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Posted at 06:50 PM ET, 10/27/2011

The low odds, high impact October snow scenario


NAM model simulation indicating total snowfall from Friday night to Saturday night (in inches). ( StormVistaWxModels.com (requires subscription))
I debated even posting this, but if I have information, why hide it? The latest North American Model (NAM) pastes the D.C. metro region with an unprecendented late October snow event. Ready for this? It simulates 4-8” of heavy, wet snow Saturday. Caution: this model has been wildly inconsistent and had the storm out to sea as of this morning, so take it with a huge grain of salt.

Importantly, this model does not represent our forecast and other models do not simulate this extreme scenario (as Wes demonstrated earlier). I’m putting it out there to illustrate a worst case scenario. If this model simulation verified, the impacts would be significant, not because much snow would stick on roads, but because the weight of heavy wet snow on trees still full of foliage would create a major power outage ris. This scenario (of at least 4”) has about a 5-10% probability of occurrence according to NOAA .

Again, the reason for posting this is for you to be aware something like this *could* happen, but very likely won’t.

Keep reading for what we actually think most likely will happen..

The most likely scenario is rain, briefly mixing with or changing to snow before ending. Accumulation is likely to be highly elevation dependent, with no accumulation inside the beltway and perhaps a coating on grassy areas in outlying north and west suburbs especially as you get into Frederick and Loudoun counties.

More substantial accumulation may well occur above 1,000 feet in the mountains. Locations along and near the I-81 corridor like Harrisonburg (Va.), Martinsburg (Wv.), and Hagerstown (Md.) may also see some accumulatin g snow.

Here’s a brief video I recorded earlier highlighting what I think will happen:

Note - our forecast will be refined tomorrow and our projections for how much snow we might see could potentially be increased or decreased.

By  |  06:50 PM ET, 10/27/2011

Categories:  Latest, Winter Storms

 
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