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The week ahead: Scorching Heat Wave to Grip DC Area

Jason Samenow @ 12:16 AM

Excessive Heat Warning in Effect from Tuesday through Thursday for Entire Area. -- Tips for staying safe.

The hottest weather since 2002 is on its way. Dangerous heat and humidity will become immersed throughout the entire region Tuesday through Thursday. The potentially record setting heat originates from the same airmass that caused upwards of 140 deaths in California. How hot will it get? A day by day snapshot follows...


Forecast Confidence: HighOn the edge of the heat. The core yet to come. The leading of edge of the massive dome of heat will approach. Under partly cloudy skies, high temperatures will reach the mid 90s. Given sticky dewpoints near 70, it will feel as hot as 100. There's about a 1/4 chance of a late day thunderstorm that could provide temporary relief from the heat and humidity.

One of the more dangerous characteristics of a significant heat wave is warm overnight lows in places with no air conditioning. Overnight tonight, urban areas may not drop below 80 degrees -- with just mid 70s in the suburbs.

HEAT WAVE PEAK -- Tuesday through Thursday

Atmospheric conditions from the top-down will support very high heat and humidity levels:
  • Several miles up, a massive ridge of high pressure will force the air to sink, compress and roast.
  • At the surface, southwest winds on the back side of a tropical high pressure area will transport plenty of juice to increase the stickiness factor.
  • The southwest surface wind blowing over the Appalachian mountains will also enhance the warmth via downsloping.


Forecast Confidence: HighSimmering. Brutal.
  • How Hot Will It Get? 97-101.
    How Hot Will it Feel? As high as 110. (Dewpoints in the low 70s)
  • Chance of tying/breaking the record high (99, in 2002)? 50%
  • Chance of t'storm to cool it off? 10%


Forecast Confidence: HighSuffocating. Oppressive.
  • How Hot Will It Get? 97-101.
  • How Hot Will it Feel? As high as 110. (Dewpoints in the low 70s)
  • Chance of tying/breaking the record high (100, in 2002)? 40%
  • Chance of t'storm to cool it off? 10%


Forecast Confidence: Medium-HighStifling. Offensive.
  • How Hot Will It Get? 96-100.
  • How Hot Will it Feel? As high as 110. (Dewpoints in the low 70s)
  • Chance of tying/breaking the record high (100, in 1930)? 30%
  • Chance of t'storm to cool it off? 30% -- Front nearing area late in the day may produce a gusty t'storm or two
Night time lows throughout this period will only cool to 79-84 in the city, and 75-79 in the suburbs.


Forecast Confidence: MediumSome relief? A cold front will be in the vicinity of the region. If it moves south of us, it will provide some relief with highs only 85-90. But don't bet on it. It's more likely the front will remain a bit to our north, keeping us in the hot/sticky airmass. However, clouds will likely keep temperatures from reaching levels seen in previous days, and t'storms (35% chance) may develop offering additional relief. Highs in the low 90s seems like a reasonable forecast.

The weekend

Forecast Confidence: MediumWarm and comfortable or hot and sticky? The bottom line is that high temperatures this weekend are likely to be between 85-95, and rain chances don't seem too high:
  • Highs will be closer to 85-90 with rain chances virtually nil if the cold front does move to our south and cooler high pressure can be build in from the north
  • Highs of 90-95 will be more likely if the front stalls and does not really penetrate south of the area, with isolated t'storms possible (30%).
I favor the hotter, second solution, but will split the difference and call for a high near 90 each day, with a 20% chance of a late day thunderstorm.


The average high this week is in the upper 80s, with the average low near 70. So far this year, we've experienced 20 days where the temperature has at least reached 90 at Reagan National (we're in a streak of 4 straight days now). Given that we'll likely add at least 4 or 5 more 90 degree days this week, it looks like there's a reasonable chance we'll reach 31 -- which is the average by the end of August.

Poll Results

With the hurricane season off to a slow start, it's not surprising visitors were conservative with their tropical "named" storm predictions last week. Half of the poll participants think we'll have fewer than 12 storms, and just 15% think we'll have 17 or more.

This week's poll gives visitors an opportunity to predict how hot it will get. Vote now!

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