Thursday, December 13, 2007

Fairly Fine Friday
Saturday, Sunday: Snowy/Sleety/Soggy/Sloppy?


Drizzle, cold. What had been expected to be a cold rain today has amounted to mostly an annoying light to moderate drizzle in the Washington metro area. By 4:00, National and Dulles had collected a mere 0.02" each, while the jackpot winner BWI had 0.04". Radar shows the bulk of the precipitation from this system from the Mason-Dixon line north and east, with moderate to heavy snow expected across portions of interior southern New York and New England.

The cold part of the forecast has materialized, however, as yesterday's midnight low of 47° is turning into today's high; temperatures are now generally in the upper 30s through the immediate area. After a drier and milder day tomorrow, a strong storm system will affect the Mid Atlantic region over the weekend.

Tonight and Tomorrow

Clearing, chilly. After any residual drizzle or light showers this evening, tonight's lows will be from the mid 30s downtown to the lows 30s in the 'burbosphere under decreasing clouds. Tomorrow will be mostly sunny and milder with highs 51-54°

Scroll down for Josh's outlook through the weekend and into next week.

Weekend Storm Outlook

The answer to the sub-headline's question is, "All of the above, the combination depending on your location and elevation." The models continue to paint a picture of a very vigorous storm emerging out of the Southern Plains on Saturday and bringing a wintry mix to the Mid Atlantic area by Saturday night and into Sunday. Although the latest runs from this morning and early this afternoon show some warming over the DC area, they also show a tendency for a strong secondary low to develop off the coast, which would keep more cold air in place. The complex dynamics of this interaction between the atmosphere at multiple levels and the land/ocean surface are not very well represented even by today's highest resolution models, so there is still plenty of room for variability in the final mix.

At this point, the best that can be said of frozen precipitation forecasts for this system is, "At least some of them will be wrong."

See Josh's Snow Lover's Crystal Ball below for more details on possible scenarios.

Historical Note

It might be just nostalgia kicking in, but the predicted evolution of this system reminds the Updater in some ways of his first experience with Washington snow, 50 years ago this month. The storm of Dec. 4, 1957 brought 11.1" of snow from a strong secondary development off the coast as the main system stalled over the upper Ohio Valley. That is still the second highest daily total ever for the month of December, but the temperature stayed at or above freezing; the daily high and low were 33° and 32°. The high 2 days before? 58°. That storm had a little more northerly course, however, and there was a very strong low over northern Quebec and Labrador.

Here's the forecast for DC and vicinity made the morning of Dec. 4, 1957:
"Today . . . wet snow and some rain ending this morning, clearing and windy this afternoon, highest 40°."

Weather map at 1am Dec. 4, 1957, from NOAA Library.

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Seasonal Outlook

Latest seasonal forecast: Click here.

Latest 3-month temperature outlook from Climate Prediction Center/NWS/NOAA.