The mix of precipitation did change back to snow very briefly overnight Wednesday, adding a dusting to an inch on top of the earlier snow and ice, mainly in areas north and northwest of downtown Washington.
How much snow fell
Storm snow totals reached about one to two inches inside the Beltway, mainly in areas along and just west of I-95, and just north of Route 50 in Maryland.
To the north and west of the Beltway, about two to three inches fell in southern Montgomery, western Fairfax, northern Prince George’s and northern Anne Arundel counties.
Amounts increased to three to six inches in central and eastern Loudoun, northwest Montgomery, northern Fauquier and Howard counties.
The heaviest totals in the region focused from western Loudoun County to around Frederick, Md., and to the north and west, where six to eight inches was common, with up to a foot in the mountains.
At the airports, Reagan National observed just a trace of snow while Dulles posted 2.3 inches and BWI Marshall 1.6 inches.
A glaze of ice for some
While snow and sleet changed to rain along and east of I-95 and mostly snow fell out toward Interstate 81, a narrow swath of freezing rain fell in the zone in between.
The National Weather Service reported a very light glaze of ice in western Fairfax and central and western Montgomery counties (between 0.05 and 0.15 inches) and a thicker coating of up to 0.25 to 0.5 inches in north central Virginia. Nearly 35,000 customers in Virginia were without power because of ice accretion on power lines, mostly in Fauquier, Culpeper, Orange, Albemarle and Louisa counties.
How was Capital Weather Gang’s forecast?
The forecast was that this storm was very challenging, as the rain-snow line was a moving target. Over the weekend, when we began predicting how the storm might play out, many forecast models suggested the storm would track just off the Mid-Atlantic coast, drawing in cold air from the north, offering the possibility of significant snow. But with time, their simulated tracks shifted inland, indicating that the storm would thus pull in more mild air off the ocean.
Knowing an inland track was a possibility, we were conservative with our initial forecasts for how much snow might fall. Even so, the initial forecast maps we issued Monday were a little too aggressive with amounts.
On Monday night and Tuesday midday, we nudged our predicted amounts slightly lower. The Tuesday midday forecast, about 20 hours before the snow began, shown below, ended up being our final call:
Overall, this forecast proved to be a very good match of the actual amounts, as shown in the map below:
Our detailed briefing on the storm published Tuesday also did an accurate job laying out the storm’s timeline and evolution and impacts region by region. We correctly forecast when the changeover from snow to mixed precipitation would occur and when cold air and frozen precipitation would return on the storm’s backside.
We were assisted by excellent computer model guidance, which helped us fine-tune our forecast.
Given the complexity of the storm and forecast challenges, we were satisfied overall with how our predictions played out.