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353
FXUS61 KPBZ 201322
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
922 AM EDT Thu Jun 20 2024

.SYNOPSIS...
A dangerous heat wave will impact the region this week. 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.

&&

.NEAR TERM /THROUGH FRIDAY/...
-- Changed Discussion --
KEY MESSAGES:

- Excessive Heat Warning for the urban areas of western PA;
  Heat Advisory continues elsewhere.
- A marginal risk of strong to severe thunderstorms this
  afternoon/evening and also Friday afternoon/evening.
-------------------------------------------------------------------

Less upper cloud coverage today will allow for highs to reach
back into the low to mid 90s and a 50-60% chance of >95
degrees, highest in the urban areas and valleys. With dew points
still in the upper 60s/low 70s, heat index values will remain
around or above 100 degrees. 50-70% chance of lows >70 tonight will
continue to provide little relief from the heat. Considering
heat effects will be cumulative, late week looks compoundingly
dangerous. The early season event, and temperatures increasing
slightly each day, will exacerbate any existing heat issues.

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.

Thunderstorm-wise, we again are going to need a trigger as the
DCAPE is in place with 1100 J/kg overlaid on 1500-2000 J/kg of
MLCAPE. This will likely have to be the lake breeze as upper
waves visible on water vapor satellite on the northern periphery
of the 596-598 dm ridge are off to our north. Weaker deep layer
flow today (~10 kt 850-300 mb mean wind) may result in nearly
stationary storms with localized heavy rainfall. Hi res ensemble
paintballs favor north of Pittsburgh with downbursts the
threat. The northern half of our area remains in a Marginal Risk
(1/5).

The same holds true for Friday afternoon and evening with
similar parameters in place. There does stand the potential to
have greater instability in place given the weak influx of
moisture. The activity on Friday will be under even weaker flow
and may again pose the risk for a flooding threat.
-- End Changed Discussion --

&&

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

- Dangerous heat continues through the end of the week with little
  relief at night.
- Excessive Heat Warning and Heat Advisory remain in effect.
- Chance of thunderstorms in the afternoon.
-------------------------------------------------------------------

The upper ridge will begin to retrograde on Saturday but still
hold strong enough for one more day providing a continuation of
the dangerous heat, and perhaps the hottest day. Ensemble 850 mb
temperatures still remain in the 22-24C range and even the NBM
10th percentile suggests low to mid 90s. Highs will climb by a
few degrees into Saturday with probabilities indicating Saturday
may be the hottest. Some records may be challenged. Due to the
compounding effects, continued heat indices at and above 100
degrees, and the WPC heat risk tool showing major to extreme
impacts, the heat headlines have been extended through Saturday.
That said, some subtle weaknesses in the flow as the ridge axis
pulls south and allow for isolated to scattered afternoon
convection to throw wrinkles in the heat, but predictability in
coverage and location is low probability.

&&

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

- Relief from the heat favored with a passing trough over the Great
  Lakes Sunday into Monday.
- A weaker ridge builds in after Monday.
-------------------------------------------------------------------

Come Sunday into Monday, the ridge retrogrades with ensemble
clusters showing respectable agreement on an upper trough
pushing down through the Great Lakes and 500 mb heights
decreasing up to 10 dm by Monday. Surface high pressure migrates
off to the east ahead of low pressure associated with the upper
trough that drags to our north, but some timing differences
with it lend lower confidence. Ensemble precipitation chances
increase overnight Sunday into Monday as a cold front may drag
through during that timeframe. Upper ridging is then favored to
build back in by mid week with highs again potentially
increasing to above 90 degrees, but heights don`t look quite as
extreme as this week.

&&

.AVIATION /13Z THURSDAY THROUGH MONDAY/...
Light/calm wind is expected overnight. Fog will be possible
primarily at FKL where evening storms boosted boundary layer
moisture.

Light winds continue on Thursday, becoming more variable into
the afternoon. Afternoon storms are expected to initiate on the
lake/land boundary and possibly allow enough outflow to initiate
convection north of KPIT. PROB30s were included for the most
susceptible ports (BVI,FKL,DUJ) for now. It is possible that
these mentions expand. Any storms will be capable of downbursts
with elevated instability and dry air.

Fog will again be possible Thursday night, mainly in areas that
receive afternoon/evening rain.

.Outlook...
Modest probability for VFR and dry weather through the week with
upper ridging, save any isolated afternoon thunderstorm chances.
Restrictions with rain may return late this weekend with a cold
front.

&&

.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:

Thursday, June 20th
Pittsburgh, PA:       95F  (1994)     78F  (1924)
Wheeling, WV:         97F  (1933)     70F  (1924)
Morgantown, WV:       99F  (1893)     75F  (1924)
New Philadelphia, OH: 95F  (1994)     71F  (2009)
Zanesville, OH:       98F  (1934)     75F  (1924)
DuBois, PA:           89F  (1991)     66F  (1996)

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...MLB/Shallenberger
NEAR TERM...MLB/Shallenberger
SHORT TERM...MLB/Shallenberger
LONG TERM...MLB/Shallenberger
AVIATION...Rackley/Milcarek
CLIMATE...MLB/SKH/CM