140
FXUS61 KCTP 281844
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
244 PM EDT Fri Jun 28 2024

.SYNOPSIS...
*Seasonably warm and pleasant today; increasing clouds tonight
*Heat and humidity spike fuels severe T-storm risk this weekend
*Refreshing/dry start to July; heat+T-storms return by the 4th

&&

.NEAR TERM /THROUGH TONIGHT/...
Mostly sunny to partly cloudy and pleasant wx conditions across
central PA for the last Friday of June. Highs temperatures this
afternoon will range from 75-85F which is quite seasonable for
this time of year or within +/- 2 to 4 degrees of the historical
average for late June.

Increasing clouds expected tonight as warm air and moisture
advection ramps up across the area. There is a strong signal
for low clouds to develop/expand late tonight into early
Saturday morning particularly east of the Allegheny spine.

Still can`t rule out a couple of showers/elevated convection
over the far NW mtns prior to 12Z; however hires guidance
appears to be focusing in on a period of heavy rain in the
following 6hr pd.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
Latest HREF now shows 40-50kt LLJ from the south southwest
driving 2+ inch pwats into NW PA Saturday morning. The QPF
response is noteworthy with both 3/6hr PMM indicating 1-2
inches during the period ending 18Z Sat. If this signal remains
bullish with later hires ensembles, a short fused FF watch may
be needed given reduced FFGs over the NW/N-central zones
fostering increased vulnerability to short duration flooding.

The early morning low clouds forecast across the central mtns
into the Susquehanna Valley, along with the potential heavy
rainfall evolving across NW PA Saturday morning both complicate
the convective forecast for later Saturday afternoon and
evening. There is a conditional element now in play which hinges
on amount of instability/destablization that can be realized.

That being said, very little change to the SPC SWO for tomorrow
with the 1730Z update. 5% tornado risk remains largely unchanged
and hail probs were removed.

The belt of strong 850mb flow will transport rich low level
moisture (dewpoints in the upper 60s to lower 70s) northeastward
along/ahead of a cold front this weekend. PWAT values are
forecast to reach 2-2.5 inches on Saturday or +2-3SD. The
anomalous, deep-layer moisture will support risk of heavy to
potentially excessive rainfall with point amounts of 3 inches
possible in places experiencing multiple TSRA.

WPC added a SLGT risk across NW PA overnight which looks good
given increasing confidence in an initial round of +RA over that
area prior to 18Z. They may even expand the SLGT risk area a bit
with the next update later this afternoon/20Z. Storm motions and
much higher FFGs (due to lack of rainfall) will be limiting
factors to reduce flood risk farther to the south and east
across the CWA (where D0 and D1 drought conditions exist).

Convection/heavy downpours should be sustained after 00Z and
probably not exit the area until after midnight/06Z Sunday.

Guidance continues to show some variability with the timing of
the main frontal passage on Sunday. Locations most likely to see
potential strong/svr t-storms are over the southeastern part of
the CWA which is included in the D3 SLGT risk SWO.

Once the cold front clears, the door will be open for another
seasonably cool/dry airmass to invade the Commonwealth. This
will result in a less humid and comfortably dry start to July on
Monday.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Roller coaster of conditions will continue in the long term.
After a comfortable summer day on Tuesday, temps and humidity
hit the big first hill climb. Risk of Heat Index values
eclipsing 100F is there for the SE/Lower Susq on Thurs. Air
temps should be >90F for each day Wed-Fri as big Bermuda high
noses all the way to the MS River. The return flow from the
GOMEX will make it soupy and min temps may not dip past 70F in
many places in the middle of the week. Model/WPC guidance hangs
a front up just to our N and keeps us in the warm sector. Daily
30-50 PoPs already in the forecast will be held onto. If you
like South Carolina in the summer, you`ll love the middle of
next week here.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
Wind will stay up overnight out of the S/Se for most terminals.
The LLJet of 40-45KTs rolls up from S to N over the
Alleghenies. 40+KT of LLWS is certain for BFD and JST. The
ceilings will lower to IFR over the east (80pct chc) as the SE
flow brings in very high Atlantic moisture. Over the west, a
warm front should be on the doorstep at 12Z and a few -SHRA or
just plain -RA will start to fall over the NW third/half of the
Central PA airspace after midnight and make the nrn tier
damp/wet by sunrise. Cigs look like they should be a little
higher over the W than E overnight according to MOS and HREF
vsby potential progs.

The low stratus is expected to lift and become broken to
scattered in the morning over the S, and gradually work
northward a bit in the mid-day and aftn. Numerous TS/SHRA will
be popping up over the NWrn third of PA in the and
thunderstorms develop later on Saturday. High moisture will make
the potential for very heavy rain and very low vsbys in the
TSRA. TSRA will continue pressing SE thru the evening and first
half of the night Sat night. The chance for showers and storms
will linger across the southeast Sunday as a cold front drags
it`s feet moving through the area. There could be fog Sat night
in the NW (BFD), but that will depend on the amt of clearing.
IFR from overnight/AM fog (Sun morning) at BFD is only a 40pct
chc at this point, and lower elsewhere as not much clearing is
expected elsewhere.

Outlook...

Mon-Tue...Dry weather with VFR conditions except perhaps some AM
valley fog N.

Wed...PM TSRA moving across from W-E.

&&

.CLIMATE...
Through 6/27, June ranks as the second warmest on record at
Harrisburg with an average monthly temperature of 76 degrees or
+3.8 degrees above normal.

&&

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

&&

$$

SYNOPSIS...Steinbugl
NEAR TERM...Steinbugl
SHORT TERM...Steinbugl
LONG TERM...Dangelo
AVIATION...Dangelo
CLIMATE...Steinbugl