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428
FXUS61 KCTP 271118
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
718 AM EDT Mon May 27 2024

.SYNOPSIS...
Severe weather is likely today, especially in the eastern half
of the state as a low pressure area passes over the Upper Great
Lakes and drags a cold front through by late evening. An upper
level trough will build into the region for the remaining
portion of the week. Occasional showers and a few thunderstorms
are expected Tuesday and Wednesday. The week will end dry and
the dry forecast should last through Sunday.

&&

.NEAR TERM /UNTIL 7 PM THIS EVENING/...
-- Changed Discussion --
Showers and a few rumbles of thunder are into the western
counties at 11Z. No severe worries yet, with mainly short cores.
But the wind could gust into the 30s/40s with them as they could
tap the mid-level winds. This area of showers/storms should lift
more to the north than the whole thing slide west to east. This
rain could keep things less active/worrisome for the late
morning and early afternoon. But, it could also add just that
much more moisture to the llvls that would add some juice. Will
tweak the timing for the rain/thunder this AM, but hold
everything the same from ~10AM onward.

Prev...
Sky clearing out over much of the area, but sat images show
patches of low clouds on some of the ridges. Fog is starting to
develop in some spots, too (generally in the valleys). High/mid
clouds will thicken up from west to east this morning as the
fog/stratus burns away. Short wave over OH is driving nocturnal
convection there and should push some TSRA into the west before
12Z. GFS is pretty fast with onset when compared to time-of-
arrival tool. But, some SHRA (or even a TSRA) could develop
ahead of the current crop. These could expand and make it a busy
morning, but the severe threat appears to be a little later in
the morning through the rest of the daylight hours when a
second, stronger upper short wave moves toward PA. The cold
front will lag the main show by a couple of hours, though.

SPC SLGT risk has been drawn back to the east a bit, likely with
an eye toward early morning arrival of the first batch of
TS/SHRA. The stable air at the sfc and relatively warm air aloft
seen on BUFKIT soundings for this morning hint that TS this
morning will not be rooted in the blyr. However, as this first
volley of storms moves east, they may tap the sfc and grow
stronger in the east - even before noon. The arrival of the
better forcing coupled with the heating/destabilized llvls
should put all the threats into play for much of the area. The
organization/storm-mode is rather a toss-up at this point with
many factors giving different hints. MLCAPE in the 1000-1200
range are not super. WBZ is low-ish, sitting at or just below
10kft in most places for some part of their respective
unstable period. The progged hodographs for this aftn are not
too compelling, either, but an SPC 5% tornado risk is a fairly
rare thing for PA (a couple times/yr). Will play up the wording
for tornadoes a little more than usual in the HWO and IDSS
briefings.

As the afternoon progresses, the western tier of counties should
get into more-stable air, and by 6-7PM, only the SErn quarter of
the area will still be in their most-unstable period. Sct SHRA
will occur along the real cfront in the evening, but they will
be going over much more stable ground.

Heavy precip is more likely in the east as in the west, as PWATs
reach near 2" in the Lower Susq by noon. But, the storms should
be moving along at 30 MPH. The multiple shots at
thunderstorms/heavy rain, and the wet ground from the rain we`ve
had over the past 12 hrs will be the main reasons for FF threat.
The threat is not high enough at this point to post a FF Watch
for any of our area. The east is where the PWATs do climb high
and where the highest chcs of having 2-3 TSRA in 6-8 hrs lie.
So, that is where WPC has painted the SLGT risk of excessive
rainfall.

Maxes today will hold in the 70s for almost everyone.
-- End Changed Discussion --

&&

.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM TUESDAY/...
As the cfront moves through in the evening, some drier air comes
in. The wind stays up in the 5-10KT range, so fog may occur, but
won`t put it in the wx grids at this point. Low clouds under the
digging longwave trough will come back into the NW quickly.
There could be a few SHRA there, but these should not push too
far into the CWA, maybe just 3-4 counties overnight. Mins in the
50s and lower 60s are still well above normal.

Upper energy under the trough should spark some SHRA and a few
TSRA on Tuesday. But, daytime temps stay near normal in the SE,
and fall short of normal by 5-6F in the NW. Didn`t want to take
the 30 PoPs any farther SE than an AOO-SEG line for Tuesday, but
isold convection is expected in the SE. In fact, at least one
HREF member pops things along the srn border (S of the lower
clouds) and rides them into the Lower Susq. Thin CAPEs and short
storms will keep the threat of SVR down to very low, if any risk
at all. But, there is high 0-6km shear (40-50KT), generally
before the SHRA/TSRA arrive.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Medium range guidance continues to point to a period of cool
weather Tuesday through Thursday, as a deep upper level trough
pivots southeastward from the Great Lakes. Cold temps aloft
should support diurnally-driven showers/storms Tue and Wed,
with the highest POPs across the elevated heat source of the
Allegheny Plateau. The best overall chance of showers should
come with the passage of a strong shortwave on Wednesday.

PoPs will fall to slight chance on Thursday as drier air moves
in on the back side of the upper trough. This will begin a trend
toward drier and warmer weather Friday into Saturday, as the
upper level trough axis shifts east of PA and high pressure
builds into the region. An approaching frontal system could
bring our next round of showers/storms by next Sunday.

&&

.AVIATION /11Z MONDAY THROUGH FRIDAY/...
A line of SHRA continues moving across central PA early this
morning with generally VFR/MVFR conds. Some drops towards IFR in
the heaviest showers remain possible across E PA with locally
gusty winds at IPT in the next hour or two. Some uncertainty in
how low vsbys/cigs get overnight but generally expect VFR/MVFR
to continue with a light breeze overnight. LLWS appears likely
in the overnight across much of central PA, especially W PA into
sunrise hours.

Guidance continues to suggest IFR-to-MVFR cigs will continue
through much of Monday across E PA. Scattered TSRA are expected
to form in the afternoon and evening, perhaps forming into a
line of convection. Some of the strongest storms (especially
across E PA) could bring about localized gusty winds and an hour
of more restrictive conditions, but confidence remains too low
to include in this TAF package. Cigs will trend higher late in
the day outside of thunderstorms as drier air works in from the
west.

Outlook...

Tue-Wed...Brief restrictions are possible in scattered showers,
but much of the time should be VFR.

Thu-Fri...Predominantly VFR.

&&

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

&&

$$

SYNOPSIS...Lambert/Dangelo
NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...Evanego/Colbert
AVIATION...Colbert/NPB