Tuesday Update: Major Snow Storm for Some, Major Ice Storm for Others?

This is a very low confidence forecast as the latest forecast models continue to indicate a more inland track of the low pressure system which is increasing the threat of sleet and freezing rain and drastically cutting down on snowfall accumulations! My map below includes Snow, Sleet (frozen rain drops) and Freezing Rain.

Any deviation in track of the area of low pressure further to the west or back to the east will have a drastic impact on whether we are digging out from snow or sleet (or both), or losing power from ice accretion from freezing rain.

Here’s a look at the latest forecast models and what they are showing for potential snowfall accumulations:

The latest European Forecast model (image below courtesy WXBell) continues to show an extremely tight gradient of snowfall accumulations along a line from Charlottesville to Baltimore.

The latest GFS forecast model (image courtesy WxBell) depicts an even warmer profile than the European, allowing sleet and freezing rain to move as far west as the Blue Ridge mountains, drastically cutting down on snowfall accumulations!

The latest Canadian forecast model shows a solution that is more of a blend of the European and GFS.  

Heavy Sleet Potential Increasing

The image below is the mean (blend) of the SREF model, showing sleet accumulations. Remember sleet is rain that freezes before it hits the ground, bouncing on contact.  Projected snowfall accumulations along the Blue Ridge and Catoctin mountains may come way down if snow changes over to heavy sleet.

Note that the latest NAM model (image below) has become more bullish depicting potential Sleet accumulations of 1 to 3″ of sleet on top of any snow that falls.

Freezing rain Potential Increasing

The other hazard that is increasing at least across portions of our region is for some freezing rain.  Remember freezing rain is liquid (rain drops) that fall and freeze on contact creating glare ice.  The highest probability of significant ice accretion from freezing rain continues to be across the southern and central Shenandoah Valley.  Some locations there could pick up over a half-inch of ice accretion on trees and power lines causing widespread outages. However the North American Model has been trending north and west with Freezing Rain moving into our Area as well.

If temperature profiles in the boundary layer of the atmosphere end up being warmer than currently forecast across our northern and western zones, the threat of freezing rain will continue to increase turning this more into an ice storm than a snow storm for areas south and east of a line from Winchester VA to Frederick MD.

The NAM model (image below) is becoming more bullish on Freezing Rain across the northern and western suburbs (including in NW Washington). If that were to materialize, gusty winds could certainly cause power outages across our area due to ice accretion on trees and power lines. 

Timing the Precipitation

  • Snow should begin to reach the ground in DC between 9am and Noon.

 

  • Snow will mix with or change over to Sleet and Freezing along/west of the interstate 95 corridor during the mid-afternoon hours before rain begins to edge into D.C. around the dinner time hour.

 

  • The low pressure system will then pull away from the Chesapeake Bay allowing for precipitation to change back over to snow before ending.

 

  • Temperatures will drop well below freezing Thursday morning allowing for a re-freeze on area roadways making for a treacherous morning commute.

I’ll do my best to put out another update this evening when the latest guidance comes in.  Now would be a good time to prepare for at least the potential for power outages due to the weight of the very wet snow and any freezing rain that may fall across parts of our area.