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Posted at 5:00 AM ET, 07/26/2010

Forecast: Heat breaks, but to briefly bounce back

By Jason Samenow

Another break possible this coming weekend

updated at 8:15 a.m.

* Storm news - Pepco: 'Multi-day restoration' | Storm video | Post Local *
* Power outage maps for Dominion Electric | Pepco | BG&E | SMECO *
* Outside now? Radar & more: Weather Wall | Tropical Tracking *
* Consec days 90+: 12; Total 90+: 42 (Apr: 2; May: 3; Jun: 18; Jul: 19) *

Today's Daily Digit
A somewhat subjective rating of the
day's weather, on a scale of 0 to 10.


Still kind of hot but so much better than the last several days.
Get the 'Digit' on Twitter


Today: Mostly sunny and less humid. Near 90. | Tonight: Mostly clear. 65-73. | Tomorrow: Partly sunny, slight chance of p.m. showers (20%). 87-91. | A Look Ahead | Get Express Forecast by E-mail


You know it's been a painfully hot summer when we're calling a high of 90 today "relief". But it is what it is. At least, the humidity will be relatively low today into tomorrow. The all-too-familiar heat and humidity combination returns Wednesday and Thursday but it's my pleasure to inform you that we *may* see temperatures hold in the 80s Friday into the weekend.

Temperatures: Latest D.C. area temperature map powered by iMapWeather (base map by Google). Click and hold on map to pan. Double-click to zoom. Refresh page to update. See larger map on our Weather Wall.

Today (Monday): Lots of sunshine today allow temperatures to reach near 90. It's a close call as to whether the 90-degree streak - at 12 consecutive days - keeps going. The humidity is substantially lower than the last several days, so it feels about 20 degrees cooler even though the air temperatures is only 10 degrees cooler. Winds from the north blow at around 10 mph. Confidence: High

Tonight: We're looking at the coolest night we've had in a while though that's not saying much. Lows drop into the mid-60s in the cooler suburbs to the around 70 downtown - which is around average, by the way. Screen on the Green-goers: no weather worries. Confidence: High

Think the 'Digit' should be higher? Vote in the Digit box above. And keep reading for the forecast through the weekend...

Pandemonium at the Lincoln Memorial as a severe thunderstorm abruptly rolls in yesterday afternoon. By CWG photographer Ian Livingston

Tomorrow (Tuesday): Sunshine starts the day but partial cloud cover develops in the afternoon as winds from the south return beginning to increase the humidity a little. Somebody could see a shower (20% chance), but most spots stay dry through the afternoon. Highs will be around 90. Confidence: Medium-High

Tomorrow Night: An isolated evening shower is possible (20%); otherwise, it will be partly cloudy and mild. Lows range from the upper 60s in the cooler suburbs to the mid-70s downtown. Confidence: Medium-High


The heat and humidity are back Wednesday and Thursday; however, conditions will not be as extreme as this past weekend. Both days highs reach the low-to-mid 90s with heat indices a few degrees above the actual air temperature. Isolated afternoon or evening showers and thunderstorms are possible (20%) Wednesday with increased activity likely (40-50% chance) Thursday as cold front moves through. Overnight lows will be the 70s. Confidence: Medium

Seasonably warm, but not hot high pressure builds into the region from the northwest Friday through Sunday. Highs each day will probably reach the mid-to-upper 80s with comfortable humidity levels. Overnight lows will mainly be in the 60s to around 70. Confidence: Medium

By Jason Samenow  | July 26, 2010; 5:00 AM ET
Categories:  Forecasts  
Save & Share:  Send E-mail   Facebook   Twitter   Digg   Yahoo Buzz   StumbleUpon   Technorati   Google Buzz   Previous: Whew! Storms move out, heat advisory canceled
Next: Baltimore making 100-degree history


Did yesterdays storm remind anyone of one we had a couple years ago, which did similar damage? I seem to remember that being even stronger and larger. Both radars had the "bow effect" which is the terminology I remember one of you CWG guys using back then.

Posted by: rocotten | July 26, 2010 7:33 AM | Report abuse

@Ian, you "Incoming" post at 3:24 p.m. yesterday was prophetic.

Power back on in Glover Park at 7:00 a.m., just as I was about to pack up the frozen food, yogurt, etc. to take to the office fridge.

Bombo, you're right. We're too darn dependent on electricity and when we don't have it, we're up the creek.

Most interesting sight: the sand at the Stoddert Playground construction site being picked up and blown by the wind. A "brown out" similar to, worse even, than last winter's white out. Glover Park-in-the-Sahara.

Of course the power conked out about three minutes before the finale of the 5 1/2 hour Bayreuth Lohengrin stream. But small potatoes compared to the lost lives, damaged homes, etc. that occured yesterday.

Hope everyone else fared reasonably well.

Posted by: JerryFloyd1 | July 26, 2010 8:01 AM | Report abuse


You're thinking of the June 4, 2008 outbreak - which was more severe. Yes, both events featured bow echoes on radar.

Posted by: CapitalWeatherGang | July 26, 2010 8:09 AM | Report abuse

Correction to above post: it was Brian, who wrote "Incoming" at 3:24 p.m. yesterday.

Ian, I think we had 58 consecutive hours (from roughly 5 a.m. Friday to just past 3 p.m. Sunday) when temperatures remained above 80 degrees at DCA. If so, is this a record. I'm equivocating because I'm not sure what the Sunday a.m. low was.

Posted by: JerryFloyd1 | July 26, 2010 8:26 AM | Report abuse

Is there a site where the radar from yesterday can be viewed? I was away from home when the storm hit, and by the time my power came on, the storms were off the radar screen. I'd love to be able to see what it looked like.

