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Posted at 10:30 AM ET, 12/23/2009

Forecast: Calm and cold before Christmas storm

By Dan Stillman

Chance of a wintry mix Friday a.m. before changing to rain

* Evolution of a monster snowstorm | How did the storm happen? *
* Outside now? Weather Wall | Later: Weather Checker *

Today's Daily Digit
 
A somewhat subjective rating of the day's weather, on a scale of 0 to 10.
 
4Cold sunshine slowly whittles away at our winter wonderland.
 
Get tomorrow's 'Digit' on Twitter tonight

EXPRESS FORECAST

Today: Mostly sunny. Upper 30s to near 40. | Tonight: Mostly clear. Teens to low 20s. | Tomorrow: Partly to mostly sunny. Low-to-mid 30s. | A Look Ahead | Get Express Forecast by E-mail

FORECAST IN DETAIL

Despite cold weather, sunshine continues to put a dent into area snow cover today and tomorrow. The next real period of interest coincides with the Christmas holiday, specifically the chance of a wintry mix during the first part of Christmas Day Friday and then, as temperatures warm, a risk of flooding late Friday into Saturday. Read on for the details as we see them now...

Temperatures: Current area temperatures. Powered by Weather Bonk. Map by Google. Hover over and click icons for more info. Click and hold on map to pan. Refresh page to update. See map bigger on our Weather Wall.

Today (Wednesday): Mostly sunny skies won't be enough to break us out of this cold streak we're on. Most spots should top out in the upper 30s to near 40, several degrees below average. At least breezes won't be much of a factor, around 5-10 mph from the north. Confidence: Medium-High

Tonight: With skies mostly clear, temperatures tumble to the chilly teens across the suburbs to near 20 or in the low 20s downtown. Confidence: High

Keep reading for the forecast through the weekend....

Tomorrow (Christmas Eve): Partly to mostly sunny and cold again tomorrow with highs maxing out in the low-to-mid 30s. A storm lurking in the central U.S. could stream increasing clouds our way toward evening. Confidence: Medium-High

Tomorrow Night: Skies become mostly cloudy the night before Christmas and there's a chance of a wintry mix by sunrise with lows in the 20s. Confidence: Medium

A LOOK AHEAD

Precipitation, possibly in the form of a wintry mix, could break out as early as before sunrise Christmas Day Friday or as late as mid-to-late morning. Temperatures warming above freezing by afternoon, possibly eventually to near 40, should turn precipitation to all rain across the area. But before then there's potential for icing, especially but not limited to north and west of the District. Confidence: Low-Medium

The combination of rain and melting snow could pose a flood risk Friday night and Saturday. But just how much rain we get remains uncertain, so for now this is more of a heads-up than a dire warning. Temperatures should stay safely above freezing through the period with Saturday highs probably in the 40s. Confidence: Low-Medium

Rain should come to an end late Saturday making way for a dry Sunday with highs in the 40s. Confidence: Medium

By Dan Stillman  | December 23, 2009; 10:30 AM ET
Categories:  Forecasts  
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Next: CWG's snow forecast: Reasonable, cautious

Comments

I know you guys are tired after working the big storm, but I think you can do better than "the 30s" for a same day forecast.

FWIW Accuweather is calling for a high of 38 in NE DC.

Posted by: psilosome | December 23, 2009 6:24 AM | Report abuse

Posted by: dprats21 | December 23, 2009 6:29 AM | Report abuse

@psilosome -- Actually, I'd be willing to bet, if you traveled their forecast zone (roughly NW Mont. Co. to SE PG County), "the 30s" is a fairly accurate representation of a fairly bland day weather wise. Is there really that big of a difference between 36 & 39? When the weather gets interesting, you'll get your details.

Posted by: Registration1982 | December 23, 2009 8:40 AM | Report abuse

NWS forecast seems a bit alarmist to me. They're reluctant to forecast a changeover to rain the further west you go. And, they're forecast highs for Loudoun are only around 35 for Xmas Day. Way underdone, IMHO.

We've seen this set-up once this year already. And in that case, the feared cold air damming was greatly mitigated by the far western track of the storm. There's a lot of warm air with this storm, as seen by the thunderstorms firing up this morning in the Plains.

I think we'll see the same evolution as we did with the last storm that tracked this far west. Warm air will rapidly scour out any leftover cold air leaving only a brief period of freezing rain. Temps will rise to the low to mid 40's.

Posted by: ThinkSpring | December 23, 2009 9:00 AM | Report abuse

@psilosome

Thanks for the comment. We are tired from the storm :). But that's not why today's forecast was "30s." Every once in a while there's enough disagreement between models, and enough variation between morning lows across the area, that it's hard to confidently pin down even a day 1 forecast to a "mid-30s" or "mid-to-upper 30s," for example. That was the case for today, in my opinion, with everything from low 30s to upper 30s to even near 40 all in play (and by the way I heard a similar forecast from another outlet while flipping the radio dial this morning).

Posted by: Dan-CapitalWeatherGang | December 23, 2009 9:24 AM | Report abuse

On a whole other subject, is there any way a link to your blog could be added to the mobile site? You're always the first place I want to check when something weathery is happening, and at times it is difficult to impossible to find a link to CWG if I'm on the mobile and not at a computer. Thanks!

Posted by: paperball | December 23, 2009 9:44 AM | Report abuse

With temps rising nicely, forecast above has been updated (to upper 30s to near 40 for today).

Posted by: Dan-CapitalWeatherGang | December 23, 2009 11:09 AM | Report abuse

@paperball

Looking into it. Thanks for the suggestion.

Posted by: Jason-CapitalWeatherGang | December 23, 2009 11:10 AM | Report abuse

Given that it does appear Santy and Rudolph will be delivering a large takeout order of Sparkling Tropical Water from Momma Nature's Caribbean Weather Grill:
If they don't want to be flooded out of their parents' basements, the fanboyz might want to use their snow day to become acquainted with the business end of a shovel and learn the fine art of downspout clearing instead of hanging out with their homies on the internets talkin' model trash and debating the relative merits of sleet vs. freezing rain.
You've Been Warned.

National up to 37 at noon.

Posted by: CapitalClimate | December 23, 2009 12:00 PM | Report abuse

This approaching storm is presenting a rather interesting weather setup.

The extended-forecast charts indicate that the triple point of the approaching occlusion could come very close to Washington as it passes through the area Friday.

Lightning data indicates rather heavy activity in the central U.S., especially on the KS/MO border. Vaisala spreads the electrical activity east to western IL, and StrikeStar US has gone from a rate of zero yesterday to 10 today. WGN is reporting sleet/freezing rain currently in Chicago.

Depending on the CAD setup we could see anything from a short-duration event to several hours of icing Christmas morning before everything changes to rain some time Christmas Day.

Posted by: Bombo47jea | December 23, 2009 1:12 PM | Report abuse

NWS afternoon update up. WSW for Shenandoah Valley. NWS continues to be hard-headed and are now even ignoring their own model data that shows the cold air being scoured away early afternoon out there.

Bad job of forecasting, NWS. They always overdo the cold air damming.

Oh, and their forecast highs for today were low again. Once again, putting too much stock into that "snowpack absorbing the sunlight" thing. It does absorb some of it, but they always overestimate its effect.

Wish they had a message board that I could post these matters on.

Posted by: ThinkSpring | December 23, 2009 3:20 PM | Report abuse

Is there any way of forecasting melt rate due to the projected rain levels/temp. combo, and then determining how much snow pack we might still have come Sunday?

Posted by: TheAnalyst | December 23, 2009 5:30 PM | Report abuse

The comments to this entry are closed.

 
 
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