PBZ issues Area Forecast Discussion (AFD) at May 13, 8:21 PM EDT714
FXUS61 KPBZ 140021
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
Issued by National Weather Service Charleston WV
821 PM EDT Tue May 13 2025
.SYNOPSIS...
An upper level low will maintain periodic showers and
thunderstorms across the region today into tomorrow; heavy rain
will be the main threat. A cold front is expected to approach
and cross the region Thursday night into Friday, with strong to
severe storms possible.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
KEY MESSAGES:
- Showers continue today
- Thunderstorms possible for eastern Ohio and south of
Pittsburgh
- Slow moving and/or training thunderstorms could create minor
flooding
- Patchy fog expected late tonight into early tomorrow morning.
-------------------------------------------------------------------
Outflow from earlier convection over the ridges has spread
across much of the region. Despite warm cloud layers aloft,
thunderstorm activity has remained mainly concentrated over
eastern Ohio and areas south of Pittsburgh. This is partially
due to lingering dry air over central West Virginia. With
effective shear below 20kts and DCAPE values under 300J/kg
across the area, severe storms are not expected. The primary
threat will be lightning and heavy rainfall from slow-moving or
training storms.
While the duration of moderate to heavy rainfall has decreased
over the ridges, isolated thunderstorms passing through these
areas could still lead to minor flooding if rainfall rates
exceed 1 inch per hour.
Showers and storms are expected to persist through late evening
and into the overnight hours as an upper-level low gradually
lifts northward from the Tennessee River Valley into the Ohio
River Valley. High- resolution models show a decreased
probability of heavy rainfall between 9pm to 11pm tonight.
With warm, moist air lingering and light winds overnight, the
potential for fog increases. Areas most susceptible include
regions south of Pittsburgh, along the ridges, and in the
vicinity of where I-77 meets I-70.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH 6 PM WEDNESDAY/...
KEY MESSAGES:
- Probability of fog decreases between 8am and 10am
- Isolated showers expected early to early afternoon
- Late afternoon/late evening thunderstorms expected across the
region Wednesday
----------------------------------------------------------------
A moist atmosphere will allow fog to persist through 10am
tomorrow.
The previously mentioned upper-level low will remain over the
Upper Ohio Valley through Wednesday, bringing additional rounds
of showers from the early to late morning hours. However, due to
the lack of a strong lifting mechanism, shower coverage is
expected to remain isolated.
Thunderstorm potential increases across the region between 2pm
to 4pm Wednesday as surface heating aligns with an approaching
shortwave. Despite weak effective shear (10-20kts) and DCAPE
values below 500J/kg, heavy rainfall remains the primary threat,
with PWATs holding near 1.50 inches- above seasonal average.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
KEY MESSAGES:
- Addition severe storm potential on Friday
- Unsettled weather through the weekend
-------------------------------------------------------------------
A lead shortwave trough, ahead of a main central CONUS trough,
is expected to approach and cross the region late Thursday
night, along with its associated surface cold front. Speed and
directional shear is expected to increase with the approach of
the trough, as instability is maintained Thursday night. Severe
storms are likely to develop to the west of the region late
Thursday, tracking eastward Thursday night. The greatest
uncertainty is the amount of instability that remains across the
Upper Ohio Valley region overnight, which would impact the
severe weather potential. Some of the latest model data
indicates the potential that these storms could be maintained
well into the overnight hours.
Model ensembles indicate a trough will track slowly eastward
across the Upper Midwest to the Upper Ohio Valley region Friday
and Saturday. The surface front is expected to slow its progress
on Friday as the upper level flow becomes parallel to the front.
Enough instability and shear is expected again by Friday
afternoon, with additional strong to severe storms possible. The
morning convection could also have an impact on this potential.
The trough axis is expected to cross the region on Saturday,
with additional showers possible. Lower chances for showers are
expected on Sunday as the trough exits. A ridge building in
behind the exiting trough, and ahead of a Western CONUS trough,
should return dry weather to the region by Monday.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Largely stratiform rain is impacting the eastern ridges in
southeast flow, with IFR ceilings at DUJ. Stouter convection
remains near ZZV, where backbuilding storms west of the airport
linger, keeping TS in the observation. Other sites like PIT and
AGC remain dry, but with MVFR ceilings. Southeast gusts will
taper a bit later this evening.
Expect convection to weaken a bit past the 01Z/02Z timeframe as
instability wanes, tapering to more scattered showers/isolated
storms tonight as upper level low pressure approaches. Lingering
moisture will lead to ceilings dropping into the MVFR category
at least at most sites, with IFR most likely at FKL, DUJ, and
ZZV according IFR probs. Patchy fog may also be an issue,
depending on how much clearing may occur.
A brief period of scattering cloud coverage could set in, mainly
south of I-80, which would lead to improvement back to VFR at
several sites during the mid-0morning period. Showers and storms
will become more likely again by afternoon after 18Z as a
shortwave approaches. Added PROB30 for thunder at several TAF
sites.
Outlook...
Restrictions and periods of showers with afternoon
thunderstorms will continue into Wednesday before the upper
level low shifts east of the region. Brief VFR under ridging
Thursday will give way to a fast-moving low pressure system
Thursday night into Friday, with a chance for strong to severe
storms, resulting in restrictions.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...Hefferan
NEAR TERM...Hefferan
SHORT TERM...Hefferan
LONG TERM...Hefferan
AVIATION...CL
Source:
PBZ issues Area Forecast Discussion (AFD) at May 13, 8:21 PM EDT---------------
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