451
FXUS61 KCTP 201644
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1244 PM EDT Mon Jul 20 2026

.WHAT HAS CHANGED...
* Severe storms Tuesday afternoon and evening are highly
  probable.

* Smoke today will be mainly over western PA

&&

.KEY MESSAGES...
1) Severe thunderstorms are a near-certainty for Tuesday
afternoon and evening. Some areas of flash flooding are also
expected.

2) Thicker wildfire smoke should stay mainly over western PA,
with levels barely noticeable in the east.

&&

.DISCUSSION...
KEY MESSAGE 1:  Severe thunderstorms are a near-certainty for
Tuesday afternoon and evening. Some areas of flash flooding are
also expected.

Severe weather is once again on the slate for Tuesday afternoon
and evening as an amplifying upper level trough heads SE across
the Great Lakes region and a strong, sub-1000 mb sfc low (just
south of James Bay Canada Tuesday afternoon) pushes a potent
cold front SE across PA late Tuesday/early Wed.

Tuesday (Day 2) has been consistently highlighted by SPC for
many days as a potentially active and dangerous weather day. The
threat for damaging wind is near certain, and could occur
anywhere over the CWA Tuesday afternoon and evening. The threat
for hail is higher than it was this past Saturday, and the
threat for tornadoes is about the same, with a mix of
supercells and line segments with mini bow echoes.

Warm air will surge northward Tuesday morning on an increasingly
anomalous S/Swrly flow in the 925-850 mb layer.

Some showers and weaker storms will roll through southern and
eastern PA late tonight in the vicinity of a warm front and/or
lee trough, perhaps helping to raise dewpoints.

It looks like a pre-frontal trough will charge in from the NW
and cross the CWA in the afternoon hours. The real cold front
will arrive in NW PA later in the evening/early Tuesday night.
It may arrive too late (some stabilization could already happen)
and have little left to work with by the time it gets into the
CWA to make much of a severe threat.

There is also a threat for localized flash flooding, but only
in places that receive multiple rounds of heavy rain. There
should be a fairly fast movement to the storm cells (ENE at
about 40 kts), limiting the threat somewhat. However, moisture
is expected to be very high, PWATs 1.5-2".

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

KEY MESSAGE 2: Thicker wildfire smoke should stay mainly over
western PA, with levels barely noticeable in the east.

An air quality alert/action day remains in effect for most of
southwestern PA where levels are expected to be unhealthy for
sensitive groups. HRRR smoke plume progs keep the thicker smoke
over western PA with much less over the east. The light wind
this morning will turn from easterly to southerly through the
day which will help to keep the near-sfc smoke from spreading
to the east.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
Mostly clear skies and dry conditions means VFR is expected to
prevail for the next 24 hours across much of Central and Western
PA airfields, while some lower MVFR cigs in showers and TSRA are
expected to move south to north across the Susq Valley and
points east late tonight/Tuesday morning as the axis of a
strengthening southerly LLJ shift east into that area.

Smoke will once again flow into central PA from the north today
and be present through this afternoon. Density of this smoke is
expected to be much lighter based on output from the HRRR/RRFS
models (which have the ability to model smoke), this smoke will
linger through at least tomorrow while still being too light to
bring visibility restrictions.

Outlook...

Tue-Wed...Brief restrictions possible in showers/t-storms with
cold FROPA expected between Tuesday/Wednesday. T-storms more
likely on Tuesday, with lingering showers possible Wednesday.

Thu-Fri...VFR Conditions.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Air Quality Alert until midnight EDT tonight for PAZ024-033.

&&

$$

WHAT HAS CHANGED...Lambert/Dangelo
KEY MESSAGES...Lambert/Dangelo
DISCUSSION...Lambert/Dangelo
AVIATION...Lambert/Bowen