182
FXUS61 KCTP 110751
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
351 AM EDT Sat May 11 2024

.SYNOPSIS...
Upper level troughing will remain over Pennsylvania this
weekend. A strong shortwave moving through the broader flow will
generate numerous rain showers and a couple of thunderstorms on
Saturday afternoon and night.

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 /UNTIL 7 AM THIS MORNING/...
Low level instability associated with pool of cold air aloft
continues to produce a few sprinkles as of 0730Z across the
eastern part of the forecast area. Further west, clearing skies,
wet ground and a calm wind has resulted in widespread valley fog
across the Alleghenies. Have issued a SPS to cover the patchy
low vsbys in this part of the state. Further east, expect
clearing skies and patchy valley fog toward dawn over the
rest of the area, as a shortwave exits the east coast and temps
warm aloft.

Temperatures are on track to bottom out from the low 30s in the
coldest valleys of the NW Mtns, to the upper 40s over parts of
the Susq Valley, where skies remain mostly cloudy through dawn.
Have added patchy frost to the NW Mtns early this morning.

&&

.SHORT TERM /7 AM THIS MORNING THROUGH MONDAY NIGHT/...
Upper level ridging in between shortwaves will result in fair
weather the first half of today, with fog dissipating between
12Z-14Z. However, expect a return of showers this afternoon and
evening associated with height falls ahead of a potent upper
level shortwave diving across the Grt Lks. Strong large scale
forcing, in combination with some minimal model cape, supports
high POPs with a tsra possible in spots. Highest POPs should
accompany the passage of the southerly low level jet and plume
of best pwats. Convection-allowing models, which should perform
well with this strongly forced system, indicate the most
concentrated band of showers/tsra should arrive over the
Alleghenies around 18Z, reach peak intensity over the Central
Mtns at peak heating around 20Z, then push into the Susq Valley
this evening. Although a brief, heavy downpour will occur in
many locations, moderate 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.

The upper trough is progged to cut off and track along the
PA/NY border tonight into Sunday morning. Low level instability
associated with this feature should result in plenty of cloud
cover and at least scattered showers lasting into Sunday
afternoon, especially over the eastern half of the forecast area.
Brightening skies and diminishing showers look likely by late Sunday
afternoon, as the upper trough exits the state and surface
surface ridging builds in from the west. Mixing down progged
850mb temps of around 4C translates to expected highs in the
low to mid 60s over much of the forecast area, with upper 50s
over the higher terrain of Eastern PA.

The upper trough is progged to lift out early next week, with max
temps rebounding +10-20F on Monday aided by a milder SW flow. A
cold front trailing low pressure in eastern Canada is fcst to
stall out over the lower Great Lakes Monday and could trigger a
shower or t-storm over the far NW mtns. Most of CPA should start
the week rain-free.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
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.

Lingering unsettled weather is possible into Wednesday, before
a ridge build this system Wed night into Thurs. 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. 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 /07Z SATURDAY THROUGH WEDNESDAY/...
Light rain has tapered off across central PA. As the low clouds
pull out of the western highlands, the nighttime microphysics
satellite channel reveals fog quickly forming in the valleys.

Diminishing winds and ample low-level moisture will likely
result in widespread fog and/or very low clouds developing
overnight across much of central PA, with IFR/LIFR conds
possible at all airfields outside of perhaps the Lower Susq
Valley. Isolated pockets of dense fog are possible in some
areas.

Cigs and vsbys should improve to VFR areawide by midday on
Saturday, before another round of rain showers pushes from west
to east across the area Saturday aftn/eve.

Outlook...

Sun...AM low cigs possible W Mtns. Sct afternoon showers/brief
reductions possible.

Mon...AM dry and mainly VFR. Showers return across the north by
aftn.

Tue...Showers/tstms and reductions developing.

Wed...Showery weather and reductions continue.

&&

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

&&

$$

SYNOPSIS...Dangelo
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/Steinbugl
LONG TERM...Steinbugl/Evanego
AVIATION...Evanego/Bowen