Tuesday: 10/13 /09
Discussion & Forecast.
The much cooler weather I forecasted for this week looks to be on target. Today will be the warmest day of the week, as we reach near seasonable levels in the mid to upper 60's. After today temps really take a nose dive, and a very unsettled period is on tap from Thursday into a good part of the weekend. The synoptic setup I'm about to go over, would be a snow lovers dream for these parts, only if it were the late Fall or winter months. But on a good note, these are the types of signs I want to see now, for bringing in that snowy and stormy winter I'm forecasting for the M/A States. Ok enough of the only "IF" it was winter talk, let's move on to this upcoming setup.
We'll start off with today, as a cold front presses south and east and moves through the region tonight. This will be the start of a very chilly air mass that will stick for the next 5 to 7 days. A rather large and strong area of High Pressure will settle in over the Great Lakes from Wednesday through the weekend. This High will supply a North to NW flow of very chilly air, for the remainder of the week.
It's to our South & Southwest where a series of weak storms systems will develop from near Texas and then extend east to the SE coast. With High pressure to the north and a stalled out front, this will setup a nice baroclinic zone for these storms to ride along. Some moderate to heavy rainfall can be expected from the Tenn Valley into the SE States for Wednesday into Thursday. During Wed night and Thursday, a more organized area of low pressure will develop just off the SE coast. The clouds will move in Wednesday night and thicken up, then periods of rain and cold weather can be expected for Thursday into Friday as this storm slowly moves NE and off the M/A coast by Friday night.
So expect periods of rain and cold conditions for both Thursday and Friday with Highs in the Upper 40's to lower 50's, and lows near 40. Winds will also begin to increase Friday into Saturday, as a stronger pressure gradient begins developing, from SE New England into much of the M/A States. NE winds of 15 to 25 Mph and gusts to 35 mph, will be common during this time. A brief break in the action will occur Saturday into Saturday night with only some showers, but continued cold and windy for much of Saturday.
I'm keeping an eye on the possibility of a second bout of rain for Later Saturday night into Sunday. This will come from an approaching trough that amplifies near the east coast. With a baroclinic zone still in place u/l vort energy will likely develop another weak surface low, near the M/A coast, and once again more rain will likely breakout from VA and northeast into the Del. Valley and NYC areas. So this will likely keep the weekend cold and quite unsettled. I'll have more details on this second storm threat later this week in my weekend outlook.
So overall expect periods of rain and cold conditions from Thursday into much of the weekend. Highs will be near 50 and lows in the upper 30's to lower 40's, for Thursday through Sunday. This will feel more like late November weather vs mid October weather. Temperature anomalies, and departures over the next 5-7 days will be below to much below normal.
Overall, total rainfall amounts should be between .25" - .75" for areas North and west of PHL. In PHL and areas to the south and east will see the heaviest amounts of rain, between .75" and 1.50" can be expected for this period Thursday through Sunday.
A more detailed forecast coming Thursday Evening with my weekend outlook.