Severe Thunderstorm Warning 84, NWS State College, PA

Area Forecast Discussion
National Weather Service State College PA
326 PM EDT Thu Jul 20 2023

.SYNOPSIS...
Low pressure over the Upper Peninsula of Michigan this morning
will track north of Pennsylvania Friday, dragging a trailing
cold front through the region. Showers and thunderstorms are
expected along and ahead of this front, and some storms may
contain gusty winds and heavy downpours this evening into
tonight.

High pressure will build into Pennsylvania this weekend, then
pass off of the east coast next week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Any lingering fog/low clouds have cleared as of midday, and cu
is rapidly building over central PA. We've even see a few
showers already popping up over the Lower Susq Valley.

Model guidance supports a partly sunny and seasonably warm
afternoon, with little in the way of organized convection.
However, falling heights and surging low level moisture
preceding a potent upstream shortwave could spawn scattered late
day convection across the northwest part of the CWA, where
modest capes and deep layer shear of 30-40kts could support a
few strong storms.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
The greater threat of severe weather should arrive in the NW
mtns around 00z, when large scale forcing ramps up ahead of a
potent mid level shortwave crossing the eastern Grt Lks. Several
convection-allowing models track a squall line from northwest
to southeast across the area this evening through the overnight
hours.

A strong southerly low level jet should advect increasing
moisture into the region, partially offsetting the affect of
nocturnal cooling and sustaining a moderately unstable
environment ahead of the shortwave. SPC continues to highlight
the NW Mtns for the best chance of damaging wind gusts late this
evening. However, strong large scale forcing could potentially
sustain a line of strong to severe thunderstorms further to the
southeast overnight.

The progressive nature of this feature and pwats not too far
from normal suggest that flooding concerns should be isolated.
The wettest HREF members produce spot amounts in the 2-3 inch
range, which could result in flooding, especially if it were to
fall where FFG is lowest over portions the Middle Susq Valley.

Expect the threat of showers/tsra to diminish markedly from
west to east late tonight, as the low level jet and plume of
higher pwats shifts east of the forecast area. After a lull in
activity early Friday, another round of convection could
accompany the passage of the surface cold front over the eastern
part of the CWA Friday afternoon. Cool temps aloft could also
support a few diurnally-driven showers across the Allegheny
Plateau.

Surface ridging and an associated low-pwat air mass is progged
to build into the region Friday night.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Medium range guidance continues to suggest a stretch of
relatively dry weather through next weekend in association with
an area of high pressure. Conditions will become more humid
into Monday as high pressure begins drifting eastwards off the
east coast. Scattered daytime convection will cover CPA on
Monday and Tuesday, with Chc PoPs during the afternoon and
evening hours before tapering off in the overnight/morning
hours. An area of high pressure south of PA will bring drier
conditions for Wednesday, with seasonable temperatures expected.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
Predominantly VFR conditions and light winds for most of the
day today and into the early evening. Showers and thunderstorms
are likely to overspread the region from the west this evening
in association with low pressure tracking across the Grt LKs.
The main uncertainties right now are on the timing of impacts.
Guidance suggests that storm mode will be mostly linear as it
moves across the state and reach out western sites near 00Z.
That line of thunderstorms will begin to approach eastern sites
by 06Z on Friday. Ceilings will drop to IFR/LIFR overnight and
fog will once again be possible in locations that see rain.

Outlook...

Fri...AM low cigs/tsra impacts possible.

Sat...Slight chance of AM low cigs W Mtns.

Sun...Patchy AM valley fog possible NW Mtns.

Mon...Isold PM tsra impacts possible.

&&

.CLIMATE...
With 13 days left in the month, 2023 ranks as the 8th wettest
July at Williamsport with total rainfall of 7.69 inches. This
total is likely to increase through month end with only 0.31"
needed to crack the top 5 wettest on record.

Top 10 wettest July at Williamsport
1.  2018 11.99"
2.  1992 9.65"
3.  1958 8.30"
4.  1928 8.02"
5.  1908 8.01"
6.  2004 7.99"
7.  1947 7.79"
8.  2023 7.69"
9.  2017 7.45"
10. 1956 7.17"

&&

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

&&

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

Hazardous Weather Outlook
National Weather Service State College PA
626 PM EDT Thu Jul 20 2023

PAZ057>059-064>066-212230-
Dauphin-Schuylkill-Lebanon-Adams-York-Lancaster-
626 PM EDT Thu Jul 20 2023

This Hazardous Weather Outlook is for central Pennsylvania.

.DAY ONE...Tonight.

Severe thunderstorms with damaging winds 60 mph or greater and
large hail exceeding 1 inch in diameter are possible later tonight.
Heavy rain and minor flooding is also possible.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Showers and thunderstorms will linger on Friday, and may still be
capable of producing damaging winds, large hail and heavy rain.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to report significant hazardous weather.

PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-049>053-
056-063-212230-
Warren-McKean-Potter-Elk-Cameron-Northern Clinton-Clearfield-
Northern Centre-Southern Centre-Cambria-Blair-Huntingdon-Mifflin-
Juniata-Somerset-Bedford-Fulton-Franklin-Tioga-Northern Lycoming-
Sullivan-Southern Clinton-Southern Lycoming-Union-Snyder-Montour-
Northumberland-Columbia-Perry-Cumberland-
626 PM EDT Thu Jul 20 2023

...SEVERE THUNDERSTORM WATCH 528 IN EFFECT UNTIL 3 AM EDT FRIDAY...

This Hazardous Weather Outlook is for central Pennsylvania.

.DAY ONE...Tonight.

Please listen to NOAA Weather Radio or go to
weather.gov/StateCollege on the internet for more
information about the following hazards.

   Severe Thunderstorm Watch.

Heavy rain is possible and may lead to minor flooding along smaller
creeks and streams.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to report significant hazardous weather.