261
FXUS61 KPBZ 191812
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
212 PM EDT Thu Sep 19 2024

.SYNOPSIS...
Mostly dry weather and above-normal temperatures will continue
through Friday. Chances of showers and storms return Saturday,
followed by higher chances early next week.

&&

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

- Scattered showers/storms in northern WV ending this evening.
- Mostly clear tonight, with patchy fog development overnight.
-------------------------------------------------------------------

The main trough along the Atlantic Coast will continue to pull
slowly eastward through tonight. Generally drier air has worked
mainly into areas near and north of I-70, resulting in a mostly
sunny day. To the south, more numerous cumulus have managed to
bloom in an environment with 1000-1500 J/kg of surface-based
CAPE. Subsidence is working against convective development here
as well, but isolated/scattered showers, and perhaps a
thunderstorm, will continue to be possible through the afternoon
mainly south of the Mason-Dixon Line and where orographic
forcing is in play.

The pattern transitions to one of transient ridging starting
tonight. Cumulus and any showers will quickly collapse by this
evening, leaving a mostly clear and calm pattern tonight. Patchy
radiation fog is expected overnight with the lingering moisture,
most likely in river valleys, as temperatures remain a few
degrees above climatology.

&&

.SHORT TERM /FRIDAY 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, with
climatologic maximums and above- normal minimums.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Lingering CU is expected to dissipate from north to south
through the late evening with increase mid-level subsidence.
Winds will continue to remain light to variable from the
north/northeast.

Patchy early morning fog is possible Friday, especially for
FKL/DUJ, with radiational cooling and light wind. Otherwise,
VFR is expected Friday under high pressure.

.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 Monday with an approaching warm front.

&&

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

&&

$$

SYNOPSIS...CL
NEAR TERM...CL
SHORT TERM...CL
LONG TERM...CL
AVIATION...Hefferan