Tuesday, July 18, 2006

Scorching Heat Could Give Way to Severe Storms

A Severe Thunderstorm Watch is in effect for the Washington area until 10pm. The Heat Advisory remains in place through 8pm. Detailed watches and warnings by county are available above.


Although no records are at risk of being broken, the Washington metro area is sweltering this afternoon under heat indexes exceeding 100 at nearly all locations. The official reading reached 97° shortly before 2pm, but a southerly river breeze knocked that back down to 94° by 3pm and another degree lower the following hour.

Shortly after 4pm, a line of thunderstorms extended southwestward from near the intersection of I-66 and I-81 in Virginia. It was expanding and moving slowly eastward.

Tonight and Tomorrow

There is a chance of thunderstorms, some possibly severe, through this evening, especially in the western and southern suburbs. Lows tonight will be in the mid to upper 70s. Tomorrow will continue to be humid, but with high temperatures near 90.

For the outlook through the rest of the week, see Jason's post below.

As Matt noted earlier, the DC area has certainly seen more extreme heat waves. What is remarkable about the current heat, however, is the breadth of its coverage across the country. The four shades of purple in the maximum temperature map for yesterday represent 5-degree intervals from 90° up to 110°. These extend literally from coast to coast. Although the smoothing in the plot doesn't show all of the detail, the individual high temperatures confirm that every one of the 48 contiguous states reported a temperature of at least 90°.

Maximum daily temperature chart at 8pm yesterday from Unisys.

Tropical Topics

Tropical Depression 2 formed this morning, and a Tropical Storm Watch has been issued for the North Carolina coast, including most of the Outer Banks. As of the 5pm Advisory, the system was very close to tropical storm strength. The depression is moving slowly toward the north with a more northwesterly track expected along with further intensification.

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Seasonal Outlook

Latest seasonal forecast: Click here.

Latest 3-month temperature outlook from Climate Prediction Center/NWS/NOAA.