Area Forecast Discussion
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FXUS61 KCTP 240246
Area Forecast Discussion
National Weather Service State College PA
1046 PM EDT Sun Apr 23 2017
A storm system over the southeastern states will begin to make
slow progress northward along the coast over the next several
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
High clouds continue to stream northward moisture swirling
around a potent upper low over TN surges our way. They are
thickest over the south, thinnest over the north.
The HRRR shows light rain just beginning to creep up over the
Mason-Dixon line counties shortly after sunrise, otherwise 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.
Broken to overcast mid/high clouds will help to curb the temp
fall across the south. Mins will be mainly between 40-45
throughout the Central and Southern counties of the state.
Clear to scattered thin high clouds will continue through most
or all of the overnight over the Northern Mountains allowing
lows to dip into the 30s with some patchy frost.
.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/...
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.
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
High pressure and associated dry air mass over Pennsylvania will
ensure widespread VFR conditions and light winds through
tonight. Latest LAMP and downscaled NAM suggest there could be
some patchy fog in vicinity of MDT/LNS early Monday morning.
However, given the expected amount of cirrus, feel significant
fog formation is unlikely.
Low pressure lifting up the east coast will spread lowering
clouds and spotty light rain into southern Pa Monday. Initially,
dry air in the low levels should keep conditions VFR. However,
model soundings and SREF prob charts suggest MVFR conditions
will become likely by Monday evening across southern Pa, with
IFR even possible at AOO/JST.
Tue...Rain/low CIGs likely.
Wed...AM rain/low CIGs possible.
Thu...AM fog possible. PM tsra impacts possible.
Fri...PM tsra impacts possible.
NEAR TERM...La Corte