577
FXUS61 KPBZ 130137
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
937 PM EDT Mon Aug 12 2024

.SYNOPSIS...
Surface high pressure will keep mostly dry conditions and
slowly warming temperatures in the forecast through mid-week.
Rain chances increase by the end of the week as a more unsettled
weather pattern develops.

&&

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

- Temperatures will remain near to below seasonal averages.
- Dry weather is forecast, with patchy valley fog north of Pittsburgh.
-------------------------------------------------------------------

Update...
Cumulus clouds have dissipated across the region as temperatures
fell below convective thresholds. Increased cloud cover some
overnight based on satellite, especially south of PIT, ahead of
an approaching shortwave trough. No other significant changes
were made for the late evening update.

Previous discussion...
Some mid and upper clouds may stream across locations mainly
south of Pittsburgh tonight, as weak shortwave energy rotates
through the approaching main trough axis. To the north, some
patchy valley fog will be possible due to relatively clear
skies, light wind, and the near to just below normal
temperatures expected.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/...
KEY MESSAGES:

- Temperatures will show a slow warming trend into midweek.
- An isolated shower or two is possible Tuesday, with a dry
  Wednesday.
-------------------------------------------------------------------

The main trough axis swings through the region on Tuesday. A
marginal moisture increase may be enough to help generate a few
light rain showers during the peak heating hours.  Still, the
presence of warm air in the mid-levels, as well as surface high
pressure providing subsidence, should keep this activity isolated at
best, as well as prevent the occurrence of thunder. Temperatures
may run a degree or two warmer as compared to today.

Forecast soundings on Wednesday indicate that a touch of warming
and drying will occur off of the surface due to mid-level
subsidence behind the departing trough. With high pressure still
in control at the surface, another dry day is forecast, with a
continued slow warming trend thanks to the rising 500mb heights.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
KEY MESSAGES:

- Dry and warm weather is forecast for Thursday.
- Forecast uncertainty increases toward the end of the week with a
  shift to a more active pattern.
-------------------------------------------------------------------

The upper trough axis will be off of the Atlantic Seaboard come 12Z
Thursday, putting the Upper Ohio Valley in northwest flow aloft
ahead of an advancing Great Lakes ridge, while surface high pressure
begins to depart. Cluster analysis shows good model agreement to
this point. One more dry day and a continued warming trend are
forecast with reasonably high confidence.

Thereafter, differences do start to increase among the ensemble
guidance, although the overall spread seems a bit less than
yesterday. The next trough advancing from the western CONUS is
expected to bump into the advancing ridge, and the models begin to
disagree on timing, as well as to the degree that the ridge is
impacted by the trough. Model clusters still show some variance,
depicting either quasi-zonal flow or troughing aloft into the
weekend, with ridging solutions becoming a bit less likely.
Nevertheless, the overall depiction shows a more active weather
pattern overall, with rain chances in the forecast for Friday into
early next week. The possible range of 500mb heights suggests that
daytime temperatures will generally remain near or just a touch
below normal through this period, while the active weather points to
minimums a bit above normal.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
VFR is expected for most airports through the TAF period. The
exception is FKL and DUJ, where IFR to MVFR river valley fog is
possible Tuesday morning. Otherwise, expect an increase in mid
and high clouds overnight ahead of an approaching shortwave
trough. In addition, a scattered to broken diurnal cumulus
layer is expected on Tuesday as convective temperatures are
reached, and as the shortwave crosses the Upper Ohio Valley
region.

The cumulus should dissipate by Tuesday evening, with mainly
clear skies expected under high pressure.

.Outlook...
VFR is expected through Thursday under high pressure. Periodic
restriction chances return Friday through the weekend with slow
moving low pressure.

&&

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

&&

$$

SYNOPSIS...22/MLB
NEAR TERM...WM/CL
SHORT TERM...CL
LONG TERM...CL
AVIATION...WM