Wednesday period for another possible winter storm,” says Capital Weather Gang winter weather expert Wes Junker. “Another shot of arctic air is forecast to drop southward into the area as a low pressure system approaches the area.  Yesterday’s model runs presented the idea of a storm tracking towards the Ohio Valley before reforming on the coast.  Today the European model has a low tracking to our south and then really bombing [explosively intensifying] off the coast.  This morning’s GFS kept the storm to our south.  There still is a lot of uncertainty about the exact evolution and track of the storm.  We’ll be watching it over the next several days as the models try to converge on a solution.”

Here’s a quick snapshot of the latest models:

* The European model develops low pressure in northern Gulf of Mexico and moves it northeast to a position off the North Carolina coast, spreading snow into the Mid-Atlantic.

European model shows strong low pressure off the North Carolina coast next Tuesday with snow over the Mid-Atlantic interior. (WeatherBell.com)

European model shows strong low pressure off the North Carolina coast next Tuesday night with snow over the Mid-Atlantic interior. (WeatherBell.com)

* The GFS model develops a storm off the Southeast coast but too far offshore to affect the region

The GFS model shows low areas of low pressure to the north and southeast of the Mid-Atlantic...largely missing the D.C. area next Tuesday. (WeatherBell.com)

The GFS model shows low areas of low pressure to the north and southeast of the Mid-Atlantic…largely missing the D.C. area next Tuesday night. (WeatherBell.com)

* The Canadian model brings a clipper-type system with some snow showers through the region, but it never really gets it act together until offshore New England. And while it forecasts some snow showers for our region, this setup may actually favor rain with the low passing to our north, which could bring in some milder air from the south before a reinforcing shot of cold.

Animation of Canadian model next Wednesday morning and evening showing storm passing to our north with perhaps just a few snow (or rain?) showers. (Environment Canada)

Animation of Canadian model next Wednesday morning and evening showing storm passing to our north with perhaps just a few snow (or rain?) showers. (Environment Canada)

Lastly, to give you a sense of the uncertainty in the forecast, consider this diagram from the European model ensemble (run last night) below.  It displays snowfall output from 50 simulations of the European model (with the data initializing the model tweaked slightly for each simulation) for Reagan National Airport over the next 10 days.

The 50 simulations from the European model ensemble from last night of snowfall at Reagan National Airport over the next 10 days.  About half show snow, half do not. Most of the snow simulations are in the Tues-Wed timeframe next week. (WeatherBell.com)

(Top) The 50 simulations from the European model ensemble from last night of snowfall at Reagan National Airport over the next 10 days. About half show snow, half do not. Most of the snow simulations are in the Tues-Wed timeframe next week. (Bottom) Accumulated snowfall from the average of the 50 simulations with time in green. (WeatherBell.com)

You can see that about half of the simulations show snow and half do not.  The average snowfall output from the 50 simulations is 2-3 inches in the Tuesday-Wednesday timeframe but the range in the forecasts should give you a clear idea that the forecast is very uncertain and it’s too soon to speculate about specifics.

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