898
FXUS61 KPBZ 121928
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
328 PM 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 with near-average temperatures.

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

Surface southwest flow and upper ridging will bring daytime
highs today to near or a degree or slightly above seasonable
averages. Dry conditions and will persist under high pressure.
Boundary layer mixing has resulted in a a few high-based cumulus
which will diminish this evening as mixing is lost.

Overnight, skies will clear and temperatures will efficiently
cool in calm to light winds. This may result in patchy fog,
primarily confined to river valleys. Because of effective
cooling, lows will bottom out near or slightly below normal.

&&

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

- Temperatures about 10 degrees above normal Thursday will cool
  to just above average behind a cold front on Friday.
- There is a 1 out of 5 risk for severe storms, notably wind and
  hail Friday morning and afternoon.

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High pressure is expected to drift east of the area on
Thursday, allowing for an enhancement of southwest flow, while
ridging pushes 582dm heights across the area. THis will result
in daytime high temperatures around 10 degrees above average
for this time of year.

Overnight, a cold front will approach from the northwest. Pre-
frontal convergence ahead of the boundary with a couple hundred
joules of elevated CAPE may allow for a rumble of thunder late
Thursday night into early Friday morning. Initial convection is
not anticipated to be strong with poor timing and fairly deep
low-level saturation. A nocturnal inversion may keep any winds
elevated.

Through the morning, daytime heating will allow surface
temperatures to rise and dry air is also expected to increase
aloft as 500mb wind back behind a passing trough. The atmosphere
may approach around 1000 J/kg of instability ahead of the cold
front. Combined with 30-40kts of 0-6km bulk shear, this will
make large hail and wind possible, primarily south of I-80, and
more likely as you go south of I-70. The SPC maintains a 1 out
of 5 risk for severe weather as these storms go through, with
the most likely window being from noon to 6pm in southwest
Pennsylvania and northern West Virginia.

Behind the Friday cold front, a brief reprieve in temperatures
is likely as highs on Friday remain near-normal, while lows
drop to around or slightly below normal with efficient cooling.
Patchy valley fog is possible.

&&

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

- High confidence in a dangerous heat wave setting up early
  next week with moderate to major heat impacts possible.

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

Dry weather returns Saturday through the weekend as high
pressure begins to build back into the region. Saturday,
temperatures remain near-normal behind the cold front.

Guidance has been consistent that a potentially-historic ridge
will continue to strengthen across much of the central and
eastern CONUS Sunday into at least early next week. WPC ensemble
clusters are highly consistent through Tuesday, indicating high
confidence in the temperature forecast. Near-record breaking
heat will build in to start off next week.

Sunday will bring minor to moderate heat risk across the area.
Significant heat will be possible with this anomalously strong
high pressure ridge, especially as we get into Monday and
Tuesday, where major heat risk is likely. 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 to
lower 70s, which would result in high enough humidity levels to
support heat indices climbing as high as 100 degrees. Heat
impacts will need to be closely monitored and headlines may need
to be considered.

Three out of four clusters maintain at least a 590dm ridge
through June 21st, with CPC suggesting that excessive heat may
last through June 23rd, indicating the potential for a long-
duration excessive heat threat. The last comparable, long-
duration heat event was from July 1994.

Impacts include heightened heat- related illnesses and
potential power grid issues with increased demand. It is
strongly encouraged to know where cooling shelters are located
and stay hydrated. Gather food, water and medication now. Make a
list of friends and family to check on and help them prepare.
Strongly consider rescheduling outdoor events. Prolonged
exposure to excessive heat was the primary cause of weather-
related fatalities in 2023.


&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
VFR conditions are expected for the majority of the TAF period.
High pressure will be slowly departing but will remain in
control. Scattered to broken VFR cumulus will dissipate by
sunset with the loss of heating. Incipient warm advection
overnight may lead to patches of mid and high clouds through the
night and into Thursday morning.

Valley fog extent may be a little less tonight given that low
temperatures are expected to warm by a few degrees. Did hang on
to some TEMPO fog at LBE/MGW late tonight, but expect most
terminals to escape any fog impacts.

Southwest wind will blow at around 10 knots both today and after
mixing commences on Thursday, with light and variable wind at
night.

.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...Milcarek
NEAR TERM...Milcarek
SHORT TERM...Milcarek
LONG TERM...Milcarek/Cermak
AVIATION...CL