128
FXUS61 KPBZ 230339
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1139 PM EDT Sat Jun 22 2024

.SYNOPSIS...
Showers and thunderstorms return Sunday with a cold front. Severe
weather is possible tomorrow afternoon and evening, with the
primary threat damaging wind, although hail and tornadoes are
possible. A brief cool down is expected through Monday before
temperatures increase yet again.

&&

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

- Mainly dry and warm overnight
-------------------------------------------------------------------

Update...
Generally dry and warm weather is expected tonight, with
increasing clouds. Made adjustments to near term clouds and
temperatures based on current observations, and near term model
data.

Previous discussion...
Into this evening and tonight, a pressure gradient will
increase a a Great Lakes low moves in. This will usher in light
southwest flow at the surface and finally begin to usher in a
different airmass. With the return of clouds tonight and light
winds, tonight may be the warmest night of the week with lows
only bottoming out in the low to mid 70s. This will keep
conditions uncomfortable for one final night.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
KEY MESSAGES:


- A 2 out of 5 risk for severe weather is forecast on Sunday
  afternoon and evening.
- Damaging wind is the primary threat, though large hail and
  tornadoes remain possible.
-------------------------------------------------------------------

Tomorrow will start with dew point at or around 70 with
temperatures in the middle to upper 70s around around 8am. By
around 10am, ahead of a pre-frontal trough, some local
acceleration of flow will allow shear to creep up, with about a
10% to 25% chance of 0-6km shear being above 30kts. As surface-
based instability creeps up with daytime heating, there is
roughly a 50% confidence of at least 500 J/kg of SBCAPE. This
does not suggest severe criteria by this point, but the
environment will continually become favorable through the
morning.

By around the noon to 4pm timeframe, a pre-frontal trough will
push through and provide weak lift for storms. Additional
heating will push SBCAPE up to >1000 J/kg with 60% to 100%
confidence, while 0-6km shear lingers around a 25% to 60% chance
of >30kts. Low confidence in shear >30kts might typically
suggest sub- severe storms are favored, but much of the shear is
forecast to be in the 0-3km layer with veered profiles. This
gives cause to suggest low- level organization is possible not
long after initial cumulus development. This might favor
tornadogenesis, should LCLs remain below 1000m (which seems
generally unlikely with the initial wave). On the other hand,
the environment will still be primed with antecedent 1000-1200
J/kg of DCAPE, which is a detriment to tornadogenesis and may
suggest higher wind threats. Dry air may also limit convection
altogether as it is entrained into updrafts. Needless to say,
confidence remains lower with initial convection, but may be
binned into 3 scenarios. 1) Convection does not occur with
forcing to weak to overcome the dry air aloft. 2) Convection
does occur and remains cold-pool balanced; this would result in
a higher tornado and hail risk. 3) Convection does occur but the
cold-pool is dominant, allowing wind threats to be maximized in
downbursts.

Some recovery is expected behind the pre-frontal trough,
followed by the cold front itself with higher chances of
convection altogether with stronger forcing in roughly the 6pm
to 10pm timeframe. Afternoon storms will influence what
convection we see for the rest of the day. If storms do develop,
they will utilize the best environment in detriment to storms
that form along the cold front itself. If storms do not develop,
the environment will remain better primed for evening storms.
Convective ensembles suggest that shear ahead of the cold front
may be a hair less, but the best shear may be more confined to
the 0-1km layer with a smoother veering profile while
instability may be conditionally more. With right moving cells
remaining perpendicular to the front, discrete cells are
possible along the line. In discrete, balanced cells, tornados
remain possible as well as a secondary hail threat.
Additionally, LCLs appear to be a bit lower than initial
convection. If the cold pool is dominant, winds remain the
primary threat in discrete cells and storms may evolve to
become more linear and accelerate as the cold pool races ahead
of them. Needless to say, there are still a lot of questions
about tomorrow, but all threats remain on the table.

Monday brings a welcome reprieve to the heat with mostly dry
conditions favored and temperatures back to near normal.

&&

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

- Above average temperatures return
- Additional severe chances return mid-week.
-------------------------------------------------------------------

As the eastern trough from Monday moves off of the coast,
northwest flow aloft will be undercut by southwest flow at the
surface as height rises ensue. There is high confidence that
additional ridging, warm advection, and southwest flow push high
temperature up to around 10 degrees above average during the
Tuesday and Wednesday period.

Tuesday is forecast to remain mostly dry accordingly, although
upstream convection could trickle down to low-probability of a
nocturnal MCS Tuesday night. Otherwise, rain chances increase
Wednesday along and ahead of another cold front. Severe
potential will need to be monitored, depending on storm timing.

The is high confidence that ridging redevelops next weekend, but
low confidence in the magnitude of height increases. Clustered
variability ranges anywhere form 588dm to 594dm. This would
suggest another anomalously warm period ahead next weekend, but
clusters devolve to some flattening or troughing by the
beginning of the following week. This alludes to the fact that
the next period of heat may be a lower duration.

&&

.AVIATION /04Z SUNDAY THROUGH THURSDAY/...
High probability for VFR to persist through tonight and much of
the day Sunday. Approach of an upper level shortwave and
associated cold front will increase shower and thunderstorm
chances after 15Z and lasting through the end of the TAF
period. Latest analysis suggests two primary waves, the first
between 15-20z (11am-4pm EDT) along a pre-frontal trough, and
the second between 21z-03z (5pm-11pm EDT) as the cold front
advances southeast. Storm intensity (and probability of terminal
impact) is likely to be highest with the second wave. Could see
restrictions to cigs/vis in and around heavier storms. Some
storms may be strong to severe, particularly with the second
wave. Damaging winds, hail, and tornadoes are all possible.

.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.

&&

.CLIMATE...
The area has the potential to break various heat-related
records.

There is a low probability many June all-time temperature
records may be at stake:

PIT: 98F (1988)
HLG: 100F (1933)
MGW: 99F (1893)
PHD: 99F (1988)
ZZV: 101F (1988,1934)
DUJ: 92F (1969)  *RECORD TIED ON 6/18/24 and 6/22/24*

Daily high maximum (left) and high minimum (right) temperature
records are at stake for:

Saturday, June 22nd
Pittsburgh, PA:       98F  (1988)     75F (1988)
Wheeling, WV:         95F (1923)      72F (2011) *Record High Tied*
Morgantown,WV:        96F (1923,1988) 73F (1988)
New Philadelphia, OH: 97F (1988)      71F (1997)
Zanesville, OH:       99F (1988)      71F (1997)
DuBois, PA:           91F(2022)       68F (2022) *Record High Brkn*

&&

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

&&

$$

SYNOPSIS...WM/Milcarek
NEAR TERM...WM/Milcarek
SHORT TERM...Milcarek
LONG TERM...Milcarek
AVIATION...Cermak/Frazier
CLIMATE...Milcarek