513
FXUS61 KPBZ 112256 AAA
AFDPBZ

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
656 PM EDT Thu Jul 11 2024

.SYNOPSIS...
Clouds will slowly dissipate overnight. Temperatures will be
close to seasonal averages. Temperatures warm Friday with dry
weather. Hot and humid conditions move in over the weekend.

&&

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

- Clouds should slowly dissipate overnight.
- Seasonably cool lows.
- Much warmer Friday but dry.
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Evening update...biggest question is what to do with the cloud
cover. Persistent SC/CU has held on all day with the thickest
mainly over W PA. 850mb flow is forecasted to shift to the west-
southwest later tonight which should help to dissipate the
cloud cover. Additionally, the cool pool aloft has moderated
somewhat. Have made adjustments to overnight cloud cover and
lows.

Previous discussion...

Building high pressure will prompt clearing skies and variable
winds. Hi- Res model guidance has been consistent that fog
development is favorable for areas north and northwest of
Pittsburgh after midnight. However, confidence is currently not
high enough that a Dense Fog Advisory will be issued, perhaps a
Special Weather Statement (SPS) for a few hours may be necessary
in the next 12 to 15 hours.

&&

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

- Heat risks increase through the period due to rising
  temperature (though with more limited humidity rises).

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Early morning fog will dissolve between 8am and 9am Friday with
diurnal heating.

Confidence remains high that above average temperatures will
return early afternoon through late evening Friday under high
pressure (prompting abundant sunshine) and warm advection from
the southwest. With deep mixing (perhaps as high as 700mb) for
areas between Zanesville, OH and Morgantown, WV, temperatures
may range between 90F to 93F. Probability of MaxTemps above 90F
from the NBM ranges between 60% to 80% within this noted region
(highest probabilities within the city of Pittsburgh due to
urban heating).

Weak moist advection over the Carolinas, from a remnant
disturbance, may stir showers along the ridges of West Virginia
and Pennsylvania after 2pm Friday. Hi-Res guidance suggests
weak convergence due to orographic lift. Noted sounding depict
mid- level warm air may cap cloud tops between 14kft to 16kft,
therefore lightning may be scarce. With mid-level flow from the
southwest, convection will likely drift towards central PA
opposed to the rest of the county warning area.

Above average temperatures will continue into the weekend as the
ridge axis strengthens over the Great Lakes. Therefore,
afternoon high temperatures and overnight lows will trend above
average by 5 degrees.

The potential for storms increases Sunday over eastern Ohio as
the ridge starts to break down with a trough developing over
central Canada.

&&

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

- An active severe weather pattern is anticipated Monday through
  Tuesday as a large trough drifts south over the Great Lakes.

- High confidence in continued heat risks continue through
  Wednesday ahead of a cold front.

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Ensembles favor a flattening of the East Coast ridge starting
Monday as a large low pressure system tracks through southern
Canada and towards the Great Lakes. With an abundant amount of
warm, moist conditions at the surface across the Ohio River
Valley (temps in the 90Fs, dew points in the 70Fs) and an
increase in the vertical wind profile, the threat for severe
storms increases Monday into Tuesday ahead of a cold front. Of
the two days, Tuesday is likely the best day for severe storms
due to the timing of the cold front.

Relief from the heat and severe weather is likely late Wednesday
into Thursday as the cold front progresses south. Near-normal
high temperatures and low temperatures are expected to return.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
A stratocu deck with predominantly MVFR cigs (locally IFR/LIFR
at FKL and DUJ) is ongoing this morning across most of western
PA and northeast WV, while much of eastern OH and the northern
WV panhandle has already cleared out. Expect these low clouds to
gradually lift and scatter over the course of the day, with VFR
anticipated at area terminals by roughly 16-18Z, with the
exception of course being FKL/DUJ where low clouds could linger
through 18-21Z before improving to VFR.

Ensemble guidance shows fog potentially building into the area
between roughly 08Z-13Z tonight. Current probabilities for MVFR
visibilities are highest (40-60%) generally around and
northeast of the PIT area in both the NBM and HREF. The HREF is
also more bullish about dense fog potential, showing
probabilities for visibilities <1 mi as high as 50-60% along and
north of I-80 compared to 20-30% in the NBM. Despite the low
probabilities in the NBM, leaned more towards dense fog in TAFs
at FKL/DUJ since those sites are typically more prone to fogging
in and calm winds and mostly clear skies should support
efficient radiative cooling.

Winds relax and veer to northwesterly throughout this afternoon
with perhaps a few gusts to 15-20 knots, followed by light winds
tonight becoming easterly Friday morning.

.Outlook...
Ensembles favor VFR prevailing through the weekend outside of
overnight/early morning patchy fog.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.

&&

$$

SYNOPSIS...22
NEAR TERM...Hefferan/22
SHORT TERM...Hefferan
LONG TERM...Hefferan/Frazier
AVIATION...Cermak