December 5, 2005
Most of the local area received between 1/4"-1/2" of snow and sleet on Saturday night, so we forecasted well for storm #1. Storm #2 will graze the area on Monday and we have not backed off of our forecast from 12/2 which calls for light snow and snow showers Monday night with minimal accumulation for Delaware County. Confidence in this forecast is medium at best, though at this time, we don't see any reason whatsoever to backpedal and alter our outlook. Delaware County was placed under a Winter Storm Watch by the National Weather Service for accumulating snows Monday night into Tuesday. According to the weather service, 5-8" of snowfall is expected Monday night into Tuesday for our area, but I must respectfully disagree with them at this time for the following reasons.
First, guidance has been fairly consistent in that it keeps most of the precip well to our South and East. Though there is a very sharp cutoff between light snow and heavy snow, high pressure will nose it's way East just enough to keep that heavy moisture confined to parts of Virginia and Southern and Eastern Maryland and South Jersey. Based on current atmospheric observations, I again see no reason to shift the axis of heavier precip any farther North at this time.
Secondly, current radar trends are ragged at best. Convection in the deep South has halted any Northern progression of precipitation. The axis of precip is aligned SW to NE and the entire axis has actually shifted ever so slightly to the South and East the past few hours. This is the time to put the models aside and go with current obs and instinct, so again, there seems to be no reason to believe that the heaviest moisture axis will shift to the North and West into the city, though we will still have a period of light snow and snow showers Monday night.
Finally, the storm that moved through Saturday night has created a flow in the pattern (a 50/50 low) that is channeling colder air into the East. This is actually acting to help nose the high pressure Eastward and is blocking the low pressure system from moving right up along the coast. The storm will emerge off of coastal North Carolina and will race Northeastward with little fanfare for our immediate area aside from very minimal accumulations.
While we do feel a period of light snow and snow showers will occur Monday night after dark, accumulations will be on the light side. A dusting to 2" of snow is likely for our area with 2-5" 'possible' down in South Jersey. Snow may mix with or change to sleet and freezing rain for a while down at the shore, so this will keep accumulations on the lesser side also.
All that being said, I must tell you that this system has been a tough one to forecast. There are still some things that could go wrong with this forecast and any minor change aloft will affect conditions greatly down at the surface. If energy in the upper atmosphere should phase faster over the Ohio Valley, that will surely pull the system closer to the coast giving the big cities a significant storm. Right now, all the players are on the field and things seem to be going as forecast with phasing holding off until the system is well East of our area. However, as I mentioned above, there will be a VERY sharp cutoff line from North to South between light snow / snow showers and heavy snow.
So, light snow and snow showers to affect Delco Monday after dark with a coating to 2" accumulation. A slight shift to the North will put us in the heavier bands of snow, which is actually what the National Weather Service is going with at this time. Again, I respectfully disagree with their call of 5-8" for our area, though they are the pros and I am the amateur. I will keep any updates posted during the day on Monday. Another system 'could' come out of the South later in the week to threaten us with more wintry weather. More details later!
S.B.
