Technical Discussion

Synopsis: 

A ridge of high pressure will hover over the state, allowing for sunny skies and dry conditions through Tuesday.  A low pressure system will approach the region as the week progresses, bringing the opportunity for rain showers through the end of the week.

Short-Term: 

The 1200 UTC runs of both WRF and GFS suggest that a ridge of high pressure will dominate the weather through Tuesday.   Accordingly, both show, in the relative humidity plots, a nice dry slot over the region as well.  There is little uncertainty in the forecast through Tuesday; mostly to fully sunny skies and dry, mild conditions.

Long-Term: 

The 1200 UTC runs of both WRF and GFS project a low pressure system to continue to evolve off the coast of Florida and move up the coast, funneling up a potentially significant amount of precipitation to Pennsylvania approximately late Tuesday through Thursday.  Even once that precipitation leaves, a well-defined upper level trough and associated surface low pressure system is projected to develop and track towards the state Thursday into Friday, with more opportunity for precipitation.  The 1200 UTC run of MOS suggests unseasonably mild temperatures in the beginning of the week, with temperatures dropping off later in the week to more seasonable ranges.

In terms of precipitation, the 900 UTC SREF run ensemble mean suggests the arrival of precipitation into the state late Tuesday night/early Wednesday morning.  The 1200 UTC run of the GEFS plumes, for the State College area, are fairly consistent on timing of the beginning of the rain event (late Tuesday into early Wednesday), but have a wide model spread of precipitation totals, between .6 inches and 2.7 inches.  The bulk of the ensemble members, though, are tending towards greater than 1.5 inches when all is said and done with this event.  For the Philadelphia area, there is similar spread, but with the bulk of the ensemble members being on the lower end of the scale.  Regardless, this looks to be a relatively significant precipitation event across the state, in both precipitation totals and duration of the event (from late Tuesday/early Wednesday through the end of the week).