874
FXUS61 KCTP 170840
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
440 AM EDT Thu Jul 17 2025

.SYNOPSIS...
* Scattered thunderstorms will form again this afternoon, mainly
  across the southern half of the Commonwealth; with a drier
  trend still anticipated for Friday into Saturday
* Heat risk peaks today; then a modest cool down with lower
  humidity levels as the week draws to a close

&&

.NEAR TERM /THROUGH TONIGHT/ ...
As we approach daybreak, small clusters of showers, with a few
embedded thunderstorms, are mostly traversing the eastern and
northern halves of the Commonwealth, in association with a
passing short-wave trough and a couple of smaller MCVs. We
expect a gradual decrease in coverage through the mid to late
morning hours, as most of the upper-level support shifts to the
north and east of PA.

Quite a bit of lower stratus clouds have formed across northern
PA early this morning, along with patchy areas of fog state-
wide, within a humid boundary layer environment. Lower clouds
and patchy fog will likely persist until mid-morning, before
starting to break up in response to daytime heating and better
vertical mixing.

We still expect a surface cool front to approach northwestern PA
by mid-afternoon, before pushing to the southeastern edge of the
state by later this evening. As this front encounters the hot,
humid, and unstable air mass out ahead of it, we do anticipate
that at least hit and miss thunderstorms will develop. In terms
of convective coverage, a couple of limiting factors appear to
be emerging. First. with the aforementioned short-wave having
shifted downstream, large-scale subsidence will be at odds with
low-level convergence along the surface cool frontal boundary.
Also, there is good model agreement that the column will dry out
significantly today, perhaps limiting the number of convective
updrafts that can form. As far as storm intensity is concerned,
there are factors at play which could favor localized
strong/damaging gusts, namely the aforementioned drying aloft
helping to enhance DCAPE values, as well as better environmental
wind flow as compared to recent days, featuring 35-40 kt flow
in the mid-levels. The excessive rainfall threat seems much
reduced today, with a lower precipitable water environment,
along with brisk cell motions to limit residence time in any one
spot.

Lastly, since our southern areas, namely the Cumberland and
Lower Susquehanna Valleys, will stay in a pre-frontal
environment the longest, it will become hot and humid this
afternoon. Since apparent temperatures will approach and locally
exceed 100f, we`ve decided to hoist a Heat Advisory from 11 am
to 8 pm.

Later tonight, as the aforementioned cool front pushes south
and east of the Commonwealth, any residual showers and
thunderstorms should quickly fade.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Friday is shaping to be a nice summer day, as a somewhat
cooler, and decidedly less humid air mass filters into the
region, accompanied by mainly sunny skies.

Dry conditions should persist Friday night into Saturday
morning, although clouds may be on the increase from southwest-
northeast, especially across the Alleghenies, as moist and warm
advection aloft already gets underway.

A returning surface warm front is expected to bring a renewed
threat of showers and thunderstorms Saturday afternoon and
Saturday night, particularly for areas west of about US-15 and
north of about I-80.

Although the air mass turns more muggy again Saturday, a good
deal of cloud cover should cap afternoon highs in the low-mid
80s range.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Once again, no significant pattern changes are on the horizon.
We`ll continue to see an elongated summertime upper ridge axis
from the southwestern Atlantic across roughly the southern half
of the CONUS, with an energetic northern stream near the
international border with Canada.

As for the daily sensible weather, recent medium-range model
guidance suggests that a shortwave trough within the above
mentioned belt of westerlies will amplify enough later this
weekend and early next week to help drive a surface cool front
down into the southern Mid-Atlantic. This would allow another
refreshing air mass to at least briefly build over the
Commonwealth later Sunday and Monday. Prior to that, though, the
passage of the cool front itself on Sunday should spark some
showers and thunderstorms.

Towards the middle of next week, longer range guidance is still
suggestive of the southern CONUS upper ridge flexing its muscle,
with accompanying height rises for PA signaling a gradual return
of heat and humidity, along with increased chances for
afternoon/evening focused showers and thunderstorms.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
06z update... Widespread lower stratus clouds, areas of fog, and
a few embedded showers, will lead to persistent IFR-fuel
alternate restrictions at KBFD, KJST, KUNV, KAOO, and KIPT
through 13-15z.

For KMDT and KLNS, although passing showers could bring brief
restrictions this morning, largely VFR is anticipated.

This afternoon and early evening, the influx of a drier and
better mixed environment will lead to primarily VFR area-wide.
Hit and miss thunderstorms are expected to form along an
incoming cool front, but any restrictions look brief. KAOO,
KMDT, and KLNS stand the best shot at having thunderstorms at
least in the vicinity.

Tonight, some post-frontal/upslope lower clouds could bring
IFR-fuel alternate restrictions for a time at KBFD and KJST.
Elsewhere, VFR should prevail for the central PA terminal sites.

S-SW surface winds around 5 kt early this morning, will shift
into the W this afternoon and increase to 12-15 kt, with gusts
into the 20s common. NW winds should diminish tonight to 5-8 kt.

Outlook...

Fri-Sat...Mainly dry through Saturday morning, with increasing
chances for afternoon/evening showers and thunderstorms.

Sun...Numerous showers and thunderstorms anticipated.

Mon...Dry conditions seem likely.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 11 AM this morning to 8 PM EDT this evening
for PAZ036-056-057-059-063>066.

&&

$$

SYNOPSIS...Jurewicz/Colbert
NEAR TERM...Jurewicz
SHORT TERM...Jurewicz
LONG TERM...Jurewicz
AVIATION...Jurewicz