Severe Thunderstorm Warning 33, NWS State College, PA

Area Forecast Discussion
National Weather Service State College PA
443 PM EDT Tue Apr 29 2025

.SYNOPSIS...
* Warmer weather will moderate humidity will last into tonight
  with numerous strong to severe thunderstorms moving across the
  Western and Northern Mountains of PA during the early to mid
  evening hours.
* Dry weather returns on Wednesday followed by periods of
  showers and thunderstorms Thursday through Saturday
* Temperature and precipitation trends have become increasingly
  uncertain into early next week due to large variations in the
  projected upper level pattern

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
A nearly north/south warm front extended near the Route 15
corridor through the Northern Mtns and Susq Valley late this
afternoon. This boundary divided a fairly clear and low humidity
airmass to its east from more more humid and increasingly
unstable airmass over the Central and Western part of the state.

High res models and NBM indicate a few discrete TSRA cells
developing across NW PA and moving quickly to the east-northeast
within the region of strongest deep layer shear and best 0-2 KM
hodographs where helicity values within that layer will exceed
300 m2/s2. These cells will have to be monitored closely as they
will have marginal LCL heights around 1 KM and the best shear
near the aforementioned warm front.

Any discrete or embedded supercells will be capable of
producing concentrated swaths of damaging winds, large hail, and
a tornado or two. The greatest risk for severe weather will be
west of I-99 and north of I-80 where an Enhanced Risk has been
issued by the SPC. On average, Pennsylvania only sees 6 Enhanced
Risks per year, so residents in northwest PA should be prepared
to take shelter as storms move through later this afternoon and
evening.

As the right entrance region of a potent upper level shifts
over the Lower Glakes and NW/NCent PA late this afternoon and
evening and sfc cold front approaches, we're seeing the expected
QLCS (now over Eastern Ohio) marching steadily east-northeast
across roughly the NW 1/3 to 1/2 of our CWA (coinciding with
recently issued SVR TSTM Watch 191.

0-3KM bulk shear of 45-50 kts will be nearly orthogonal with
this line, which will create a highly favorable setup for mini
bows/broken-s signatures and localized damaging wind gusts of
70-80 kts from descending mid level jets accentuated by evap
cooling within the fast moving storm cells.

Forward speed of the aforementioned line will be 40+ kts.

Expect the convection to slowly weaken later this evening
(02Z-03Z) as it approaches the Lower Susq Valley, which lies at
the eastern edge of SPC's DY 1 Slight Risk Area.

Temperatures into early this evening (and for that matter until
the cold front pushes through) well above seasonal normals
today. Max temps ranging from the upper 70s over the N Mtns, to
the mid 80s in the valleys of South-Central PA will be 15-20 deg
F above normal. South-Southwesterly winds will gust between 25
30mph this afternoon across the Western Mtns and about 5-10 mph
lower in the east.

Lingering showers will shift into the Susq Valley late this
evening along the low level jet and plume of highest pwats.
However, can't rule out a late night shower associated with the
arrival of the weakening cold front, which should track from the
NW Mtns around midnight to the southeast part of the forecast
area by dawn Wednesday. Most likely rainfall totals by late
tonight based on ensemble plumes range from around 0.25 inches
over the Allegheny Plateau, to near zero over areas southeast of
Harrisburg. HREF indicates localized totals of >1 inch are
possible near the NY border. As such, the risk of flooding with
this system remains very low. Lows at daybreak Wednesday will
range from the upper 30s in northwest PA behind the cold front
to near 60 in southeast PA.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
Latest guidance supports warm and dry weather Wednesday, as the
cold front stalls out south of the Mason-Dixon Line and high
pressure noses into PA from the Grt Lks. However, the boundary
will remain close enough to justify low POPs across the
southwest part of the forecast area. For most, it should be
another perfect spring day with a refreshing northwest breeze,
low humidity, and abundant sunshine. Good day to mow the grass
with more widespread rainfall expected Thursday into Saturday.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Efficient radiational cooling will support a frost risk across
the northeast zones/Endless Mtns late Wed night into early
Thursday morning with fcst min temperatures in the mid to upper
30s. The growing season for this area does not activate until
5/11, so no frost headlines will be issued. Meanwhile, more
clouds and higher dewpoints keep lows near 50F along the PA/MD
border.

