Latest Guidance Significantly Increasing Ice Amounts in DC Metro

The latest trend in this evening’s forecast model guidance from both the American and European models have increased the amount of ice accumulation across the DC Metro Area Saturday afternoon through the overnight.  If these trends hold, the Winter Weather Advisories currently in place across parts of the DC Metropolitan Area may be upgraded to Ice Storm Warnings!

Ice Storm Warnings are issued when ice accretion (accumulation) from freezing rain is at least a quarter-inch which is capable of causing tree damage and scattered to widespread power outages.

Winter Weather Advisories are issued when ice accretion from freezing rain is expected to remain under a quarter-inch.

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Walk Like a Penguin

Dew points are currently sitting in the mid teens across the Washington Area setting up a textbook Cold Air Damming (CAD) situation. As precipitation begins falling through the dry mid levels of the atmosphere, temperatures at the surface will drop into the middle 20s and hold steady through the event allowing for all precipitation to freeze on contact.

Ice accretion between a tenth and a quarter of an inch will accumulate on trees, power lines and roadways causing treacherous travel conditions. The 100 car pile up in Dallas-Ft. Worth yesterday was a result from only a tenth of an inch of ice.  

Winter Storm Warnings or Ice Storm Warnings are likely along and east of Interstate 95 with a Freezing Rain Advisory likely for locations further north and west.

The image below is from the latest North American Model (NAM) showing sleet (orange) and freezing rain (pink) impacting the DC region beginning Saturday morning and wrapping up by noon on Sunday.

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