National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 140008
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
808 PM EDT Thu Aug 13 2020

.SYNOPSIS...
A stationary frontal zone wavering over southern PA will
maintain a chance of scattered, locally heavy downpours tonight
into Friday. Unsettled conditions with cooler temperatures are
forecast for the upcoming weekend.

&&

.NEAR TERM /UNTIL 7 AM FRIDAY MORNING/...
Quick update for cancellation of flash flood watch for York and
Lancaster Counties.

Previous discussion 736 PM EDT...

Moist/unstable airmass with sfc dewpoints in the 65-70F range
resides across the southern tier of CPA. 23UTC SPC mesoanalysis
shows zone of 500-1000 J/kg of MLCAPE helping to fuel isolated
downpours. The loss of heating should fade the convection with
POPs trending lower into tonight. Latest CAMs support the
bearish trend.

Quite an airmass change heading into the northern 1/2 of the CWA
with a mainly clear sky and comfy dewpoints in the low-mid 50s.

Odds are increasing that the flash flood watch may be able to
expire before 04Z expiration. Will coordinate with PHI/LWX.

Low dewpoint air will allow min temps to dip into the 50s across
the northern tier, creating a favorable setup for radiational
valley fog with air/water temps exceeding 20F. Temps stay
muggy across the south central/southeast zones with lows around
70F in the lower Susquehanna Valley metro areas.

&&

.SHORT TERM /7 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
A repeat of today is in store for Friday with sct/nmrs storms
again forming mainly in the aftn. One change may be that the
storms may actually creep more to the north on Friday with an
upper level trough developing in the OH Valley. Maxes look very
very similar to today, as well.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
By Friday evening, split flow produces a weak broad upper
trough over the lingering frontal boundary to our south. This
will bring a surge of moisture into the Commonwealth Saturday
afternoon and Sunday. Anomalous southeasterly 850-mb flow
(approaching record values for this time of year) will help
funnel ample moisture into the Middle Atlantic. Have upped PoPs
in the SW starting Saturday afternoon and maintain higher PoPs
farther east through Sunday evening. Despite the GFS being the
outlier earlier in the week, other models have gradually trended
toward a wetter solution. Still, ample uncertainty remains. The
NAM brings almost no rain to north of the Mason-Dixon line
Saturday and Sunday, while the GEFS mean sits at widespread
storm total precip exceeding 1" and spotty 2" amounts across
south central PA. Opted to ramp up PoPs across south-central PA
where confidence is highest in rain occurring, but shaved off
about 20% of QPF from a blend of NBM, WPC Guidance, and the
SuperBlend.

The weak surface trough will stick around through Monday before
a cold front sweeps through the Commonwealth, marking the end
of an unsettled stretch and ushering in cooler and drier
weather.

The Climate Prediction Center 6-10 temperature outlook favors
below normal temperatures in central PA. This will be a welcome
relief after a prolonged stretch of warm weather. Additionally,
the arrival of high pressure by the middle of next week seems to
favor a drier than normal stretch for a little bit.

Precipitation chances ramp up again across the southern tier by
late week, but no significant impacts are expected.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
00Z TAFS sent.

Isolated showers and storms across the south, but not near
any TAF sites at this point.

Some fog and lower clouds possible late, but rainfall less
widespread today than in recent days, thus I did not hit
fog and low clouds very hard.

Friday at this point looks mainly dry, similar to what
we had today, thus only used VCSH across the south.

More in the way of widespread showers possible for later
Saturday into Sunday Night, but still a ways out. Much
of our area could remain between systems to the southeast
and southwest of our area.

Outlook...

Sat-Sun...More in the way of widespread showers possible.
Mon...Still a chance of showers and storms.
Tue...Clearing skies.

&&

.CLIMATE...
A daily record high temperature of 87 degrees was tied at
Bradford on 8/13. The previous record was set in 1988.

&&

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

&&

$$
SYNOPSIS...Steinbugl
NEAR TERM...Steinbugl
SHORT TERM...Lambert/Dangelo
LONG TERM...RXR/Banghoff
AVIATION...Martin
CLIMATE...Gutierrez