-- Discussion containing changed information from previous version are highlighted. --
128
FXUS61 KPBZ 201736
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
136 PM 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 TONIGHT/...
KEY MESSAGES:

- Excessive Heat Warning for the urban areas of western PA;
  Heat Advisory continues elsewhere.
- Heat index values ranging from 100F to 110F.
- Isolated to scattered thunderstorms possible again this afternoon
  with downbursts the primary threat.
-------------------------------------------------------------------

Less upper cloud coverage today has allowed temperatures to climb 4-
8 degrees warmer at noontime than those of 24 hours ago. As a
result, cumulus have started to pop across the area with the
achievement of convective temperatures. Thunderstorm-wise, we again
are going to need a trigger as the DCAPE is in place with 1200 J/kg
overlaid on 1500-2000 J/kg of uncapped MLCAPE. This will likely have
to be the lake breeze or any remnant boundary settled across the
area 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 very
slow moving storms with localized heavy rainfall. Hi res ensemble
paintballs favor north of Pittsburgh with downbursts again the
threat, but these weakly forced setups are often handled poorly by
CAMs. The northern half of our area remains in a Marginal Risk (1/5).

Highs are favored 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. A 50-70% chance of lows >70
tonight will continue to provide little relief from the heat.

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.

Convection will wane after sunset and give way to a warm, muggy
overnight period. Light wind and mostly clear skies may again
allow for patchy fog development in the river valleys; hi res
ensemble probabilities for visibility restrictions are 30-50%.

&&

.SHORT TERM /FRIDAY 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 /18Z THURSDAY THROUGH TUESDAY/...
-- Changed Discussion --
VFR conditions and light/calm wind will continue as high
pressure remains the dominant feature across the region. Have
kept TSRA mention out of TAFs with no apparent trigger to
initiate convection in latest guidance or obs. Best chance
would be FKL if convection develops along an area of lake-
breeze convergence.

.Outlook...
Mainly VFR and dry weather will continue outside of any isolated
thunderstorms. Restrictions with rain may return late this
weekend with a cold front.
-- End Changed Discussion --

&&

.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
SHORT TERM...MLB/Shallenberger
LONG TERM...MLB/Shallenberger
AVIATION...88
CLIMATE...