486
FXUS61 KPBZ 031137
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
737 AM EDT Wed Jul 3 2024

.SYNOPSIS...
Shower and thunderstorm chances increase later today and the
risk will hang around through Friday as a series of upper level
disturbances cross the region. Expect well above normal
temperature through the holiday weekend, with dry weather
returning Saturday and Sunday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
KEY MESSAGES:

- Risk for scattered showers and storms increases later this
  afternoon.
- Well above normal temperatures.

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

The eastern ridge will flatten today as a couple of upper level
waves cross the region. The first will move across the north
late this morning and early this afternoon. Do not expect much
rain with the first wave as much of its energy will be used to
displace the ridge. It will likely bring an increase in high
clouds and cu. A second wave, further south of the first one,
will cross late this afternoon and evening. This wave should
spark scattered convection, moving it across Ohio late this
afternoon and reaching western PA by early evening. Latest CAM
models are showing an unorganized line of convection that
weakens as it moves eastward. This is mainly due to a lack of
surface based instability and a cap thanks to very warm air
aloft. There will be descent shear, so this will help to
strengthen updrafts if they can mature.

Warm air advection will be ongoing throughout the day which will
push high temperatures into the upper 80s to near 90 today.
Surface dewpoints will also be increasing, so it will get rather
muggy.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
KEY MESSAGES:

- Showers and thunderstorms possible tonight and Thursday, with
  low probability threat of severe weather.
- More widespread storm coverage expected Friday.

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

Isolated to scattered showers and storms remain possible tonight as
the shortwave exits northeast and a weak front sinks into
northern PA. Loss of heating should limit severe potential,
with storms continuing to rely on elevated instability.

Thursday will feature additional convection along a slowly
crossing boundary that may stall and somewhat washout over the
region late in the day. A shortwave will cross and help to push
the front southward, but it will be difficult with the zonal
flow aloft.

Localized flash flooding remains a concern given near-record
PWAT values and near parallel upper flow with the surface
boundary; however, marginal instability and weak lapse rates may
limit maximization of rainfall rates. Thursday evening will see
a downward trend in convective activity, with mostly isolated
to scattered storms generally south of I-70.

A stronger shortwave trough will enter the lower Ohio River
Valley Friday and promote broad jet-aided ascent for the
forecast area. This setup is likely to generate more widespread
shower and thunderstorm coverage Friday. Environmental
conditions remain variable amongst ensemble models but mean
SBCABE around 1000 J/kg, PWAT above 90th percentile, and
30-40kts 0-6km shear suggest potential for hazardous weather in
the form of damaging wind and flash flooding.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
KEY MESSAGES:

- High probability for dry weather and slightly above average
  temperature the rest of the weekend.

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

Long range patters suggest troughing will persist over the
Central Plains, leaving the Upper Ohio River Valley within weak
southwest flow (and likely within a dry slot). There is fairly
high confidence in dry weather and slightly above normal
temperature occurring Saturday through Monday until the next low
pressure system potentially crosses Tuesday.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
VFR is expected through most of today as the upper ridge over
the area begins to shift south. Southwest winds expected through
the day, with infrequent gusts up to 20kt developing after mid
morning and lasting through the afternoon.

Scattered showers and thunderstorms are expected this evening
with an approaching shortwave. Some uncertainty remains with
timing and coverage, so continued to carry VCTS. The most
favorable instability for storms should remain just west of the
area over central OH.

Hi-res ensembles depict high probabilities (>70%) for stratocu
development with MVFR/IFR cigs towards the tail end of the TAF
period (around or shortly after sunrise Thursday).

.Outlook...
Ceiling restrictions are expected Thursday morning along with a
few isolated showers. Additional rounds of showers and
thunderstorms (with occasional restrictions) are expected
Thursday afternoon through early Saturday as the front slowly
crosses. VFR should return Sunday under high pressure.

&&

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

&&

$$

SYNOPSIS...22/Frazier
NEAR TERM...22
SHORT TERM...22/Frazier
LONG TERM...Frazier
AVIATION...Cermak/Rackley