303
FXUS61 KPBZ 060144
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
944 PM EDT Sat Oct 5 2024

.SYNOPSIS...
Dry, quiet weather will continue under high pressure. Much
warmer and more humid conditions will spread into the region on
Sunday in advance of a seasonable strong cold front.
Thunderstorms, some perhaps strong to severe, will be possible
across eastern Ohio into western Pennsylvania Sunday afternoon
into the early evening with the passage of that cold front. Dry
and much cooler conditions will return for next week.

&&

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

- Dry conditions continue.
- Possible aurora borealis tonight?

-------------------------------------------------------------------

The forecast remains on track this evening...

Clear skies will continue through tonight under deep
tropospheric ridging. The potential impact of the X9.1 solar
flare and any coronal mass ejection remains to be seen, but
given all the Internet hype, it seems that most everyone is
aware at the potential for northern lights tonight. As far as
sky conditions are concerned, we`re looking at an optimal setup
with a very deep dry atmosphere and no Moon related light
pollution. Temperatures will fall into the 50s and eventually
40s for most overnight, so dress warmly! As for whether or not
the Northern Lights make an appearance in our region, or when
that will occur, Space Weather science is still fairly new and
limited by few measuring instruments in the vast 93 million
miles of space that exists between Earth and the Sun. Beyond
noting that a G3 (strong) Geomagnetic Storm Watch remains in
effect, which means it`s *possible* for us to see them, there
are many many other factors at hand here. We defer to the Space
Weather Prediction Center for further details at
www.swpc.noaa.gov

&&

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

- Unseasonably warm and dry early
- Strong to severe thunderstorms expected late Sunday
  afternoon/evening.

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Large scale height falls, potentially exceeding 100m by 00Z
Monday, will begin early Sunday as mid-tropospheric ridging
shifts eastward, and a deep closed mid-level low moves across
southern Canada to eastern Ontario by 00Z Monday. Ahead of the
large scale trough and an attendant surface cold front,
seasonably strong low level warm air/moisture advection will
occur Sunday morning into the early afternoon. Model agreement
in both placement and magnitude of the key 500mb features is
exceptionally high, with almost no variance in the LREF
clustering. While we may start in the 40s, it`s going to be a
coat to shorts type of day as temperatures soar into the upper
70s to lower 80s by afternoon. Dewpoints will likewise ramp
upward, with a pre-frontal ribbon of lower 60F values expected
by mid afternoon.

Spatial overlap between the aforementioned surface
thermodynamics, cooling mid level temperatures, and large scale
forcing for ascent all suggest a strong likelihood that a
deepening Cu field should break through sometime around 20Z. It
seems to reason that this would occur first off Lake Erie where
a stout lake breeze boundary should further aid in low level
ascent, with activity rapidly spreading southeast and zipping
southwestward along the cold front. The window for severe
weather is relatively small given both fast system speed, and
that we are now pre-7PM sunsets.

NBM joint probabilities of 500 J/kg CAPE and 30 knots of
effective deep layer shear have risen markedly since yesterday,
now basically at 100% over much of eastern Ohio into northwest
PA at 21Z. When increased to 1000 J/kg, HREF probabilities are
still 50-80% over the same region. NBM mean CWASP values of
70-80%+ further suggest that severe weather potential in the
4-8PM window tomorrow is increasing. As you might expect, an
SPC upgrade to a slight risk is forthcoming for much of the
area.

The combination of ample deep layer shear and cold mid-level
temperatures will support both large hail and damaging winds as
storms rapidly grow upscale. Damaging wind threat may be
enhanced at lower-than-usual wind speeds by ongoing drought
conditions (snapping). There is a very narrow window of an hour
or two early in storm development, where forecast hodographs are
rather favorite for storm- relative helicity for the most
southward moving cells -- if they can remain discrete. While
tornadoes aren`t the primary severe weather concern at the
moment, that threat over northwestern PA cannot be entirely
discounted.

The severe weather threat should rapidly decrease by 00Z and the
lingering thunderstorm/precipitation threat should clear the
Laurel Highlands into the WV mountains before 10 PM.

&&

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

- Dry weather and cooler temperatures are expected under
  northwest flow.
-------------------------------------------------------------------

After the passage of the front Sunday night, a much cooler air
mass will return to the area with temperatures dropping some 20
degrees for highs on Monday, ending up in the low 60s.

Stout high pressure and strong model consensus suggest that
below normal temperatures and large diurnal swings will dominate
next week. Per the previous discussion, there is a signal toward
low temperatures falling into the 30s by Friday morning with a
re-enforcing surface ridge. As noted, a few cooler solutions
within the ensembles may prompt at least pockets of frost, with
the sheltered Canaan Valley of West Virginia almost certain to
see a deep hard freeze. The Climate Prediction Center (CPC) has
a 20% chance of below average temperatures between October 11th
and 13th.

It should come as no surprise that prolonged low-mid level
ridging will maintain or worsen drought conditions through the
middle of October. Whatever rainfall accompanies Sunday`s cold
front is not expected to make a significant impact into the 4+
month rainfall deficit.

&&

.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
VFR conditions are forecast for the vast majority of the TAF
period under high pressure.

Some high clouds may begin to show up ahead of a frontal
boundary expected to arrive during the late afternoon/evening of
Sunday. Deep mixing and a tightening pressure gradient should
lead to 15 to 20 knot gusts by midday. For the 30-hour PIT TAF,
did introduce a PROB30 for possible thunderstorms starting after
21Z--here is potential for strong wind gusts and hail with
these storms.

.Outlook...
A cold front is expected to move into the area bringing the
chance for showers and thunderstorms Sunday afternoon/evening.
Some of the storms may produce strong wind, hail, and brief IFR
restrictions.

High pressure is expected to settle into the area early next week and
usher in a return of largely VFR conditions.

&&

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

&&

$$

SYNOPSIS...Bookbinder
NEAR TERM...Bookbinder/MLB
SHORT TERM...Bookbinder
LONG TERM...Bookbinder
AVIATION...Hefferan