Posted by: scienceteacher3 | July 26, 2010 8:26 AM | Report abuse


This is really fast loop, but check it out

Posted by: CapitalWeatherGang | July 26, 2010 8:34 AM | Report abuse

What's a bow echo? and what factors influence how severe a weather event is going to be?

Posted by: paperball | July 26, 2010 8:50 AM | Report abuse

Fast and furious storm yest. afternoon. Dropped only 0.08" in Western Loudoun. Did manage to split a pear tree right out our kitchen window. Fortunately, no house damage and now waiting for "tree guy" to stop by to give est. as to removing rest of what's left of tree. Power out for 5 hours.

Posted by: worldtraveler83 | July 26, 2010 8:57 AM | Report abuse


Bow echo info

There are a lot of factors that influence how strong thunderstorms get -- but the primary two are the amount of instability (which is driven by temperature contrast and sunshine) and wind shear (turning of the wind with height which promotes rotation)

Posted by: CapitalWeatherGang | July 26, 2010 9:03 AM | Report abuse

I know I'm probably jumping the gun (okay, I am, but I am so sick of this summer already), but how will the excessive heat affect the fall foliage? Is it going to be more brown than anything else?

Posted by: phan1 | July 26, 2010 9:27 AM | Report abuse

@phan1, my first fully summer here (1966) was hot and very dry, but the fall color was spectacular and the ensuing winter snowy. Go figure... However, I'd imagine CWG has a better statistic handle on fall leaf color probabilities.

If we have a many more years like this one, we could have a surfeit of loblolly pines, live oak, etc. and not much fall color and I'll be pantin' for Scranton!

Posted by: JerryFloyd1 | July 26, 2010 9:59 AM | Report abuse

JerryFloyd1, that "incoming" post was from Brian. I was out already! I think I personally busted yesterday down till an hour or two beforehand... did pick up on the winds on radar before they were warned but expected much less overall.

Posted by: Ian-CapitalWeatherGang | July 26, 2010 10:00 AM | Report abuse

Thanks for the info! I can't say I understand it all or would be able to recognize a bow echo on the radar, but I always appreciate how helpful you are with explaining the weather.

Posted by: paperball | July 26, 2010 10:49 AM | Report abuse

I'm a little disappointed by the recap of the storms in the Metro section. There seems to be the standard media desire in significant events like these to paint a picture that little warning was given. The piece in particular highlights a pool where a dangerous situation unfolded with large objects being tossed around. But there is no mention of the fact that the local NWS office did a great job yesterday, issuing severe t-storm warnings with extra lead time, even highlighting that these were particularly dangerous storms.
Can someone inquire what kind of procedures are in the place at this pool to be aware of severe weather arriving? For all of the people caught off guard yesterday, there is personal responsibility to be aware of an approaching weather threat, especially for one in which the proper warning is available for those paying attention.

Posted by: foul_throw | July 26, 2010 11:12 AM | Report abuse

I'm with foul_throw. The T-storm watch went up. ~2pm and the storms hit about 3-3:30. And there was a 40% chance of storms. You don't have to be a weather junkie to be prepared.

In Michigan Park we had a very short, intense period of sideways rain at 3:30. The lame pictures I got inspired me to finally learn the video features of my camera.

The power went out about 4. It came back on 'round midnight, not long after we got the generator going. (BTW, the generator is completely separate from the household grid, so no worries for the PEPCO crew.)

Posted by: kperl | July 26, 2010 12:08 PM | Report abuse

As I may have posted yesterday, my area got mainly a half-hour of heavy rain with some wind at the start and a little thunder on the tail end of the storm. Looks as though Montgomery County and parts of D.C., P.G. County and Loudoun County got hit hardest.

I had no power outage, but areas served by PEPCO seem to have been especially hard hit. This is NOT the first time that PEPCO has had a rather hard time dealing with power outages. It has also happened in other severe storms [e.g. 6/4/2008] and a couple of ice storms. I think they also had quite a few issues during the first February blizzard earlier this year when all the heavy wet snow fell, and they also took several days to restore power after Isabel's remnants hit the area. By comparison, BG&E, Dominion and the co-ops in this area have been doing a better job at power restoration--though SMECO has been slow at times with ice-storm restoration, possibly due to rural power service. However NOVEC has the same rural/suburban setup as SMECO, and I rarely hear of any NOVEC or Rappahannock EC outages lasting more than a day. Occasionally Dominion Power outages last a while--when damage to the distribution system is extensive. Undergrounding of power lines in my neighborhood is cutting down on storm-related outages.

Bow echoes occur on radar when high straight-line winds in thunderstorms tend to push the cloud formation outwards into the shape of a drawn bow--the surface wind blows outward in the direction the arrow would fly. I have a theory that the spiral feeder bands of a tropical cyclone consist of a series of bow echoes which spin around the central eyewall. The individual cells within a feeder band tend to spiral inward and eventually get absorbed into the eyewall. During the most intense Category 5 hurricanes more than one eyewall has been known to form. One interesting feature of a mature hurricane is that it assumes a shape similar to that of a spiral galaxy. The big difference--we do not seem to have observed any "barred spiral" hurricanes, at least since satellite observation began around 1960, possibly showing that the dynamics are different at the size level of stars, as compared to the size level of water droplets, etc.

Posted by: Bombo47jea | July 26, 2010 1:20 PM | Report abuse

My thoughts go out to any, all of you who may not have power in your homes. I am one of the only ones among my friends/coworkers, who still has power after those storms. Two trees almost hit my home, but by & large I was unscathed. Good luck to all of you - hopefully there is power at your workplaces :-/

Posted by: Camden-CapitalWeatherGang | July 26, 2010 1:34 PM | Report abuse

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