904
FXUS61 KPBZ 181845
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
245 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.

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

2PM Update:

The Heat Advisory for the Pittsburgh metro region have been
upgraded to an Excessive Heat Warning due to urban heating
impacts and prolonged period of historic heat. This event may be
comparable to the 1994 heat wave or worse and needs to be taken
seriously.

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:

- Heat continues to build with probabilities pointing to
  Thursday and Friday being the hottest days of the week.
- Chances for afternoon convection decreases.

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

The ridge becomes centered over the region by Wednesday, with
ensembles continuing to show heights of 597-599dm. With surface
high pressure centered a little farther west, the threat for
convection will be decreased Wednesday afternoon, through
ensembles do indicate low-end probabilities mainly north and
west of Pittsburgh. For this reason, did introduce low-end PoPs
primarily across the I-80 corridor for Wednesday afternoon.
Probabilities for storms look even lower on Thursday and Friday
afternoons, but remain non-zero. Focus again would likely be
north of Pittsburgh.

With similar conditions, temperatures on Wednesday look to be
similar to Tuesday. Probabilities for high temperatures > 95
both Thursday and Friday are the highest of the week, though the
ridge will begin to break down on Friday. The higher
probabilities are also more widespread Thursday and Friday, with
much of the area in the 50-85% range both days.

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.

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/...
KEY MESSAGES:

- Hot temperatures continue into the weekend, but the heat wave
  will begin to break.
- Cooler temperatures are possible, at least temporarily by
  early next week.

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

The upper level ridge will break down this weekend and become
suppressed well to the south as an upper trough crosses the
Great Lakes. However, ensembles indicate this is unlikely to
have a significant impact on Saturday`s temperatures, with hot
weather continuing into the first half of the weekend.

Ensembles show good agreement on the upper trough crossing into
the Great Lakes by Sunday, which should finally bring relief
from the heat and an increase in rain probabilities. At present,
Sunday`s temperatures still appear well above average, but much
more tolerable than prior days. Post frontal cold advection on
Monday may finally drop temperatures back to a semblance of
normal, at least temporarily.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
Any impacts to terminals today will be solely due to
thunderstorms. Convection is expected initiate mid afternoon and
persist into the late afternoon and evening. With a pulse
convective mode, outflows boundaries will be the biggest
concern. Opted to maintain VCTS to all terminals today to
account for the uncertainty in location ands timing. Once again,
conditions due to fog overnight will be dependent on location
of convection. Expect light and variable winds through the day
with the exception of thunderstorms.

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

The only variance may come with isolated afternoon convection
on Wednesday, but upper ridging should suppress coverage and
potential initiation.

&&

.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:

Pittsburgh, PA:       98F  (1988)
Wheeling, WV:         100F (1933)
Morgantown, WV:       99F  (1893)
New Philadelphia, OH: 99F  (1988)
Zanesville, OH:       101F (1988,1934)
DuBois, PA:           92F  (1969)

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

Tuesday, June 18th
Pittsburgh, PA:       97F  (1994)     73F  (1905)
Wheeling, WV:         95F  (1944)     71F  (2018)
Morgantown, WV:       95F  (1994)     70F  (2018)
New Philadelphia, OH: 95F  (1994)     72F  (2017)
Zanesville, OH:       99F  (1944)     73F  (1944)
DuBois, PA:           89F  (2018)     69F  (2018)

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
SHORT TERM...Rackley/22
LONG TERM...Rackley/34
AVIATION...Shallenberger
CLIMATE...Hefferan