388
FXUS61 KPBZ 130645
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
245 AM EDT Thu Jun 13 2024

.SYNOPSIS...
Dry weather with above average temperatures for Thursday ahead
of scattered thunderstorms on Friday with a passing cold front.
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 and mostly sunny with highs near 10 degrees above average.
- Slight chance of a shower north of I-80 after midnight.
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Light wind and a mostly clear sky will allow the surface to radiate
effectively overnight with again some patchy river valley fog
possibly in the pre-dawn hours. Hi res ensemble probability favors
south of I-70 and not as widespread as Tuesday night. Any fog will
quickly dissipate after sunrise.

Surface high pressure will drift to the east today. An increasing
gradient on its backside ahead of approaching low pressure will
induce a southwesterly wind with warm advection and a mostly sunny
sky pushing highs up to 10 degrees above average in the mid 80s.

Upper level clouds increase tonight as a cold front approaches from
the northwest. Ahead of it, a weak shortwave and surface trough may
try to drag some showers/a rumble of thunder north of I-80 just
after midnight, but latest hi res ensemble indicates a low
probability precip chance. Nocturnal timing with a developed surface
inversion should limit any wind threat, and MUCAPE is nothing to
write home about with poor mid-level lapse rates, so overall this
should be unimpactful.

&&

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

- Cold front will bring showers and thunderstorms on Friday with a
  Marginal Risk (1/5) for severe weather.
- Dry weather and near normal temperatures for Saturday.
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The aforementioned cold front will sag through during the day on
Friday with showers and thunderstorms developing along it. Its
likely arrival time to our northern counties in the morning hours
should preclude the bulk of any severe concerns north of Pittsburgh.
Even south of Pittsburgh, which will have more residence time ahead
of the boundary for daytime heating to drive instability, there`s
some uncertainty as to how much destabilization will be able to
occur with cloud cover moving in by the morning hours. Shear will
not be a hindering factor with probability for >30 knots of 0-6
km at 90%+. The severe threat will be highest south of
Pittsburgh where the chance for both 1000 J/kg of CAPE and 30
knots of shear is around 50-60%. Primary threats will be
damaging wind and hail, and we remain in a 1/5 risk for severe.
With ensemble mean precipitable water values nearing 1.4-1.5",
any shower or thunderstorm could bring a brief period of heavy
rain with it as well.

A renewed push of drier and cooler air will arrive in northwest flow
behind the front and drop lows Friday night to a couple ticks below
normal. Could see some areas of river valley fog develop. Heights
rise into Saturday as upper ridging builds and surface high pressure
establishes to the north. Temps won`t rebound much with the
northerly component to the flow in the wake of the boundary and
dew points will likely mix out some in the afternoon given the
dry airmass in place providing a pretty comfortable day. Enjoy
it... we won`t be saying that again for a while.

&&

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

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

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 as
surface high pressure establishes off to our east. Significant
heat will be possible with this anomalously strong ridge,
especially Monday and beyond, when major heat risk is likely.
NBM probabilities for high temperatures reaching 95+ degrees
continue to go up, and are now widespread 50-70% 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 to,
and potentially exceeding, 100 degrees. If dew points do hold
toward the lower end of that spectrum, we may be able to make a
run at 100 degree air temperatures (last time at PIT was
7/15/95); NBM probabilities for that threshold are now up to
50% in spots. Only acting to exacerbate the prolonged heat
effects will be a 60-80% chance of low temperatures greater than
70 degrees through the end of the week. Heat impacts will need
to be closely monitored and headlines may need to be considered.

Three out of four clusters maintain a 594dm ridge through June
21st with the one exception being a much lower probability
solution than the others. CPC suggests 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. There may be little relief at night. 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 /07Z THURSDAY THROUGH MONDAY/...
Slowly departing high pressure will keep general VFR conditions
in place through the TAF period. The exception may be patchy
river valley fog, though warmer overnight temperatures will
limit coverage. The most likely terminals to experience vis
restrictions will be FKL/DUJ.

Light and variable winds overnight will becoming southwesterly
at around 10 kts with daytime mixing.

.Outlook...
Restrictions in showers and thunderstorms return early Friday
with another passing disturbance.

&&

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

&&

$$

SYNOPSIS...MLB
NEAR TERM...MLB
SHORT TERM...MLB
LONG TERM...MLB/Milcarek
AVIATION...Rackley/22