-- Discussion containing changed information from previous version are highlighted. --
067
FXUS61 KPBZ 230732
AFDPBZ

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

.SYNOPSIS...
Showers and thunderstorms are expected at times today with the
approach and passage of a cold front. Some of the storms could
be severe this afternoon and evening, with damaging wind the
main hazard. Generally dry weather and more seasonable
temperatures are expected Monday and Tuesday as high pressure
builds in.

&&

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

- Showers and thunderstorms return at times today with a
  crossing cold front
- Severe storms are possible this afternoon and evening
- Cooler temperatures tonight
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Early morning temperatures remain warm this morning. These
readings could break the record warm lows for the day, if not
for temperatures falling before midnight tonight after the
passage of a cold front.

A shortwave, and its associated surface cold front, will
approach the region today. A prefrontal trough, associated with
convection across the Midwest, will track across the Upper Ohio
Valley region later this morning and early afternoon. While a
weakening trend is expected in this convection, showers and
thunderstorm chances will escalate as the trough approaches. A
low level will also support this activity as it tracks across
the region.

The storms are expected to increase in strength again this
afternoon as diurnal instability builds. In addition, the
surface cold front is expected to cross the region from W-E from
early afternoon through early evening. Additional thunderstorm
development is expected along, and ahead of the front.

Ensemble based MU CAPE is progged between 1500 and 2000 j/kg
this afternoon, with some operational CAMS and ensemble max
values around 2500 j/kg. 0-6km shear is also expected to
increase to 35-40kt at the same time. A relatively strong wind
field aloft, along with mid level dry air, should result in a
damaging wind potential for storms with organized updrafts. CAMS
output shows DCAPE levels 1000-1200 j/kg this afternoon/evening
ahead of the front. A veering wind profile/curved hodographs
indicate a tornado potential as well, especially with discrete
cells. The Storm Prediction Center has placed the forecast area
in a Slight Risk for severe storms today. The main hazard is
expected to be damaging wind gusts, though with the veering wind
profile isolated tornadoes are also possible. The hail
potential remains limited.

Uncertainty remains in how the prefrontal trough will affect
destabilization ahead of the front, and how strong storms will
become along the trough in the afternoon. There is also
uncertainty in how much the dry air aloft will affect updraft
strength.

The front will complete its passage this evening, with shower
and thunderstorms exiting the region. Generally dry and cooler
weather is then expected overnight as surface high pressure
begins to build under a crossing trough aloft.

High temperatures will be cooler today, though still around 5-8
degrees above average. Lows tonight should drop into the lower
60s for most locations, with upper 50s in some outlying areas.

&&

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

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

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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
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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 /08Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
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.

.Outlook...
Lingering showers and low probability thunderstorms are possible
through early Monday morning amid cold advection and crossing of
the upper trough axis.  High pressure and northerly flow aloft
will establish dry and more seasonable conditions for the start
of the next work week.
-- End Changed Discussion --

&&

&&

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

&&

$$

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