571
FXUS61 KPBZ 110712
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
312 AM EDT Fri Jul 11 2025

.SYNOPSIS...
Scattered afternoon and evening thunderstorms expected daily
through the weekend with the highest chance on Sunday as a weak
cold front crosses the area. The first half of next week may be
drier ahead of another late week disturbance. Temperatures will
remain above normal.

&&

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

- Isolated to scattered afternoon/evening showers and storms
- Heavy rain and damaging downburst winds still possible with
  any stronger storms
- Warming trend with temperatures potentially exceeding 90F in
  river valleys and urban metros.

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

Little change to the pattern is expected through the near term
as we remain under weak flow aloft but a warm and humid airmass
at the surface. Weak mid-level height rises could provide a
slight boost in subsidence, but enough instability is still
forecast to support isolated thunderstorm chances during
afternoon hours. Once again, attempting to peg down exact
timing and location of development would be a losing battle,
given weak forcing/flow and the influence of remnant outflow
boundaries from previous days. While overall ensemble trends
suggest higher coverage in the ridges and to the east (HREF
probabilities for SBCAPE >1000 J/kg are maximized over western
PA and northeast WV), would have to believe that remnant outflow
and the lake breeze could still play a role elsewhere. Regardless,
mean HREF soundings suggest PWATs near 1.5" which coupled with
the weak steering flow will maintain the potential for locally
heavy rainfall in any thunderstorms that do develop.
Additionally, upwards of 1000 J/kg of DCAPE is forecast,
supporting a downburst threat in any stronger storms.

Outside of convection, temperatures will generally climb into
the upper 80s, though urban metros and river valleys could see
temps reach 90F as NBM probabilities for exceeding that are
40-60% in those areas.

Any showers or storms that form during the day will dissipate
after sunset with the loss of daytime heating, giving way to
another mild and potentially foggy night. NBM probabilities for
low temperatures staying at or above 70F are highest (70-90%) in
river valleys and urban metros, with moderate chances (40-60%)
elsewhere except for the ridges and north of I-80 where they are
below 30%.

&&

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

- Scattered afternoon and evening showers and storms Saturday
- Heavy rain and damaging wind threat with stronger storms on
Saturday
- Wetter on Sunday with a passing cold front
----------------------------------------------------------------

Diurnally driven convection will continue on Saturday with weak flow
aloft. Ensemble mean PWAT values remain similar to earlier this
week, around 1.5", and a 60-80% chance of SBCAPE values >1500 J/kg.
DCAPE values sit around 800-1100 across the 00z CAMs again
supportive of a very localized heavy rain and downburst threat. With
a weak flow aloft, flash flooding is another threat as the storms
will be slow moving. Pegging down exact timing and location of
development again is very difficult, especially with the influence
of remnant outflow boundaries from previous days. There are
suggestions that it may be more terrain driven with higher coverage
in the ridges to the east, however, remnant outflow and the lake
breeze could again play a role.

Outside of convection, there is an increased probability that
temperature have up to a 90% in the urban areas and valleys (55%-75%
elsewhere) to reach 90F Saturday.

Sunday looks to be the wettest day of the weekend as low pressure
tracking across the Great Lakes drags a surface cold front through
the area. The best shortwave support will track north of Lake Erie,
but there will be a plenty warm and moist airmass in place for the
boundary to work upon. Due to the faster speed of the frontal
boundary, the threat for flooding will come from training. There is
high confidence that the cold front passes on Sunday, but the
deterministic guidance suggests a later timing which would impact
any severe or flooding threat.

Machine learning suggests there could be a severe threat, contingent
on an afternoon to evening timing, but organized severe weather
seems less likely given weak vertical wind shear as the strongest
flow remains to our north.

&&

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

- Wetter on Sunday with a crossing boundary
- Potentially drier first half of next week ahead of another
  low pressure system passage by mid to late week
- Temperatures remain above average
-------------------------------------------------------------------

Following the low on Sunday, the associated mid-level trough swings
through on Monday and could provide more afternoon and evening
showers and storms. Ensembles do deviate with the post-frontal
environment as some suggest a surface high quickly building in while
others don`t bring the high in quite that quickly allowing for
another unsettled day. NBM still supports 30-60% PoPs, highest to
the southeast, however, it will trend drier if the more progressive
solutions are correct. Not much of an airmass change is likely
behind the front, so still expecting above average highs on Monday.

Tuesday and Wednesday show indications of being drier across the
board as aforementioned high pressure does settle in and upper
ridging builds from the southwest. This will allow temperatures to
climb with warm advection in southwesterly flow bumping 90F
probability back up to 50%-70% on Tuesday and 70%-90% on Wednesday,
again highest in the urban areas. Ensembles track yet another low
pressure system out of the Great Lakes Thursday into Friday which
will likely bring another cold front through and return rain
chances. Being 7+ days out, there is still plenty of disagreement on
timing and amplification of the mid-level trough, however, it`s less
likely that we keep the dry weather around through the end of the
week.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
A moist boundary layer combined with calm wind and partly clear
overnight skies will foster strong radiational cooling that
results in fog between 06z-12z. An analysis of fog/stratus last
night showed that the UPS fog method (focusing on daytime
minimum dew point and the time overnight temperatures reach that
value) performed well. The biggest variable change between last
night and tonight is the lack of rain to reinforce surface
moisture and diurnal mixing that introduced some drier air to
the surface. Thus, following a similar methodology, fog
probabilities have trended lower (but still present) at most
terminals through early morning.

Insolation will burn off any developed IFR/LIFR fog/stratus by
mid morning and aid in isolated thunderstorm development after
18z Friday. Hi-res modeling is bearish on potential, favoring
locations in western PA and northern WV, so kept prob30 wording
for those terminals.

Outlook...
A weakly forced but warm/humid environment is favored through
Saturday that will allow for intermittent periods of
showers/thunderstorms. Confidence is likely to be lower on
timing various rounds of precipitation as well as the resultant
cig/vsby impacts they could have during the morning hours.

More significant upper-level and surface boundary movement
appears to arrive Sunday, which will create a better focused
period for convection and restriction development.

&&

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

&&

$$

SYNOPSIS...MLB
NEAR TERM...Cermak/MLB/Shallenberger
SHORT TERM...MLB/Lupo
LONG TERM...MLB/Lupo
AVIATION...Cermak/Frazier