PBZ issues Area Forecast Discussion (AFD) at Jun 21, 7:33 PM EDT
668
FXUS61 KPBZ 212333
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
733 PM EDT Sat Jun 21 2025
.SYNOPSIS...
A dangerous heat wave is expected to impact the region through
mid-week. Near record breaking high temperatures could occur
Monday and Tuesday. Thunderstorm chances may return mid to late
week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
KEY MESSAGES:
- Dry weather continues
- Warm conditions overnight (+10F)
---------------------------------------------------------------
Quiet and dry weather will continue overnight as ridging builds
into the Ohio Valley. Despite relatively clear skies and light
wind, overnight lows will bottom out around 10 degrees above
normal for this time of year. This will begin a long stretch of
well above normal nighttime temperatures.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY NIGHT/...
KEY MESSAGES:
- Extreme heat threat ramping and peaking Monday and Tuesday.
- Potential record high and low temperatures.
- Extreme Heat Warning in effect Sunday - Wednesday.
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The weather story beginning on Sunday and continuing through next
week is a prolonged period of dangerous, extreme heat; an Extreme
Heat Warning is in effect for Pittsburgh metro and surrounding
counties and a Heat Advisory is in effect elsewhere beginning
Sunday.
The first day of significant heat occurs on Sunday with height rises
of 4-6 dam as we're engulfed by the 596 dam contour on all ensembles
resulting in highs likely to top 90 degrees across most of the area.
Heat indices will reach 100-105F, highest in the valleys and urban
areas. Plenty of subsidence will keep the area dry.
Ensembles exhibit uniform certainty on a strong upper ridge building
across the eastern CONUS with a 100+% chance of 500 mb heights >595
dam; probability suggests heights sit between 596-598 dam Sunday-
Tuesday with some regression beginning on Wednesday. Ensemble mean
850 mb temperatures soar to 20-22C. NBM probability for highs >90F
is remarkably high at 95-100% Sunday through Wednesday, but of note
is that NBM probabilities and statistical distribution in a high-
predictability can often be artificially inflated when post-
processing is applied to a small spread in the distribution like we
have in this case for MaxTs. What this means is that the more likely
high temperature might fall a degree or two below the NBM post-
processed mean (perhaps the 90-95F range as opposed to widespread
95F+), especially with forecast dew points in the mid 70s. Last
year's period of extreme heat showed that the NBM handled the dew
points pretty well while overdoing the MaxTs by a couple degrees, so
it's most likely that we find a middle ground with low to mid 90s
temps and low 70s dew points. Either way, heat indices are very
likely to reach the 100-105F range for several consecutive days.
Compounding the effects of extreme daytime heat will be little
relief at night as probability for lows >70F is 80-90+% Sunday-
Wednesday nights.
Record lows and highs may be in jeopardy... see the climate section
for more. In preparation, it is a good idea to find out more about
your local cooling shelters and consider altering outdoor plans to
at least outside of the afternoon peak heating window.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
KEY MESSAGES:
- Low predictability showers and storms possible Wednesday and
Thursday.
- Lower confidence in how long the extreme heat hangs around.
-------------------------------------------------------------------
By mid-week, we may re-introduce severe weather and flash flooding
again as the heat begins to subside, though by that point the lower
predictability convective development will play a large role in
whether or not heat headlines need extended beyond Wednesday. This
looks possible Wednesday but more likely Thursday and Friday as some
subtleties in the flow/regression of the ridge allow for convective
potential riding atop it. Ensemble forecast soundings indicate that
plenty of DCAPE (750-1200 J/kg) should be available with weak
effective shear (10-15 kt) underneath the ridge and increasing PWAT
values to 1.5-1.8" all supportive of slow moving storms with heavy
rain and downburst potential. Should these become more widespread
and higher confidence, MaxTs/AppTs on Thursday and Friday may
not be as high as currently forecast. NCAR's medium-range
machine learning guidance has increased the probability of
severe weather to 30-40% over our region for the Thursday/Friday
timeframe.
