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First Full Day of Spring?

Matt Ross @ 1:00 AM

12pm Update

Radar looks impressive to our south and west, but most of the precip is not reaching the ground as the air is very dry. The 20% scenario described at the bottom is now the most likely scenario. Look for overcast skies through this evening. Flurries and maybe a snowshower are possible between now and 8pm with little or no accumulation expected. Most likely to see some flakes are those in the southern suburbs and elevated areas to our west. I will update as needed this afternoon.

The dominant story is today's possible winter weather. See complete details below. After this system exits we will see below average temperatures continue through the weekend with highs in the upper 40s to low 50s and lows in the 30s. Another approaching storm system late this week into the weekend looks like it will develop far enough offshore that it misses our area.

Winter Storm Forecast: Tuesday, March 21
9am to 12pm: Light snow/sleet overspreads area.
12pm to 3pm: Snow, possibly mixing with sleet downtown and SE.
3pm to 6pm:
Precip tapers to flurries NW, drizzle SE
7pm to 12am Wed:
Patchy light snow or flurries possible
Storm Impact: Travelcast:Schoolcast (Tues.):

Scenarios for Today's Event from Snowiest to Least Snowy

10% chance:

All model indications are wrong, and the storm is further north, colder, wetter, and slower with the coastal low having more of an impact. The metro area sees 2-4" mostly on non-paved surfaces, but with some accumulation on side streets, sidewalks, bridges and overpasses. Snow tapers off late in the evening with some refreeze possible overnight in the far western suburbs and other elevated locations.

20% chance:

The suppression to the south indicated by some of the latest model guidance is incorrect, and the metro area receives moderate snowfall from mid-morning to mid-afternoon before tapering off. The temperatures hold steady in the lower 30s allowing some sticking to paved surfaces during heavier bursts. The metro area receives 1-2" mostly on grassy surfaces. Higher amounts and slicker streets possible in elevated areas to the north and west.

50% chance and most likely:

Snow spreads from WSW to ENE after the morning rush hour. During a 6 hour window from 9am to 3pm there will be periods of steady snow, particularly in the southern suburbs and western foothills. Snow will taper to flurries/drizzle during the afternoon and the entire system will be out of here by mid-evening. Some of the higher spots and southwestern spots will see 1"+ with over 2" in elevated areas well to our west and southwest. The vast majority of the metro area will see less than 1". Accumulation will be limited to grassy surfaces for most of the metro area as temperatures remain at or above freezing for the event. Snow may mix with sleet and rain at times, especially when precipitation rates are lighter. During heavier bursts, snow may stick to some side streets, sidewalks, bridges and overpasses, but will melt rapidly except in the favored areas. Some areas, especially downtown, Arlington and Alexandria will report little or no accumulation, while higher spots in the favored suburbs may see a blanket of white on lawns, cartops, and shrubbery.

20% chance:

The majority of the metro area sees little or no steady precipitation. Just some flurries, sprinkles with no accumulation. Places to the north may see just mostly overcast skies, while places well to the south and west see a several hour period of steady precipitation.

What Others are Forecasting

During the 11pm broadcasts last night, Veronica Johnson at Channel 4 was calling for 1-2" with higher amounts to the south. Topper Shutt was more conservative at Channel 9 with a forecast of 1" or less with more to the south. Doug Hill at Channel 7 was calling for a trace to 2". The National Weather Service was calling for 1-2" with a winter weather advisory for most of the metro area and a snow advisory for the far western locations.

Stay tuned for frequent updates as needed.

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