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171
FXUS61 KPBZ 192120
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
520 PM EDT Wed Jun 19 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 /UNTIL 6 AM THURSDAY MORNING/...
-- Changed Discussion --
KEY MESSAGES:

- Excessive Heat Warning for the urban areas of western PA;
  Heat Advisory continues elsewhere.
- Diminishing but still-present threat of isolated storms with
  downburst potential, mainly north and west of Pittsburgh.
-------------------------------------------------------------------

It`s been a stark contrast when comparing this afternoon to the
past couple. Instead of widespread 90s and downburst-producing
thunderstorms, thick cirrus has prevented the attainment of
convective temperatures across our region, as well as keeping
temperatures below 90 degrees in many cases. Convection to this
point has been confined to western Ohio and a couple of brief
showers right along the Lake Erie shore. If any convection did
manage to get going, it would find an environment characterized
by 2000-2500 J/kg of MLCAPE, 1000-1200 J/kg of DCAPE, and less
than 25 knots of effective shear to the north of Pittsburgh,
certainly supporting a downburst/local heavy rain threat.
However, the cirrus and the lack of a focusing trigger to this
point have kept things quiet. Will leave a small PoP in the
northern and western counties for a few hours, but convective
prospects for today are dimming.

Temperatures will also be adjusted downward 1-3 degrees areawide
into this evening due to the lingering cirrus. Overnight, localized
patches of fog will be possible again tonight and most likely
in the river valleys to the southeast of Pittsburgh, where
clouds may thin the most. Low temps tonight will once again be
in the lower 70s in many areas, allowing for little relief from
the heat overnight.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY 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.
- Slight chance of thunderstorms in the afternoon.
-------------------------------------------------------------------

Less upper cloud coverage on Thursday and Friday will allow for
highs to reach back into the mid 90s and a 70-80% chance of >95
degrees, highest in the urban areas and valleys. Highs will
climb by a few degrees into Saturday with probabilities
indicating Saturday may be the hottest. Some records may be
challenged. With dew points still in the upper 60s/low 70s, heat
index values will remain around or above 100 degrees. 50-80%
chance of lows >70 will continue to provide little relief from
the heat at night. 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.

Weak upper waves on the northern periphery of the 596-598 dm ridge,
along with a lake breeze, may again allow for some pop up
thunderstorms in the afternoon both days. Best chances Thursday will
be Pittsburgh and north, potentially slightly further south on
Friday, based on latest hi res ensemble guidance with a similar
environment to Wednesday with a 60-90% chance of >1000 J/kg of CAPE.
Weaker flow aloft may keep shear values slightly less in the 15-20
kt range. This would still be sufficient for scattered storms
capable of downbursts with modeled DCAPE >1000 J/kg.

&&

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

- Heat continues into Saturday and heat headlines have been extended
  through Saturday evening.
- Relief from the heat favored with a passing trough over the Great
  Lakes Sunday into Monday.
- A weaker ridge builds in after Monday.
-------------------------------------------------------------------

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. 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.

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 /21Z WEDNESDAY THROUGH MONDAY/...
Thunderstorms continue to look less likely this afternoon as
warm air aloft (indicated by latest aircraft obs and rapid
update soundings) should keep convection largely capped off.

Winds remain light and variable with a generally southerly
component.

.Outlook...
High probability for VFR and dry weather through the week as
strong ridging develops aloft. 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:

Wednesday, June 19th
Pittsburgh, PA:       97F  (1994)     74F  (1905)
Wheeling, WV:         95F  (1933)     70F  (2021)
Morgantown, WV:       94F  (1994)     72F  (2018)
New Philadelphia, OH: 92F  (1994)     70F  (2018)
Zanesville, OH:       94F  (1994)     75F  (1897)
DuBois, PA:           87F  (2001)     66F  (1975)

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/CL
SHORT TERM...MLB
LONG TERM...MLB
AVIATION...Rackley/Shallenberger/88
CLIMATE...MLB/SKH/CM