975
FXUS61 KPBZ 210827
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
427 AM EDT Fri Jun 21 2024

.SYNOPSIS...
A dangerous heat wave will impact the region into the weekend.
A Heat Advisory and Excessive Heat Warning are in effect through
Saturday. This event is highly unusual for our region and could
be worse than the 1994 heat wave. Isolated afternoon
thunderstorms may pose a damaging wind threat today and Saturday
mainly north of Pittsburgh.

&&

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

- Dangerous heat continues through Saturday with little relief at
  night.
- Excessive Heat Warning and Heat Advisory remain in effect
  through Saturday.
-------------------------------------------------------------------

The muggy and warm air mass in place will continue this morning
with lows still above 70 and some patchy, dense at times, fog in
place. Heading into the day, the heat dome in place will
continue and become the main catalyst in potential storm
development today. Current trends show the upper ridge shifting
slightly leaving a noticeably weaker cap in play today. With MU
CAPE values this afternoon topping near 1500-2000 J/Kg, most
likely, convection will initiate to the northwest along the
lake breeze and outflow into the northern PA counties initiating
storms mainly north of Pittsburgh. Thus once again, the main
threat will be wind and a Marginal risk is in play today. It is
also worth mentioning that popular convective allowing models
show little to no initiation today. However, an outflow thrown
off from a distant storm in OH is all it takes. As the case for
the past week, the heat will be oppressive in between storms
even worst after a storm passes increasing humidity.

For tonight, with high confidence in lows remaining >70, this
will provide little relief from the heat at night. Considering
heat effects will be cumulative, the weekend looks
compoundingly dangerous. The early season event, and
temperatures increasing, will exacerbate any existing heat
issues.

For the day on Saturday, the upper ridge in place for one last
gasp and much warmer temperatures, there stands the chance for
the cap to remain intact on Saturday and as such, the SPC has
only included a few counties in the northeast in a Marginal. NBM
probs for Saturday drop off a bit with pops around 25% to 35%
and mainly in the north for Saturday. Still, will at least
mention thunderstorm chances but confidence is low on severe
potential at this time for Saturday.

Potential impacts include heightened heat-related illnesses and
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. Make a list of friends and family to
check on and help them prepare. Prolonged exposure to excessive heat
was the primary cause of weather-related fatalities in 2023. For our
region, this heat wave may be compared to our worse than June of
1994. Please see the Climate section below for more numerical
details on the kinds of records that may be in jeopardy.

&&

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


- Relief from the heat favored with a passing trough over the Great
  Lakes Sunday into Monday.
- Cold front will return precipitation chances as well as a
  severe potential Sunday into Sunday night.
-------------------------------------------------------------------

By Saturday night, the pattern begins to shift as the ridge over
the region begins to flatten over the Great Lakes and Northeast.
This will begin to usher in a period of change as the pattern
shifts to a cooler pattern. Its quite possible that still warmer
temperatures during the day will lead to low temperatures
Saturday night greater than 70 degrees. NBM probs suggest this
is the case at least in OH, where 50% to 70% chance of low
temps above 70 degrees.

By Sunday, the first solid cold front in quite awhile drops
southeast across the Great Lakes and Upper OH Valley. This
forcing takes aim during the afternoon and evening around prime
peak heating. NBM probs suggest a 60% to 70% chance of surface
based CAPE over 1000 J/Kg. That said, it`s mostly into eastern
OH and it drops to 40% for > 1500 J/Kg. The shear available is
decent and along the front. Thus, while the timing and certainty
is at best moderate, SPC has issued a Marginal Risk of severe
weather for Sunday. This most likely will be a wind threat
given the shear and potential lack of CAPE. This will need
monitored.

The front moves through on Sunday night as ridging attempts to
move in behind the boundary. There stands the chance for
afternoon convection on Monday behind the front owing to a post
frontal trough enhanced by the lake breeze. Though chances will
be low.

