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Posted at 09:35 PM ET, 05/27/2012

Forecast: Holiday heat and humidity take their toll on air quality; t’storm today?

Code Orange Air Quality Alert: Unhealthy for sensitive groups

9:30 pm Update: No severe warnings have been in effect as the storms have rolled south/southeast through the heart of the metro area (earlier there were Severe Thunderstorm Warnings for southern Frederick, northern Montgomery and northern Loudoun counties). But they’ve still been strong with gusty winds, heavy rain and lightning. A little more than halfway through the area now, the storms continue on across the southern and eastern suburbs over the next hour or so.

7:40 pm Update: A nasty line of severe storms approaching from the northwest could reach near Frederick around 8:30-9 p.m., and then may advance toward the closer-in metro area. But, it’s possible the storms may weaken or dissipate as they get closer. Follow radar and any severe warnings on our Severe Weather Tracking Station below, and our real-time updates on our Twitter feed displayed above.

From 5 a.m. ...

EXPRESS FORECAST

Today: Partly sunny & humid. 20% chance of p.m. t’storm. Upper 80s to near 90. | Tonight: Isolated evening t’storm? Near 70 to mid-70s. | Tomorrow: Partly sunny & humid. Near 90 to low 90s. 30% chance of p.m. t’storm. | A Look Ahead | Get Express Forecast by E-mail

TODAY'S DAILY DIGIT

A somewhat subjective rating of the day’s weather, on a scale of 0 to 10


Muggy & hot with compromised air quality. Enjoy the holiday heat with lots of water (to drink & to swim!). Get the Digit on Twitter| Discuss on Facebook

FORECAST IN DETAIL


Beaches & pools still look like a great bet through Monday even though we can’t rule out a late-day thunderstorm (20% chance today, 30% tomorrow). While outside, please take care to drink water & lather on the sunscreen. Note that air quality may not be great – today it’s Code Orange - until we hopefully get a cold front to clear the air a bit by Wednesday. That’s also when forecast confidence sinks due to uncertainties related to what is currently Subtropical Storm Beryl (cooler than a tropical storm) off the Southeast coast.


Radar & lightning: Latest regional radar shows movement of precipitation and lightning strikes over past two hours. Refresh page to update. Click here or on image to enlarge. Or see radar bigger on our Weather Wall.

Today (Sunday): Any early cloudiness should burn off fairly quickly to reveal partly sunny skies. Temperatures then warm steadily toward afternoon highs in the upper 80s to near 90, maybe low 90s for the sunniest spots south of town with low elevation and away from water. The sun is very strong now, and muggy dew points in the upper 60s to near 70 pushes the afternoon heat index into the low-to-mid 90s. Keep in mind a 20% chance that a late-afternoon shower or thunderstorm sneaks in from the north. Confidence: Medium-High

Tonight: Any evening thundershowers should be isolated (20% chance). Light breezes from the south around 5-10 mph move that otherwise stagnant air just a bit. It’s another warm and partly cloudy evening with temperatures falling through the 80s into the 70s. Overnight lows range from near 70 outside the Beltway to the mid-70s downtown. Confidence: Medium-High

For related traffic news, check out Dr. Gridlock. Keep reading for the forecast through the weekend...

Tomorrow (Memorial Day): Looks like a classic scorcher with high humidity and highs from near 90 to the low 90s. Overall, skies should be somewhat sunny, but also hazy with all the muggy-feeling water vapor in the air. Afternoon thunderstorm chances increase to about 30%. Meanwhile, air quality may be Code Orange again or even Code Red (we’ll keep you posted), so take it easy with regard to any strenuous activity outdoors. We may be fortunate to have a light breeze at times. Confidence: Medium

Tomorrow night: After a 30% chance of an evening shower or thunderstorm, temperatures drop down to levels similar to tonight. Look for lows from near 70 to the mid-70s. Luckily we could have a hint of a breeze overnight, to mitigate the mugginess if only slightly. Confidence: Medium

A LOOK AHEAD

On Tuesday a cold front pushing in from the west, potentially combined with a feed of tropical moisture from the south, raises shower and thunderstorm chances to around 40%, especially in the afternoon. If storms do develop, watch out for some gusty winds and heavy rain. Highs should reach near 90 before any rain arrives. Confidence: Low-Medium

Forecast confidence dips further for Wednesday given uncertainties regarding where the cold front stalls out and the ultimate path taken by the remnants of Subtropical Storm Beryl. For now we’ll have to keep a chance of showers and thunderstorms in the forecast with highs somewhere in the mid-80s to near 90. Confidence: Low

By Camden Walker  |  09:35 PM ET, 05/27/2012

Categories:  Forecasts

 
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