915
FXUS61 KPBZ 142337
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
737 PM EDT Fri Jun 14 2024

.SYNOPSIS...
There is high confidence Sunday will be the start of a
particularly dangerous, historic, long- duration heat wave for
western Pennsylvania, northern West Virginia, and eastern Ohio.

&&

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

- Severe probability lowering as instability weakens with the
  loss of daytime heating.
- Patchy fog may develop within river valleys, notably south of
  Pittsburgh.
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630pm update...
The main areas of convection will continue to shift south and
east of the region ahead of the surface cold front. Lingering
passage of the front may still allow for isolated convection as
it provides enough lift with up to 1000 J/kg MLCAPE available.
Amid approximately 50kts of effective shear, a severe threat
(mainly wind and hail) remains possible but decreasing in
probability. Instability will continue to decline with the
setting sun and should allow for further erosion of the Severe
Thunderstorm Watch area this evening.

As dry weather and clearing skies develop tonight amid building
high pressure, there will be a battle between incoming drier
air/mixed wind and radiational cooling/boundary layer moisture.
Localized occurrences of fog may develop where the cooling and
residual moisture are maximized, likely favoring river valleys
south of Pittsburgh.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
KEY MESSAGES:

- Dry weather Saturday and Sunday.
- Near normal temperatures Saturday with a jump to 5-10 degrees
  above normal on Sunday.
-------------------------------------------------------------------

Heights rise into Saturday as upper ridging builds and surface high
pressure slides in to the north. Temps won`t rebound much in
northerly flow in the wake of the boundary and dew points will
likely mix out some in the afternoon with a dry boundary layer
providing a pretty comfortable day.

Upper ridging begins to build stronger making a run at 588-590dm by
Sunday to kick off the first day of increasingly hot conditions.
Surface high pressure establishes off to our east and southwest flow
on the west side of the 850 mb ridge axis will induce warm
advection with ensemble 850 temps up to 15-17C. This will
support widespread upper 80s with even a 40-70% chance of 90F+
for Pittsburgh south and west.

&&

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

- High confidence in a dangerous heat wave setting up early next
  week with major heat impacts possible.
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Guidance has been consistent that a potentially-historic ridge will
continue to strengthen across much of the central and eastern CONUS
into the middle of 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.

Significant heat is looking increasingly likely with this
anomalously strong ridge from Monday and beyond when major to
extreme heat risk is likely. NBM probabilities for high
temperatures reaching 95+ degrees continue to go up, and are now
widespread 60-90% across the area. 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 Monday and beyond (last time
at PIT was 7/15/95); NBM probabilities for that threshold are
now up to 60% on Tuesday with ~50% chance for the remainder of
the week. 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 at least a 594dm ridge through
June 22nd with the one exception being a lower probability solution
than the others. Return intervals of these heights dating back to
1979 are just about out of the climatological range. CPC suggests
that excessive heat may last through June 24th, indicating the
potential for a long-duration excessive heat threat. The last
comparable, long-duration heat event was from June 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 /00Z SATURDAY THROUGH WEDNESDAY/...
Isolated showers and thunderstorms will slowly move southeast
through 04z ahead of the surface cold front. After frontal
passage, localized areas of patchy fog may develop where rain
reinforced boundary layer moisture. This lends to KMGW and KDUJ
as the most plausible but some maintenance of mixed winds and
dry advection make it a lower probability occurrence.

VFR and dry weather with light northerly wind is likely the
rest of the TAF period with building high pressure.

.Outlook...
High probability for VFR and dry weather through the middle of
next week as strong ridging develops aloft. The only variance
may come with isolated afternoon convection starting Monday, but
upper ridging should suppress coverage and potential initiation.

&&

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

&&

$$

SYNOPSIS...Milcarek
NEAR TERM...Frazier/Milcarek
SHORT TERM...MLB/Milcarek
LONG TERM...MLB/Milcarek
AVIATION...Frazier