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.

The latest European Forecast Model below shows a significant increase in the amount of freezing rain falling across the metropolitan area during this winter event.  If this trend continues the National Weather Service may have to upgrade some of the advisories to Ice Storm Warnings.

Latest European Freezing Rain Accumulation:

If Freezing Rain ends up being the predominant precipitation type, a quarter to one-third of an inch of ice could accumulate in downtown Washington! That amount of ice would certainly be enough to cause power outages and tree damage.

Interestingly, the latest American short range ensemble forecast (SREF) model (image below) is in relative agreement with the European model and shows a quarter of an inch of ice getting into DC, parts of northern Virginia and the eastern suburbs of Maryland (Prince Georges and Anne Arundel counties).

Let the window-casting begin! If Sleet (ice pellets) ends up being the predominant precipitation type instead of freezing rain (liquid that falls as rain and freezes on contact) — then of course we could see higher amounts of liquid but less ice accretion on trees/power lines. Remember sleet simply bounces when it falls and doesn’t cause a glaze of ice on everything which weighs on tree limbs and power lines. That is why Freezing Rain is the WORST precipitation type during winter — by far the most destructive.