PBZ issues Area Forecast Discussion (AFD) at Jun 23, 4:42 PM EDT754
FXUS61 KPBZ 232042
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
442 PM 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 /UNTIL 6 AM MONDAY MORNING/...
KEY MESSAGES:
- Severe weather possible this afternoon with wind being the
primary threat, although tornadoes could not be ruled out.
- Cooler temperatures tonight.
-------------------------------------------------------------------
4:45pm update... Severe Thunderstorm Watch has been issued for
all of our PA counties, the WV Panhandle, and parts of eastern
OH until 10PM.
Thus far, despite MLCAPE around 1000 J/kg as per latest RAP
analysis, storms have struggled to gain a lot of vertical extent
beyond around 15,000 feet as a cap evident on our 18z sounding
is preventing growth above that layer. If repeated updraft
attempts and/or stronger forcing from the cold front itself can
erode and punch through that layer, stronger cores tapping into
intruding mid-level dry air may pose a damaging wind potential
into the evening as DCAPE subsequently increases. Below that
15kft layer though, there is plenty of shear packed into the 0-1
km layer with low level MLCAPE in excess of 100 J/kg sufficient
for updraft shearing and stretching. Veering of the wind field
in the low levels isn't quite as pronounced as initially
modeled, but latest KPBZ VAD profiles indicate >100 m2/s2 0-1 km
SRH, thus any right moving shower or storm (SE direction) could
tap into enhanced streamwise vorticity and pose a localized
tornado threat given LCL heights around 750-1000 meters. All
that said, weakly rotating, generally low topped gusty showers
have been the dominant feature to this point as we await the
arrival of the cold front and the strongest forcing.
Some instability generation is expected throughout the afternoon,
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.
Just ahead of and along the front, mesoanalysis indicates up to
1300 J/kg of DCAPE. 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. Hail seems quite low probability with dry air
dislocated from the hail growth zone and storm heights in excess
of 40kft-50kft needed.
Storm chances will persist across much of the area until the
cold front arrives this evening. 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 /6 AM MONDAY MORNING 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. As the 12Z
mesoscale guidance begins to come in, it has been a bit more
bullish on convective development in central Michigan. Its also
suggests that convective elements deteriorate as they head
southeast into ridging and drier air, but it will warrant
watching Tuesday and Tuesday night.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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. This will also largely depend on a
favorable arrival time.
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 /21Z SUNDAY THROUGH FRIDAY/...
Scattered to numerous showers and thunderstorms are expected
along and ahead of an advancing cold front this afternoon and
evening (favoring 19z-00z). Storm strength may be dependent on
degree of surface heating, but risks exist for damaging wind and
small hail along with the typical vsby/cig restrictions in
heavier rain.
Isolated showers may persist after FROPA this evening given
delayed passage of the upper level trough axis. However, its
crossing overnight will foster cool, dry advection that will end
shower activity and begin to erode post-frontal stratocu.
Ensemble models vary in degree/timing/cover of that clearing,
with residual boundary layer moisture favoring pockets of low
VFR to MVFR cigs near FKL/DUJ/LBE/MGW.
Building high pressure will support VFR and reduced afternoon CU
Monday. Expect deeper mixing and residual surface gradients to
foster 20-30kt NW afternoon wind gusts.
.Outlook...
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.
Thereafter, high pressure and ridging aloft should support
multiple days of dry weather.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...Milcarek
NEAR TERM...MLB/Milcarek
SHORT TERM...WM/Milcarek
LONG TERM...WM/Milcarek
AVIATION...Frazier
Source:
PBZ issues Area Forecast Discussion (AFD) at Jun 23, 4:42 PM EDT---------------
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