Quasi-stationary front will pivot and lift northward as a warm
front across CPA on Thursday as a sfc low tracks from near
Chicago into Lake Huron by 02/12Z. Expect shower activity to
ramp up particularly in the western/northwestern portions of the
CWA through Thursday night in association with strongest 850mb
moisture flux and IVT. Thursday night looks very mild for the
first night of May 2025 with min temps 55-65F or +15 to +25
degrees above climo.

Scattered convection is likely to accompany the trailing cold
front on Friday with daytime highs ranging from 65-70F in the
NW mtns and 75-85F in the south central/southeastern ridges and
valleys. Severe storm potential remains limited based on the D4
discussion from SPC. However, WPC excessive rainfall outlooks
carry a marginal risk Thu/Fri with an emerging trend toward more
rain (wetter on the margin) on Saturday tied to a frontal wave.
POPs were increased vs. NBM to start the first weekend of May.

What appeared to be firm drying trend and nice stretch of wx
dominated by high pressure from Sunday into early next week has
now faded away -- as medium range models and ensembles show a
more blocky pattern over the Lower 48 and potential cutoff low
developing somewhere over the Eastern U.S. This spread keeps
confidence much lower than average on sensible wx details due
to very uncertain upper level flow details.

&&

.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
VFR conditions are certain (100% confidence) through 29/23Z
across the Central PA and Susq Valley airfields and KJST,
while lowering convective bases will lead to a transition to
MVFR CIGS at KBFD with a Tempo Group for TSRA at KBFD through
00Z Wed. A similar short-lived, 1 hour or so tempo group may
need to be included between 23-01Z respectively at KJST and KUNV
as the southern edge of a line of TSRA (now along the PA/OHIO
border moves east-northeast at 40 KTS.

Westerly wind gusts within thunderstorms during the early to mid
evening are expected to be briefly over 40 KTS at KBFD, KJST
and KUNV ; however, lower confidence on the magnitude of wind
increases further east into the Susq Valley as the storms will
begin a weakening trend late this evening.

The associated cold front will push SE through the region
between about 00Z NW (01Z KBFD) and 07-08Z in the KMDT and KLNS
areas. A 5-8 hour period of MVFR CIGS and a few additional
showers area expected at KBFD and KJST near and in the wake of
the cold frontal passage later tonight, while the Central Ridge
and Valley airfields see prevailing conditions mainly in the
lower end of the VFR category following the cold front.

Wed...A few lingering showers across primarily SW PA.

Thu...Showers/t-storms return areawide, restrictions possible.

Fri...Showers with restrictions possible.

Sat...Showers early. Improving late.

&&

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

&&

SYNOPSIS...Lambert
NEAR TERM...Lambert
SHORT TERM...Lambert
LONG TERM...Steinbugl
AVIATION...Lambert/NPB

Hazardous Weather Outlook
National Weather Service State College PA
330 PM EDT Tue Apr 29 2025

PAZ004>006-010>012-017>019-024-025-033-034-037-041-042-045-046-
301930-
Warren-McKean-Potter-Elk-Cameron-Northern Clinton-Clearfield-
Northern Centre-Southern Centre-Cambria-Blair-Somerset-Bedford-Tioga-
Northern Lycoming-Sullivan-Southern Clinton-Southern Lycoming-
330 PM EDT Tue Apr 29 2025

...SEVERE THUNDERSTORM WATCH 191 IN EFFECT UNTIL 10 PM EDT THIS
EVENING...

This Hazardous Weather Outlook is for central Pennsylvania.

.DAY ONE...This afternoon and 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.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to report significant hazardous weather.

PAZ026>028-035-036-049>053-056-301930-
Huntingdon-Mifflin-Juniata-Fulton-Franklin-Union-Snyder-Montour-
Northumberland-Columbia-Perry-
330 PM EDT Tue Apr 29 2025

This Hazardous Weather Outlook is for central Pennsylvania.

.DAY ONE...This afternoon and tonight.

Isolated to scattered severe thunderstorms with damaging winds 60
mph or greater and large hail exceeding 1 inch in diameter are
possible this afternoon and evening.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to report significant hazardous weather.

PAZ057>059-063>066-301930-
Dauphin-Schuylkill-Lebanon-Cumberland-Adams-York-Lancaster-
330 PM EDT Tue Apr 29 2025

This Hazardous Weather Outlook is for central Pennsylvania.

.DAY ONE...This afternoon and tonight.

Isolated strong to severe thunderstorms with gusty winds are
possible this evening.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to report significant hazardous weather.

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