320
FXUS61 KPBZ 111206
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
806 AM EDT Thu Jul 11 2024

.SYNOPSIS...
Mostly dry weather with seasonable temperature is expected
today. Above normal temperature will return Friday into next
week while chances increase for periodically active weather
beginning Sunday.

&&

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

- Lingering cold advection may result in light precipitation in
  northwest PA.

- Most locations will be dry with seasonable high temperature
  and increasing afternoon sunshine.
-------------------------------------------------------------------

Residual low-level cool advection (mainly below the 700mb layer)
will support low probability light rain showers/drizzle and
stratus cloud coverage this morning across most of the forecast
area.

Lifting of an upper trough northwest through the day while a
residual sagging trough remains parked over the western Great
Lakes will favor dry weather and slow erosion of the stratus
deck. Area temperature will be near the daily average, though
locations north of I-80 may end of below average where stratus
erosion may be late enough to limit afternoon insolation.

High pressure will support a quiet overnight period with mostly
clear skies and light wind. Strong radiational cooling may favor
patchy river valley fog as a result, but probabilities of
widespread impact are low.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
KEY MESSAGES:

- Heat risks increase through the period due to rising
  temperature (though with more limited humidity rises).

- Ensembles favor dry weather.
-------------------------------------------------------------------

The Upper Ohio River Valley will generally remain positioned
between a weak upper trough over the western Great Lakes and
the Atlantic ridge. Even as tropical moisture encroaches from
the Carolina coast, high pressure and dry southwest flow will
maintain a quiet weather pattern for the region. The main
alteration is an influx of warm air that will raise area
temperature each day (50 to 80% probability of highs >= 90F for
Saturday). The lack of similar rises in area dewpoint will keep
the probability of a heat advisory low, but heat risks are still
a concern given the above normal temperature and bountiful
sunshine.

The only potential notable deviation during this period is low
probability showers/thunderstorms forming off a Lake Erie breeze
Saturday afternoon coincident with the passage of a weak
shortwave. Ensembles are pessimistic of this outcome, but a few
higher-res deterministic models offer hints worthy of a PoP
mention.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
KEY MESSAGES:

- Periodic thunderstorm chances return with potential for an
  active severe weather pattern.

- High confidence in continued heat risks to start the week,
  but trending downward based on potential convective
  alterations of environment.
-------------------------------------------------------------------

Ensembles favor a shift of the broad western CONUS ridge center
eastward Sunday through the middle of next week that will shift
the NW flow pattern towards the Upper Ohio River Valley. Though
variations in shortwave timing/strength/details exist,
confidence is increasing that a more activity weather pattern
will developing starting Sunday afternoon through the middle
next week as shortwaves drop through the NE quadrant of that
western CONUS ridge. Broadly, this pattern overtop a warm, humid
environment lends itself to a series of MCSs traversing the
Great Lakes region that are capable of producing severe weather
(typically in the form of damaging wind). AI severe weather
modeling continues to agree with this diagnosis and suggests a
potential for multiple rounds of thunderstorms capable of
producing severe weather. The catch, as many times as it can
be, is that convective expectations one day will likely be
influenced by storm evolution the day prior (and upstream).
Thus, it remains too early to be certain on any one period (or
multiple) that could pose the greatest risk.

Beyond that, ensembles favor well above normal temperature to
persist as surface flow should offer warm, moist advection. This
then offers a continuation of heat risk concerns through the
period. However, confidence is not high in this holding for many
of the same reasons above; convective evolution may offer
under-forecasted cloud cover and/or precipitation that limits
diurnal heating that won`t be well modeled at this time. Model
spread in max temperature highlights this by increasing spreads
between 25th/75th percentile outcomes. Due to the likely series
of thunderstorms and the influx of potential convective cirrus,
the temperature forecast was trended toward the 25th percentile
for Tuesday/Wednesday.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
A stratocu deck with predominantly MVFR cigs (locally IFR/LIFR
at FKL and DUJ) is ongoing this morning across most of western
PA and northeast WV, while much of eastern OH and the northern
WV panhandle has already cleared out. Expect these low clouds to
gradually lift and scatter over the course of the day, with VFR
anticipated at area terminals by roughly 16-18Z, with the
exception of course being FKL/DUJ where low clouds could linger
through 18-21Z before improving to VFR.

Ensemble guidance shows fog potentially building into the area
between roughly 08Z-13Z tonight. Current probabilities for MVFR
visibilities are highest (40-60%) generally around and
northeast of the PIT area in both the NBM and HREF. The HREF is
also more bullish about dense fog potential, showing
probabilities for visibilities <1 mi as high as 50-60% along and
north of I-80 compared to 20-30% in the NBM. Despite the low
probabilities in the NBM, leaned more towards dense fog in TAFs
at FKL/DUJ since those sites are typically more prone to fogging
in and calm winds and mostly clear skies should support
efficient radiative cooling.

Winds relax and veer to northwesterly throughout this afternoon
with perhaps a few gusts to 15-20 knots, followed by light winds
tonight becoming easterly Friday morning.

.Outlook...
Ensembles favor VFR prevailing through the weekend outside of
overnight/early morning patchy fog.

&&

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

&&

$$

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