Squall Line could deliver threat of damaging wind gusts this Evening

A cold front accompanied by a squall line will approach the Washington Region late this evening.  Damaging wind gusts are possible, especially just south and west of the Washington Region across north-central Virginia and the Shenandoah Valley.  A strong low-level jet stream and wind shear (winds changing direction and speed with altitude) would typically indicate the potential for severe thunderstorms (some containing a tornado threat) however the missing ingredient will be instability (CAPE) as the sun will have set well before the arrival of the cold front.  Regardless, the Storm Prediction Center has placed the DC Region under a marginal risk for severe thunderstorms with damaging wind gusts being the primary threat between 9 PM and 1 AM late this evening.

Timing the arrival of the squall line (a line of convection containing gusty winds and heavy rainfall):

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