176
FXUS61 KPBZ 142129
AFDPBZ

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

.SYNOPSIS...
A cluster of strong to severe storms continues to track across
Ohio today. Sub-severe wind gusts are expected in eastern Ohio.
Remnant showers may continue during the overnight period. The
synoptic pattern favors strong to severe storms Monday into
Tuesday.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
KEY MESSAGES:

- A mesoscale convective system (MCS) continues to track across
  eastern Ohio this afternoon; severe winds have been noted
  along portions of the squall line.
- Sub-severe winds and lightning are expected for portions of
  eastern Ohio through 7pm.
- Remnant rain showers from the MCS may continue into the
  overnight period. Rain totals are expected to stay below 0.25
  inch.
-------------------------------------------------------------------

A mesoscale convective system (MCS) continues to track through
Ohio this afternoon. Severe wind gusts have been measured and
observed (trees/utility lines down) in western Ohio as the rear
inflow jet advances along the leading edge of convection.
KILN`s radar measured 55mph within the boundary layer with this
feature.

For eastern Ohio, 40 to 45mph wind gusts are anticipated along
the leading edge of the squall line. The Columbus terminal
radar (TCMH) measured 40mph at 100ft at 5pm. Special Weather
Statements (SPS) will continue to be issued for sub-severe wind
gusts before the MCS eventually dissolves between 7pm and 9pm.

Remnant showers, associated with the tracking MCS may slowly
advance into western Pennsylvania after dark. However,
confidence on widespread rainfall of more than 0.10 inches is
low (less than 20%). The heaviest rainfall will likely be west
of Pittsburgh, PA due to the overall track of the MCS.


&&

.SHORT TERM /6 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 /21Z SUNDAY THROUGH FRIDAY/...
Mainly VFR conditions are expected today under the continued
influence of high pressure. Expect a few/sct CU with diurnal
heating and potential for an occasional SW wind gust to 20kts.

Uncertainty continues with in regards to the evolution of an MCS
currently crossing out of IN into western OH. This system is
expected to dive southeastward across OH and possibly clip the
ZZV around around 21-22z. TEMPOs have been added to account for
this impact. Elsewhere, other than an isolated shower or two,
the area will remain dry through the evening.

Another decaying MCS may impact the area overnight, but again,
there is low confidence on this and models are handling the
setup very poorly. A fresh round of storms is also possible
Monday afternoon, but this will largely depend on the evolution
of the previous system.

Westerly winds will gust to near 20 kts Monday afternoon

.Outlook...
Periodic shortwave movement will lend to thunderstorm chances
through mid week, peaking Wednesday 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 Thursday and ensure another period
of VFR and dry weather.

&&

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

&&

$$

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