I provide a weather email service for people in MD. I am a storm chaser & Skywarn spotter. For daily weather tidbits follow me on Twitter: @wxmanMD.
By: cws6196 , 4:06 AM GMT on January 28, 2013
The Winter Weather Advisory issued due to the anticipated mixed frozen precip in the morning has been extended, starting earlier (3:00am) and ending later (12:00pm in central MD). A look at the radar shows the mixed precip moving in faster than the models showed. This could mean it will end sooner, although it also means there is the potential for more ice. The upper atmosphere is warming as the southerly flow and warm front advance, but the lower layers are still well below freezing as is the surface as a result of the days of freezing temps and snow cover. But, for those north and west of Baltimore you could see a dusting of snow before it turns to freezing rain. Those in S MD, looking at the precip to your west you will note it is all rain. But, as that precip moves east and saturates the dry air ahead of it, it will drop the temp of the dry air causing the precip to change over to freezing rain.
Many are concerned about how much ice will accumulate. While I understand the concern, mainly for tree damage and loss of power, but to be honest, any ice on the ground during the morning commute will be a safety hazard. While the main highways may be fine, walkways, bridges and secondary roads will not. The Federal Gov is telling their employees to stay off the roads until 10:00am; not a bad idea.
TIMING: The mixed frozen precip (snow, to sleet to freezing rain) will be around 2:00 - 3:00am ending around 10:00am or a bit sooner if the system continues to come in quicker.
If you are curious as to the difference between sleet and freezing rain it has everything to do with atmospheric layer temperatures. Sleet forms when the upper atmosphere is cold but the surface is warmer. The ice crystals form and fall, but as they get closer to the surface they begin to melt. Freezing rain is the opposite (like we will encounter Monday) wherein the upper atmosphere is warm and the surface is below freezing. The precip falls as rain, freezing as it nears the surface.
I am still watching the storm potential for Wednesday afternoon as well as the snow potential for Friday. Follow me on Twitter (@wxmanmd) for weather updates and tidbits.
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