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Posted at 10:00 AM ET, 03/ 4/2009

Forecast: Warming Up, Slowly but Surely

By Dan Stillman

Very cold today but 60s on the horizon

* We Grade Our Snow Forecast | Later: Weather Checker Grades Us *


Today: Still quite cold, but light winds. Mid-30s. | Tonight: Mostly clear. Upper teens to low 20s. | Tomorrow: Partly sunny. Upper 40s to near 50. | A Look Ahead


It was this day in 1873 that D.C. recorded its all-time low temperature for March -- 4 degrees above zero. This morning wasn't as cold as that, but it was our second bitterly cold one in a row. Slowly but surely, however, you'll notice a warming trend, which could climax with temperatures well into the 60s this weekend. Hello, spring.

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): The only thing better about this morning compared to yesterday morning is the light winds. Even with tons of sun, sunrise temperatures in the teens and single digits only climb several degrees higher than yesterday -- to afternoon highs in the mid-30s. Confidence: High

Tonight: Mostly clear with lows down to the low 20s downtown, and near 20 with some upper teens in the burbs. This "warm up" is working its magic rather slowly I'd say. Confidence: High

Keep reading for the forecast through the weekend...

Snow blankets the residential landscape in Northwest D.C. Monday morning. By CWG photographer Ian Livingston.

Tomorrow (Thursday): The warming trend continues, finally getting us back to near our average high for this time of year. Look for partly sunny skies with highs in the upper 40s to near 50. Confidence: Medium-High

Tomorrow Night: We'll be substantially warmer than the previous few nights. A warmer air mass moving in from the south combined with the blanketing effect of partly to mostly cloudy skies should give us lows in the 30s. Maybe a sprinkle overnight or toward morning. Confidence: Medium-High


Could see a morning sprinkle on Friday. Otherwise, partly sunny skies and a nice breeze from the southwest should get us well into the 50s to near 60. Confidence: Medium

Our spring awakening continues Saturday as highs reach well into the 60s. Even 70 may not be out of reach. As of now I think a warm front will stay far enough north to leave us precipitation-free. Remember to set your clocks ahead one hour on Saturday night, the start of daylight saving time. Confidence: Medium

We're looking at another dry and warm day Sunday -- highs in the 60s to near 70 -- as long as a cold front off to the west doesn't arrive faster than currently anticipated. Confidence: Medium

By Dan Stillman  | March 4, 2009; 10:00 AM ET
Categories:  Forecasts  
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Interesting that DCA is 10 degrees warmer than IAD and 12 degrees warmer than BWI. Is that the effect of the river?

Posted by: bjackrian | March 4, 2009 7:42 AM | Report abuse


Yes...and the urban heat island effect.

Posted by: Jason-CapitalWeatherGang | March 4, 2009 7:50 AM | Report abuse

why would the river make it warmer? is it like a heat sink - warming during the day etc... is dca colder in the day?

Posted by: walter-in-fallschurch | March 4, 2009 8:10 AM | Report abuse

i know in summer places near rivers/streams etc are cooler, urban heat island aside, but i thought that had more to do with evaporation. i suppose in summer, water temps are almost always lower than air temps so there's a simple radiative effect. what is the temp of the potomac river these days?

Posted by: walter-in-fallschurch | March 4, 2009 8:53 AM | Report abuse


Unless the river is frozen and covered by ice (which it is not), it will tend to have a warming effect on clear nights in winter (water temp is above freezing and water is a dark heat absorbing surface--as opposed to ice which is white and reflective). Also, the low elevation plays a role in addition to the heat island effect.

Posted by: Jason-CapitalWeatherGang | March 4, 2009 9:04 AM | Report abuse

is the summer daytime cooling effect similar, or is it primarily due to evaporation being endothermic?

Posted by: walter-in-fallschurch | March 4, 2009 9:18 AM | Report abuse

Tuesday morning was definitely colder up on the Blue Ridge than today. Tuesday morning we got down to 2.7F, but today we were above 10.

I don't fully understand the impact on elevation. I know that some grape growers like east facing mountain slopes because they don't tend to get as much frost. At 1900 ft, we're often around 5 degrees colder than the bottom of the mountain. But some mornings, cold air apparently likes to settle in the low areas (cold air sinks and warm air rises).

Posted by: spgass1 | March 4, 2009 9:19 AM | Report abuse

is it low pressure at high altitude causing low temps?

Posted by: walter-in-fallschurch | March 4, 2009 9:30 AM | Report abuse


Yes, if you have a wind off (easterly component) the river in the summer, it will produce a cooling effect.

Posted by: CapitalWeatherGang | March 4, 2009 9:53 AM | Report abuse

Also, re: DCA temp -- The wind never did go calm at National last night or early this morning. So, we end up with an unimpressive low of 20. Meanwhile, Dulles tanked all the way down to 8 degrees.

Posted by: Dan-CapitalWeatherGang | March 4, 2009 10:37 AM | Report abuse

Generally speaking it will be colder at higher elevations due to lower pressure, but there can be inversions -- particularly on clear, calm nights, where it's colder in valleys - because cold air sinks.

Posted by: CapitalWeatherGang | March 4, 2009 10:51 AM | Report abuse

I was amazed at how much snow melted yesterday, despite the sub-freezing temps. I'd say about 20 percent of my yard is bare ground now. At this rate, it will be all be gone by the weekend. I think the piles in parking lots, etc., will last longer, however.

Posted by: steske | March 4, 2009 11:00 AM | Report abuse

CapWeatherGang, thanks for the simple explanation.

One other phenomenon I've noticed more than once, including yesterday morning, is that sometimes the low temperature will be recorded after dawn. It seems counterintuitive that it would get a little colder while it's already getting light outside.

Posted by: spgass1 | March 4, 2009 11:02 AM | Report abuse

I think the ground continues to radiate/lose heat until the sun hits it more directly?

Posted by: manassasmissy | March 4, 2009 11:28 AM | Report abuse

DCA also reported clouds much of the night in some form which probably slowed radiational cooling. IAD did not report as much in the way of this... though not sure if that's just a reporting difference as they are relatively close.

Posted by: Ian-CapitalWeatherGang | March 4, 2009 11:40 AM | Report abuse


Noticed the same in my yard. Never underestimate the power of the March sun!

Thankfully, all of this stuff will be gone by the weekend. Can't wait for the warm up coming.

Posted by: ThinkSpring | March 4, 2009 11:51 AM | Report abuse

Preliminary 3-7 day charts show a few changes from yesterday. Cold front moves through late Sunday; warm front is south of us Tues.-Wed. Main forecast change is warmer Sunday; possible unsettled weather next week.

Note for steske: Two factors are probably in play: The March sun is warming ground locally and evaporation from solid to gas by sublimation is occurring even at temperatures below freezing when humidities are low. In addition warmer ground could be melting some snow from the bottom up. I've noticed the snow disappearing in Arlington, too. When snow sublimes, less black ice forms at night.

Posted by: Bombo47jea | March 4, 2009 12:15 PM | Report abuse

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