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Posted at 05:00 AM ET, 07/22/2011

Forecast: Extreme and dangerous heat creeps upward today, continues tomorrow

Sweat Ceiling 2011

Excessive heat warning today and Saturday
Code red air quality today: unhealthy for general population
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Today's Daily Digit
 
A somewhat subjective rating of the
day's weather, on a scale of 0 to 10.

 
HOT. Inconvenient, unhealthy and potentially dangerous. Summer's equivalent to a Snowmageddon? I think so.
 
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EXPRESS FORECAST

Today: Terribly hot, unhealthy air quality. 99-104. | Tonight: Isolated evening storm? Muggy. 77-84. | Saturday: Mostly sunny, p.m. storms possible. 97-102. | Sunday: Partly sunny, p.m. storms possible. 93-98. | A Look Ahead | Get Express Forecast by E-mail

FORECAST IN DETAIL

Perhaps the most extreme (heat + humidity) day or two in the last few decades is upon us. Heat illnesses are possible in these prolonged extreme conditions, so please take it easy so that your body does not go into shock. In this airmass, it simply cannot cool itself effectively even when in the shade — much less in the sun. On a note of public service, please help The Community Partnership for the Prevention of Homelessness: Call (202) 399-7093 if you see someone on the street and are concerned about how they are doing in the heat. Transportation to a D.C. cooling center can be provided. Yeah, D.C. is used to heat, but be extra careful out therein this weather!

Today (Friday): Super awful. Hazy, water vapor-laden air will catapult toward 100 and above, with a small, but non-zero, chance at tying D.C.’s all-time record high temperature of 106. Temperature alone doesn’t tell the story. Combining the heat with mugginess and air stagnation, we could see dangerous heat indices approach 120. Wear lightweight and loose-fitting clothing when possible and drink plenty of water. While an isolated thunderstorm (10-20% chance) can’t be ruled out late day, luck may serve best the folks far north of town (toward PA). Confidence: Medium-High

Tonight: Akin to the Mississippi delta — or Singapore — with uncomfortably muggy temperatures only dipping barely into the 70s outside the Beltway, probably only to the low 80s downtown. Note that when low temperatures don’t dip below 75F overnight, heat-related deaths climb substantially. Please check on your elderly relatives & neighbors. Confidence: Medium-High

Keep reading for the oppressive forecast through the weekend...

Tomorrow (Saturday): If you must go out and exert yourself, please stay in the shade and drink a ton of water. Humidity stays high and skies are pretty sunny, quickly boosting temperatures toward the 100 degree mark — a range similar to Friday, if not a touch lower due to higher odds of clouds/showers late day. Still, D.C. could perhaps more easily break its Saturday record (101) versus Friday’s (103). Heat indices are again worrisome, in the 110-115 range. A 30% chance of a thunderstorm (could be strong+) by evening does exist, but I’m not going to pin my hopes on it. Confidence: Medium

Tomorrow night: Besides an outside chance of a shower or storm (10%) I would just call it mostly cloudy and muggy as heck. Low temperatures are in the mid-70s to low-80s (downtown). Confidence: Medium

Sunday: The worst is over, but it still doesn’t look good. A slightly “cool” breeze from the north helps reduce the hazy, muggy conditions just a bit. Currently I am expecting highs to stay under 100, in the mid-to-upper 90s. While a chance (30%) exists for a few heat-breaking showers and storms, I worry we’re not in the stormiest of patterns. We’ll keep an eye on it — and fingers crossed. I still would remain vigilant about air quality today and try running indoors at the gym, versus outside. Would you please? Confidence: Medium

A LOOK AHEAD

Sunday night: The atmosphere does remain very moist with plenty of water vapor just hanging around. Low temperatures stay high with this blanket of insulation, in the range of low 70s to upper 70s. Confidence: Low-Medium

Monday & Tuesday may be pretty similar and, luckily more reminiscent of a typical D.C. summer, which is still pretty warm unfortunately. Highs head for 90 or just above both days, but we may catch a break in the streak if we're lucky. There’s that near continual summertime 20-30% chance of afternoon showers and storms. Seems nicer, but there are hints of more heat behind this. Confidence: Low-Medium

By  |  05:00 AM ET, 07/22/2011

Categories:  Forecasts

 
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