557
FXUS61 KCTP 112214
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
614 PM EDT Sat May 11 2024

.SYNOPSIS...
Upper level troughing will remain over Pennsylvania this
weekend with a potent shortwave tracking over the state tonight
into early Sunday. The upper trough will lift out early next
week, then a cold front will likely push through Tuesday. A wave
of low pressure is likely to track south of Pennsylvania next
Wednesday.

&&

.NEAR TERM /THROUGH SUNDAY/...
Rain band sliding east on time. Models have it slow/drag a
little as it starts to exit the ern zones. Trended a little that
way with the PoPs. TSRA moving in from PBZ`s area seem to be
weakening quite nicely from their earlier strength in ern OH.
The airmass these are moving over currently is very much like
ours, locally, at this time, rain-cooled and seemingly stable.
However, current RAP soundings are still a little unstable just
above the blyr with (+) CAPE area topping out around 20kft at
JST and AOO in the next 2-3 hrs. So, the thunder should hold on
until it gets into the CWA by a county or two, and maybe
deeper. Small hail was observed as the storms came thru KPIT,
and the RAP WBZ is around 5-6kft in the Laurels, so some tiny
hail may also be possible in our SW zones, too.

The shortwave driving these storms/showers will continue into
the central mtns and Susq valley. Have not made too much of a
mention of TS after the first two tiers of counties in the west,
but there could be a little farther east than that.

Prev...
Upstream trough digging southeastward from the central GLAKS is
bringing a return to showers this afternoon as the upper low
tracks to southern Ontario by 00z Sun. Strong large scale
forcing, in combination with some minimal model cape, supports
high POPs with a tsra possible in spots, although areas east of
the Alleghenies will largely be stably stratified. Some activity
west of the mountains this evening will have the highest
likelihood of producing an isolated lightning strike. Showers
should reach peak intensity over the Central Mountains between
20-21z, and then push into the Susq Valley this evening.
Although a brief, heavy downpour will occur in many locations,
modest PWAT values indicate that rainfall should generally not
be very heavy. Ensemble mean qpf of 0.2 to 0.4 inches represents
the most likely rainfall by late this evening.

Upper trough continues to dig southeastward, cutting off along
the PA/NY border later tonight into Sunday morning. Aurora
watchers *MAY* be able to see some color tonight between the
cloud breaks, but we believe those will be few and far between.
Steep lapse rates under the upper low center will support plenty
of cloud cover tonight and Sunday and at least scattered
showers lasting into Sunday afternoon. Highs for Mothers Day
will range mostly through the 60s with upper 50s in the higher
terrain of the Alleghenies.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
The upper low lifts out Sunday night and Monday with improving
conditions for Monday, and temperatures moderating thanks to a
milder southwest flow. A cold front trailing low pressure in
eastern Canada is fcst to stall out over the lower Great Lakes
Monday and will trigger some showers or a t-storm over the NW
mtns Monday afternoon, but it appears most of Central PA should
start the week rain-free.

A wave of low pressure will approach from the Ohio Valley
Tuesday before crossing the area Tuesday night. This system
will be accompanied by a renewed chance of rain and perhaps
some thunder.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Lingering unsettled weather is possible into Wednesday, before
a ridge builds in Wednesday night into Thursday. This will
support the longest period of dry and sunny weather we have seen
in awhile. The overall upper level pattern heading into next
weekend looks rather blocky - which is typical for this time of
year - but also results in much lower confidence/predictability.
Such a pattern supports changeable weather with temperatures
oscillating around average for this time of year. Some data
suggest a cut- off low pressure system could bring a slight risk
of heavy rainfall on 5/18 per the latest CPC 8-14 day hazards
outlook.

&&

.AVIATION /22Z SATURDAY THROUGH THURSDAY/...
At 21z, A band of rain showers is pushing from the central mtns
into the Susq Valley. This band could briefly drop vsbys to
MVFR across the Susq Valley during the early evening hours.

Additional showers (and some thunder) are pushing into western
PA early this evening. This activity should make it into the
western highlands before sunset, and then weaken as it
progresses eastward from there late this evening.

Expect cigs to drop to IFR at BFD and JST overnight, as
upsloping westerly flow develops. Farther to the east, the
central mtns and Susq Valley are progged to see their cigs dip
to MVFR overnight.

Sunday will see northwesterly flow develop across the area, with
gusts to 15 kts possible across the southern Alleghenies (JST,
AOO). Cigs should slowly improve as the day progresses, with the
slowest improvement expected across the western highlands.
There could be a few diurnal rain showers by afternoon, esp
across eastern PA.

Outlook...

Mon...Morning fog across the east/Susq Valley. Showers return
across the north by aftn.

Tue...Showers/tstms and reductions developing.

Wed...Showery weather and reductions continue.

Thu...Slow improvement, with a few lingering showers possible.

&&

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

&&

$$

SYNOPSIS...DeVoir/Fitzgerald
NEAR TERM...DeVoir/Dangelo
SHORT TERM...DeVoir/Fitzgerald
LONG TERM...Banghoff
AVIATION...Banghoff/Evanego