-- Discussion containing changed information from previous version are highlighted. --
032
FXUS61 KPBZ 190250
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1050 PM EDT Tue Jun 18 2024

.SYNOPSIS...
A dangerous heat wave will impact the region this week. A Heat
Advisory and Excessive Heat Warning are in effect through Friday.
This event is highly unusual for our region and could be worse
than the 1994 heat wave.

&&

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

- Excessive Heat Warning was issued for the urban areas of
  western PA; Heat Advisory continues elsewhere.
- Heat index values could range from 100F to 110F.
- Isolated to scattered downbursts are possible once again this
  afternoon.
- Isolated flash flooding may occur with slow training storms.

-------------------------------------------------------------------

8PM Update:

Current conditions show waning surface based instability across
the area as inhibition increases. This is reflected on the
weakening trend in storms to the north and near Tusc as well as
the cell moving into Wetzel county. This trend is expected to
continue and will need to update pops in the next couple of
hours to address this change.

Previous Discussion:

The ridge will continue to amplify today, with surface high
pressure centered off the east coast. Rising heights aloft
should boost temperatures to range between the mid-90s to
upper-90s. Isolated thunderstorms may disturb the heat process.
However, due to the potential of downbursts today, the impacts
may be considered worse due to potential power outages.

Despite strong subsidence from the ridge, orographic effect,
and a minefield of outflow boundaries from Monday`s storms,
isolated to scattered thunderstorms are likely again today.
Rapid destabilization resulting from strong surface heating
along with weak shear will favor downbursts once again, with
potential for severe winds. The Storm Prediction Center (SPC)
continues to highlighted much of the region in a Marginal (1/5)
risk. Along with strong winds, PWAT values are abnormally high
(PIT 12Z sounding measured 1.80", while the climatological
average suggests values of 1.12") and with weak flow flash
flooding could be problematic.

Given the unknowns of initiation and complexity of the outflow
boundaries currently lying across the area, location and
coverage of storms is difficult to pinpoint. Best timing once
again appears to be in the mid/late afternoon, with storms
quickly diminishing in the evening hours.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
KEY MESSAGES:

- Confidence is high that hot conditions will continue through
  Friday, Excessive Heat Warning and Heat Advisory remains in
  effect.
- Chances for afternoon convection decreases.

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The ridge axis remain situated across the East Coast through the
weekend. 500mb heights will range between 596 dm to 598 dm
through Thursday as the ridge extends into Newfoundland and
Quebec. Record breaking afternoon high temperatures and
overnight maximum low temperatures continue in this time period.

The hottest time period is expected to be Thursday into Friday
where mid-90s to upper-90s; the NBM 25th percentile suggests
low to mid-90s across the region.

Elevated high temperatures and dewpoints will keep heat indices
at and above 100 through the period. Low temperatures will also
remain elevated with the probability > 70 around 50-80% both
nights.

Considering heat effects will be cumulative, late week looks
particularly dangerous. The early season event, and temperatures
increasing slightly each day, will compound 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.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
-- Changed Discussion --
KEY MESSAGES:

- Hot temperatures are expected to continue into Saturday; heat
  products may need to be extended in the next 24 to 48 hours.
- Relief from the heat may return with a passing trough over the
  Great Lakes Sunday into Monday.

-------------------------------------------------------------------

The upper-level ridge will continue hot and humid conditions
into the region through Saturday. Heat products may need to be
extended.

Ensemble models project a trough forming over the Midwest and
ejecting into the Great Lakes Sunday into Monday that may bestow
some relief to the Ohio River Valley. Temperatures may still
remain above average, but Heat Advisories/Warnings may not be
necessary.
-- End Changed Discussion --

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
High pressure will maintain VFR through the period, with the
possible exception of patchy overnight river valley fog.
Probability of this is low, and did not include in TAFs.

Afternoon thunderstorms will be much less likely on Wednesday.
And storms that do form are expected to stay generally north of
I-80. Have included a PROB30 for FKL to account for this.

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.
-- 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:

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)

&&

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

&&

$$

SYNOPSIS...Hefferan
NEAR TERM...Hefferan/Shallenberger
SHORT TERM...Hefferan
LONG TERM...Hefferan
AVIATION...Rackley/Shallenberger