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Posted at 05:00 AM ET, 07/21/2011

Forecast: Dangerous heat through Saturday

Hottest Friday, with slight fade Sunday

* Excessive heat warning noon to 8 p.m. today & Friday *
Code orange air quality - unhealthy for sensitive groups
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1 p.m. today: Live video discussion about heat wave

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

 
The only reason this isn't a zero is that it will be even worse Friday
 
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EXPRESS FORECAST

Today: Sunny and extremely hot and humid. 97-102. | Tonight: Clear and muggy. 74-80. | Tomorrow: Excessive heat and humidity, isolated p.m. t-storms. 97-104. | Get Express Forecast by E-mail

FORECAST IN DETAIL

A potentially deadly combination of heat and humidity is upon us. We have not seen a combination of heat and humidity this intense in a number of years. Excessive heat warnings are in effect from noon to 8 p.m. both today and tomorrow, when heat indices may near or exceed 110 degrees. If you must be outside for extended periods of time (e.g. folks attending the Civil War festivities in Manassas), hydrate frequently and take indoor breaks. We have the chance to challenge high temperature records and may also set record high minimum (night time) temperatures. This heat and humidity fest only slowly fades into early next week.

Today (Thursday): A blazing sun and a weak breeze from the southwest push temperatures steadily up. The air is so humid you could probably wring water out of it. And yet, the chance of a shower is close to nil. Highs today range from the upper 90s to lower 100s (record high 104). Afternoon heat indices range from 105-110 (dew points in the low-to-mid 70s). Confidence: High

Tonight: Relief from the heat only comes from a lack of sunshine as temperatures struggle just to get out of the 90s in the evening. Barely a breath of breeze is no comfort either. Lows range from the mid-70s to near 80 or even a little higher downtown. Confidence: High

Keep reading for the forecast through the weekend...

Tomorrow (Friday): It is hard to believe that this day could be worse but the potential is there. However, there is one catch, a few afternoon thunderstorms could cut highs short of record levels (record high 103) in a few spots. Unfortunately, only about 20% of the area is likely to get that relief. The rest of us get an award for just surviving. Keep your water bottle full! Winds are light from the west. Highs range from the upper 90s to lower 100s. Heat indices in the 110 to 115 range. Confidence: Medium-High

Tomorrow night: Sultry is a good word for the end of the work week. Outdoor tables go begging with evening readings in the 90s. The only relief comes from a scattering of thunderstorms (30% chance). Overnight lows work hard to make the mid -70s burbs to near 80 in the city. Confidence: Medium-High

A LOOK AHEAD

Saturday shows only a sliver of improvement. Humidity remains oppressive. Mostly sunny skies and such a warm start allow the thermometers to ratchet up with little impediment. I am not so sure the DCA (Reagan National) record of 101 is even safe. Highs should be mid-90s to near 100 with heat indices again to 110 or so. There is a slight chance, 20%, of a thundershower by evening but for most of us just more heat. One piece of good news, this is hump day, the peak of our normal annual temperature profile. From here it is all downhill. Sounds good for at least a couple of months. Lows should be in the mid-to-upper 70s. Confidence: Medium-High

Sunday is still only slightly cooler despite a breeze from the north. The problem is that all the thundershowers look likely to be south of us and this keeps us in the intense sunshine. The main improvement should be lower, albeit still significant, humidity. Highs should top out in the mid-to-upper 90s. Evening temperatures only slowly return to the 80s. Lows settle in the low-to-mid 70s. Confidence: Medium

Monday is again slightly cooler and slightly less humid but emphasis on slightly. Skies start sunny but clouds are likely to increase by evening as a weak disturbance approaches. There is a slight 20% chance for an evening thundershower. Highs should be low-to-mid 90s. Confidence: Medium

By  |  05:00 AM ET, 07/21/2011

Categories:  Forecasts

 
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