393
FXUS61 KPBZ 260040
AFDPBZ

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

.SYNOPSIS...
Mainly dry weather is expected tonight. Strong to severe
thunderstorms will be possible Wednesday afternoon and evening
with a crossing cold front. Isolated flooding is also possible
with heavy rainfall. Temperatures will trend upwards into the
weekend.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
KEY MESSAGES:

- Mainly dry conditions are expected overnight, though light
  showers may be possible for some.
- Mild temperatures with increasing humidity overnight.

-------------------------------------------------------------------

Evening Update...
Convective-allowing models have backed off on the chances for
shower and storms overnight tonight in our area. The PIT 00Z
sounding shows a dry deep-layer profile and with no development
or even percolating occurring upstream, that solution is a bit
more believable right now than the alternative. As such, lowered
PoPs across much of the area at least through Midnight. Some
light shower activity could be possible on the fringes of our
area, primarily north of I-80 and over central/eastern Ohio,
during later overnight hours and into Wednesday morning.
Elsewhere, dry weather is expected tonight but mild temperatures
and increasing humidity as moisture gradually returns from the
west and dense cirrus prevents much radiative cooling.

Previous Discussion...
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 /6 AM WEDNESDAY MORNING 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 TUESDAY/...
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.
-------------------------------------------------------------------

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 /01Z WEDNESDAY THROUGH SUNDAY/...

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 increase shower and thunderstorm
coverage mainly after 18z on Wednesday, with showers then
continuing until cold frontal passage around 06z Thursday.
Confidence has increased in mainly dry conditions tonight
through most of Wednesday morning, so have removed prior mention
of showers and thunderstorms for that timeframe. There remains
some uncertainty with timing of storm initiation after 18z. Afternoon
storms will carry potential for damaging winds, large hail, and
possibly isolated tornadoes.

Southwesterly winds will diminish overnight, then gust 15-20kt
Wednesday afternoon. Wind become northwesterly Wednesday night
behind the front.

.Outlook...
Showers and thunderstorms will taper off Wednesday evening,
though MVFR to IFR ceilings will linger with cold FROPA. 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...Cermak/Hefferan
SHORT TERM...Hefferan
LONG TERM...Hefferan
AVIATION...Rackley/Frazier