830
FXUS61 KCTP 161813
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
213 PM EDT Mon Jun 16 2025

.SYNOPSIS...
* Rain chances continue through Wednesday, with highest chances
  for locally heavy rainfall across western PA on Tuesday.
* A warming trend emerges for Wednesday and Thursday, fueling
  some potential for severe thunderstorms on Thursday.
* A brief drop in temperatures for Friday, with temperatures
  increasing steadily into the beginning of next week, with
  some heat-related concerns on Sunday and Monday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Current mesoanalysis continues to show fairly stable air over
central Pennsylvania as of 17Z/1pm EDT with light radar returns
over the Susquehanna Valley and light returns along the
Allegheny Front. The bulk of model guidance continues to outline
continued stable conditions into the evening hours, which will
continue to limit locally heavy downpours in any showers and
thunderstorms. Increased upper-level flow is also allowing for
showers to move relatively quick to those stationed over
Somerset County as (approximately) this time yesterday, thus
mitigating flood concerns for the bulk of central Pennsylvania
in the near-term. Scattered showers are still expected; however,
and focus on shower coverage later this evening will turn
closer to the Laurel Highlands with increasing low-level
moisture while coverage becomes lower across the Susquehanna
Valley.

Recent (12Z) HREF probabilities outline high (> 90%) chances of
fog formation across the higher elevations of central
Pennsylvania overnight, with easterly flow continuing overnight
and ample low-level moisture in place. As of Monday afternoon,
it`s likely too early to consider issuing fog headlines for the
overnight; however, given more expansive coverage tonight, some
potential will exist for a fog headline again this evening into
Tuesday morning. Temperatures under low clouds/fog will not
radiate as efficiently, with low temperatures overnight ranging
from the upper 50s across the northern tier to the lower 60s
across the Cumberland Valley.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
PWAT values begin to increase Tuesday and continue into
Wednesday with best forcing overhead as a surface boundary warm
front moves into southern Pennsylvania. Relatively warmer air
will work into the western half of the forecast area, allowing
for more instability in place than previous days on Tuesday and
Wednesday to allow for thunderstorm mentions across the western
highlands. Of note, shear has increased for Tuesday afternoon
across western Pennsylvania along a warm front with sufficient
instability and moisture in place to promote some severe threat
mainly in a corridor between I-99 and I-81 during the evening
hours with some potential continuing further east. At this time,
no mentions in the D2 SWO; however, would not be perplexing to
see a MRGL added in subsequent outlooks.

From a hydrology perspective, rainfall is expected to be
efficient across western Pennsylvania (where PWAT values
approach 1.75") which will bring into account flooding concerns
on Tuesday, outlined by WPC`s D2 MGRL ERO across the western
half of the area, with the SLGT risk encompassing portions of
southwestern Pennsylvania. Precipitation on Wednesday will be
stationed west of the area, thus limiting large-scale flooding
concerns.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Influence of the upper-level trough continues into the long-term
period before gradually drifting eastward by Friday. Period of
most interest in the long-term will be Thursday, especially in
the afternoon/evening hours with some severe potential in the
cards across much of central Pennsylvania. Low pressure
stationed across southern Canada with warm front stretched into
the northern Atlantic and a cold front stationed across the
Ohio Valley will allow for some residence time in the warm
sector ahead of an afternoon approach by a surface cold front.
Ample moisture will remain in place, with dew points in the
upper 60s to lower 70s across the eastern half of the forecast
area. This threat is also noted in the Storm Prediction Center
D4 Severe Outlook, with a 15% contour. Cold frontal passage
timing has stayed somewhat consistent in model guidance with
some wiggle room still in place for timing differences. At this
point, do want to outline that joint probabilities for
instability and shear parameters Thursday afternoon across the
Lower Susquehanna are on an upward trend (i.e. severe threat is
looking more plausible on Thursday).

Cold frontal passage brings in relatively dry conditions for
Friday with upper-level heights beginning to increase. Given
relatively dry air in the wake of the cold front, have undercut
NBM dewpoints slightly for the afternoon hours on Friday.
Diurnal showers and thunderstorms will remain in the cards for
the weekend, as temperatures trend well-above seasonal averages
with relatively humid conditions into next week. High
temperatures generally in the upper 80s (N PA) to the low-to-mid
90s (S PA) are expected on Sunday and Monday, with head index
values pushing close to the century mark for the first time this
calendar year. HeatRisk also is beginning to light up for heat-
related impacts on Sunday, with widespread moderate (level 2/4)
risk conditions with areas of the south-central mountains and
western Pennsylvania reaching into the major (level 3/4) risk
for heat-related impacts.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
High confidence in low-end MVFR to IFR/LIFR cigs persisting
into Tuesday morning across Central PA, thanks to a moist low-
level east/southeasterly flow off the Atlantic Ocean. Patchy
light rain and drizzle is possible as well, with cigs hovering
near or below alternate minimums.

Cigs may improve a bit across across the Laurel Highlands and
southern Alleghenies (JST and perhaps AOO) by Tuesday aftn, as
a warm front attempts to lift northeastward into the area.
However, this front will be accompanied by an increasing chc of
showers and t-storms from SW to NE across Central PA.

Outlook...

Wed...VFR/MVFR with showers and thunderstorms possible, as warm
front pulls north of area.

Thu...Predominantly VFR, although strong PM t-storms are
possible with a cold frontal passage.

Fri-Sat...Predominantly VFR, with a slight chance of a rain
shower north.

&&

.CLIMATE...
Astronomical Summer (solstice) officially arrives on Friday,
June 20, at 10:42 p.m.

&&

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

&&

$$

SYNOPSIS...NPB
NEAR TERM...NPB
SHORT TERM...NPB
LONG TERM...NPB
AVIATION...Evanego
CLIMATE...Steinbugl