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Posted at 05:00 AM ET, 07/19/2011

Forecast: Muggy with storm chance today; brutal heat Thursday into weekend

(post originally published at 5 a.m.)

10:15 a.m. update: As it’s already 88 degrees, looks like we’ll reach the high end of our temperature range today with mid-90s. Factor in the high humidity (dew point currently 73), heat indices probably pass 100 this afternoon.

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A somewhat subjective rating of the
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A split day: you probably won't care for the humidity, but the cloud canopy and storms at times may hold temps somewhat in check.
 
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EXPRESS FORECAST

Today: Partly to mostly cloudy, humid, scattered storms. 88-94. | Tonight: Partly cloudy, very muggy. 70-77. | Tomorrow: Partly to mostly sunny, hot and humid. Isolated storms. 92-96. | Get Express Forecast by E-mail

FORECAST IN DETAIL

The well-advertised big heat wave is still building into our area with peak hot conditions expected Thursday into the weekend. Dangerous heat levels appear likely as high temperatures surge into the upper 90s to low 100s, near record territory. For today, though, extreme heat is held in check by clouds and what we call “ridge riders”. These thunderstorm complexes ride along the fast-moving jet stream flow on the edge of the hot ridging pattern. Today, we are right along their path.

Today (Tuesday): The core of the approaching big dome of heat will be out in the Midwest today. This will keep the door open for thunderstorms and showers today (60% likelihood - best chance in the afternoon and evening) including some chance this morning (best chance north and west). Especially later today, severe weather can’t be ruled out with gusty winds, hail, and heavy downpours. Plenty of humidity will persist with highs ranging from the upper 80s to mid-90s (heat index levels 95-100), depending on varying cloud cover from partly sunny to mostly cloudy. Winds mainly from a westerly direction. Confidence: Medium-High

Thundercast:

Probability: 60%
Coverage: Scattered
Most Likely Timing: Some chance morning, better chance evening

Tonight: The air is thick with humidity with partly cloudy skies and an isolated chance of a storm or shower (20%). Lows range from the low 70s to the upper 70s (warmest in the city). Light and variable winds. Confidence: High

Keep reading for the forecast through the weekend...

Tomorrow (Wednesday): The hot air mass from the middle of the nation edges closer, offering more sunshine (partly to mostly sunny skies), and more heat/humidity. A few thunderstorms could be set off here, so we’ll carry a 30% risk of especially afternoon/evening storms around the area. Highs in the low-to-mid 90s. Light winds from the south and southwest. Confidence: Medium-High

Tomorrow night: Another night that is heavy with humidity as temperatures drop into the low-to-mid 70s in the suburbs to mid-to-upper 70s in the city. Partly cloudy skies. Confidence: Medium-High

A LOOK AHEAD

Thursday through Saturday could be the biggest heat event of this summer with highs Thursday 98-102 (DC record: 104), Friday 99-104 (DC record: 103), and Saturday 99-103 (DC record 101). Partly to mostly sunny skies. Humidity should remain at moderate levels, which means some brutal heat index levels (105-110). This is dangerous stuff where we highly recommend that you limit peak daytime physical activity as much as possible (or rather, avoid it all together). We have a 20% risk of thunderstorms Thursday and Friday with a 30% chance on Saturday. Very muggy overnight periods with lows in the mid-to-upper 70s in the suburbs to only around 80 degrees in the city. Confidence: Medium

Sunday still looks hot and humid with highs in the low-to-middle 90s, but an approaching cold front means a better chance of showers, storms, and shade-inducing cloud cover that could lower temperatures from our forecast. It looks like a 40% chance of showers and storms. Low temperatures Sunday morning are still in the muggy mid-to-upper 70s. Confidence: Low-Medium

By  |  05:00 AM ET, 07/19/2011

Categories:  Forecasts

 
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