659
FXUS61 KPBZ 150133
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
933 PM EDT Sun Jul 14 2024

.SYNOPSIS...
Strong to severe storms may impact the Ohio River Valley
through Tuesday as multiple mesoscale convective systems form
upstream. A passing cold front Wednesday will return near-normal
temperatures and dry weather to the region.


&&

.NEAR TERM /UNTIL 7 AM MONDAY MORNING/...
KEY MESSAGES:

- Dry weather is anticipated for a large portion of the near
  term.
- Patchy fog may form early Monday morning in eastern Ohio due
  to remnant moisture in the boundary layer from the passing
  mesoscale convective system (MCS) over the last 6 hours.
- Convection chances increase after 6am Monday with a new
  disturbance developing in the Midwest.
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An mesoscale convective system (MCS) had dissolve over the last
2 hours and quiet weather has return to the region.

Light winds and remnant moisture from advancing precipitation
associated with the MCS, may create patchy fog for eastern Ohio
early tomorrow morning. However, the probability is low (less
than 10%) that fog will be considered "dense" (less than 0.50
miles).

A new disturbance, currently developing over southern Wisconsin
and northern Illinois, will track southeast and into the Ohio
River Valley over the next 12 hours. Convection form in our
county warning area (CWA) just before dawn. However, probability
of severe winds associated with storms is considered low (less
than 10%) through 7am. Therefore, only lightning will be the
main threat.

&&

.SHORT TERM /7 AM MONDAY MORNING THROUGH WEDNESDAY NIGHT/...
KEY MESSAGES:

- Active weather with several convective rounds presenting
  potential severe hazards until the passage of a cold front on
  Wednesday.

- Heat risks are present Monday/Tuesday but will be dependent
  on convective evolution and resultant cloud cover.

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

Convection may be ongoing at 12Z Monday, as whatever complex/MCS
can form continues to cross the region. Decaying
convection/lingering clouds could lead to a less favorable
environment for convection into Monday afternoon at least from
Pittsburgh on east. Clearing may be a bit more likely in eastern
Ohio by the afternoon hours, which could allow sufficient
destabilization for a fresh round of storms, paired with another
mid-level shortwave. CAPE on the order of 1000-2000 J/kg is
possible by afternoon, perhaps even higher in Ohio, with weak
shear and sufficient DCAPE to support mainly a damaging wind
threat and a secondary large hail threat where CAPE is more
favorably accumulated in the -10C to -30C hail growth zone. CSU
machine-learning guidance generally agrees with this. The
overall tornado threat appears low given the low shear, although
QLCS-type mesovortices could be a concern. There is also still
some potential for a more robust MCS to arrive later Monday
evening as well, although the threat of concentrated wind damage
should be a bit less for the Upper Ohio Valley as compared to
upstream areas. Nevertheless, the areawide SPC marginal day 2
risk is justified.

Uncertainty only increases from here. Further rounds of
convection are possible ahead of the eventual frontal passage
thanks to weak shortwave passages Tuesday and Wednesday. Again,
damaging wind continues to be the primary threat mode. A more
stout shortwave trough dropping into the Great Lakes on
Wednesday will finally help to push a cold front along for an
eventual Wednesday afternoon/night passage, bringing a more
concentrated precipitation area Wednesday, but then an end to
the convective threat behind it.

Of course, heat and humidity will continue to be part of the
story during the early part of the week. The potential for
advisory-level heat index values of 100 or more on Monday (and
Tuesday for that matter) will be highly dependent on convective
extent and timing. With 850mb temperatures expected to reach or
exceed 20C over a good portion of the region, a lack of cloud
cover could lead to sufficient sunshine to get surface
temperatures into the mid 90s for some on either day, leading
to the higher heat index values. However, more abundant cloud
cover could keep temperatures below 90 and therefore stunt the
heat impact. Due to this, will hold off on any heat-related
headlines for now, hoping that time and additional near-term
information will lead to increased clarity. More concentrated
clouds and precipitation on Wednesday should limit heating below
advisory thresholds.

&&

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

- A drier and cooler pattern will ensue on Thursday and continue
  into next weekend.

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

The cold front should complete its passage Thursday morning, perhaps
stalling over the Central Appalachians/Middle Ohio Valley, with
expanding high pressure across the Great Lakes and northeast
CONUS into next weekend. Drier weather and cooler temperatures,
perhaps falling a few degrees below normal, can be expected
through Friday night.

The shallow upper troughing in place Thursday and Friday may be
replaced by rising heights Saturday/Sunday in response to increased
troughing over the Central Plains. This could also bring moisture
back from the south, leading to increased diurnal precipitation
chances, mainly southeast of Pittsburgh. A warmup back to seasonable
temperatures can also be anticipated.

&&

.AVIATION /01Z MONDAY THROUGH FRIDAY/...
The decaying MCS from earlier will spread weakening showers
across ern OH, nrn WV and nwrn PA this evening. Amid diminishing
buoyancy resultant from dewpoints in the low 60s, there is
considerable uncertainty if any will persist long enough to
impact any terminal, so VCSH was limited to a brief window
before sundown.

There appears the potential for fog overnight near ZZV as the
low-level airmass has moistened considerably in the wake of
earlier storms, with overnight conditions of light wind and
radiative cooling favorable for a drop in vsby.

By morning, a decaying midwestern-CONUS MCS may impact the
region. Most likely area of restrictions in SHRA is near FKL,
while MVFR cigs are possible at most terminals for a few hours
between 15/0900-1300 UTC.

Although there is much higher confidence in the presence of
deeper moisture Mon afternoon as swly wind aids in the ewd
return of high dewpoints, the convective evolution across the OH
Valley has very-low confidence during the afternoon.

The boundary layer nevertheless will be deep by mid-day Mon,
and MLCAPE will be sufficient for strong storms. But given the
uncertainty, have tried to time VCTS to the hours of best
convective potential at each site during the early- to mid-
afternoon timeframe. Greatest likelihood of broader convective
coverage is north of an axis from PHD-PIT-IDI, but scattered
storms will be possible elsewhere.

.Outlook...
Periodic shortwave troughs will lend to thunderstorm chances
through mid-week, peaking Wed with the approach and passage of
a cold front. Timing and coverage will be difficult to ascertain
even a day out due to the strong impact of prior days`
convective evolution.

High pressure is favored by Thu to ensure another period of VFR
and dry weather.

&&

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

&&

$$

SYNOPSIS...Hefferan
NEAR TERM...Hefferan
SHORT TERM...CL
LONG TERM...CL
AVIATION...Kramar/Rackley/Frazier