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 , 5:29 AM GMT on March 04, 2013
LOTS OF INFO; PLEASE READ ALL THE WAY THROUGH This has not been a typical winter: we had snow on Christmas Eve, the first time in a decade; model data has not been good; we have been dry slotted; had storms simply die out over us; very little snow accumulation (in most, not all, areas); and now a March storm that if it happens would be the first in the past 14 years! Here is what the local NWS wrote to the area forecasters this evening: A STRONG LATE-SEASON WINTER STORM IS EXPECTED TO IMPACT THE MID-ATLANTIC REGION LATE TUE THROUGH WED. AFTER LOOKING OVER 12Z MODEL GUIDANCE...WHICH HAVE COME INTO BETTER AGREEMENT...THERE IS INCREASING CONFIDENCE OF A SIGNIFICANT SNOWFALL FOR AT LEAST PORTIONS OF THE AREA.
Much of the model data is coming in and although there are some consistencies in the output I still can't say for sure how much we will get. In previous posts I have explained my concerns about snow accumulating in March; now add to the list the chance that we may have rain before it turns to snow. Rain will melt the first layer of snow, and it also skews forecast amounts since it is impossible to figure out how many inches are lost due to rain melt and how long it will rain before turning over to snow. One other caution, one which I do not believe will happen this time, but one I do need to mention: part of the dynamics of this storm is for the main Low to phase (join) with a weaker Low. As we have seen this winter, as two Low systems phase there is a dry slot created as the energy transfers from one Low to another. We already had one storm go bust because of the dry slot. I don't really think it will happen this time, but we do need to be aware of it.
But, with that said, I can make some educated guesses as to what is possible (although many people would say that is all forecaster do anyways).
TIMING: Looks to be late Tuesday evening (near midnight) into late Wednesday.
PRECIP TYPE: Those in W MD and N of DC should see all snow while the rest of us should see rain at the start turning to snow as Wednesday progresses. Those in S MD and along the Bay may turn over to snow a bit later Wednesday. Late Wednesday afternoon into the evening everyone should be all snow.
SNOW TYPE: This should be a wet and heavy snow. This means shoveling and plowing will be very difficult. We could see power outages as tree limbs come down and power lines snap under the weight of the snow. Since this will start as rain the roads can't be pre-treated and will have to wait for the snow to begin to salt, therefore many roads may be slippery.
ACCUMULATIONS: This may change, but right now most of MD should see more than 6 inches with those around DC, N and W could see 18+". S MD is a bit trickier but I still see 4-6+". This all depends on how long the rain lasts and the exact position of the Low off the coast.
FORECAST CONCERNS: Right now I think my forecast is on track, but as I have been mentioning there is the potential for either a complete bust or only a couple inches of snow. There are some data hints that this could actually be stronger than forecast, and if so we all could be looking at over a foot of heavy snow.
UPDATE: I will have another update later Monday when I see the morning data. I am also watching the Low currently in the W to see if it is moving and positioning as the models said it would. What the Low is doing in reference to what the models said helps me to see not only what the Low's position may ultimately be, but also which models to watch and which aren't producing well.
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