Nation’s hottest heat this week to focus on D.C. area; Heat Advisory issued

* Heat Advisory for DC and Baltimore from noon to 7 p.m. on Tuesday *

Thursday's maximum heat indices are forecast to be highest in the Mid-Atlantic region (National Weather Service)

Thursday’s maximum heat indices are forecast to be highest in the Mid-Atlantic region (National Weather Service)

The summer’s hottest weather (at least so far) is here, and promises six straight days with temperatures that feel like 100 or higher. Unluckily for residents of the Mid-Atlantic, the worst of the heat wave concentrates here, with the corridor from Richmond to the District in its epicenter.

The cause

A large heat dome, or area of high pressure at high altitudes, has moved from the Atlantic (the so-called “Bermuda High”) into the interior eastern U.S.

GFS model simulation of the heat dome, depicted by red shades over eastern U.S., starting today (Monday) and evolving through Friday, when it weakens and moves offshore.

GFS model simulation of the heat dome, depicted by red shades over eastern U.S., starting today (Monday) and evolving through Friday, when it weakens and moves offshore.

This heat dome is going to meander west and then east over the next five days, keeping the Mid-Atlantic in its grasp. Even as it edges somewhat west of our region, the clockwise circulation around it will push air over the mountains causing it to sink, compress, and heat up by the time it reaches us. And then, even after the dome shifts to our east later this week and weakens a bit, it will pump more humid air into the region – compensating for its lack of heating power.

How hot?

GFS model temperature and dew point forecasts for D.C. (top), and heat index forecasts (bottom)

GFS model temperature and dew point forecasts for D.C. (top), and heat index forecasts (bottom)

Every day, air temperatures will reach at least the low-to-mid 90s, with mid-to-upper 90s likely Tuesday through Friday. Factoring in the humidity, maximum heat indices will generally be in the 100 to 105 range, but 105 to 110 levels are possible in the Wednesday through Friday period.

These high temperature should be below record levels, which are 100, 104, 103, 102 and 103 this week Monday through Friday.

When does it end?

A cold front sweeps through the region Saturday into Sunday, so this heat wave doesn’t look like it will be sustained. As the National Weather Service wrote in its discussion this morning:

BUT IN GOOD NEWS…AS OF NOW THIS DOES NOT APPEAR TO BE ONE OF THE PROLONGED 2-3 WK LENGTH HEAT WVS THAT THIS AREA SOMETIMES XPRNCS IN JUL. MDLS HV SHOWN UPR LVL TROF MOVG OVR ERN N AMERICA FOR THE WKND AND STILL DO.

Perspective

The last three summers were the three hottest on record. While this summer is running slightly warmer than average, as hot as it feels this week, recent years have been hotter and for longer stretches of time.

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