Period of Heavy Snow During Thursday Morning Rush Hour

Rain develops late this evening, washing away the brine and roadway treatments just in time for a period of moderate to heavy snow between 5am and 11am across the DC region.

Temperatures

Temperatures will start out above freezing tonight and then are forecast to fall at or below freezing during the morning rush hour.

A period of heavy snow combined with temperatures falling to near freezing and rain that has washed away the roadway treatments could make for a slippery morning rush hour especially on secondary roadways.

Potential Snow Accumulations

A two to three hour period of heavy snow will likely accumulate on elevated and grassy surfaces making for a picturesque winter wonderland.

I expect between 1 and 2 inches for most with the favored colder spots north and west of the city potentially picking up 3 inches.

Bundle up! Temperatures will hold steady in the lower 30s on Thursday and then plunge during the afternoon and evening commute as arctic air begins to infiltrate the DC area.


Saturday Evening Update on High-Impact Winter Storm

Models are in good agreement on the track of Sunday’s storm with the only variable being how quickly surface temperatures rise above freezing on Sunday evening.

Snow Arrives between 3 and 6PM

Major Icing a Concern from Freezing Rain

Read More

Snow and Ice Map Posted for Winter Storm

Warm Air Intrusion Looks to Win Out 

Unfortunately the forecast models continue to track Sunday’s storm system inland during the evening hours which will allow for warmer air at 850mb (the mid-levels of the atmosphere) to be pulled westward off of the Atlantic on top of the cold air at the surface. This sets up a scenario where heavy snow will change over to sleet and freezing rain with ice accumulations causing extremely treacherous travel across the Mid-Atlantic as well as the potential for power outages.

Heavy Snow Develops Sunday Afternoon

Snow should develop areawide on Sunday between 4 and 6PM becoming heavy for several hours before a change over to sleet and freezing rain between 8 and 10pm. A snow thump of a few inches are likely before the change over to a wintry mix.  Confidence remains low on exactly when the transition will take place and how soon locations west of interstate 95 change over to rain (cold air at the surfaces may prove more stubborn causing an increased threat of an ice storm across the western and northern suburbs of DC).

 European Model Holds Steady

The heaviest precipitation should begin to taper off after midnight on Monday (Sunday night) with some wrap around snow showers likely on the back side of the storm system. Winds will become gusty during the storm with scattered power outages likely due to the ice accumulations on top of the snow.

Snowfall Accumulation Potential 

Below is how much snow I think will fall across the Greater Washington DC Region

Potential Ice Accretion from Freezing Rain

I remain concerned about locations along the interstate 81 corridor where a quarter of an inch of ice is possible before the system pulls away.  If sleet were to become the predominant precipitation type, then the risk of power outages would decline. Remember sleet is frozen rain drops that bounce when they fall, freezing rain is the liquid that falls as rain and then freezes as glare ice on all untreated surfaces.

Please refrain from traveling Sunday afternoon/evening across the Mid-Atlantic interstates as conditions will deteriorate rapidly.

Also please note this is an extremely tricky forecast as forecast models always try to scour out cold air at the surface too soon.  If freezing rain holds on long across the DC Metro, we may be looking at more of an Ice Storm with power outages due to the gusty winds.

Now is the time to prepare for possible power outages and stock up on items in case you were to lose your power.