991
FXUS61 KCTP 181455
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1055 AM EDT Sat May 18 2024

.SYNOPSIS...
An upper trough overhead will slide east through the evening.
High pressure will start to build into the region on Sunday
accompanied by generally rain-free conditions that are expected
to persist through the middle of next week. A storm system
should arrive Wed, and perhaps generate severe weather and heavy
rain.

&&

.NEAR TERM /UNTIL 11 PM THIS EVENING/...
An MCV appears to be passing over Adams/York Cos late this
morning. This should be the back edge of the good larger scale
forcing for the rain across the SE. Some breaks could develop
there, but it is the clouds over the wrn high terrain that are
breaking up nicely. The clearing will only result in taller cu
developing as we`ll have some instability and allow for a few
TSRA this aftn, and perhaps into early evening. Slight
subsidence behind the vort max could help suppress SHRA for the
SE half of the area this aftn. Expect the SHRA there for the
rest of the day to be much more scattered. A much more
hidden/subtle feature may be some leftover forcing from earlier
+SHRA over PIT. Will need to watch for some deeper cu and
perhaps heavier rain in the Laurels. Thicker cloud cover
elsewhere will break up more slowly, and perhaps not develop any
breaks at all. Maxes on track, esp considering the heating in
the W/NW.

&&

.SHORT TERM /11 PM THIS EVENING THROUGH 6 PM SUNDAY/...
Plenty of clouds will linger tonight and any breaks that develop
after midnight will likely lead to locally dense fog as sfc
dewpoints will stay moderately high and in the mid 50s in most
locations. Low temps will occupy a tight range between 52
(Northern and Western Mtns) and 58 deg F throughout the Lower
Susquehanna Valley and points just to the west.

Sunday is looking increasingly nice with high pressure
eventually allowing a good deal of sunshine throughout and
salvaging the second half of the weekend. Decreasing deep layer
moisture and a northerly wind component along with ridging at
the sfc and aloft should help highs recover nicely with temps
around 80F fcst in the NW Alleghenies and mid to upper 60s
elsewhere.

We are likely to see some areas of fog again Sunday night, and
temps will continue to trend warmer with dry weather persisting
into early next week with highs on Monday reaching the upper 70s
to mid 80s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
A dry start to the extended period will be likely with high
pressure ridging building over the mid-atlantic region and a
deep surface low parked over the central plains. High pressure
and dry air will stay in place through Tuesday before the upper
level trough pushes them both out by Wednesday afternoon. 850mb
temps of near 16C along with surface warm air advection suggest
high temperatures could reach the mid 80s on Tuesday and
Wednesday.

By the middle of next week, upper troughing will move across
Pennsylvania and support a better chance for showers and
thunderstorms. At the surface, there remains plenty of model
uncertainty about the timing of a cold front. The mean timing is
Wednesday afternoon, but individual models bring precipitation
as early as Tuesday evening and as a late as Thursday morning.
If the front moves through Wednesday afternoon or evening, it
could produce the first threat for severe weather in some time
given the aforementioned WAA bringing greater instability.

After the front moves through, considerable uncertainty exists
in terms of how much and how frequent rain will be. A chance of
showers remains in place through the end of the week despite
zonal flow aloft providing little in the way of synoptic
forcing. The next chance for a widespread soaking rain will come
during the weekend with a center of low pressure developing
across the Ohio Valley by Friday afternoon.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
At 1120z, IFR persist over the northwestern highlands (BFD,
south to KFIG and KDUJ) overnight, with borderline IFR/MVFR
cigs expected over the central mtns (AOO, UNV). Interestingly,
JST and AOO are in what we see as brief period of VFR, thanks
to compensating subsidence, warming and drying within the left
rear quad of the 110 kt upper level jetlet. They should fall
back into MVFR to IFR later this morning and continue through
this afternoon. IPT has dropped to low- end MVFR cigs, while the
Lower Susq Valley remains low- end VFR (~4 kft cigs).

Conditions will deteriorate across the Lower Susq Valley this
morning as cigs continue to drop and an approx 3 hour period of
light to moderate rain moves in with 2-3 tenths additional QPF
expected. Look for fairly steady state conds elsewhere.

Patchy light rain will persist into the afternoon southeast of
the Allegheny Front, along with low-end MVFR cigs. For the
western highlands, cigs should improve to MVFR (perhaps even
low-end VFR) this afternoon although scattered rain showers are
possible.

Outlook...

Sun...Morning low cigs/fog possible. Becoming VFR by afternoon.

Mon...Patchy AM fog possible. Otherwise, becoming VFR.

Tue...Predominantly VFR, w/ no sig wx expected.

Wed...Sct to widespread SHRA/TSRA return.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SYNOPSIS...Lambert
NEAR TERM...Dangelo
SHORT TERM...Lambert
LONG TERM...DeVoir/Bowen
AVIATION...Lambert/Evanego