Technical Discussion

Synopsis:

A low-pressure system will move through the state today, bringing rain showers changing into snow showers later in the day. The passage of an associated cold front will drop temperatures somewhat significantly as the day progresses. Expect mostly cloudy skies on Saturday and Sunday with lingering snow showers possible, especially in northern regions of the state.  Another disturbance will approach the state by Monday, creating an opportunity for windy conditions, rain showers, and even a possible thunderstorm.

Short-Term:

The 0000 UTC runs for the WRF and GFS models both indicate a deepening low pressure system approaching the state from the southwest. The surface low will pass through the state by this afternoon, off to the northeast.  All model runs show a nice swath of precipitation associated with the low pressure system.  The 18Z run of the GEFS plumes shows strong consistency in the timing and extent of the precipitation, as is to be expected in such a short-term forecast.  By tomorrow morning, the accumulated precipitation (liquid equivalent) is projected to be between 1 inch and 1.5 inches, with the majority of the ensemble members supporting precipitation amounts on the higher end of the range.  The plumes also indicate mainly rain for the first part of the day today, changing over to snow by evening.  Some ensemble members even have a little bit of freezing rain into Sunday.  The SREF probability fields for NE PA, initialized at 1500 UTC, indicate a very high probability for rain showers throughout the day today, switching over to a high probability for snow, especially in more northern regions and the mountains.

Long-Term:

Another low pressure system is projected to evolve over the Midwest over the weekend and affect the state on Monday.  It's too early predict with any strong certainty if the passage of the system will spark thunderstorms, but early guidance suggests that it is a possibility, along with strong winds and rain showers.