Technical Discussion @ 12 AM on Friday April 30


Synopsis

High pressure will bring warm weather and scattered CU to the region FRI and SAT.  A storm system moving in from the west on Saturday will spark storms in the afternoon with more widespread rainfall on Sunday.  Cold front will finally pass through on Monday morning bringing temperatures back to seasonable levels with partly cloudy skies.

Friday-Tuesday

A warm day on Friday as flow backs to southwesterly ahead of storm system over Midwest.  Expect scattered CU throughout the day which will allow for good daytime heating.  Temperatures will climb into the 70s and low 80s, especially across SE, NSQ, and CR.  Winds will slacken for the first day in a while.  Overall a great spring day with above average temperatures.  Patchy CU remains for Friday night and nighttime minimums will be much warmer than of late with temperatures at dawn on Saturday in the 50s.  Dewpoints expected to rise on Saturday as southerly flow continues to pump more moisture into the region.  Biggest question on Saturday is how warm we get/how much sun we see.  Went on the warm side for now as MOS tends to be too cool ahead of a front and expect only scattered clouds during the day.  Some places will mostly likely reach 90 for the first or, in some cases, second time this year across warmer locations.  Expect isolated t-storms in the afternoon across the eastern two-thirds of the Commonwealth.  Convection will die down at night due to lack of heating.  Sunday will be the biggest day for precip as cold front approaches the region.  Juicy air ahead of front should spark convection Sunday afternoon.  Big model spread at this time with frontal passage timing which leads to questions on how strong the storms could be on Sunday.  Either way, rain and thunder is likely on Sunday afternoon and night.  We expect the cold front to finally pass through on Monday, early AM leaving some scattered showers, especially across the eastern half of the state.  A thing to note is that latest 0z NAM is much slower with FROPA and if correct would hold back front until midday Monday.  Like the progressive thinking at this point but this should be watched in later shifts...plenty of time to refine timing.  Seasonable temps and partly cloudy conditions return for Monday and Tuesday.


Daniel DePodwin

Head of Forecasting Operations--Campus Weather Service

Technical Discussion 4-19

Technical Pennsylvania Forecast Discussion

Updated 6:41 PM ET 4/18/2010

SYNOPSIS…

High Pressure will build across the Great Lakes as low pressure lingers over SE Canada during the next few days. The high will slide into the Ohio Valley by Tuesday, as low pressure pushes in behind it. A weak cutoff low will form over the Southeastern US, with another low and its associated fronts sliding into the Great Lakes and eventually into the Northeast by Wednesday night into Thursday.

 

Short and Long Term…

Clouds will temporarily decrease overnight tonight for much of PA, with cooler temperatures. Seasonal temps and SCT to OVC conditions will return with a weak N flow. Some uncertainty exists in the models over the amount of CU, as the high low level RH persist through Wednesday on some runs. However, all models agree on no precipitation for PA through TUE, as a ridge builds in from the Great Lakes. Cutoff will develop over the SE, before it marches to the ENE. A weak relatively cold front associated with low over SE Canada will slide in behind the cut off low on WED and THU, as the low moves out to sea. All of the state will see a CHC of showers on Wednesday night or Thursday, with some FRZ precipitation mixing in across the NERN zones and the higher elevations. A little bit of uncertainty on how much precipitation some of the zones will see, but all models seem to favor the front drying out as it passes. Temperatures should stay seasonal until front passes.

Forecaster: Michael Kozar

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Michael Kozar

The Pennsylvania State University
College of Earth and Mineral Sciences
Integrated Undergraduate/Graduate of Meteorology, Class of 2011