-- Discussion containing changed information from previous version are highlighted. --
395
FXUS61 KPBZ 100952
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
552 AM EDT Thu Jul 10 2025

.SYNOPSIS...
A typical warm and moist summer airmass will remain in place
this week and allow scattered afternoon and evening
thunderstorms to develop over the Upper Ohio River Valley each
day. Thunderstorm chances will be a bit higher this weekend as a
weak cold front sags into the area from the Great Lakes.

&&

.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:
- Patchy dense fog lifting this morning.
- Isolated showers and thunderstorms.
- Main threats are wind and flash flooding.
- Patchy fog possible again tonight.
---------------------------------------------------------------

A stabilized airmass is noted near and north of a stalled surface
boundary across eastern OH to southwestern PA. The airmass is
currently characterized by cool temps and dew points in the mid to
upper 60s. Areas of low visibility have been reported at various
airports across the region along with satellite confirming areas of
fog. Areas of patchy fog will lift with diurnal heating by 8AM/9AM.

An upper level trough over the eastern Great Lakes will bring moist
and unstable environment to the region. This results in diurnal
thunderstorms that are isolated in nature and poorly organized. With
the upper level flow weakening, these storms are expected to be slow
moving in nature. Precipitable water values are forecast around
1.5" which will be high enough to support locally heavy rain.
With the slow-moving storms and the moisture, there is the
possibility for localized areas of flash flooding.

Mid levels are forecast to be drier today. With some additional
DCAPE, there is a slightly higher potential for wet microbursts.
Strong wind is possible with thunderstorms today.

After sunset, the probability for showers and storms will
significantly decrease. With the moisture expected to remain
stationary, there is a chance for patchy fog to develop again
tonight.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
-- Changed Discussion --
KEY MESSAGES:
- Weak troughs moving along northern edge of subtropical high  will
support scattered diurnal thunderstorm development
- Low probability of severe and flash flooding at any one point but
a couple spots could see significant weather each day
- Temperatures a bit above normal with a gradual warming trend
  peaking out on Saturday around 90FF
----------------------------------------------------------------

Currently, the region is seeing a common summer pattern with an
upper-level high over the southwestern U.S. and an upper-level
trough over the Great Lakes. Combined with a westerly flow aloft,
seasonably moist and unstable airmass settles in the area with daily
rounds of diurnal thunderstorms that will be poorly organized/more
isolated with weak shear. Upper level flow is expected to remain
weak through the weekend, so expect slow moving storms.
Precipitable water values around 1.5" on Friday and Saturday,
will be high enough to support locally heavy rain. This combined
with the slow moving storms could result in localized flash
flooding.

Not much organization for the thunderstorms and coverage will
be scattered with very sparse coverage of heavy rainfall and
damaging winds each day. It is likely that only 1-2 locations
each day are impacted by significant weather while most
locations will remain dry.

Expect a gradual warming trend into this weekend with maximum
temperatures peaking around 90F on Saturday.
-- End Changed Discussion --

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
KEY MESSAGES:
- Weak front brings better chance of thunderstorms Sunday
- Not much cooling with temperatures remaining about 5 degrees
  above normal
-------------------------------------------------------------------

The pattern is not expected to change a lot. Even with weak
summer flow regime, a good bit of spread on the timing and
intensity of weak troughs drifting through the Ohio Valley and
Great Lakes.

Looks like best shot for a weak front to enhance thunderstorm
chances will be on Sunday. Probabilities for severe weather,
based on the ECMWFE, are highest on Sunday. Precipitable water
values will increase from about 1.5" to the 1.75-2.00" range,
which will also bring a higher threat of heavy rain and flash
flooding.

Pattern for Monday thru Wednesday becomes a bit more complex
and uncertain as we could see a series of weak trough/ridge
couplets. There is chance for a dry day or two in that time
range, however, there is low confidence at this time.
-- End Changed Discussion --

&&

.AVIATION /10Z THURSDAY THROUGH MONDAY/...
Patchy fog development currently observed across the region has
potential to become more widespread by sunrise based off latest
forecast soundings showing MRI values favoring fog over stratus
and crossover temperatures dipping down to between -3 to -5F
based off TDs during max mixing yesterday afternoon. Latest
ensembles/blends show a 20-50% chance of IFR vis restrictions
in general between 4 and 8AM this morning, and nealy identical
probabilities for MVFR vis restrictions. So at appears to be an
all or nothing situation, and will make amendments to current
TAFs early prior to sunrise once it becomes more apparent which
scenario plays out.

Any fog is likely to dissipate quickly around mid-morning
with a broad return to VFR conditions. Storms are possible
after 18z and will present as more scattered in coverage. Timing
will be difficult to pin down with development potentially off
of Lake Erie`s lake breeze initially, with subsequent initiation
driven by storm outflow. Any showers/storms could bring brief
heavy rainfall and gusty wind. PROB30 was included at all sites
for now, pending refined mesoanalysis later this morning, which
could help identify targeted areas and timing.

Outlook...
A weakly forced but warm/humid environment is favored through
the end of the week 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 over the weekend, which will create a better
focused period for convection and restriction development.

&&

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

&&

$$

SYNOPSIS...Craven
NEAR TERM...Lupo
SHORT TERM...Craven/Lupo
LONG TERM...Craven/Lupo
AVIATION...88