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Monday snow: First Accumulation Forecast

Jason Samenow @ 4:00 PM

WINTER STORM WATCH IN EFFECT FROM LATE TONIGHT THROUGH TUESDAY MORNING

Next update: ~7pm

11:30am update: Guidance continues to conflict significantly for Monday's storm. Winter Storm Watches posted to our south. National Weather Service calling for 3-5" for our area. Tony Pann of WUSA also going with 3-5". Chuck Bell of NBC4 calling for a 70% chance of 4"+, which is what NOAA's Hydrometeorological Prediction Center forecasts (it also suggests a 40% probability of 8"+). I'm sticking with 2-4" for now as a first call but will re-assess later. My accumulation map is posted below.

As I have documented in previous posts, the models which forecasters use as tools for predicting the weather have been flip flopping on the possible snow event on Monday and Monday night. Regrettably, there has been virtually no consistency nor continuity in this guidance. Some guidance suggests a major snowstorm for our area (6"+), other guidance suggests a near-miss (nada, zip). While uncertainties remain large, the models provide clues about the overall pattern which seems conducive for a moderate snow event Monday afternoon and evening.



Overall storm assessment

Storm Impact:
Travelcast (for Monday night/Tuesday):
Schoolcast (for Tuesday):


Most Likely Snow Accumulations Across The Region


Most likely scenario: Low pressure will develop in Alabama and Georgia today and move northeastward towards the Carolina coast tomorrow. A swath of snow will develop north and west of the low, with the possibility of snow beginning in our area late Monday morning and continuing into the evening. Daytime snowfall may not accumulate due to warm ground and surface temperatures, but conditions will deteriorate after about 4pm.

Most likely accumulation: 2-4" over the greater Washington, DC area -- greater amounts possible in central Virginia. An accumulation map will appear here by noon.

Alternative scenarios: 1) The low takes a more suppressed southerly track, heading out to sea, with mostly flurries for our area and no accumulation. 2) The low takes a more westerly track in a more amplified flow patten, with significantly heavier precipitation amounts -- but also the possibility of mixing with sleet.

Tune into WeatherTalkRadio (AM 680 WCBM, also streaming on the web) with Tony Pann and Justin Berk at 3pm today on what is sure is to be a lively show.

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