653
FXUS61 KPBZ 231408
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1008 AM EDT Sun Jun 23 2024

.SYNOPSIS...
Storms will increase in coverage this afternoon and evening
before and along a cold front. Some may be severe, with wind
being the primary threat, while isolated tornadoes could not be
ruled out. Temperatures drop to near-normal on Monday before
increasing, yet again, next week.

&&

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

- Severe weather possible this afternoon with wind being the
  primary threat, although tornadoes could not be ruled out.
- Cooler temperatures tonight.
-------------------------------------------------------------------

In reference to the 12Z sounding and current radar imagery,
severe convection is not anticipated for the AM hours. The pre-
frontal trough is clearly defined by stratiform rain with
embedded convective elements, but the morning sounding shows
subsidence has set up a mid-level cap around 10k-15k feet.

As the trough pivots around the low and enters our area, the
linear forcing become a bit less defined which may indicate a
weakening of the stratiform elements. In areas that do receive
rain, precipitation in the profile will saturate and potentially
erode the mid level cap via wet-bulbing. In regions that do
not, we will have to rely solely on heating to overcome the cap.

One thing is clear, once the cap is overcome, mature storms are
possible in up to 1000-1500 J/kg MLCAPE. Storm chances will
persist across much of the area until the cold front arrives
this evening. Despite the homogeneous probabilities of storm
development ahead of and along the trough, the environment will
be evolving throughout the day.

Behind the trough, meso-analysis indicated a DCAPE minimum of
400-600 J/kg before 4pm, although wind threats will remain
possible with storm motion near 40kts. A low-jet behind the pre
frontal trough will stretch the 0-3km shear up to around
30-35kts, with most of that packed in the lowest 1km in a veered
profile. This would suggest a favorable environment for
tornadoes in right moving storms, although there is only a 15%
to 30% chance LCLs are below 1000m, which would be unfavorable
for tornadoes. Overall, the threat cannot be ruled out,
dependent on low-based storms. Hail seems quite low probability
with dry air dislocated from the hail growth zone and storm
heights in excess of 40kft-50kft needed.

Some instability generation is expected throughout the day,
along with a reinforcement of mid-level dry air along and just
before the front that may suggest wind threats increase in
probability throughout the day and remain maximized along the
front in 1200-1400 DCAPE. Should this realize, storms will
likely be cold pool-dominant, in-detriment to tornadogenesis,
though stretching and boundary ingestion will remain in the
cards.

Tonight will bring a welcome cool-down into the 60s and even 50s
with cold advection, clearing, and decreasing shower chances
behind the front.

&&

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

- Mainly dry weather returns
- Seasonable temperatures return Monday, warmer Tuesday

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

The upper trough will cross the NE CONUS Monday, as surface high
pressure builds in underneath. This should result in dry and
seasonable weather. Mainly clear skies and light wind should
result in radiational cooling Monday night. Most locations will
see lows in the 50s. Patchy river valley fog is also expected.

Rising 1000-500mb heights and warm advection should return
temperatures to above seasonable levels on Tuesday. A couple of
MCSs are expected to develop across the Midwest region Tuesday
night. Some operational models brush these complexes near the
Upper Ohio Valley region late Tuesday and Tuesday night. Given
the placement of the low level jet upstream, and the tendency
for MCSs to follow the 1000-500mb thickness pattern, think these
will stay to our west at this time.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
KEY MESSAGES:

- Thunderstorms likely with a Wednesday cold front
- Cooler Thursday, followed by a warming trend
- Dry Thursday and Friday, before another front approaches
  Saturday
-------------------------------------------------------------------

The next shortwave trough, and associated surface cold front, is
expected to approach and cross the region on Wednesday, with
showers and thunderstorms likely. Strong to severe storms will
be possible, if current model projections of shear and
instability levels verify.

High pressure is expected to return dry weather to the region
Thursday and Friday. Seasonable temperatures are expected
Thursday, before a return to above average readings on Friday as
heights rise and warm advection occurs.

The next approaching cold front will return shower and
thunderstorm chances back to the forecast at the start of the
weekend.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
VFR will continue before an upper level shortwave and
associated cold front returns shower and thunderstorm chances
this afternoon and into the evening. Latest guidance suggests
a prefrontal trough from 15-20z followed by a 21z-03z cold front
FROPA. Could see restrictions to cigs/vis in and around heavier
storms. Some storms may be strong to severe, particularly with
the cold front.

Dry, cool advection will erode most lingering stratocu after
FROPA, but upper trough axis crossing during overnight hours may
offer low probability showers and low VFR/MVFR cigs along I-80
corridor and the higher terrain (FKL/DUJ/LBE/MGW).

.Outlook...
High pressure and northerly flow aloft will establish dry and
more seasonable conditions for the start of the next work week.

Ensembles hint at potential MCS moving SE out of the Great Lakes
sometime between Tuesday night through Thursday morning ahead of
the next upper level shortwave. This is will need to be
monitored for terminal impacts; the weather pattern is likely
dry thereafter.

&&

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

&&

$$

SYNOPSIS...Milcarek
NEAR TERM...Milcarek
SHORT TERM...WM
LONG TERM...WM
AVIATION...Frazier/88