844
FXUS61 KPBZ 210508
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
108 AM EDT Sat Jun 21 2025
.SYNOPSIS...
A dangerous heat wave is expected to impact the region beginning
Sunday through mid-week. Near record breaking high temperatures
could occur Monday and Tuesday. Thunderstorm chances may return
mid to late week.
&&
.NEAR TERM /THROUGH TODAY/...
KEY MESSAGES:
- Isolated fog chances early this morning.
- Dry and warm conditions expected today
---------------------------------------------------------------
Quiet and dry weather expected early Saturday morning. Isolated
fog can`t be ruled out for areas that received showers and/or
storms over the last 12 hours. Fog potential will rapidly
decrease after dawn.
A building ridge over the Ohio River Valley will keep the region
warm and dry today. Convection, currently over the Midwest,
will likely track over the Great Lakes over the next 12 to 24
hours. The general focus for strong to severe storms is north of
I-80, towards the PA/NY state line. Probability of thunder has
decreased for our northern counties with the latest run of the
National Blend of Model (NBM), especially with increasing warm
advection from the southwest. The Storm Prediction Center`s
(SPC) Marginal Risk for the potential of severe storms will
likely be trimmed in the next update.
&&
.SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...
KEY MESSAGES:
- Extreme Heat Watch in effect Sunday into late Wednesday
- Heat index values will likely climb above 100F during the
late afternoon
----------------------------------------------------------------
Dangerous heat is expected to begin Sunday, with 12-hour height
rises of 2 to 4 dam supporting a strong warming trend as the
ridge axis pivots over western Pennsylvania early next week.
High temperatures are expected to exceed 90F across much of the
region and even climb into the mid-90s for a few climate sites.
Widespread subsidence will help maintain dry and mostly clear
conditions throughout the period.
An Extreme Heat Watch remains in effect for the entire County
Warning Area (CWA) from Sunday though late Wednesday. With heat
index values projected to range from 103F to 106F near the city
of Pittsburgh, an Extreme Heat Warning is being considered for
Allegheny County and surrounding areas. A Heat Advisory may be
more appropriate for locations outside of the metro region.
However, worsening conditions based on impacts may warrant
upgrading a Heat Advisory to an Extreme Heat Warning.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
KEY MESSAGES:
- Excessive heat threat ramping and peaking Monday and Tuesday.
- Potential record high and low temperatures.
- Excessive Heat Watch in effect through Wednesday.
- Low predictability showers and storms possible Wednesday and
Thursday.
-------------------------------------------------------------------
The story of the long term is a prolonged period of dangerous,
excessive heat.
Ensembles exhibit quite a bit of certainty on a strong upper ridge
building across the eastern CONUS with a 90+% chance of 500 mb
heights >590 dam. Ensemble mean 850 mb temperatures soar to 21-23C.
NBM probability for highs >90F is remarkably high at 80+% Sunday
through Thursday, but of note is that NBM probabilities and
statistical distribution in a high-predictability period of heat can
often be artificially inflated/widened 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 most likely high
temperature falls a degree or two below the NBM post-processed mean
(more likely 90-95F) and true probabilities for >95F aren`t quite as
high as suggested. Dew points are progged to be in the mid 70s, and
last year`s period of extreme heat showed that the NBM handled the
dew points pretty well while overdoing the MaxTs, so it`s most
likely that we find a middle ground with low to mid 90s temps and
upper 60s/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 excessive daytime heat will be little
relief at night; probability for lows >70F is 80-90+% Sunday-
Wednesday nights. The Excessive Heat Watch remains in effect, and
further decision on warning vs. advisory will likely come within the
next 24 hours. Record lows and highs may be in jeopardy as well...
see the climate section for more. In preparation a few days out, 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.
One thing to keep in mind is that at times we can get affected by
diurnally driven clouds and precipitation in these patterns with
such warm temperatures and plenty of near-surface moisture. This
looks most likely on Wednesday and Thursday as some subtleties in
the flow/regression of the ridge allow for convective potential atop
it. Some of this convection could be on the strong to severe. NCAR`s
medium-range machine guidance highlights the Ohio River Valley has
an area for hazardous weather (15-30% chance) for Wednesday into
Thursday. With light winds and dry air aloft, downbursts are
expected to be the primary threat followed by localized flooding.
&&
.AVIATION /05Z SATURDAY THROUGH WEDNESDAY/...
VFR is expected through the TAF period as a ridge of high
pressure builds across the Upper Ohio Valley region. Expect a
few diurnal cumulus clouds, and some passing mid/high clouds
streaming SE of convection well to our north. Calm wind will
increase from the southwest to less than 10kt today.
Outlook...
VFR is expected through Tuesday under a strong ridge. A
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...Extreme Heat Watch from Sunday morning through Wednesday
evening for PAZ007>009-013>016-020>022-029-031-073>078.
OH...Extreme Heat Watch from Sunday morning through Wednesday
evening for OHZ039>041-048>050-057>059-068-069.
WV...Extreme Heat Watch from Sunday morning through Wednesday
evening for WVZ001>004-012-021-509>514.
&&
$$
SYNOPSIS...Hefferan
NEAR TERM...Hefferan
SHORT TERM...MLB
LONG TERM...MLB
AVIATION...WM
CLIMATE...MLB