Synopsis…
A large upper level cut off low is going to remain entrenched over the southern portion of Appalachia for the majority of the work week. This system will create a series of surface lows that will move up the east coast creating mild temperatures and persistent rainfall.
Short-term (Monday through Wednesday)
Although we are currently in a brief break from the wet weather, I expect the rain to reform overnight at that cut off low continues to spin over the eastern seaboard. The rainfall will be widespread and heavy, especially overnight tonight with the non-mountainous regions (SE, CR, NS) seeing the heaviest rainfall. There is all chance of thunderstorms associated with this precipitation shield as denoted by moderate Lifted Index values over south eastern portions of the state. Although, severe weather is not expected with this system, if a storm cell gets lucky and heads up the Chesapeake or Delaware Bay, we could see the possibility of a severe thunderstorm in the South east tonight or tomorrow. The upper level low will dissipate Tuesday night allowing for clearing overnight and the chance for a bit of sunshine on Wednesday. Depending on the amount of sunshine on Wednesday, MOS could end up being WAY TOO COLD FOR THE WEDNESDAY HIGH TEMP.
Long-term(Wednesday night through Friday)
The cut off low will strengthen overnight on Wednesday as it pulls in energy from a trough making its way through Canada. However, the GFS and WRF have this occurring at drastically different parts of the country. The WRF has the low developing over Alabama and Mississippi and this allows for the system to pull in more moisture from the Gulf causing heavy rain for Thursday and into Friday. The WRF also pulls in the moisture from what may be TS/Hurricane Nicole, only adding to the Heavy rainfall. The GFS has the low developing over Georgia and South Carolina which causes the majority of the moisture to stay off to the east of Pennsylvania with only the SE region seeing significant rainfall on Thursday and Friday. Since the WRF has been trending East and the GFS is now trending West, we decided to split the difference and forecast somewhere between the two model runs for now and allow for the shifts after us to pin down the forecast as our uncertainty reduces.
Longer-term:
This system will finally clear out on Saturday, but look at the 540 height line as well as the 0 degree Celsius line below Pennsylvania this weekend. Although, I doubt the lake effect snow the models currently are showing will actually occur, it will be quite chilly by the end of the weekend
RJ Patrizio
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