PBZ issues Area Forecast Discussion (AFD) at Jul 11, 7:21 AM EDT
666
FXUS61 KPBZ 111121
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
721 AM EDT Sat Jul 11 2026
.WHAT HAS CHANGED...
Areas south of I-70 were included in a Marginal Risk for severe
storms this afternoon. Otherwise, no major changes were made to
the forecast.
&&
.KEY MESSAGES...
1) Isolated to scattered showers and thunderstorms today, more
numerous south of I-70
2) Dry and warm for much of the upcoming week
&&
.DISCUSSION...
KEY MESSAGE 1...
A cold front was analyzed from west central PA to central OH.
This front will drift southward today, as another shortwave
tracks across the Ohio Valley region. Scattered showers and a
few thunderstorms are expected to develop along and ahead of the
front through the day, with the most numerous coverage south of
I-70. ML CAPE is progged to be around 1000 j/kg south of the
I-70 corridor, tapering off to lesser values to the north. 0-6km
shear is also expected to remain from 20-30kt, keeping the
potential for severe storms low. The Storm Prediction Center has
included some areas south of the I-70 corridor in a Marginal
Risk, or level 1 out of 5, for damaging wind gusts with any
storm that is able to maximize the steeper lapse rates in the
afternoon.
PWATs are expected to be lower than yesterday, reaching 1.6
inches for areas south of I-70. HREF FFG exceedance
probabilities, and 12 hr max precip, indicates the highest
potential for flash flooding just south of the forecast area,
though some localized flash flooding will be possible south of
the I-70 corridor this afternoon into early evening. Because of
the uncertainty in convective coverage, the lower probabilities
of exceeding flash flood guidance, and a relative lack of heavy
rain in much of this area yesterday, did not issue a flood
watch at this time. Will monitor for any changes in this
potential. Areas to the north should see some dry advection
today, with PWATs decreasing to 1-1.4 inches. In addition, dry
air aloft could also at least somewhat limit the potential for
showers/storms.
The flow aloft is progged to veer to the NW this evening, which
should accelerate the southward speed of the surface front.
Shower/storm chances should quickly diminish this evening with
the exiting front.
KEY MESSAGE 2...
Model ensembles indicate a strong ridge across the central CONUS
will shift eastward through mid to late week. Rising 500 mb
heights and subsidence under the ridge should result in dry and
warmer weather through much of the week. The peak of the warmth
is expected to be on Wednesday, when the highest 500 mb heights
are across the region. Highs should reach around 90/lower 90s
for most locations outside of the higher terrain. A gradual
decrease in temperatures are then expected by late week as the
ridge begins to break down, and NW flow aloft develops. There is
some chance for showers/storms by Friday into Saturday with any
disturbances embedded in the flow.
&&
.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
The onset of diurnal heating/mixing will lift IFR/LIFR stratus
and fog towards VFR by 18z this afternoon, with some variances
in timing as well as varying degrees of MVFR cu development.
Enough upper forcing to the south with residual area moisture
should yield another round of thunderstorms capable of gusty
wind (25-35kts) and heavy rain (dropping vsbys to 1SM or less)
for terminals south of I-70 (ZZV/MGW). Isolated storms can't be
ruled out north of this line but confidence in development and
positioning is too low for stronger mention beyond VCSH
(PIT/AGC/BVI) or a limited prob30 (HLG/LBE).
Subsidence and building high pressure favors VFR for most of the
overnight period; lingering near-surface moisture where dry
advection is too late to arrive may allow for another early
morning stratus/fog period (favoring LBE/MGW/ZZV).
Outlook...
High confidence in widespread VFR by Sunday afternoon under the
influence high pressure. Outside of localized river valley
morning fog, these conditions persist through at least mid
week.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
DISCUSSION...WM
AVIATION...Frazier
Source: PBZ issues Area Forecast Discussion (AFD) at Jul 11, 7:21 AM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202607111121-KPBZ-FXUS61-AFDPBZ)
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