487
FXUS61 KPBZ 171744
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
144 PM EDT Mon Aug 17 2026

.WHAT HAS CHANGED...
Updated aviation for 18z TAFs.

&&

.KEY MESSAGES...
1) One more day of scattered showers and a thunderstorm before
dry weather returns on Tuesday.

2) Rain chances ramp back up on Wednesday with a passing cold
front and could linger at least through week`s end.

&&

.DISCUSSION...
KEY MESSAGE 1...
A cloudy start to Monday with remnant moisture from Sunday`s
storms will stunt warming into the early afternoon hours.
Moisture will pool ahead of a southward sagging cold front,
really a dew point front, as a weak 700 mb wave slides along the
boundary this afternoon. This lift will be enough to spark off
scattered showers and a few thunderstorms within the plenty
moisture-rich airmass still in place on the warm side of the
boundary with dew points in the low 70s and PWAT value of 1.86
inches on our 12z sounding.

Modification of the profile to warm surface temperatures a few
degrees does suggest MLCAPE values nearing 1000 J/kg with effective
shear values in the 15-20 knot range, though with deep layer
moisture, the primary hazard today will be locally heavy downpours.
Cloud bearing wind vectors sit roughly parallel to the southward
moving boundary, so will have to watch for an areas that could sit
under a heavier shower or storm, but motion should be enough to
preclude a notable flood concern. HREF probability of >1" of rain in
an hour peaks at 40-60% south of Pittsburgh with a ~30% chance of
>2" total through tonight. Will especially keep an eye on areas hit
hardest in the past 24 hours (Wetzel and Marion Counties) where one
hour flash flood guidance ranges from 0.90 to 1.25 inches. Elsewhere
to the north of Pittsburgh, most of the day should be dry as
cool/dry advection in northerly flow is providing more of a fall
look to the satellite imagery with cooler 850 temps less than 10C
moving over a warm Lake Erie providing some low lake-induced clouds.
Those should also erode into this evening with increased mixing and
advection of much drier deep column air.

Tuesday will be dry areawide with quasi-zonal mid-level flow and
weak surface high pressure providing a comfortable mid-August day
with highs in the upper 70s and low 60s dew points.

KEY MESSAGE 2...
Our one day of relief from showers and storms quickly fades
into the past as yet another cold front moves through on
Wednesday. Return flow will pull better Gulf moisture back into
the local area again, though not to the extent we saw over the
past weekend, with ensemble mean PWAT values climbing back up to
~1.5" and dew points to the upper 60s. Right entrance region
jet dynamics and weak PVA will aid in synoptic ascent, and a 40+
knot mid-level jet increase deep layer shear. That said,
surface CAPE appears to be a primary limiting factor with NBM
mean around 300-600 J/kg and only getting to 1000 J/kg with the
90th percentile values contingent low probability clearing in
the morning and push of higher dew points. CIPS analogs is not
excited about any severe or flooding with the front, so we
shouldn`t be looking at any significant threat either way on
Wednesday.

The question beyond that point is the progression, or lackthereof,
of the front. Mid-level flow turns more zonal and subsequently more
parallel to the front suggesting it slows/stalls absent any
mechanism to give it a kick to keep moving. NBM dew point spread as
a proxy for boundary placement basically suggests it could stall
anywhere from I-80 to I-70, though ensemble clusters lean toward
slow progression south Thursday and Friday focusing the best rain
chances along and south Pittsburgh by the second half of the day on
Thursday. Obviously will have to watch for repeated rounds of
rain over the same areas, but generally weak forcing might lend
more toward scattered, diurnally driven showers and storms with
the highest coverage on Thursday afternoon as a shortwave tracks
across the boundary. NBM 90th percentile 24 hour totals sit
about as high as 1.75", so the rainfall totals ceiling should
be a bit lower than we`ve seen in the past week. Machine
learning pegs a lower end flood risk.

Said shortwave likely gives the stalled boundary the punch it
needs to exit our area by the weekend, though a troughy pattern
likely keeps us active with longer range AI & ML guidance
suggesting our next severe weather risk popping up on Saturday.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Weak cold front currently extends from roughly KPHD to KPIT to
KIDI and is drifting south. Airmass remains moist and marginally
unstable and a band of showers with a few rumbles of thunder are
along and south of the cold front as it sags slowly south.

Brief IFR visibility restrictions are expected with the showers
but things should improve by early evening with possible
exception of KMGW which may linger a bit longer.

Gradual clearing this evening will then likely set up for areas
of fog and stratus with IFR to LIFR expected at many of the
ports from 08 to 13z.


Outlook...
Other than early morning fog, VFR is then expected through
early Wed under high pressure. Restriction and shower/thunderstorm
chances expected Wed and Wed night with the approach and
passage of a cold front. VFR returns Thu and Fri under high
pressure.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.

&&

$$

DISCUSSION...MLB
AVIATION...Craven