845
FXUS61 KCTP 220938
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
538 AM EDT Mon Jun 22 2026

.WHAT HAS CHANGED...
Level 2/5 severe T-storm risk expanded over the southern tier
of central PA for this afternoon and evening

&&

.KEY MESSAGES...
1) Scattered severe thunderstorms with locally heavy rainfall
are possible across the southern tier/third of central PA this
afternoon and evening

&&

.DISCUSSION...
KEY MESSAGE 1: Scattered severe thunderstorms with locally
heavy rainfall possible across the southern tier/third of
central PA this afternoon and evening

Steady warm advection rain has expanded across the northern
tier early this morning. This leading edge rain is likely tied
to 850mb wind max downstream of dampening mid level shortwave
trough/remnant MCV in the Ohio Valley. Hires guidance focuses
mean QPF in the 0.50-0.75 inch range to the north of I-80
through 18Z with local rainfall amounts possibly exceeding 1
inch by early afternoon.

Attention shifts to the south this afternoon and evening as
a warm front will lift north of the MD line to a position
somewhere between I-80 and US-22. Sfc dewpoints are projected to
surge into the upper 60s to the south of the warm front where
some cloud breaks should allow for at least modest destabilization.
The moderately sheared and conditionally moist/unstable convective
environment should promote scattered t-storm ignition into peak
diurnal heating. The initial storm development is expected to
evolve into forward propagating clusters with a strong to
locally damaging wind threat. As convection intercepts the
northward moving warm front over the southern tier of CPA,
locally backed flow and more favorable low level shear may
support the development of at least transient supercells with
some tornado potential. SPC has expanded the level 2/5 slight
risk to include the entire southern tier/third of CPA (areas
near and south of US-22) along with corresponding severe wind
and 2% tornado probs.

Heavy rainfall will also be a concern with pwat values between
1.5 and 2 inches. This is around the 95th percentile for this
time of year and would support intense rain rates perhaps as
high as 2-3"/hr. A warm cloud depth in excess of 11,000 feet
and tall, skinny CAPE profiles also support a heavy rain signal.
WPC has maintained a level 2/4 slight risk for excessive
rainfall (ERO) over roughly the southern third of the forecast
area where isolated instances of flash flooding will be
possible, particularly in training/repeat storms over urban
areas. The two limiting factors going against a more considerable
flash flood threat are the ongoing dryness/drought conditions
focused over the LSV and fairly progressive storm motions.

-----------------------------------------------------------------

Much drier conditions are expected for Tuesday and Wednesday as
high pressure builds into Pennsylvania. A slight warming trend
is expected, with high temperatures expected to be in the 70s
and low 80s through the end of the week. An upper level
disturbance moving through the region on Thursday and Friday
will bring the next chance for showers and thunderstorms to
Central PA, though there are still some timing differences in
the models as to when rain will be most likely.

Temperatures continue to warm up into the weekend, with most of
the area expected to see highs in the 80s by Sunday. A major
pattern change upstream over the Pacific/Intermountain West this
weekend could spell a return of more typical hot and humid
conditions to close out June and begin July.

&&

.AVIATION /09Z MONDAY THROUGH FRIDAY/...
Low pressure over the Lower Ohio Valley early today will move
northeast this morning and reach South-Central PA by early this
evening.

Rain associated with warm air advection (WAA) ahead of this low
will continue to move ENE and expand across the NW half of PA
this morning.

Initial lack of any appreciable SFC or ML instability will
support showers of varying intensity and mainly VFR flying
conditions prior to 16Z.

SHRA/TSRA becoming more numerous through the midday and
afternoon hours. Embedded thunderstorms are possible within the
WAA rainband as overrunning warm/moist air introduces
instability within the mixed-phase layer (~50 J/kg MUCAPE
between -10C to -30C), enabling lightning production.

Ceilings will trend lower during the daylight hours today as the
aforementioned low tracks over the Commonwealth &
showers/storms grow more widespread, with lower confidence in
ceiling restrictions across the Lower Susquehanna Valley
(KMDT/KLNS) deeper into the warm sector.

Restrictions in visibility will become likely with the passage
of any heavier showers/storms this afternoon as precipitable
water values climb to anomalously high values (PWATs >1.5")
supporting locally heavy rain, especially where 2 or 3 TSRA
train over the same area.

Another factor to flight ops will be LLWS as a result of a
fairly strong southerly/southwesterly LLJ ahead of the system,
High confidence of lower cigs and vsbys at KBFD/KJST at this
time.

Lastly, Convection-Allowing Models (CAMs) suggest a line of
thunderstorms may develop along a pre-frontal trough this
afternoon, with potential impacts at KMDT/KLNS between roughly
18Z-21Z.

Decent deep-layer wind shear (0-6 km shear around 40 kts) +
adequate instability (MLCAPE between 750-1000 J/kg) will support
organized convection with this trough, along with the
possibility for gusty winds and perhaps some locally severe
weather.


Outlook...

Tue...Lower chances of showers, mainly VFR.

Wed...Mainly VFR, watching for precipitation chances though in
the evening/overnight.

Thu...Restrictions possible in another round of
evening/overnight.

Fri...Restrictions possible in another round of daytime/evening
showers.

&&

.CLIMATE...
5th driest June 2026 (MTD) on record (of 132 years) at
Williamsport with total monthly precip 0.73"

9th warmest average high temperature of 84.4 degrees at
Harrisburg for June 2026 (MTD) on record (of 138 years)
10th driest June 2026 (MTD) on record at Harrisburg with total
monthly precip of 0.58"

&&

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

&&

$$

WHAT HAS CHANGED...Steinbugl
KEY MESSAGES...Steinbugl
DISCUSSION...Steinbugl
AVIATION...Lambert/Teare
CLIMATE...Steinbugl