455
FXUS61 KPBZ 192259 AAA
AFDPBZ

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
659 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 FRIDAY/...
KEY MESSAGES:

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

Evening update...no major changes needed. Have adjusted the
timing to end the showers over N WV and made some minor tweaks
to the cloud cover. Rest of the forecast is in good shape.

Previous discussion...

The main trough along the Atlantic Coast will continue to pull
slowly eastward through tonight.

The pattern transitions to one of transient ridging starting
tonight. Cumulus and any showers will quickly collapse 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 NIGHT 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 /00Z FRIDAY THROUGH TUESDAY/...
General VFR through the forecast period. Patchy early morning
fog is possible Friday, especially for FKL/DUJ, with radiational
cooling and light wind.

Scattered CU should develop with daytime heating Friday.

.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...22/CL
SHORT TERM...CL
LONG TERM...CL
AVIATION...Hefferan/22