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10-Day Outlook: Hold On to Your Hats!

Josh Larson @ 10:00 AM

Today's Forecast

Today's weather will feature a blend of clouds and sun with unseasonably warm temperatures -- some 20-25 degrees above normal for this time of year. Afternoon highs will range from 60-65 degrees across the immediate DC metro area. Foggy once again overnight with lows ranging from the upper 30s to the mid 40s.

Pattern Overview:

Saying that temperatures over the next 10 days are likely to continue the past 10 days' trend of at least 5 degrees above normal does not do justice to the immense volatility in the weather we're likely to experience over the next 5 days. We're looking at an exceptionally potent cold front (and associated deep area of low pressure):
  • which may bring a risk of both thunderstorms and snow!
  • which is likely to drop temperatures some 40+ degrees:
    • ... from readings in the 60s on Friday
    • ... to readings in the 20s by Saturday
Thereafter, the weather will settle down considerably: Sunday will feature seasonably cold weather before temperatures moderate again to above normal levels by Monday, likely continuing well into next week. We remain locked in pattern where there is little in the way of sustained Arctic air available and where the atmosphere aloft favors a general trough over the West and a ridge (and mild, southwesterly flow) over the East.* (see end of post)

The next 5 days (Jan 12-16)
Forecast highs/lows: 51/34 (normal = 42/27)
Forecast precip: above normal

Friday's high temperatures will, like today, also be at or above 60 degrees in most locations thanks to a continued very strong southernly flow aloft; though the day will start mostly clear (but foggy), we're likely to see increasing cloudiness as the day wears on -- ahead of the aforementioned cold front.


Expect showers and thunderstorms to develop sometime between 10pm Friday and 4am Saturday. Severe thunderstorms are possible (50%), and there is even a slight risk (10%) of tornadoes. Scattered showers will linger into the morning hours Saturday. Winds will pick up dramatically: expect winds of 20-40mph, with damaging gusts to 60mph possible. By late afternoon, temperatures will drop into the mid 40s with a few scattered showers remaining. By evening, temperatures will plunge into the 30s. Widely scattered snow showers may develop during the evening or overnight hours, perhaps ending as a burst of heavy, wet snow, which may bring a coating on some grassy surfaces. High winds are likely to continue through the overnight hours, with windchills in the single digits possible.

Pictured above: the 500mb vorticity/height fields from the NAM model centered over Saturday night; courtesy NCEP

For the rest of the first 5 days...Sunday will feature partly sunny and sharply colder temperatures. Highs will be near 40, but blustery NW winds 15-30mph will produce wind chills in the teens. Snow squalls are likely over the western mountains and a rogue snow shower cannot be ruled out over the remainder of the forecast area. Clear and cold Sunday night, with lows in the 20s. Monday's weather will calm down, with sunny skies and milder temperatures approaching 50 degrees for highs.

The following 5 days (Jan 17-21)
Forecast highs/lows: 51/33 (normal = 42/27)
Forecast precip: near normal

In comparison to the weather over the next 5 days, the weather over the following 5 days will be considerably more settled. During the period next Tuesday through Saturday high temperatures are expected to range from the upper 40s to mid 50s, with overnight lows mostly in the 30s. With continued significant model disagreement, it remains difficult to accurately forecast or time specific weather features, though there are indications that showers are possible on Tuesday or Wednesday of next week.

*Note: My colleague at the Climate Prediction Center points out the following important observation: we have noticed "a sudden stratospheric warming taking place in the northern polar region. This warming, of about 30 degrees C in the last few days is usually followed by a negative AO pattern due to the warmth, and hence high heights, seeping down into the upper troposphere. If this were to verify, then the eastern part of the country would revert to below normal temperatures, and possible above normal snowfall."

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