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Posted at 8:50 AM ET, 07/28/2009

Forecast: Back to the 90s Today; Pop-Up Storm?

By Matt Rogers

Stagnant, summery pattern stays in place

* UnitedCast | Saturday Evening Storms: Recap and Pictures *
* New! Get CWG's Express Forecast by E-mail: Sign Me Up *


Today: Partly to mostly sunny. 30% chance of a p.m. storm. 89-92. | Tonight: Partly to mostly cloudy. Isolated shower or storm? 70-75. | Tomorrow: Mostly cloudy. 60% chance of showers/storms. 84-88. | A Look Ahead


After only making the upper 80s yesterday, temperatures are poised to return to the 90s today. Combine that with the continued high humidity and we have a fairly uncomfortable day with afternoon heat indices peaking in the low-to-mid 90s. Fairly typical, though, for late July. Shower and thunderstorm chances trend higher tomorrow and linger through the weekend as warm and humid air sticks around.

Today (Tuesday): Partly to mostly sunny skies should allow temperatures to surge well into the 80s by lunchtime, and eventually to afternoon highs in the low 90s, with light winds from the south/southwest at 5-10 mph. Like yesterday, we could see a few lonely thunderstorms pop up during the afternoon and evening. Chances that you'll see one look to be about 30%. Confidence: Medium

Probability: 30%
Coverage: Isolated

Tonight: An isolated shower or storm is possible. But otherwise, partly cloudy skies are expected during the evening with partly to mostly cloudy skies overnight. Lows in the low-to-mid 70s along with more of those light winds from the south/southwest. Confidence: Medium-High

Keep reading for the forecast through the weekend...

A view of an isoated thunderstorm yesterday evening as it moves northeast away from the District. Shot from Glover Park, by Capital Weather Gang photographer Ian Livingston.

Tomorrow (Wednesday): The forecast gets trickier as an area of low pressure is expected to track near the area. The exact path of the heaviest precipitation is not yet clear. But overall, shower and thunderstorm chances should be higher than today -- around 60%, mainly from early afternoon into evening. Mostly cloudy skies will likely keep highs to the mid-to-upper 80s. Confidence: Low-Medium

Tomorrow Night: Mostly cloudy skies with a continued shower and thunderstorm risk (40% chance), especially before midnight. Lows in the low 70s. Confidence: Low-Medium


Thursday and Friday should see more of the same with humidity on the high side, partly cloudy skies, and a running threat of afternoon/evening showers and thunderstorms (40% chance). Highs should range from the upper 80s to around 90, with Thursday and Friday night lows in the upper 60s (outer suburbs) to near 75 (downtown). Confidence: Low-Medium

Don't look to the weekend for much change as partly cloudy skies and high humidity hang around. Highs should range through the upper 80s with lows in the low-to-mid 70s. For now, I'll call for a 40% chance of showers/storms each day. But we'll try to get a better handle on the details as the weekend pulls closer. Confidence: Low-Medium

New indications suggest a stronger cold front will reach the area early next week that could offer a respite from the recent heat and humidity.

By Matt Rogers  | July 28, 2009; 8:50 AM ET
Categories:  Forecasts  
Save & Share:  Send E-mail   Facebook   Twitter   Digg   Yahoo Buzz   StumbleUpon   Technorati   Google Buzz   Previous: UnitedCast: Very Warm and Humid
Next: My Dangerous Encounter With Hurricane Katrina


I was driving west on 50 from Chantilly toward Loudoun last night around 9:15 - that nice cell in central Fauquier was putting on an absolute light show...and within 15 minutes - it had stopped. From non-stop bolts and flashes in the western sky to absolute darkness. It was pretty wild. There was a TS warning up for this cell all the way to my place in Southern Loudoun, but I guess the last vestiges of daytime heating knocked this bad boy out very quickly. Not a drop of rain in Loudoun from this one.

Posted by: DullesARC | July 28, 2009 7:38 AM | Report abuse

Yes, activity yesterday was VERY isolated. We had a heavy thundershower pop up between 7-8pm over Columbia Heights yesterday evening with a very heavy, persistent the sun was still shining! -Matt

Posted by: MattRogers | July 28, 2009 7:50 AM | Report abuse

I hope that even isolated storms hold off today. I have to move my boat back downriver from the DC Channel to her home port. We'll be out there at 3:00pm; even if we don't get hit by a storm, we may fry in our own sunblock!

Posted by: --sg | July 28, 2009 8:39 AM | Report abuse

Our sunshine has certainly come in faster and strong today vs. yesterday and this should push those temperatures up. I think we'll see scattered cloud cover by our 3pm time, but any storms should be even more widely may be the driest day of the a good day to try, just don't fry! -Matt

Posted by: MattRogers | July 28, 2009 8:50 AM | Report abuse

DullesARC: We too were watching that storm ... we pooh-poohed our son when he said he saw lightning, we too thought it was too late in the day for a pop-up but it was indeed a fast mover .... so fast that it dropped just a trace of rain before moving on. we were disappointed!

Posted by: weathergrrl | July 28, 2009 9:06 AM | Report abuse

a very heavy, persistent the sun was still shining! -Matt

My grandmother used to say if it was raining and the sun was shining, the devil was beating his wife!

Posted by: waterfrontproperty | July 28, 2009 9:48 AM | Report abuse

I remember MY grandmother saying it too. Wikipedia has some interesting information regarding "sunshowers". Apparently, the Germans say, "When it's raining and the sun shines, the devil is beating his grandmother: he laughs and she cries."
Wiki link Thanks for reminding me of that! -Matt

Posted by: MattRogers | July 28, 2009 10:10 AM | Report abuse

Actually the "sunshower" phenomenon is fairly frequent early and late in the day when there's a convective cloud overhead and the sun is at an angle close to the horizon. This setup is also responsible for most observed rainbows since you need to have both the sun shining and rain falling in order to see a rainbow. The trick is to look at the spot OPPOSITE from the sun's location in the sky. If the sun is shining in the southwest, look towards the northeast in order to see the rainbow.

Remember: Rainbow at morning, sailors take warning: The sun is rising in the east; the rainbow is visible through rain APPROACHING from the west.

Rainbow at night, sailor's delight: The sun's setting in the west; the rainbow is visible through rain DEPARTING to the east.

This rule is the same as that for red sky in the morning or evening, and holds most strongly in our temperate latitudes. It is less applicable at subtropical/tropical latitudes where tropical waves and cyclones often APPROACH from the EAST. This is why evening red sky in the east or southeast in the tropics may often [but not always] herald the approach of a tropical storm or hurricane.

Posted by: Bombo47jea | July 28, 2009 12:07 PM | Report abuse

Arriving home last night in Michigan Park-DC around 7:30 to a few splattering raindrops, I lamented that we appeared to be missing yet ANOTHER thunderstorm. Then, the skies opened up as the storm formed over central and NE DC. We had a steady downpour for 35 to 40 minutes, resulting in .80 inches in my rain gauge, even as I could see clear skies and setting sun to the north and west. Yeah!! Bring on more rain!!

Posted by: TominMichiganPark | July 28, 2009 12:46 PM | Report abuse

Thank you, Matt and Bombo both! Doing a last check now before I head out. I did indeed see a rainbow yesterday evening, so I'll take it as a good omen and get my boat back downriver!

Posted by: --sg | July 28, 2009 12:47 PM | Report abuse

Bombo47je - good post. shame on me, a Physics major back when...

Posted by: LoudounGeek | July 28, 2009 2:41 PM | Report abuse

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