Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
517 am EDT sun may 3 2015
high pressure over the southern Appalachians will drift east and
off the Carolina coast tonight. A developing southwesterly flow
will lead to warmer temperatures that will continue through at
least the middle of the upcoming week.
Near term /until 6 PM this evening/...
11-3.9 infrared satellite loop and surface observation indicating just some patches of
middle level ac clouds roaming about the area early this morning.
A ridge of high pressure extending north/south across the susq
valley was providing very light and variable wind...and dry
dewpoints leading to strong radiational cooling of the air near
Mesoscale observation show temperatures have plummeted well into the 30s throughout
the normally cold valleys up north. Coudersport in Central Potter
County take the prize for the ice box so far this morning with a
temperature of 30f at 0815z. Readings in the 40s to lower 50s were common
throughout most of the rest of central Penn and the susq valley.
Temperatures will fall another 2 or 3 degree f over the next few hours with
mins at sunrise varying from the low-middle 30s across the northwest
mountains...to 45-50f in the lower susq valley. The coldest spots in
the north should dip to about 28f with frost.
Patchy fog and areas of low clouds are possible for a few hours
around daybreak across Lancaster Colorado...where models pool ll moisture
in vicinity of old surface trough.
For the rest of today...nice early may weather is on tap. Aside
from some patchy high based cumulus or Alto cumulus...and some thin
cirrus...conditions will be mostly sunny to sunny.
High temperatures this afternoon will be similar...if not a degree or two f
warmer than Saturday...ranging from around 70 across the northern
mountains...to between 74 and 78f in the southern valleys.
Short term /6 PM this evening through 6 PM Monday/...
deepening...though still relatively weak southwesterly flow will lead to
just some patchy high based strato cumulus and Alto cumulus clouds with very
light surface wind. Temperatures should be about 5 degree f milder early Monday
compared to sunrise Sunday. Still...a few middle to upper 30s should
be scattered about the cold spots of the northern mountains
Monday will feature morning sunshine followed by scattered-broken afternoon
cumulus. Any chance for rain showers/thunderstorms and rain should be across the northwest mountains and limited
to late in the afternoon and evening as a cold front sags southeast from
Long term /Monday night through Saturday/...
shortwaves tracking east across southern Canada to north of the
Great Lakes will help push a backdoor-style surface cold front into
central or southern PA by early Tuesday. The front will waver near or
more likely just to the south of the Mason-Dixon line into the
middle of the upcoming week...and will serve as a focus for
clouds and showers mainly along and north of the boundary.
The latest ensemble data shows above normal precipitable waters along the east-west
frontal zone which is usually a good indicator of at least climatology
or better probability of precipitation but due to the north-S model quantitative precipitation forecast differences will utilize
a blend and cap probability of precipitation around the high chance level /40-50 percent/ for
From the middle to later part of the week...the global numerical
model and ensemble guidance shows low pressure moving east from
the northern High Plains to the western Great Lakes/upper Midwest
by Friday. This should allow the western portion of the east-west frontal
zone to be lift northward through the Ohio Valley while the eastern segment
weakens and wavers just west/south of the PA and Ohio/WV/MD borders.
In general the precipitation pattern should be more Summer-like with weak
forcing under high heights aloft and scattered diurnal shower/isolated thunderstorm
activity near the boundary and perhaps initiating over the western high
terrain. Therefore kept probability of precipitation in the schc to low chance range Wednesday-Friday
with gradual increase into the weekend as the plains frontal
Temperatures should average near to above normal through the period.
Aviation /09z Sunday through Thursday/...
no big changes needed for 09z taf package.
Only a few middle level clouds to the east.
Expect VFR conditions today...with rather light winds for this
time of year. A taste of fine Spring weather.
An approaching cold front may trigger some showers across
north central PA on Tuesday. The front will likely slow and
create low ceilings/showers again on Wednesday. The front may push to the
south on Thursday.
Tuesday...VFR early...then rain showers in the north.
Wed-Thu...more showers possible.