795
FXUS61 KCTP 121656
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1256 PM EDT Sat Jul 12 2025

.SYNOPSIS...
* Continued seasonably warm and humid through much of the coming
  week
* Although at least hit and miss, afternoon and evening focused
  showers and thunderstorms are expected through Monday, the
  most widespread activity, featuring locally heavy downpours,
  will be Sunday afternoon and evening
* Tuesday looks primarily rain free

&&

.NEAR TERM /THROUGH TONIGHT/...
Convection starting over the Laurels and Allegheny Plateau.
Marine layer which socked in the SErn third of the area this
morning is thinning and lifting. Expect deep convection to start
there soon, too. The weak forcing dropping down across NY will
help more SHRA/TSRA than Friday develop. Flow/shear is still
weak, and cell movement could be anyone`s guess, and are thus
far acting that way. The high PWAT values and sfc dewpoints will
make for more heavy-rainers than a worry for severe gusts today.
But, a taller core or two could produce a downdraft strong
enough to make a 40-50KT gust. Relatively low DCAPEs (400-600J)
and warm cloud argue against it, though.

Prev...
Clear-partly cloudy skies covered much of the Commonwealth early
this morning, with patchy areas of lower clouds and river valley
fog across central and northern portions of the state. Also,
some maritime origin lower clouds have slowly been backing into
the far eastern counties as we approach sunrise. A small
convective cluster, owing to low-level warm advection and some
short-wave support, was crossing eastern Lake Erie into western
NY, but expectations are that this area of showers and storms
will both weaken and stay north of the Commonwealth this
morning.

By mid-late morning, patches of lower clouds and valley fog are
expected to burn off, yielding hazy sunshine, very warm and
sticky conditions for much of the daylight hours Saturday.
Afternoon highs should range from the mid 80s over the higher
terrain, to the lower 90s in the typically warmer valleys of
south-central PA. Apparent temperatures could reach the mid-
upper 90s in some of these same valley locales.

Although PA will generally be in a synoptic environment
characterized by height rises aloft and a lack of focusing low-
level boundaries today, enough instability should bubble up for
widely scattered and terrain favored convection to form by
later this afternoon and early evening. We think that most of
the focus will be from about the Middle Susquehanna Valley up
into the Endless Mountains region. Although coverage should be
relatively isolated in the grand scheme, a seasonally sultry air
mass, weak shear, and slow/erratic cell motions could lead to
locally heavy rainfall, with point amounts of 2-3" suggested by
model probability matched mean values.

Later tonight, convective coverage should wane with diurnal
stabilization, although some of our high-resolution models are
suggesting that isolated activity could continue well into the
overnight. For now, we have fairly low probabilities (around
20%) for late night showers and storms.

It will be another sticky night, with lows ranging from the mid
60s over the higher terrain, to the lower 70s in the Cumberland
and Susquehanna Valleys.

&&

.SHORT TERM /SUNDAY/...
Model guidance remains consistent in depicting widespread
coverage of showers and thunderstorms for central PA Sunday
afternoon and evening, as a surface cool front approaches from
the west, along with some height falls aloft. Since the main
synoptic-scale westerlies are expected to remain well north of
the state on Sunday, creating a weak shear environment, any
severe concerns from localized damaging winds seem to take a
back seat to heavy rainfall considerations. Pooling of late day
and evening surface dew points (up to the mid 70s) from the
Susquehanna Valley up into the Endless Mountains region should
lead to columnar precipitable water values near 2". This,
combined with the potential for slower cell motions and training
from the aforementioned weak shear pattern, along with
sensitive antecedent soil conditions from recent rainfall,
raises concern for localized excessive rainfall. Model
probability matched means suggest point amounts of 2-3" and
given the above described pattern, up to 4" on a very localized
basis is not out of the realm of possibilities. We`ll continue
to highlight heavy convective rain potential in our Hazardous
Weather Outlook and briefing packages.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
The aforementioned slow-moving cold front will continue to
progress across central Pennsylvania Sunday night and throughout
the day on Monday, with current guidance progged to have the
surface cold front overhead by sunrise on Monday. Little
residence time in the warm sector will allow for less
destablization across the area, with dry air west of the cold
front allowing for drier conditions to prevail west-to-east as
the day progresses. Front pulls further east and out of the area
Monday evening into Tuesday morning, allowing for a brief
period of no precipitation across central Pennsylvania through
the morning hours on Tuesday.

As the cold front continues across central Pennsylvania on
Monday, PWATs in the 1.50"-2.00" range will continue to promote
some potential for isolated instances of flash flooding across
eastern Pennsylvania which remains consistent with WPC`s
Marginal Risk for Excessive Rainfall. Flooding potential will
also be exacerbated by antecedent rainfall, so will need to
continue to monitor rainfall trends through the weekend with
regards to the flooding threat on Monday.

Large-scale pattern remains fairly consistent; however,
allowing for continued chances for diurnally driven showers and
thunderstorms across central Pennsylvania throughout much of the
long-term forecast period. Focus for precipitation Tuesday
afternoon/evening will be stationed across the southern tier of
Pennsylvania with increasing coverage during the afternoon hours
on Wednesday, Thursday, and Friday.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
Low deck lifting and thinning now, and deep convection is firing
on the high ground. additional thunderstorms will be climbing up
through the next 6-8 hrs. Confidence levels are currently
running about 30-40% for the Susquehanna Valley TAF sites, so
either a PROB30 or TEMPO group was employed at KIPT, KLNS, and
KMDT. It is anticipated that coverage will be sparse enough
farther west to precludes its mention at KAOO, KUNV, KJST, and
KBFD.Confidence on storm motion is also very low. They will be
slow-moving.

Overnight into Sunday, we fully expect another marine layer
cloud deck to form and push inland. If anything, it could go a
little farther westward by early Sunday, with a low-level E-SE
flow in place for at least parts of the region. KLNS, KMDT, and
KIPT have high confidence (70-80%) of restrictions. We`re less
sure at KUNV and KAOO (30-50%), while low cloud development
seems unlikely at KJST and KBFD.

Outlook...

Sun...Numerous SHRA/TSRA developing ahead of a CFRONT.

Sun night-Mon...CFROPA; Widespread SHRA/TSRA, mainly southeast.

Tue-Wed...Mainly VFR. Isold PM TSRA poss, mainly south.

&&

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

&&

$$

SYNOPSIS...Jurewicz
NEAR TERM...Jurewicz/Dangelo
SHORT TERM...Jurewicz
LONG TERM...NPB
AVIATION...Jurewicz/Dangelo