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.