472
FXUS61 KCTP 190324
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1124 PM EDT Sat May 18 2024

.SYNOPSIS...
An upper trough overhead will slide east through the late
evening with showers decreasing by late tonight. High pressure
will start to build into the region on Sunday accompanied by
generally rain-free conditions that are expected to hold through
the middle of next week. A storm system should arrive late
Wednesday into Thursday bringing the next chance of showers and
thunderstorms to the area.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Isolated open cellular showers continue to roam areas from the N
Central Mountains to the WC Mountains late this evening as upper
low upper low tracks off the coast and drier air works southward
behind the upper trough axis. Showers will taper by late tonight
with clearing skies and light winds allowing areas of fog to
form overnight. Some fog could become locally dense in the
predawn hours. Lows will range from the mid 50s to around 60.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY NIGHT/...
High pressure rolls in for Sunday. Clouds/fog in the AM clear
out nicely. However, just enough instability develops and enough
moisture lingers to pop a couple of SHRA. Literally just a few
with the highest probability (30pct) over the SErn hill tops.
Maxes in the 70s will be pretty normal. We are likely to see
some areas of fog again Sunday night with the sky clearing out
better, but dewpoints not dipping out of the m50s.

A decent and mostly rain-free stretch of weather is expected
Monday through Wednesday morning, with high pressure dominating
the sensible weather conditions and bringing the driest weather
we`ve seen in a few weeks. We are timing the next weather system
into central PA by Wednesday afternoon. Scattered showers and
thunderstorms may approach western areas by late Wednesday
afternoon, but it looks like most areas stay dry until after 00z
Thurs.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Late evening update holds minor changes to the long-term
forecast, most notably have capped PoPs at Chc Wednesday
evening into Thursday as both GFS/ECMWF models have
showers/thunderstorms along the cold front breaking up as they
enter central PA. Ensemble plumes still outline higher chances
of PoPs in this timeframe so have decided to just cap instead of
trim PoPs at this time.

Prev...
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 rain as 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 /03Z SUNDAY THROUGH THURSDAY/...
03Z Update: Minimal changes outside of slightly later (1-2hr)
later on fog development overnight with generally the same time
for mixing out. A period of MVFR cigs possible tomorrow compared
to earlier guidance but VFR expected by the afternoon hours.

Prev...
The main concern overnight will be fog formation at all
airfields across central PA. The bulk of recent guidance
outlines IFR conds in the 04-07Z timeframe, with most likely
timing between 05-06Z where the potential for calm/light winds
becomes slightly higher. This is echoed in recent RAP model
soundings, thus have these restrictions in with moderate
(50-60%) confidence. There is some uncertainty in regards to
which airfields go down to 1/4SM vsbys and VV cigs after during
the early morning hours Sunday morning. Highest confidence
(40-50%) remains at AOO/UNV/IPT, with some potential for these
conds at JST/BFD. Further to the SE, cannot rule out some lower-
level clouds (below 300ft AGL) to bring LIFR conds to LNS with
moderate (40-50%) confidence while retaining IFR conds at MDT
based on a combination of RAP/GLAMP guidance.

After sunrise, some lingering low cigs/vsbys remain possible
through 14Z Sunday before rapid improvement (in a 1-2 hour
period) towards VFR is expected by the late morning. Once conds
prevail to VFR, expect these conditions to continue through 00Z
Monday.

Outlook...

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

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

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

Thu...Chc of TSRA.

&&

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

&&

$$

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