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Posted at 03:33 PM ET, 01/13/2013

Behind today’s busted forecast: the wedge always wins


Temperatures at about 5,000 feet (or 850 mb) this afternoon are around 12-15 C, which - ordinarily - translates to temperatures near the ground in the 70s F (at least mid-20s c) *if* there is sunshine (and not a cold layer of air near the ground). (WeatherBell.com)
We had talked about it for days. A big push of southerly air at high altitudes was supposed to warm us up today - big time. Instead, a very shallow layer of cool air or a “wedge” got stuck and proved too much to overcome, obliterating earlier forecasts for highs in the 60s or even near 70.

We won’t get out of the 50s today and we may not go above 55 in the immediate D.C. area. Meanwhile in Staunton, Va. it’s 70. So cruel.


The warm air at higher altitudes coming over top of the cool air at the ground caused the thick blanket of fog. (This is known as advection fog - we wrote about this last month under similar circumstances ). The graphic above shows the orientation of the wedge as marked by the warm front in west central Va. cutting southeast towards Virginia Beach. South of the wedge, temperatures rise into the 70s. To the north, it’s mainly in the 50s and foggy - as illustrated by conditions in the District this afternoon.

This wedge was caused by high pressure off the coast of New England, the circulation around which delivered this clammy air. Even though this marine weather system is not particularly impressive or strong, it’s proven to be enough to spoil what appeared to be a promising January thaw.

By  |  03:33 PM ET, 01/13/2013

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