&&

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

- A weaker ridge builds in after Monday night leading to drier
  quieter weather on Tuesday.
- Active weather returns for Wednesday and Thursday.
-------------------------------------------------------------------

A lingering post frontal trough will allow for the potential of
a few showers and storms on Monday Night. Its likely that the
storms remain below severe limits but confidence on this is low
at this time.

Quieter conditions expected into Tuesday as a flat ridge begins to
build over the Plains and surface high starts to develop around the
Great Lakes as heights begin to rise. Temperatures are expected to
rise into the upper 80s to lower 90s but early ensemble indications
are that it won`t be as oppressive as the past week`s event. In
fact, the weaker ridge will allow a couple shortwave troughs
pass over the area and into the Great Lakes/Upper OH Valley on
Wednesday and Thursday, leading to increasing confidence of
active weather through the middle of next week.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
VFR is expected for the majority of the TAF period at most
airports. The exception is FKL, MGW and HLG, where they will
likely see some early morning MVFR fog.

The CU rule and model soundings indicate a scattered to broken
cumulus layer will develop by mid morning. A weak surface
boundary is expected to drop southward this afternoon. Model
ensemble output shows 1000-2000 j/kg of CAPE as the boundary
moves through. Wind flow aloft is light, though dry mid level
air will create a damaging wind threat with any storm that
becomes organized. The timing, coverage and location are still
uncertain, precluding more than a VCTS inclusion in the TAFs at
this time.

Storms and the cu layer should dissipate this evening with the
loss of heating.

.Outlook...
Mainly VFR is expected through Saturday night, outside of
isolated afternoon and evening thunderstorms on Saturday.
Restrictions are likely Sunday, along with showers and
thunderstorms, as a cold front crosses the region. VFR is then
expected again Sunday night through Tuesday under high pressure.

&&

.CLIMATE...
The area has the potential to break various heat-related
records.

There is low probability that climate sites approach the
highest temperatures recorded in the 21st century:

Pittsburgh, PA:       98F  (7/7/2012)
Wheeling, WV:         98F  (7/7/2012)
Morgantown, WV:       101F (7/7/2012)
New Philadelphia, OH: 101F (7/7/2012)
Zanesville, OH:       101F (7/7/2012)
DuBois, PA:           101F (7/22/2011)

There is a modest probability many June all-time temperature
records may be at stake:

PIT: 98F (1988)
HLG: 100F (1933)
MGW: 99F (1893)
PHD: 99F (1988)
ZZV: 101F (1988,1934)
DUJ: 92F (1969)  *RECORD TIED ON 6/18/24*

Daily high maximum (left) and high minimum (right) temperature
records are at stake for:

Friday, June 21st
Pittsburgh, PA:       95F  (1933)     73F  (1934)
Wheeling, WV:         99F  (1933)     69F  (2016)
Morgantown, WV:       95F  (1953)     72F  (1988)
New Philadelphia, OH: 94F  (1994)     72F  (2016)
Zanesville, OH:       97F  (1988)     72F  (1997)
DuBois, PA:           89F  (1991)     68F  (1988)

Saturday, June 22nd
Pittsburgh, PA:       98F  (1988)     75F  (1988)
Wheeling, WV:         95F  (1923)     72F  (2011)
Morgantown, WV:       96F  (1923,1988)73F  (1988)
New Philadelphia, OH: 97F  (1988)     71F  (1997)
Zanesville, OH:       99F  (1988)     71F  (1997)
DuBois, PA:           91F  (2022)     68F  (2022)

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Heat Advisory until 8 PM EDT Saturday for PAZ007>009-013-015-
     016-022-031-074-076>078.
     Excessive Heat Warning until 8 PM EDT Saturday for PAZ014-020-
     021-029-073-075.
OH...Heat Advisory until 8 PM EDT Saturday for OHZ039>041-048>050-
     057>059-068-069.
WV...Heat Advisory until 8 PM EDT Saturday for WVZ001>004-012-021-
     509>511.

&&

$$

SYNOPSIS...Shallenberger
NEAR TERM...Shallenberger
SHORT TERM...Shallenberger
LONG TERM...Shallenberger
AVIATION...WM
CLIMATE...CM