684
FXUS61 KCTP 270746
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
346 AM EDT Thu Jun 27 2024

.SYNOPSIS...
*Showers and thunderstorms with locally heavy rainfall will
 settle southward to the Mason Dixon line by midnight.
*Partly to mostly sunny and less humid Thursday and Friday
*Return of summertime heat+humidity will fuel thunderstorms for
 the last weekend of June; seasonably cooler & dry start to July

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
5H trough axis moving into central PA late this evening with
good dry punch reaching into western PA and 40+ kt 850 mb jet
driving sfc cold front across the region. Fairly long lived MCV
tracked across the Pittsburgh metro area into the Laurel
Highlands through the mid evening hours producing persistent
velocity couplets and a developing linear squall line that has
pushes into the South Central Mountains by 02z. Some discreet
cells ahead and south of the aforementioned convective line have
also been producing locally strong wind gusts, and we`ll
continue to watch these marginally severe storms for the next
few hours until they clear southern and southeast portions of
the Lower Susq River Valley by 06z.

Earlier question about how much recovery would occur over
southern half of central PA has been answered, with the
consensus winning out that it would be hard to destablize
sufficiently to support widespread severe convection. Still,
marginal cells and bowing line segments will still be watched as
the 40+ kt 850 mb jet drives the cold front southeastward
through 06z, producing heavy downpours, wind gusts over 40 mph
in areas and still the threat of isolated damaging wind gusts.
Showers and isold tsra should move through southern PA through
late tonight with decreasing activity after midnight.

Even with the heavy downpours, the rest of tonight`s rainfall
falls into the beneficial category for central and south central
PA where many areas throughout the southern tier have been bone
dry in recent weeks. Thus, runoff and flash flooding concerns
are very low.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY NIGHT/...
Large scale subsidence and the arrival of much drier (less
humid) air behind the exiting cold front will lead to fair and
seasonable conditions Thursday. Surface high pressure building
over the region should result in fair and cool weather Thu night
with valley fog formation likely given air/water spreads 20-30
degrees. Partly cloudy and slightly warmer conditions are
likely Friday, as low pwats persist over PA and a return
southerly flow develops as the surface high passes off the
coast. Latest model data suggests some showers and storms may
develop Friday night over the western portion of the forecast
area.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Latest medium range guidance is showing an unusual lack of
spread among its members, all of which track a surface low
north of PA Saturday, with a trailing cold front coming through
Sat night into early Sunday. The lack of spread with regards to
timing of the front, combined with progged GEFS pwats of
+2-3SD, supports an increasing confidence in showers/tsra
Saturday. A leading warm front could produce showers/tsra as
early as Friday night and a slowing cold front could cause
convection to linger into Sunday, mainly over the southeast
counties. However, ensemble plumes indicate the most widespread
convection should occur Sat afternoon and evening.

There is some potential for severe wx Saturday PM, as decent
mid level flow overspreads an increasingly moist warm sector.
Ensemble plumes currently indicate moderate CAPE in the 1000
J/kg range and model 0-6km shear is in the 35-40kt range. If the
cold front slows enough, severe wx would also be possible
across the eastern edge of the forecast area Sunday PM.

Latest EPS and GEFS both support fair weather with near to
slightly below normal temps and low humidity early next week
associated with high pressure building east from the Grt Lks. A
seasonably cool and dry start to July!

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
Widespread low stratus has developed across northwestern PA
including the Alleghenies. IFR conds are likely at BFD and JST,
with LIFR possible between 09z and sunrise. Downslope flow and
some wind will probably keep IPT/UNV/AOO from getting as bad
(low) of conditions overnight. But, some IFR is possible at
those locations, too (less than a 50% chc), and fog can not be
ruled out at MDT and LNS if the midlevel clouds move out before
sunrise.

All TAF sites will be VFR by mid morning Thursday. Winds will
remain from the NW with gusts generally less than 20 kts.

Outlook...

Fri...Generally VFR.

Sat-Sun...Thunderstorm impacts possible.

Mon...Generally VFR.

&&

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

&&

$$

SYNOPSIS...DeVoir/Steinbugl
NEAR TERM...DeVoir/Steinbugl
SHORT TERM...Lambert/DeVoir/Fitzgerald/Steinbugl
LONG TERM...DeVoir/Steinbugl
AVIATION...Dangelo/Colbert