Tech Discussion 2-23-2011

SYNOPSIS

The sunny conditions experienced today will soon be a thing of the past as a powerful storm system approaches Pennsylvania. The storm, which is currently developing over the southern plains, will intensify overnight tonight. This system will then swing up the Appalachian Mountains tomorrow morning bringing precipitation to the state by tomorrow afternoon. A cold soaking rain will be the signature of this storm with much of the mountainous areas seeing over an inch of rainfall. Although most of the precipitation associated with this storm will fall as rain, a wintry mix is possible north of the Interstate 80 corridor Thursday night. The low pressure system will vacate the region by Friday night leaving a weak area of high pressure in its wake. This high pressure system will allow for clouds to decrease on Saturday before our next system moves into the area on Sunday, bringing precipitation back to the commonwealth for the beginning of the next work week.

Short Term (Now until Thursday night)

The sunshine that we saw today will be the laat we see for a short while. This evening, the 500mb ridge keeps the state relatively dry for the night, but that will chance as positive vorticity aadvection begins to occur with the presence of an incoming low. The PVA helps develop the system we see later in the week, but it is starting to develop now. A low pressure system hanging near the southern plains will begin to move in tomorrow, showing as an increase in clouds for the better part of Thursday. The PVA feeding the low will help create a warm front that helps force the precipitation that we will see Thursday night going into Friday. As the precipitation moves in, the 540 dam line bends northward into NY, showing that rain will be the most likely precip type that will fall. Temperatures will remain in the upper 30s to low 40s  for the most part on Thursday, with some areas  with the clouds and moisture helping to keep the state above freezing as the storm progresses overnight.

 

Long Term (Friday into Sunday Night)

With the rain falling in the morning comes a bit of a warmup. The warm front associated with the  low will move through early morning Friday, and that rain lingers for most of the afternoon, and as a cold front pushes through Friday evening, high pressure behind the front quickly builds in to dry out the state for Saturday morning.Friday afternoon's rain will be blown by some decent winds due to the tight pressure gradient behind the front. The 18z WRF has the low moving straight out of the central plains while the 12z GFS gives it a more coastal track, and it hints at sending the center of the low right through the state. Another low is under development in the southern plains, and a band of clouds from that long stretches over the state throughout the day Saturday into Sunday morning. Cloudiness will be the story for Sunday morning as clouds begin to move out during the day. Temperatures will recede into normal late February conditions beyond the rain and cold front as we wait for Spring to come again.

Steven C. Engblom Jr.
Department of Meteorology
College of Earth and Mineral Sciences
Class of 2013