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A Messy/Icy Thursday...Then What?

Josh Larson @ 8:00 PM


8:00pm: Everyone in the immediate DC area, as far as I can tell, is just seeing plain old rain, with temperatures in the mid 30s. Rain will continue until late tonight. Still be careful, as a few slick spots may be out there, particularly on elevated surfaces and in the usual cold spots. I am not expecting a refreeze tonight, so kids do your homework. -Jason

2:30pm: Temperatures in the immediate DC Metro area are creeping to near 32 degrees. It is likely that within the next hour many spots will see a changeover from freezing rain to plain rain; some spots, however, may still remain slick through the late afternoon. Also, note that areas 15+ miles north or west of the Beltway may continue to see freezing rain through the late afternoon.

1:00pm: An initial burst of mainly snow and sleet brought a dusting to an inch of accumulation for most areas; a lull in precipitation is now giving way to a period of sleet and freezing rain. Temperatures range from 28 at IAD and BWI to 32 at DCA. It is likely that a mix of sleet and freezing rain will continue for many spots for the next couple hours as temperatures hold steady or very slowly creep up. Untreated surfaces remain slick in many locations, so take it slow if you're outside.

10:30am: A band of moderate snow, perhaps mixed with sleet, is developing over the immediate DC Metro area from SW to NE. This band will likely bring a dusting to an inch of snow in many spots by noon. Temperatures range from the mid to upper 20s in most locations, with dewpoints in the upper teens to lower 20s. Once precipitation becomes heavy, air temperatures will likely drop a few degrees to the mid 20s. Untreated roads will likely quickly become slippery.

Today's Forecast

For the second Thursday in a row, we will be seeing a messy, wintry mix. As noted in previous posts, however, the atmospheric setup and details differ from last week's events, but, unfortunately, like last week's events, this is a very complicated weather setup and, therefore, remains a lower-than average confidence forecast. Like last Thursday, a few miles might make the difference between 32/frozen precip and 33/liquid precip.

  • Burst of snow/sleet will develop mid morning; dusting to 1" accumulation
  • Snow will quickly turn to a mix of sleet and freezing rain by early afternoon
  • A period of freezing rain is likely during the early to mid afternoon
  • An icy coating may develop on untreated surfaces prior to changeover to plain rain by 6pm

Winter Storm Forecast: Thursday, December 15
Click to Enlarge
9 am to 11 am: snow/ sleet develops; SW to NE
11 am to 2 pm: snow/sleet to freezing rain; icy accumulation possible
2 pm to 6 pm: freezing rain changes to all rain from SE to NW
6 pm to 1 am: rain, heavy at times
1 am to 5am: rain tapers
Storm Impact: Travelcast: Schoolcast:

Pattern Overview

The high temperature over the past ten days has averaged a whopping 12 degrees below normal (37 compared to 49). For instance, yesterday morning's temperatures were in the single digits or teens over the entire local area, and highs only made into the mid 20s. This bitter cold has been the result of a persistent STRONG TROUGH over the eastern US which has allowed frigid air to drain right into our region from Canada and the Arctic. Though there will be some short-term letup to the cold Friday and Saturday, it appears that appreciably below-normal temperatures will return, and continue to persist, over the next week to 10 days -- mostly on the order of 5-10 degrees below normal. More winter weather precipitation events are certainly possible over this period.

The next 5 days (Dec 15-19)
Forecast high/low: 40/26 (normal = 46/32)
Forecast precip: near normal

After today's raw and messy weather, expect improving (and much milder) conditions on Friday. Though a stray flurry cannot be ruled out during the morning hours Friday, partly sunny skies and windy conditions will emerge by afternoon. Expect highs in the mid 40s with overnight lows in the upper 20s. Saturday will feature partly to mostly sunny skies with temperatures near 43/25. Sunday will feature increasing clouds with cooler temperatures near 39/24. There is some indications that low pressure may develop to our south on Sunday, bringing a slight chance (~20%) of snowfall late Sunday into Monday. Otherwise, it will be partly to mostly cloudy and cold with temperatures near 36/20 on Monday.

The following 5 days (Dec 20-24)
Forecast high/low: 39/25 (normal = 45/31)
Forecast precip: below normal?

The forecast for the next 5 days is one of medium confidence. It appears that during this period we may have a lull in storminess, with a less energized southern jet stream; below-normal temperatures will likely persist, though some models hint at a possible moderation in temperatures to normal (or even above-normal) temperatures by Christmas time. For Tuesday through Thursday of next week expect partly to mostly sunny conditions with generally dry weather and highs ranging from 35-40 and lows ranging from 20-25. Friday and Saturday will likely feature partly sunny skies, low chances for precipitation with highs 40-45 and lows 25-30.

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