PBZ issues Area Forecast Discussion (AFD) at Aug 1, 2:00 AM EDT328
FXUS61 KPBZ 010600
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
200 AM EDT Sat Aug 1 2026
.WHAT HAS CHANGED...
No significant changes were made to the forecast. A conditional
potential for severe storms and locally heavy rainfall continues
for Sunday.
&&
.KEY MESSAGES...
1) Continued dry through most of today
2) Showers and thunderstorms return tonight and Sunday, with
unsettled weather next week.
&&
.DISCUSSION...
KEY MESSAGE 1...
Shortwave ridging is expected to maintain dry weather for most
of the day as it slides east of the region. A shortwave trough
was analyzed across the Midwest this morning. Increasing
moisture ahead of this wave will continue to result in mid and
high level clouds streaming across the region today. Shower and
thunderstorm chances will begin to increase later this afternoon
across Ohio west of I-77 as a lead, initial shortwave approaches
in SW flow ahead of the main trough. Highs are expected to be
near seasonable levels.
KEY MESSAGE 2...
The lead shortwave is expected to cross the region tonight, with
some support from a relatively weak low level jet. Elevated
instability could maintain a couple of thunderstorms as well.
The latest HREF probabilities for am inch of rain overnight are
less than 10 percent across the region, though some signal for
some higher QPF is seen across NW PA.
Some decrease in coverage of showers and thunderstorms is
expected Sunday morning after the passage of the initial
shortwave, and as the low level jet weakens. The main shortwave
trough is progged to deepen into a stacked closed low through
the day Sunday, as it drifts across the Midwest and Ohio Valley
region. Most model guidance indicates a potential dry slot
between the initial wave, and the main trough. If some breaks in
the cloud cover develop, this could result in increased diurnal
instability, with more cloud cover resulting in the opposite.
Current ML CAPE projections generally range from 500-1500 j/kg,
depending on the amount of breaks in the clouds that occur.
0-6km shear is expected to range from 30-40kt, with the higher
values across Ohio. At the same time, a weak surface cold front
is expected to drift across the Upper Ohio Valley region, which
could be the focus for more numerous showers and thunderstorms
in the afternoon and evening.
The severe potential will be highly dependent on the amount of
clearing and destabilization that occurs. The region continues
under a Marginal Risk, or level 1 out of 5, for severe storms
Sunday afternoon and evening. This still appears reasonable
with the amount of uncertainty in diurnal destabilization. The
main hazard is expected to be damaging wind. PWATS are progged
to range from 1.6 to 1.8, which has trended downward slightly in
the most recent model guidance. Locally heavy rainfall is
possible, especially where any training would occur.
Showers and thunderstorms should continue into Sunday night as
the main shortwave trough drifts across the Upper Ohio Valley
region. The severe weather potential is expected to wane with
diminishing instability.
Ensemble guidance indicates the upper low will persist across
the Upper Ohio Valley region as it weakens through midweek. The
low/trough should exit the region by late week, though broad
upper troughing is expected to persist across the region through
late week. This pattern should result in mainly diurnally
driven, daily shower and thunderstorm chances.
&&
.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
VFR is expected through much of the day as high pressure moves
east of the region. Mid and high level clouds, ahead of an
approaching shortwave trough, will continue to stream across the
region through the day. A lead disturbance ahead of the main
trough should spread showers and a few thunderstorms across the
area tonight into Sunday morning. Included predominant showers,
with prob30s for overnight convection.
A decrease in shower and thunderstorm activity is expected
early Sunday, though low level moisture should result in some
MVFR cigs across the area.
Outlook...
Periodic restrictions in scattered to numerous showers and
thunderstorms are expected on Sunday, especially during the
afternoon and evening. Periodic shower and thunderstorm chances
will continue, especially during the afternoon and evening,
through midweek as an upper low/trough lingers across the Upper
Ohio Valley region. In addition, early morning fog and stratus
will be possible with low level moisture in place.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
DISCUSSION...WM
AVIATION...WM
Source:
PBZ issues Area Forecast Discussion (AFD) at Aug 1, 2:00 AM EDT---------------
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