484
FXUS61 KCTP 171917
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
317 PM EDT Fri Jul 17 2026

.WHAT HAS CHANGED...
* Severe thunderstorm risk upgrade to level 3/5 (Enhanced) for
  Saturday afternoon through Saturday evening

&&

.KEY MESSAGES...
1) Wildfire smoke will result in unhealthy air quality and
reduced visibility today and into early Saturday

2) Severe thunderstorms with damaging winds and heavy rainfall
are possible Saturday afternoon through Saturday evening

&&

.DISCUSSION...
KEY MESSAGE 1: Wildfire smoke will result in unhealthy air
quality and reduced visibility today and into early Saturday

Visible satellite shows main smoke layer over the southwest
quadrant of the CWA this afternoon. Hires model data shows this
layer slowly pivoting and retreating to the north/east late
tonight through early Saturday as the mean flow shifts to the
southwest. The worst/unhealthiest air quality will impact the
area from this afternoon through early Saturday morning before
conditions improve by Saturday afternoon.

Statewide code PURPLE Air Quality Alert for July 17th

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

KEY MESSAGE 2: Severe thunderstorms with damaging winds and
heavy rainfall are possible Saturday afternoon through Saturday
evening

SPC upgraded most of central PA to level 3/5 severe t-storm risk
driven by 45% damaging wind probability.

As the smoke clears, scattered to numerous thunderstorms are
forecast Saturday. The latest model projections support an
increasingly favorable severe storm environment including
strengthening deep layer wind fields and rich low level
moisture. A remnant surface front initially draped from southern
NJ into western PA will lift northeastward as an effective warm
front, in advance of a cold front trailing low pressure
tracking across southern Quebec toward northern Maine.

The departing/exiting smoke layer would be helpful in allowing
for strong diurnal heating and moderate instability. However,
it`s unclear how much early day, warm advection/elevated
convection and associated cloud cover will complicate future
convective rounds during the afternoon and evening hours. Should
adequate clearing/heating occur, steep low level lapse rates on
sounding profiles will support a rather favorable wind damage
threat. In addition to the wind-damage threat, some hail and
tornado potential may also evolve with any supercell
development, particularly in the vicinity of the warm front
given the presence of favorable effective SRH. The southward
advancing cold front should be a catalyst for second or third
round late day/evening storms with duel wind/tornado threat
especially near remnant outflow boundaries.

Southwesterly low-level flow ahead of the front will transport
a high PW (>2") airmass into CPA. Strong synoptic forcing,
driven by an amplifying trough over the Northeast and favorable
upper jet dynamics, and deep warm-cloud depths will support the
potential for very heavy rain rates to produce isolated flash
flooding concerns. WPC has kept all of central PA in a level 1/4
MRGL excessive rain outlook for Sat PM. Some considerations
were discussed for potential flood watch with PHI/LWX, but
decided to hold off for now given fairly progressive storm
motions and somewhat localized spatial FF risk.

A drying trend is expected Sunday with noticeably lower
humidity allowing for a pleasant day and relatively cool night.
However, latest RRFS shows some near sfc smoke returning to CPA
from the Great Lakes. This could result in reduced air quality
and hazy sky conditions.

Additional bouts of rain/t-storms are possible into the
workweek. The next severe wx focus will be on Tuesday 7/21 with
SPC already highlighting a 15% prob (equivalent to SLGT risk
level 2/5). Forcing for this medium range severe outlook appears
fairly robust and would take stock in this risk manifesting at
shorter ranges.

Temperatures will trend near to slightly below historical
averages through late week into month-end with some noticeably
cooler nights possible.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
Ongoing visibility restrictions due to wildfire smoke
(primarily MVFR-IFR) will gradually extend back into our
northern/eastern terminals (KBFD/KIPT) as light winds trend
southwesterly ahead of a system moving across the Great Lakes.
These winds will increase to around 10 kts through Saturday
morning, allowing for the plume of smoke to fully push northeast
of our area by the afternoon. A return to VFR is expected once
the smoke is scoured out, with exceptions being temporary
restrictions in any heavier showers/thunderstorms that develop
tonight/tomorrow, along with possible MVFR ceilings in the
morning and afternoon given increasing moisture & cumulus field
development.

Later tonight and into Saturday morning, a cluster of showers
will develop along the leading moisture edge (PWATs increasing
to 1.5"-2.0") as moisture filters in out ahead of the Great
Lakes system, with a few thunderstorms being possible as this
activity progresses west to east across the Commonwealth.
Additional thunderstorms will develop within the warm sector of
this system across our region Saturday afternoon and evening,
some of which may produce gusty winds, heavy rain, and flight
restrictions.

Outlook...

Sun...Lingering -SHRA with restrictions possible early (primarily
driven by low ceilings), with VFR favored otherwise.

Mon...Mainly VFR.

Tue-Wed...Restrictions possible in showers/t-storms with cold
FROPA expected between Tuesday/Wednesday.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Air Quality Alert until midnight EDT tonight for PAZ004>006-
010>012-017>019-024>028-033>037-041-042-045-046-049>053-
056>059-063>066.

&&

$$

WHAT HAS CHANGED...Steinbugl
KEY MESSAGES...Steinbugl
DISCUSSION...Steinbugl
AVIATION...Teare