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 , 4:53 PM GMT on November 25, 2012
Well it appears the local media are now mentioning what I have been saying for a number of days now; snow is possible Tues. I don't blame them for waiting since they have protocols to follow, and honestly, this storm is a tricky one.
DISCUSSION: It appears a low pressure system will move just south of us and go off the coast. Since low pressure spins counterclockwise, the position of the low is important for our precip type. The further south it leaves the coast the more cold air it will bring down from the north as we would then be on the NW side of the spin. Any deviation from the track will change our position in relation to the spin and so change the air temp. Surface temps will be above freezing while the upper air will be colder. Typically, as precip falls it brings with it the colder air (colder air is heavier than warmer air). This being said, can the surface temps drop enough to support snow accumulations? It is possible.
CONCERNS: As I mentioned in my last post, I do have some concerns which would inhibit snow accumulations. Those concerns still remain, but, nonetheless, snow accumulation is possible. For it to happen though we will need the low to be in the right spot, the cold air to filter down, and not too much rain at the onset of the storm.
TIMING: For most, the precip should start sometime before noon on Tuesday and last through the morning rush hour on Wed. When/if the precip changes to snow will it happen? Not sure yet, but at this time my best guess is later in the afternoon Tuesday.
PRECIP TYPE: I am waiting on this until late tonight or Monday. But, as I have been saying, it appears the storm will start with rain, changing to mixed precip then to all snow as the column of air cools. More to come in my next update.
HOW MUCH: I really don't want to yet pin that down until I have a better idea of the track of the low and the surface temps. Those west of Baltimore City and along the MD/PA line would see the most, but I do see accumulations all the way into Baltimore City. On average I would say about 2 inches is safe, but don't yet quote me. Those in S MD will most likely see only rain, but snow is not yet out of the question. Depends on the path of the low.
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