Something to monitor in the coming days: With the focus for
strong to severe storms remaining at the US/Canada border, the
potential for wildfires may develop. Depending on how the upper-
level pattern evolves, this could lead to degraded air quality
in the long term. However, this outlook is contingent on the
development of wildfires sparked by lightning in heavily forest
areas to our north.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
High confidence in VFR conditions throughout the TAF period.
There is some indication winds will remain light to calm and
out of the SSW overnight, veering SW with mixing during the
daytime Sunday. Moisture aloft may make a scattered cu deck
more likely at FKL/DUJ than other ports, along with the highest
chances of gusts >=15kts during peak mixing. Scattered cu
coverage decreases to the SW.
Outlook...
VFR is expected through Tuesday under a strong ridge. Potential
for restrictions and showers/thunderstorms return Wednesday as
the ridge begins to drift south.
&&
.CLIMATE...
Daily record high maximum (left) and daily record high minimum (right)
temperatures will be in jeopardy starting this coming Sunday:
Sunday June 22nd
Pittsburgh, PA: 98F (1988) 75F (1988)
Zanesville, OH: 99F (1988) 71F (1997)
Morgantown, WV: 96F (1923,1988) 73F (1988)
Dubois, PA: 92F (2024) 69F (2024)
Wheeling, WV: 95F (1923, 2024) 72F (2011)
New Philadelphia, OH: 97F (1988) 71F (1997)
Monday June 23rd
Pittsburgh, PA: 95F (1894) 76F (1888)
Zanesville, OH: 96F (1899) 70F (1975)
Morgantown, WV: 95F (1899) 71F (1957)
Dubois, PA: 88F (1966) 66F (2017)
Wheeling, WV: 94F (1948) 69F (2013)
New Philadelphia, OH: 97F (1988) 72F (1948)
Tuesday June 24th
Pittsburgh, PA: 96F (1882) 72F (1884)
Zanesville, OH: 98F (1930) 73F (1937)
Morgantown, WV: 94F (1921, 1949) 76F (1924)
Dubois, PA: 88F (1966) 67F (2013)
Wheeling, WV: 98F (1933, 1943) 73F (1908)
New Philadelphia, OH: 94F (1964) 70F (1975)
Wednesday June 25th
Pittsburgh, PA: 98F (1988) 75F (1952)
Zanesville, OH: 101F (1988) 72F (1952)
Morgantown, WV: 94F (1921, 1952, 1988) 74F (1952)
Dubois, PA: 91F (1966) 67F (2000)
Wheeling, WV: 97F (1943) 75F (1952)
New Philadelphia, OH: 92F (1966, 2002, 2005) 68F (2013)
Thursday June 26th
Pittsburgh, PA: 95F (1966) 75F (1952)
Zanesville, OH: 97F (1952) 73F (1952)
Morgantown, WV: 96F (1952) 74F (1952)
Dubois, PA: 91F (1966) 66F (2000)
Wheeling, WV: 96F (1943, 1952) 73F (1952)
New Philadelphia, OH: 99F (1988) 71F (2022)
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Heat Advisory from 11 AM Sunday to 8 PM EDT Wednesday for
PAZ007>009-013-015-016-022-031-074-076>078.
Extreme Heat Warning from 11 AM Sunday to 8 PM EDT Wednesday
for PAZ014-020-021-029-073-075.
OH...Heat Advisory from 11 AM Sunday to 8 PM EDT Wednesday for
OHZ039>041-048>050-057>059-068-069.
WV...Heat Advisory from 11 AM Sunday to 8 PM EDT Wednesday for
WVZ001>004-012-021-509>513.
&&
$$
SYNOPSIS...Hefferan/Rackley
NEAR TERM...Rackley/88
SHORT TERM...MLB
LONG TERM...Hefferan/MLB
AVIATION...Milcarek
CLIMATE...MLB
Source: PBZ issues Area Forecast Discussion (AFD) at Jun 21, 7:33 PM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202506212333-KPBZ-FXUS61-AFDPBZ)
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