LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Confidence continues to increase in a widespread, soaking
rainfall from late Wednesday through Thursday. Surface low
pressure will track northward into Pennsylvania as its parent
upper trough interacts with an upper low to our northeast,
pulling a plume of moisture into Pennsylvania from the Atlantic.
The trough becomes negatively tilted as it approaches the
region, which should center the strongest synoptic scale forcing
right over Central PA Wednesday night into Thursday morning.
NBM QPF ranges from right around an inch over northwestern PA,
to an inch and a half for areas east of I-99 and south of I-80.
It is worth noting that there are still quite a few ensemble
members that suggest portions of south-central PA could see
upwards of 2 inches of rain. WPC has expanded the marginal risk
of excessive rainfall to include all of Central Pennsylvania,
but with the drier than normal conditions over the past few
weeks, the rainfall should largely be beneficial.
In addition to the rainfall, winds will be gusty on Thursday
with a fairly tight pressure gradient around the low. Winds
gusts of 20 to 30 mph are expected, with some gusts to 35 mph
possible in the higher terrain of the Alleghenies.
While there are still some timing differences in the models,
expect rainfall to gradually taper off late Thursday into early
Friday as the low begins to move off to the north. Lake effect
and upslope rain showers will continue through the weekend as
upper troughing remains in place over the northeastern United
States. High temperatures through the weekend will remain near
to slightly below normal, generally ranging from the upper 40s
to the mid to upper 50s. Lows will be in the 30s and 40s.