798
FXUS61 KPBZ 120705
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
305 AM EDT Wed Jun 12 2024

.SYNOPSIS...
Continued dry weather and a warming trend is expected through
Thursday. Thunderstorms return on Friday. There is medium to
high confidence in a heat wave next week that may bring moderate
to major heat-related impacts.

&&

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

- Dry conditions and warming temperatures expected under
  building high pressure.

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

A fair amount of cirrus can be seen passing overhead on the
latest satellite imagery. This may impede the formation of
widespread fog this morning, though patches could still form
under any breaks in the clouds around sunrise. Any fog that does
form will dissipate quickly after sunrise with the onset of
diurnal heating and mixing. Dry weather and a warming trend in
temperatures are expected today and tonight as high pressure
builds over the region. High temps this afternoon will be
slightly above seasonal normals. Meanwhile, dry air and calm
winds support effective radiative cooling tonight, which should
still allow lows to dip down to or slightly below normal. Patchy
valley fog cannot be ruled out as well tonight, particularly in
and around river valleys.

&&

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

- Warmer temperatures expected, roughly 10 degrees above normal.
- A passing shower and rumble of thunder are possible Thursday
  night mainly north and northwest of Pittsburgh.

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High pressure shifts east of the area Thursday, allowing for
light southwest winds and subsequent warm air advection to set
up, resulting in daytime highs climbing to around ten degrees
above seasonal normals. An approaching disturbance and cold
front will result in increasing cloud cover and possibly a
thunderstorm or two late Thursday night, primarily for areas
north and west of Pittsburgh. Model soundings suggest elevated
marginal instability and mid-level dry air will be present,
supporting a low-probability (but non-zero) threat for hail and
strong straight-line winds, though overnight convection should
be elevated which would help temper the latter threat.

&&

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

- Thunderstorm chances return Friday along a passing cold front,
  primarily during the morning and afternoon hours.
- Growing confidence in a potential heat wave setting up early
  next week with moderate to major heat impacts possible.

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

The better chance for showers and storms will occur along the
cold front itself as it pushes through the area Friday morning
and afternoon. The timing of the cold front will be important,
as a faster/earlier passage will mean less available instability
as it moves through during the morning before peak daytime
heating. A slower/later arrival and passage would allow for
greater instability to develop ahead of the front, potentially
resulting in more intense thunderstorms in an environment that
will also see roughly 30-40 knots of 0-6km bulk shear. At this
time, the best chance for better instability (upwards of 1000
J/kg) will be in areas east and south of Pittsburgh. That said,
any storms along the cold front will carry at least some low-
end potential to become strong or severe. The primary threats
would be hail and damaging straight-line winds. The passage of
Friday`s cold front brings a brief "cool down" as highs Friday
and Saturday remain around or just a few degrees above normal
(down from the roughly 10 degrees above normal on Thursday). Dry
weather returns Saturday through the weekend as high pressure
begins to build back into the region.

Long range guidance has been consistent that a ridge will
continue to strengthen across much of the central and eastern
CONUS Sunday into at least early next week. This will quickly
bring hot temperatures back to the area through that time. There
is a growing concern that significant heat will be possible
with this anomalously strong high pressure ridge, especially as
we get into Monday and Tuesday. NBM probabilities for high
temperatures reaching 95+ degrees continue to go up, and are now
widespread 40-60% across the area, with pockets as high as 80%.
These higher probabilities are especially prevalent in lower
elevation areas (e.g., river valleys) and urban centers, which
tend to be warmer than surrounding areas. In addition, dewpoints
are currently forecast to remain in the mid 60s, which would
result in high enough humidity levels to support heat indices
climbing as high as 100 degrees. If these trends in guidance
continue, heat impacts will need to be closely monitored and
headlines may need to be considered.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
Valley and river fog has begun to develop tonight as calm wind
and efficient radiating under a broken shield of cirrus allows
for a cool airmass to settle over the relatively warmer waters.
It should remain confined to the valleys given the dry airmass
overhead with dew points in the 40s, but hi res ensemble
probabilities reach near 50% for VIS impacts down to IFR to
reach FKL/DUJ in the overnight hours. LBE may see periods of
MVFR but confidence is lower there. Elsewhere, VFR will prevail
with the SCT to BKN cirrus as upper moisture moves overhead.

Fog will dissipate by 14z and give way to a VFR day with light
westerly wind as high pressure establishes.

.Outlook...
VFR conditions are expected under building high pressure
through Thursday. Restrictions in showers and thunderstorms
return early Friday with another passing disturbance.

&&

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

&&

$$

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