River Flood Warning 4, NWS State College, PA

Area Forecast Discussion
National Weather Service State College PA
Issued by National Weather Service Binghamton NY
558 AM EDT Thu May 15 2025

.SYNOPSIS...
* Daily chances for thunderstorms continue through Saturday
  with potential for damaging winds and localized flooding.
* Temperatures trend warmer Friday and Saturday with a notable
  uptick in humid/sticky weather.
* A cold front will bring much colder temperatures and less
  rainy/more sunny weather later this weekend and early next
  week with breezy conditions.

&&

.NEAR TERM /THROUGH TONIGHT/...
Low ceilings, reduced visibility and some drizzle evident all
across Central PA this morning as persisent southeast flow
continues to keep moisture locked into place. Weak ridging aloft
has contributed to a decrease in shower activity overnight and
daybreak temperatures are generally in the 50s.

Later today, the upper low that has enveloped the region over
the past couple days will continue to lift northeast, but will
be replaced by an approaching and rather vigorous northern
stream upper- level wave. Lingering energy aloft from the
opening up and former cutoff low could still well produce
diurnally favored showers and thunderstorms this afternoon, with
most of the coverage probably occurring near and east of US-15.
Although precipitable water values look a little lower today
than previous days, any sustained convection over
hydrologically sensitive areas will have to be watched.
Fortunately, most of the rain/storms today should fire up east
of the areas that got hit hard by rainfall the last couple days.
A Marginal Risk of excessive rainfall is in place for all of PA,
but the most vulnerable locations are in Somerset and Bedford
County.

Good news is we should see more sunshine by this afternoon as
winds turn more southerly and ridging builds in. Highs today
will moderate nicely compared to yesterday, generally in the 70s
across the region (+10F day over day). By this evening, a warm
front will lift through the Commonwealth and bring the potential
for more showers and storms overnight. The best
shear/instability is not expected to make it into central PA,
but decaying storms will roll through during the predawn hours
and linger into Friday morning. SPC has hoisted a MRGL risk for
the western half of PA where a few storms could produce some
gusty winds or small hail. Daybreak temperatures on Friday will
be around 60F areawide.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Latest guidance indicates a lull in the precipitation during the
late morning and afternoon on Friday following the passage of
the warm front. Southwest flow will continue to funnel moisture
up into the northeast US as dewpoints reach their highest values
so far this year (in the mid to upper 60s). It will feel
noticeably humid as well. Highs in the 80s across the area
appear likely with the only exception being if thunderstorms can
fire up in the afternoon.

Another round of convection appears likely Friday night into
Saturday morning (yet again decaying as it moves across
Pennsylvania from the Midwest). Severe weather appears a bit
more likely with this round as 2500J/kg of MLCAPE overlaps with
sufficient shear in the evening. The SPC Slight Risk gets into
southwest PA, but would not be surprised to see an eastward
expansion across southern PA with subsequent updates.

By Saturday, a cold front will approach the Commonwealth with a
convective outflow boundary likely surging out ahead of it from
the previous night's convection. The outflow boundary will
encounter a warm and moist airmass that could lead to
development of sustained strong thunderstorms on Saturday
afternoon. Still some uncertainty with how quickly a line of
thunderstorms will congeal Saturday afternoon, but southeast PA
would be favored for a primarily damaging wind threat, as
outlined by SPC's Slight Risk (level 2 out of 5) that covers
York and Lancaster County. With all 3 rounds of storms,
progressive storm motions should limit the risk of signficant
flooding, but cannot rule out some isolated issues for locations
who's soil moistures/creeks are already running high.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
The latest model timing now brings a surface cold front through
PA a little faster than earlier model runs (by later Saturday
night). Although some upper-level energy could still produce
isolated showers on Sunday, an overall drier trend should be
underway.

Early next week (Monday and Tuesday), a confluent NW flow
pattern aloft over the Commonwealth will encourage the approach
of expansive surface high pressure and a dry, cooler air mass.

By the middle of next week, once the upper ridge line passes off
the coast, the approach of the next disturbance aloft and
surface warm front should bring a renewed threat of showers.

&&

.AVIATION /10Z THURSDAY THROUGH MONDAY/...
Reduced ceilings and visibility evident across the entire area
this morning as southeast flow continues to keep low
clouds/moisture locked in. Conditions should gradually improve
into this afternoon as winds turn to come out of the south. VFR
conditions should prevail by this evening everywhere. A few
scattered showers and thunderstorms are possible this afternoon,
but predicability remains too low to prevail any thunder.

Conditions will deteriorate again tonight. A decaying line of
thunderstorms could bring some restrictions to western airfields
before daybreak Friday with gusty winds possible.

Outlook...

Fri...Morning storms (some could be strong), improving
conditions in the afternoon.

Sat...Mainly VFR, isolated PM showers/storms.

Sun...Some improvement, as a series of cold fronts move
southeast of the area.

Mon...Mainly dry with VFR conditions. Perhaps a shower
early at BFD and JST, with MVFR CIGS early at these sites.

&&

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

&&

SYNOPSIS...Jurewicz/Banghoff
NEAR TERM...Jurewicz/Banghoff
SHORT TERM...Jurewicz/Banghoff
LONG TERM...Jurewicz/Banghoff
AVIATION...Banghoff/Martin

Hazardous Weather Outlook
National Weather Service State College PA
Issued by National Weather Service Binghamton NY
447 AM EDT Thu May 15 2025

PAZ028-037-041-042-046-049>053-056>059-063>066-160900-
Juniata-Tioga-Northern Lycoming-Sullivan-Southern Lycoming-Union-
Snyder-Montour-Northumberland-Columbia-Perry-Dauphin-Schuylkill-
Lebanon-Cumberland-Adams-York-Lancaster-
447 AM EDT Thu May 15 2025

This Hazardous Weather Outlook is for central Pennsylvania.

.DAY ONE...Today and tonight.

The probability for widespread hazardous weather is low.

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

Strong to severe thunderstorms with gusty winds are possible
Friday and Saturday. Isolated flooding may also occur. In addition
to typical afternoon thunderstorms, a few strong storms may occur
overnight.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to report significant hazardous weather.

PAZ004>006-010>012-017>019-024>027-033>036-045-160900-
Warren-McKean-Potter-Elk-Cameron-Northern Clinton-Clearfield-
Northern Centre-Southern Centre-Cambria-Blair-Huntingdon-Mifflin-
Somerset-Bedford-Fulton-Franklin-Southern Clinton-
447 AM EDT Thu May 15 2025

This Hazardous Weather Outlook is for central Pennsylvania.

.DAY ONE...Today and tonight.

Strong to severe thunderstorms with gusty winds are possible
late tonight into early Friday morning. Locally heavy rainfall from
thunderstorms could produce flash flooding.

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

Strong to severe thunderstorms with gusty winds are possible again
Friday afternoon and overnight. Flooding is possible in locations
that have had significant rainfall recently.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to report significant hazardous weather.