Technical Discussion

Synopsis:

A significant system will bring heavy rain to much if not all of Pennsylvania.  A semi-stationary cold front will act as the track for a second wave of energy and moisture from the Gulf of Mexico, making this a multi-day event. 

Short-term:

High clouds will build across the state today, and in some parts in the west, will almost completely diffuse the sunshine.  Temperatures will be warmer today than previous days due to sunshine and southerly flow ahead of the front.

Medium-term:

The attempt at consistency between forecast zones was to put in place these guidelines: looking at the 12-hour SREF probability of .5 inches or greater of precip – if it was yellow or greater, forecast for "heavy rain" – if it was between blue and yellow, forecast for "rain, heavy at times."  Rainfall amounts were determined with SREF plumes.

There appears to be some effect by Lake Erie on rainfall amounts as seen especially in SREF probability maps, which reduces rainfall amounts over and just south of the lake.  While no one could explain why this could be, the striking and apparent anomaly was respected in the forecast for Erie.

There are some regions where wind could be significant, even for just a 6 hour period.

Temperatures fall during the day on Wednesday in many locations, especially in western and central PA.  This is important to point out in the remarks, especially as there could be a transition to snow in the precip.

Long-term:

Snow showers develop behind this system.  I believe I was appropriately liberal with extending snow showers or flurries across much of western PA, as well as indications of accumulations where appropriate.  If anything, State College is not snowy enough.