-- Discussion containing changed information from previous version are highlighted. --
236
FXUS61 KPBZ 141939
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
339 PM EDT Fri Jun 14 2024

.SYNOPSIS...
A 2 out of 5 risk of severe weather will persist today in
storms along a cold front. There is high confidence Sunday will
be the start of a particularly dangerous, historic, long-
duration heat wave for western Pennsylvania, northern West
Virginia, and eastern Ohio.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
-- Changed Discussion --
KEY MESSAGES:

- A 2 out of 5 risk for severe storms are possible today.
- Temperatures will remain near normal.
-------------------------------------------------------------------

3:45pm Update:

Initial convection in eastern Ohio has become more contaminated
as it has merged into a line, which has locally raised flooding
concerns and lowered severe concerns for now. That being said,
severe still cannot be ruled out given the environment and may
be more likely if storms start moving right. This will be
monitored over the coming hours. Otherwise, the front is
starting to show up on radar moving into the watch area now.
This will bring the final chance of severe as it progresses and
storms continue and/or initiate.


2:35pm Update:

With the 18Z sounding, we are noticing that the MLCAPE is
sitting around 1000 J/kg with moist adiabatic profiles
immediately above, with some mid level dry adiabatic profiles
from 750mb to 600mb. There is also upper dry air with a cap, but
those temperature are still below parcel temperatures. This has
indicated that storms are capable of tapping into dry air aloft,
which has increased confidence of downburst potential and hail
growth. A severe thunderstorm watch has been issued accordingly.

.. Previous Discussion..

We have seen some pre-frontal development in storms that
initiated overnight in a pre-frontal trough. We have already
seen these storms intensify to near-severe criteria. These will
severe as a litmus test for future development. These storms
have developed in an environment with around 35-40kts of
effective shear and around 500 J/kg MLCAPE.

As the pre-frontal trough and cold front drift south, the
environment will only get more favorable, with shear forecast to
get as high as 40kts to 50kts and SBCAPE as high as 1500-2500
J/kg. Supercell composites are as high as 1-2. This is also in
an area which is showing progressive clearing, which will allow
the low-levels to destabilize. DCAPE is now modeled as high at
800-1100 J/kg in the same area. This is a notably higher than
the prior forecast, which may indicate increasing severe
potential in in southeast Ohio, southwest Pennsylvania, and
northern West Virginia.

For these reasons, the SPC has decided to upgrade to a 2 out of
5 risk for severe weather today. The strong shear and mid-level
dry air will contribute to both wind and hail threats in the
area. Hail threats will be locally higher in storms should any
supercells develop. The 12Z sounding also had 1.3" PWATS, which
is close to the 90th percentile, meaning training storms
contribute to localized flash flooding.

Cooler and drier air will arrive overnight behind the cold front
with a drop in dew points. Lows will drop a few degrees below
normal, and patchy river valley fog is possible with clearing.
-- End Changed Discussion --

&&

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

- Dry weather Saturday and Sunday.
- Near normal temperatures Saturday with a jump to 5-10 degrees
  above normal on Sunday.
-------------------------------------------------------------------

Heights rise into Saturday as upper ridging builds and surface high
pressure slides in to the north. Temps won`t rebound much in
northerly flow in the wake of the boundary and dew points will
likely mix out some in the afternoon with a dry boundary layer
providing a pretty comfortable day.

Upper ridging begins to build stronger making a run at 588-590dm by
Sunday to kick off the first day of increasingly hot conditions.
Surface high pressure establishes off to our east and southwest flow
on the west side of the 850 mb ridge axis will induce warm
advection with ensemble 850 temps up to 15-17C. This will
support widespread upper 80s with even a 40-70% chance of 90F+
for Pittsburgh south and west.

&&

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

- High confidence in a dangerous heat wave setting up early next
  week with major heat impacts possible.
-------------------------------------------------------------------

Guidance has been consistent that a potentially-historic ridge will
continue to strengthen across much of the central and eastern CONUS
into the middle of next week. WPC ensemble clusters are highly
consistent through Tuesday, indicating high confidence in the
temperature forecast. Near-record breaking heat will build in to
start off next week.

Significant heat is looking increasingly likely with this
anomalously strong ridge from Monday and beyond when major to
extreme heat risk is likely. NBM probabilities for high
temperatures reaching 95+ degrees continue to go up, and are now
widespread 60-90% across the area. These higher probabilities
are especially prevalent in lower elevation areas (e.g., river
valleys) and urban centers, which tend to be warmer than
surrounding areas. In addition, dewpoints are currently forecast
to remain in the mid 60s to lower 70s, which would result in
high enough humidity levels to support heat indices climbing to,
and potentially exceeding, 100 degrees. If dew points do hold
toward the lower end of that spectrum, we may be able to make a
run at 100 degree air temperatures Monday and beyond (last time
at PIT was 7/15/95); NBM probabilities for that threshold are
now up to 60% on Tuesday with ~50% chance for the remainder of
the week. Only acting to exacerbate the prolonged heat effects
will be a 60-80% chance of low temperatures greater than 70
degrees through the end of the week. Heat impacts will need to
be closely monitored and headlines may need to be considered.

Three out of four clusters maintain at least a 594dm ridge through
June 22nd with the one exception being a lower probability solution
than the others. Return intervals of these heights dating back to
1979 are just about out of the climatological range. CPC suggests
that excessive heat may last through June 24th, indicating the
potential for a long-duration excessive heat threat. The last
comparable, long-duration heat event was from June 1994.

Impacts include heightened heat-related illnesses and potential
power grid issues with increased demand. It is strongly encouraged
to know where cooling shelters are located and stay hydrated. There
may be little relief at night. Gather food, water and medication
now. Make a list of friends and family to check on and help them
prepare. Strongly consider rescheduling outdoor events. Prolonged
exposure to excessive heat was the primary cause of weather-related
fatalities in 2023.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
The cold front is working its way towards the I-80 corridor.
FKL and DUJ are more than likely done with convection for today,
and will remain VFR through the TAF period (save for perhaps
patchy valley fog towards morning). To the south, thunderstorms
on at least a scattered basis are expected as the front sink
south, exiting the area during the early evening. Have used 2-3
hour TEMPO groups to try to time the window of highest
opportunity for each terminal to experience a storm. Any storm
will be capable of brief IFR to LIFR visibility, variable wind
gusts to 40 knots, and cloud-to-ground lightning. confidence in
this level of impact at any one TAF site is quite low and thus
not mentioned in the TAFs.

In the wake of the front, winds shift to northwesterly and
skies begin to clear again as drier air moves into the region.
VFR conditions are then expected for the rest of the forecast
period, although patchy valley fog may be a concern late
tonight.


.Outlook...
Largely VFR conditions are then forecast Saturday through
Wednesday as a strong ridging pattern develops over the region.

&&

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

&&

$$

SYNOPSIS...Milcarek
NEAR TERM...Milcarek
SHORT TERM...MLB/Milcarek
LONG TERM...MLB/Milcarek
AVIATION...CL