Afternoon Technical Discussion - 10/17/11

CWS Tech Disco – 10/17/11 Afternoon

Synopsis:

Clear skies will remain overnight and into early Tuesday, with temperatures again remaining mild. A strong area of low pressure will move into the region Wednesday, bringing significant rainfall to the state through the middle part of the week. Temperatures will fall ahead of clearing skies as we move into the next weekend.

Short-Term (Overnight-Tuesday Afternoon):

A weak area of high pressure over the region has provided mostly sunny skies and mild temperatures reaching into the 60s for this afternoon. These mostly clear conditions should continue overnight, with only a few high cirrus clouds to content with. Temperatures will likely fall to near-normal levels, reaching the low 40s in most areas. Finally, winds should continue to die down overnight as the large area of low pressure that gave us strong winds over the weekend continues to move away.

Tuesday will not be a bad day, weather wise, with temperatures reaching back towards the 60 degree mark again. Clouds will thicken during the course of the day, however, with skies mostly cloudy in many regions by nightfall. Tuesday should be dry, in accordance with American operational and ensemble models. The 12z ECMWF has a small chance for precip banding across the state, but we feel this chance will be minimized.

Long Term (Tuesday Evening – beyond):                      

The whole story changes by Wednesday morning, however, as a powerful synoptic storm sets up shop across the area. This system will strengthen as it is drawn up the coast, pushed by a strong upper-level trough. All regions of Pennsylvania will see rain on Wednesday, with the east and west edges of the state likely to pick up the greatest amounts over the course of this storm. Models largely agree with rainfall entering the state very early Wednesday morning. While the exact strength and track of the storm's center are not certain yet, its size will mean that will likely not matter. Rainfall amount forecasts are still rather variable, but according to SREF plumes, expect near an inch of rain in the W and NW regions and near 1.5" in Philadelphia.

Meanwhile, SREF plumes forecast accumulated rain of near three-quarters of an inch in State College.

The bulk of the rain should clear the state throughout Thursday, especially Thursday morning. There will likely be a few remaining lake effect rain showers in the NW lasting into early Friday, but these should be nothing more than a nuisance shower. Expect skies to clear dramatically behind the system as another area of high pressure builds for the weekend, albeit bringing with it colder temperatures.