-- Discussion containing changed information from previous version are highlighted. --
569
FXUS61 KPBZ 151740
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
140 PM EDT Sat Jun 15 2024

.SYNOPSIS...
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After a dry and comfortable overnight period, a large ridge
will build over the region Sunday and remain in place through
the rest of next week. A prolonged and potentially dangerous
heat wave is anticipated under this ridge.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
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KEY MESSAGES:

- Dry weather and comfortable conditions tonight.
-------------------------------------------------------------------

Surface high pressure over the eastern Great Lakes will continue
to drift eastward tonight, while 500mb heights begin to rise
ahead of an approaching ridge. A mostly clear sky is expected,
save for a few patches of high clouds. Low dewpoints will
promote a comfortable overnight period. Minimum temperatures
will end up near or just below seasonal norms. That will be the
last time for a while that we will be able to say that.
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&&

.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
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KEY MESSAGES:

- Dry weather continues.
- Noticeably warmer temperatures on Sunday.
-------------------------------------------------------------------

The upper ridge axis will arrive on Sunday and park itself over the
eastern Great Lakes and the Upper Ohio Valley, while the 500mb high
at the core of the ridge begins to expand over the Carolinas. As the
surface high moves off of the New England coast, wind will veer to
the south and create strong warm advection into our region.  This
will provide continued dry weather and a noticeable upward bump
in high temperatures on Sunday, some 7 to 11 degrees areawide.
Some urban/valley locations will likely reach the 90 degree
threshold - representing the start of a likely lengthy run of
such temperatures.

A dry and balmy Sunday night is forecast, with lows in the mid and
upper 60s. After this, the heat is on.
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&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
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KEY MESSAGES:

- High confidence in a dangerous heat wave setting up next week
  with major heat impacts possible.
-------------------------------------------------------------------

The numbers have changed slightly, but our overall expectations
have not changed for this period. We are looking at a
potentially historic heat wave for Pittsburgh and the Upper Ohio
Valley, with impacts to public health and utilities a strong
possibility.

Model cluster analysis continues to paint a high-confidence picture
of the overall pattern. An anomalously strong 500 mb ridge will
persist over the eastern CONUS Monday through Friday, reaching
its peak during the Wednesday/Thursday period, before
potentially becoming a bit more muted Saturday. Both the EPS and
GEFS means have 500mb heights of 595dm or higher during that
period, and some deterministic runs are even a bit higher. This
sets the stage for a prolonged period of high temperatures well
into the 90s. NBM means are in the lower to mid 90s as a rule
through this period. There is a good possibility that these
values are underdone. Probabilities of 95 degree or higher
temperatures are in the 60 to 80 percent range for a large
portion of the forecast area (especially valleys and urban
areas) during the Tuesday to Thursday period to begin with.
Also, given the strength/position of this ridge, precipitation
chances are quite low, especially during the mid- week period,
which will promote an increasing dry surface that will promote
higher temperatures. Cloud cover will be fairly low as well, and
given that sun angles are at their annual peak, insolation will
add another warming factor. Considering all of this, will
follow the lead of the previous shift and run with close to the
75th percentile NBM values for high temperatures, while using
the mean for low temperatures. This means that the forecast will
include highs in the upper 90s for much of the region, with
valley and urbanized areas still having the potential to reach
100 degrees. This level becomes a bit more likely if dewpoints
end up on the lower end of the expected mid 60s to lower 70s
range. NBM probabilities for triple digit heat have tailed off
slightly, into the 25 to 50 percent range in favored
valley/urban areas.

When considering dewpoints, heat index values in the 100 to 110
range are in the cards for a few days.  There does remain some
uncertainty in how widespread and long-lasting these kind of heat
index values will be from day to day.  This nominally has
implications for what kinds of heat-related headlines would be
appropriate. However, we feel that this event will have a length and
impact that the standard criteria may not capture. For example,
there is a strong possibility of 95 degree or higher temperatures at
the Pittsburgh climate site for at least five straight days next
week (NBM probs 70 percent or greater each day). This kind of heat
wave last happened at Pittsburgh in 1994. Matching or even exceeding
that standard will no doubt have many societal impacts. Thus, to
keep awareness high and capture this potential impact, an Excessive
Heat Watch has been issued for the entire forecast area for Monday
through Friday. Decisions on heat related advisories and/or warnings
will be made by future shifts, but at this time, highlighting the
entire period without getting too bogged down in details seemed
prudent. Uncertainty for Saturday heat starts to increase to the
point that it was not included in this watch product.

There are a couple of failure modes to this forecast that could
occur, at least on a localized basis. Non-zero chances of
isolated convection exist, particularly in the terrain.
Localized breaching of any capping inversion could in theory set
of a convective chain reaction, leading to more clouds and
precipitation areawide than expected. Slight differences in
ridge positioning may allow for a bit more cloud cover,
particularly in eastern Ohio, that could provide a potential
cooling effect. Current thinking is that these concerns can`t be
totally dismissed, but are small enough for now to expect
widespread heat impact.

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. Gather food,
water and medication now. Make a list of friends and family to
check on and help them prepare. Strongly consider rescheduling
outdoor events. 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.
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&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
VFR conditions, dry weather, and light winds from the north are
likely for the remainder of the TAF period under high pressure.

Winds will shift from south Sunday evening.

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

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

&&

.CLIMATE...
The area has the potential to break various heat-related
records. In this climate section, we will attempt to address
some of the higher-profile historical temperature records.

First, we cannot rule out that some sites approach all time
record high temperatures:

Pittsburgh, PA:       103F (7/16/1988, 8/6/1918, 7/10/1881)
Wheeling, WV:         106F (7/22/1934, 8/6/1918)
Morgantown, WV:       105F (8/26/1893)
New Philadelphia, OH: 102F (7/17/1988)
Zanesville, OH:       106F (7/14/1936, 7/25/1934)
DuBois, PA:           101F (07/22/2011)

There is moderate 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)

Due to the how early in the summer this heat wave is, there
is a high 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)

Due to the duration of the heat, sites will also approach records
for consecutive days greater than 95F (dates are the day the
streak ended):

Pittsburgh, PA:       6    (6/20/1994, 8/11/1900)
Wheeling, WV:         8    (7/15/1936)
Morgantown, WV:       9    (9/16/1997, 7/19/1892)
New Philadelphia, OH: 5    (7/27/2016, 7/10/1988)
Zanesville, OH:       9    (9/4/1953)
DuBois, PA:           3    (7/9/1988)

And it should go without question that daily high maximum (left)
and high minimum (right) temperature records are at stake for:

Monday, June 17th
Pittsburgh, PA:       95F  (1994)     75F  (1892)
Wheeling, WV:         99F  (1936)     69F  (2004)
Morgantown, WV:       95F  (1967)     72F  (1939)
New Philadelphia, OH: 95F  (1967)     69F  (2022)
Zanesville, OH:       99F  (1936)     72F  (1994)
DuBois, PA:           89F  (1994)     66F  (1892)

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...
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PA...Excessive Heat Watch from Monday morning through Friday
     evening for PAZ007>009-013>016-020>022-029-031-073>078.
OH...Excessive Heat Watch from Monday morning through Friday
     evening for OHZ039>041-048>050-057>059-068-069.
WV...Excessive Heat Watch from Monday morning through Friday
     evening for WVZ001>004-012-021-509>514.
-- End Changed Discussion --

&&

$$

SYNOPSIS...CL
NEAR TERM...CL
SHORT TERM...CL
LONG TERM...CL
AVIATION...Hefferan
CLIMATE...Milcarek