494
FXUS61 KPBZ 122249 AAA
AFDPBZ

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
649 PM EDT Fri Jul 12 2024

.SYNOPSIS...
Above-average temperatures are expected through early next week
before a cold front returns more seasonable temperature late
week. A more active pattern is expected Sunday through midweek,
favoring increasing chances for thunderstorms each afternoon.

&&

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

- Temperatures trend warmer with heat risk becoming moderate by
  Saturday.

- Isolated convection is possible, but unlikely each afternoon.

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For the evening update...removed mention of PoPs as strong
subsidence and deep mixing, bringing drier air to the surface,
is dissipating any activity that moves toward the CWA. Rest of
the forecast is in good shape.

Previous discussion...

With little environmental change overnight, patchy river valley
fog is likely once again. The biggest limiting factor will be
any lingering mid-level clouds associated with the passage of
the upper trough axis.

The warming trend continues on Saturday as broad zonal flow and
rising heights aloft drive much of the region back in the 90s.
Minimal forcing and warm air aloft should largely suppress most
convection, but CAMs do still hint at enough surface heating
Saturday afternoon for destabilization. The main triggering
mechanism for any convection would be an Erie lake breeze. The
result could be brief, isolated thunderstorms favoring northwest
PA in the afternoon, quickly collapsing after sunset.

&&

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

- Increasing heat risk expected as temperatures sit 5 to 10
  degrees above the daily average.

- A more active pattern begins Sunday with a series of crossing
  shortwaves and possible MCSs.

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A more active pattern begins Sunday as the first in a series of
shortwave troughs crosses out of the Great Lakes. CAMs highlight
a possible MCS crossing out of Michigan and into northern Ohio
during the early afternoon hours, eventually decaying as it
moves across our area late afternoon or early evening. Some
scattered convection may also be possible ahead of this feature,
and CAM soundings indicate a possible downburst environment with
significant DCAPE near 1500 J/kg. However, considerable
uncertainty remains with this setup. In particular CAMs tend to
perform poorly with MCSs in a weakly forced environment.
Destabilization ahead of the MCS will also depend on the amount
of surface heating and moisture availability given lingering
warm air aloft and the lack of notable moisture. This could be
hampered by increasing cloud cover, though current forecasts put
much of the area in the 90s by mid-afternoon. CSU-ML
probabilities extend a 5-15% area into eastern OH and most of
WV/PA.

A similar, but possibly more potent, setup is expected on Monday
as another shortwave crosses out of the upper Midwest and
through the Great Lakes region. This pattern will again be
conducive for MCS development somewhere upstream and moving
towards our area during the day. Considerable uncertainty
remains and will likely be dependent on Saturday`s evolution,
but it`s worth noting that the CSU- MLP highlights an area of
30-45% severe probs into eastern Ohio. This will certainly be
something to watch as we get in range of the CAMs.

Regarding temperature, the warming trend continues through the
short term, with much of the area from PIT south solidly in the
mid-90s by Monday afternoon. Monday`s HeatRisk outlook
highlights most of the area as a major risk. However, early
afternoon iso/sct convective development or an earlier arriving
MCS could suppress these highs a bit each afternoon.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
KEY MESSAGES:

- An active severe weather pattern is anticipated through
  Wednesday morning, subsiding thereafter.

- Heat risks could be maximized Tuesday, but will be dependent
  on convective evolution and resultant cloud cover.

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The basic synoptic pattern continues through midweek as
shortwaves continue to cross the area. Models continue to
highlight MCS movement near or through the region on Tuesday
before a surface cold front passes Wednesday. Uncertainty
remains high as Tuesday`s environment will once again be
predicated on the previous day`s convective evolution.

Prior to the cold front passage Wednesday, the hot and humid
environment may also lead to notable heat risk for the region
as air temperatures on Tuesday again approach the mid 90s and
heat indices cross the 100 degree Heat Advisory threshold. The
main limiting factor is potential for thunderstorms to shut-off
daytime heating and/or provide excessive cloud cover that stunts
surface warming.

Ensembles favor the cold front passing Wednesday, but spread
exists in the shape of the upper trough and how quickly
drier/cooler conditions return for all locations. Most locations
should experience dry and seasonable weather Thursday, but storm
chances may linger in southern zones if the front ends of
stalling south.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
VFR forecast through the period. Much of the cu will dissipate
later this evening. Fog is still a threat early Saturday
morning, but less so as temperatures have warmed about 10 to 15
degrees higher today. Have included the mention of fog at FKL
and DUJ with FKL possibly seeing LIFR fog shortly before
sunrise.

Any late night fog will quickly burn off after sunrise.

More cu is anticipate on Saturday as surface dewpoints rise and
moisture increases above the BL.

.Outlook...
Ensembles favor VFR prevailing through Sunday outside of
overnight/early morning patchy fog. The likelihood of
restrictions with convection will increase Monday and Tuesday.

&&

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

&&

$$

SYNOPSIS...Rackley
NEAR TERM...Rackley/22
SHORT TERM...Rackley
LONG TERM...Rackley/Frazier
AVIATION...22