Area Forecast Discussion
Issued by NWS State College, PA-- Remove Highlighting --
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FXUS61 KCTP 281150
Area Forecast Discussion
National Weather Service State College PA
750 AM EDT SUN AUG 28 2016
A warm front over western Pennsylvania will push east into the
region this morning...followed by the passage of a weak cold front
tonight and Monday morning. This pair of frontal systems will
bring scattered showers and thunderstorms to mainly the northwest
half of the state this afternoon and tonight. Another period of
warmer than normal and mainly dry weather will follow for Monday
into early Wednesday. A stronger cold front will move southeast
across the commonwealth Wednesday followed by a refreshingly
cooler airmass with low humidity Thursday through Saturday.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Tranquil conditions prevail across the region early this morning
with moderate sfc dewpoints in the low-mid 60s and just some areas
of mid and high clouds (mainly across the northwest third of the
state. The current sfc dewpoints will mark the low temp in many
locations. Some locations across the northern mtns could see some
localized low clouds and patchy fog for an hour or two around
A few stray showers could brush the far nw zones during the mid
to late morning hours thanks to the combination of the warm front
over that region (and enhanced uvvel over the boundary) and
theta-e advection focused near the nose of a 30 kt swrly LLJ.
Will have to monitor the situation for potential isolated...strong
to svr tsra across the central and nrn mtns of the state this
afternoon and early evening.
Very warm air aloft (8-9C at 700 mb) during the day today may
make it hard to fire up many showers or storms. However...a
ribbon of 1.5-2 inch PWAT air...the approaching warm/cold frontal
tandem...and an elongated mid/upper shear axis will combine to
bring a band of 1500-2500 j/kg sfc-based cape and sfc-6km wsw bulk
shear of around 25-30 kts across NW PA later today and this
SPC has expanded their Marginal Risk for SVR slightly south and
east today to cover practically all of the nrn mtns...and a
smaller portion of the central mtns today...within the fairly
narrow warm sector.
Gusty (and highly localized damaging) westerly winds will
accompany some of the stronger storms in the 18Z Sunday - 01Z
Monday period in the MRGL Risk area.
Above normal temps will continue today with similar maxes (or
perhaps just a few deg f lower than Sat`s across the Susq Valley).
Highs expected to range from the mid 80s (mtns) to near 90F in the
Lower Susq Valley.
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
The weak cold front slowly sags SE through the state tonight and
Monday. Best LLVL forcing/warm advection and cyclonic/convergence
LL flow (via a 1-2 sigma 850 mb jet) will move off to the north of
PA by tonight. This (along with increasing blyr stability) will
support a quickly diminishing threat for showers/tsra after 03Z
Close proximity of the front near or just south of the Mason/Dixon
Line Monday afternoon and the tail end (RR Quad) of an 80-90kt
upper jet will provide ample llvl convergence and broad, gentle
uvvel aloft to produce isolate shra and tsra Monday afternoon in
far souther PA.
Lows tonight will range through the 60s, and high temps Monday
will vary from near 80F across the NW Mtns, to near 90F in the
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
The extended period looks like it will feature a transition from
a persistent upper-level ridge over the eastern United States to
a weak upper-level trough by mid to late week. As a result,
above-normal temperatures through the Tuesday-Wednesday timeframe
will transition to near or a little below normal by the end of the
A weakening cold front will push slowly SE through the
Commonwealth tonight and early Monday Sunday night into Monday
morning accompanied by isolated to scattered
showers/thunderstorms. The frontal boundary is expected to wash
out near or just south of the Mason/Dixon line during the day
Monday. Abundant low-level moisture, mesoscale convergence and
some orographic lift/heating via the east to NE low level flow
regime across the mountains of SW PA will focus the best chance
for showers and scattered thunderstorms there Monday afternoon.
Monday night through Wed morning looks to be dry with generally
light wind and just the possibility of patchy early morning valley
Medium range guidance agrees with a second-stronger cold front
pushing SE across the area Wednesday afternoon or early Thursday,
with a renewed chance for showers and thunderstorms.
This front will be followed by a cool-down for the end of next
week. Max temps should be mainly in the 70s Thursday into the
weekend over the northern and western higher terrain, with low to
mid 80s elsewhere as an upper trough amplifies from central
Quebec...to the Mid Atlantic Piedmont.
.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
Local visibility restrictions in BR/FG will give way to VFR by
13z. Scattered TS are forecast to develop across the NW 1/2 of
the airspace this afternoon ahead of a weak boundary pushing
southeast from the Lower Great Lakes. Showers may continue along
the boundary into the evening as it sinks southward toward the MD
border. Light winds and high boundary layer moisture could result
in some low cigs and fog after midnight into early Monday morning.
Mon...VFR. Isold PM TS possible southern 1/4 airspace.
Tue...Patchy AM fog, then VFR.
Wed...Sct PM TS impacts possible.
Thu...No sig wx expected.
LONG TERM...La Corte/Lambert