473
FXUS61 KPBZ 251911
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
311 PM EDT Tue Jun 25 2024

.SYNOPSIS...
Remnants of a mesoscale convective system may impact the region
after 1pm today. Heavy rain showers and sub-severe wind gusts
may occur. The threat for strong storms increases Wednesday
with a new disturbance.

&&

.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:

- Remnant showers from a mesoscale convective system is
  currently tracking through the region in eastern Ohio.

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A mesoscale convection system (MCS) continues to dive south,
within an elongated ridge. Precipitation chances have remained
west of Pittsburgh due weak instability. There was a brief
period of thunder near Coshocton/Muskingum County earlier, along
the edge of the MCS. However the threat has subsided and rain
showers remain.

With increasing cloud coverage from outflow of the MCS and
precipitation chances, temperatures north of I-70 will likely
trend near average. Areas south may trend 5 degrees above
average.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
KEY MESSAGES:

- Showers and thunderstorms are likely Wednesday with a new
  disturbance.
- All threats (flooding, tornadoes, hail, and wind) appear
  promising early afternoon through late evening.
- Storm Prediction Center continues to have a Slight Risk for
  portions of our region, Weather Prediction Center continues
  the Marginal risk for flooding.
-------------------------------------------------------------------

An ejecting shortwave out of the Midwest will regenerate showers
and storms Wednesday across the Ohio River Valley. A few storms
may be considered strong to severe if conditions permit,
damaging wind gust and hail will be the main threat. However,
the tornado threat is considered slightly above the
climatological average given directional and vertical wind
shear. Based on Hi-Res model ensembles, the joint probabilities
of bulk wind shear (>= 30kts) and instability (CAPE >= 500J/kg)
are elevated between the period of 1pm to 8pm Wednesday.
However, storms could evolve as early as 10am under a warm,
moist unstable air mass.

The severe threat will likely evolve into a flooding threat as
the day progresses, especially late evening with ongoing
convection. With PWATS well above the climatological average
(1.65" to 1.90") and training showers and storms under zonal
flow, swaths of 1 to 2 inches may occur across the region
Wednesday night. If these noted high amounts occur over urban
areas in a short time period, flash flood products will need to
be issued.

The severe weather and flash flood threat will likely decrease
after midnight as the shortwave tracks east.



&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
KEY MESSAGES:

- Dry, quiet weather is expected Thursday.
- Probability of above average temperatures increase Friday
  into Saturday.
- Shower and thunderstorm chances return Saturday into Sunday
  with a new disturbance.
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In the wake of Wednesday`s shortwave and associated front,
temperatures return to normal and dry conditions resume as high
pressure builds in across the region.

A warming trend in temperatures is forecasted Friday and into
the weekend as heights gradually rise, reaching about 588-590dm
by Saturday. If showers and storms are absent for a prolonged
period of time, apparent temperatures could range from 95F to
100F. However, confidence is still low on heat impacts given
long range ensembles tracking a new trough over the Great Lakes
and could stir strong to severe storms.

Dry conditions and near to slightly above normal temperatures
are forecast early next week as high pressure resumes control.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
An MCS will continue to weaken/move SSW of the region this
afternoon, with low probability for thunderstorm and moderate
rain shower impact at ZZV. Convective cirrus and VFR condition
is favored the rest of the afternoon and evening period as
subsidence maintains a stable environment.

An upper level shortwave will approach the area late tonight
into Wednesday with an associated surface cold front. Confidence
is high that this wave will help foster increased shower and
thunderstorm coverage between 15z-00z Wednesday. Confidence is
significantly lower on timing and progression of convection
starting as early as 09z. Available convective modeling shows a
large range of storm evolutions through this period as they
struggle to handle the altered environment the current Ohio MCS
is causing. TAF leans a bit into HRRR and HRW ARW modeling given
better handling on current weather; but variability in outcomes
for both storms and area restrictions is high.

.Outlook...
Showers and thunderstorms will taper off (with longer delay in
restriction improvements) with cold FROPA Wednesday evening.
High pressure and rising heights aloft is favored to support VFR
and dry weather Thursday/Friday.

The next upper level shortwave and surface cold front will
increase thunderstorm and restriction chances Saturday.

&&

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

&&

$$

SYNOPSIS...Hefferan
NEAR TERM...Hefferan
SHORT TERM...Hefferan
LONG TERM...Hefferan
AVIATION...Frazier