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Posted at 03:14 PM ET, 06/27/2012

Massive heat wave moving east, excessive heat watch Friday for D.C. and Baltimore areas

Friday afternoon temperatures simulated by the ECMWF model (
A heat wave of historic proportions, linked to the “epic” wildfire conditions in Colorado, is on the move towards the Tennessee Valley, the South, and mid-Atlantic. An excessive heat watch has been issued for the Washington, D.C. and Baltimore regions Friday, as the heat index - what it feels like- may near 110 degrees.

To the west, the heat’s been so hot that 9 all-time record highs were tied or set in cities/towns in four states Tuesday (source: CapitalClimate) , including Colorado Springs (101) and Denver (105). Not to mention, 156 daily record highs were established from the Rockies to the mid-South.

Area covered by Friday’s excessive heat watch (National Weather Service)
This heat is oozing east and southeast.

By Friday, the core of this monstrous heat wave will cover the region from roughly St. Louis to Columbia, SC, where temperatures will likely reach 105, if not higher - challenging not only daily but also monthly records. But the heat’s overall reach will extend well beyond that.

As we reported yesterday, highs may reach the century mark in 18 states in the eastern half of the U.S. Friday - which include Virginia and Maryland (plus Washington, D.C.)

The heat continues through the weekend, at least.

How hot is it going to be in the Washington, D.C. and Baltimore region?

Forecast weather map for early Sunday showing a stationary front over northern mid-Atlantic (National Weather Service)
The mid-Atlantic will be situated on the northern edge of the heat dome. The forecast is complicated a bit by the proximity of a stationary cold front that will be parked either over us or just to our north. If the front stays far enough north, much of the region could close in on or even exceed 100 daily Friday through Sunday.

But if the front sags far enough south, D.C./Baltimore might only experience mid-90s over the weekend. The closeness of the front may also serve as a trigger for some gusty afternoon or evening thunderstorms.

* Friday is likely to be the hottest of the three days, when the region has the best chance of hitting 100 or higher. There’s an outside chance Washington, D.C. could flirt with the June monthly record of 102.

This heat index forecast map for Saturday indicates values reaching 105-110 arpund Washington, D.C. and Baltimore (NOAA)
* Both Saturday and Sunday may be a few degrees cooler if the front droops south a bit. Mid-to-high 90s seem most likely. But there’s a chance it’s equally hot as Friday.

These are less than ideal weather conditions for the AT&T National golf event at Congressional.

What are the daily record highs in Washington and Baltimore? Could they be broken?

Here are the daily record highs at the three airports:

June 29:

Reagan National (DCA): 101 (1934)
Dulles (IAD): 95 (1991)
BWI: 105 (1934) a monthly record

June 30:

DCA: 100 (1959)
IAD: 98 (1964)
BWI: 100 (1959)

July 1:

DCA: 102 (1901)
IAD: 94 (1968)
BWI: 103 (1901)

All three of Reagan National’s records will be a challenge to break, but none are out of reach. Dulles has a good chance to break records all three days. BWI’s records are a stretch Friday and Sunday; Saturday’s is within reach.

What about the humidity?

Dew points in the mid-Atlantic - depending on the position of the front - will vary from the mid-60s to low 70s. This means moderate-to-high humidity, adding 5-10 degrees to the heat index or feels like temperature. Peak afternoon values will range from 100-110 all three days.

When does the heat wave end?

The Washington, D.C. area may experience some modest relief early next week (low 90s for highs), but the heat may re-load around July 4 and 5.

Unfortunately, from the Rockies and Plains to the mid-South, no real relief from excessive heat is in sight.

By  |  03:14 PM ET, 06/27/2012

Categories:  Latest, U.S. Weather, Local Climate, Extreme Heat

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