Area Forecast Discussion
Issued by NWS State College, PA-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KCTP 232004
Area Forecast Discussion
National Weather Service State College PA
404 PM EDT Sun Apr 23 2017
A frontal boundary will remain stalled to the south of the
state into Monday as an elongated east/west ridge of high
pressure drifts across the commonwealth.
An upper level cut off low drifting across the Southern
Appalachians will help to slowly strengthen an area of surface
low pressure along the southeast coast by Monday evening. This
surface low will likely turn north and move slowly up the
East Coast Tuesday and Wednesday bringing residents across the
eastern half of Pennsylvania showers, or even a few periods of
steadier rain Tuesday into Wednesday.
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Abundant Sunshine and a light and variable to easterly
wind will prevail through the rest of the daylight hours
with just an increase in in cirrus/cirrostratus occurring over
the southern half of the state.
Temps are nearing their forecast maxes in the low-mid 60s in
most places, while readings were still holding in the mid to
upper 50s across the Laurel Highlands, where the thickest high
cloud cover has occurred.
It will remain dry tonight with a ridge of high pressure holding
on across the northern tier counties of PA, while the northern
extent of deepening, moist easterly flow off the Atlantic
advects north to near the Mason/Dixon line well after midnight.
Variable amounts and thickness of high, then mid clouds will
help to curb the temp fall across the south (in the otherwise
cool and bone dry airmass). Mins will be mainly between 40-45F
throughout the Central and Southern counties of the state.
Mainly clear skies should continue through most, or all of the
night aver the northern mountains with temps dipping into the
30s and some patchy frost forming.
.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
The aforementioned upper low will deepen and cut off over the
Southeastern states Monday before taking a left hand turn and
drifting north along the Mid Atlantic Coast later Monday through
The main core of the anomalously strong, moist southeasterly
winds (approx -3 sigma U-component of the 850 mb wind), will
move from VA and NC Late Monday, to Southern and Eastern PA by
Tuesday afternoon. This translates into gradually lower and
thickening clouds Monday and Monday night with some light rain
or showers expected to spread in from the south during the mid
to late afternoon hours across the far south, before reaching
the Interstate 80 corridor around or shortly after midnight
Rainfall does not look heavy on Monday, as the best
moisture/easterly wind anomalies pointed to the south of the
state and the sfc low will still be down near Myrtle Beach.
Similarly mild high temps are expected across the northern PA
TAF sites, while temps cooler than Sunday by some 8-10 deg F
are forecast across the south.
Mid to upper 50 deg highs for the south Monday could be a few to
several deg F on the high side.
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
-- Changed Discussion --The period of Monday Night to Tuesday Night will be dominated
by the flow around a slow moving cut-off low which eventually
will pass to our south and east. This system will bring clouds
and light rain to the parts of our region for several days. The
models are in fair agreement on timing and position of this low.
However as we get into Tuesday around 12Z the ensembles begin
to diverge. The bands of precipitation should begin to streak
through the region, mainly the east Tuesday morning. Timing and
position of the low will change whether or not different
portions of central Pennsylvania get precipitation. Have
adjusted the orientation and adjusted POPS accordingly. The
gradient will be tight on any precipitation amounts. Once this
system goes by it will get warm fast. It should feel like
summer through the second half of the week.
As the 500 hPa low fills and the attendant moves to our
northeast the chance of rain should fall off Wednesday into
Wednesday evening. Our 850 hPa temperatures will rise rapidly
Wednesday and it should be noticeably warmer Wednesday relative
to Monday and Tuesday.
Thursday into Saturday the 850 hPa temperatures will be well
above normal, mainly in the 14 to 16C range and we will be on
the western edge of a rather impressive early season subtropical
Thursday through at least Saturday should be very warm and
humid. We should have several days with high temperatures around
Thursday into Friday will see the passage of large upper level
trough. Have left broad POPS as this trough will move a
corresponding front through.
-- End Changed Discussion --
.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
Nice, VFR flying conditions will prevail through the rest of the
daylight hours today with just a gradually increase in high
clouds across southern PA. Winds will be from the NE to East at
5-9 kts in many locations, though some gusts into the teens
will occur across the Laurels INVOF KJST.
Patchy light rain could push back into the far, southern tier
counties of PA early Monday morning, as a complex storm system
forms across the southeast states and drifts slowly north up the
Some rain could get into central areas later Monday afternoon or
evening, and perhaps into northern PA Monday Night.
Potential for a wet day on Tuesday, as a complex low lifts
northeast along the coast.
Improving conditions for Wed as the upper low and the moderately
strong llvl easterly flow heads northeast toward the New England
Showers and thunderstorms spreading eastward, along and
ahead of a cold front on Thursday.
Mon...Patchy rain spreading slowly northward.
Tue...Rain/low CIGs likely.
Thu...A chance of showers and Thunderstorms.