-- Discussion containing changed information from previous version are highlighted. --
621
FXUS61 KPBZ 200706
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
306 AM EDT Fri Sep 20 2024

.SYNOPSIS...
-- Changed Discussion --
Seasonably hot weather is expected through the weekend with a
marginal chance of severe storms Saturday, mainly east of I-79.
A wetter pattern is becoming increasingly likely next week.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
KEY MESSAGES:

- Seasonably hot weather; record breaking heat potential for New
  Philadelphia and DuBois.
-------------------------------------------------------------------

Any lingering fog is expected to clear rapidly beyond sunrise
with mixing. Temperatures are expected to climb rapidly into the
day today with upper ridging and surface southerly flow under
high pressure. With how warm conditions have been, it is
difficult to believe the average high for Pittsburgh this time
of year is 74. With temperatures forecast to climb into the 80s
(and even 90s for eastern Ohio), highs will be around 10 to 15
degrees above average. New Philadelphia has a shot at beating
their record high of 89F (1965), and DuBois may approach their
record high of 84F (1965).

Temperatures will cool under clear skies tomorrow night, but
should be limited by dew points and light winds. This will keep
lows slightly above average. Fog appears less likely overnight
save insulated valleys with larger dew point depressions and
some winds.
-- End Changed Discussion --

&&

.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
KEY MESSAGES:

- Dry and quite warm Friday.
- Shower and storm chances areawide on Saturday. A few of the
  storms could be strong.
---------------------------------------------------------------------

Friday will feature dry weather and quite warm temperatures as
transient ridging passes over the region. Plenty of sunshine and
high temperatures of 10 to 15 degrees above seasonal norms can
be expected.

There continues to be a bit better confidence in shortwave
energy riding over the top of the ridge, crossing the Great
Lakes Friday night and the Upper Ohio Valley on Saturday. An
increase to around 1.4 inch precipitable water values is noted,
and lift will be provided by the shortwave, and potentially left
exit region dynamics from a 250mb jet dropping from the Upper
Midwest. So, PoPs in the chance range certainly appear
appropriate at this stage. The main question then becomes the
potential for strong convection.

The NBM has a 40-60% potential for 1000 J/kg of surface-based
CAPE during the afternoon on Saturday over a good portion of the
area. 0-6km bulk shear of 30-35 knots is also possible despite
weak low-level flow, as is 700-800 J/kg of DCAPE. If these
ingredients can come together at a favorable time, then a low-
end threat of damaging wind gusts and perhaps hail could be
realized in the stronger storms. However, there remains some
timing uncertainty regarding cloud cover/precip arrival (which
would impact potential SBCAPE levels), and some model soundings
also point to large amounts of dry air aloft that could hinder
updraft development. The potential bears watching, but the
threat level remains fairly low for now.

Rain chances taper off Saturday evening as the wave passes to
the east, and as subsidence and drier air settle into the
region. Patchy fog will remain possible yet again, particularly
if rain does occur.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
KEY MESSAGES:

- Dry and warm Sunday.
- Rain chances increase starting early next week, with
  temperatures moderating closer to seasonable levels.
-------------------------------------------------------------------

Most model scenarios show a brief return to ridging on Sunday,
lending high confidence to a forecast of dry weather and quite warm
temperatures. Values pushing 90 degrees cannot be ruled out in
eastern Ohio (10-30% chance according to the NBM).

Uncertainty starts to increase markedly thereafter.  There continues
to be disagreement regarding how quickly the ridge axis gets pushed
east Monday into Tuesday, which has implications for the start time
for increasing PoPs. From here, although there is a wide
discrepancy with detail regarding individual waves, there is
still at least medium confidence in a midwestern trough setup,
which could lead to increased moisture flow and precipitation
chances during the mid- week period - which could have a
positive impact on the ongoing drought. With the increased
potential for clouds and rain, temperatures will likely show
less of a diurnal range than is typical for late September,
leading to above normal maximums and minimums.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
Patchy early morning fog is possible with efficient radiational
cooling and light winds, primarily for FKL/DUJ but also
possibly around MGW/LBE (though generally shorter duration and
less dense at the latter terminals).

Otherwise, VFR and light winds are expected throughout the TAF
period. Scattered diurnal CU should develop during late morning
and afternoon with bases starting in the 3-5kft range, gradually
lifting to 6-8kft before dissipating around sunset.

.Outlook...
Low chances for restrictions in thunderstorms are possible
Saturday with a crossing shortwave trough. VFR returns Sunday
under high pressure before restriction potential returns early
next week with an approaching warm front.

&&

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

&&

$$

SYNOPSIS...Milcarek
NEAR TERM...Milcarek
SHORT TERM...CL
LONG TERM...CL
AVIATION...Cermak/Hefferan/22