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FXUS61 KPBZ 221929
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
229 PM EST Fri Nov 22 2024

.SYNOPSIS...
Lower elevation rain and high elevation snow will continue into
Saturday morning before drier weather slowly returns to the
region as the potent low pressure system exits east. Moderate
temperature is expected Sunday into Monday with the rest of the
week likely featuring periodic rainfall chances and dipping
temperature.

&&

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

- Blizzard-like conditions on going or will peak through late
  this evening for WV higher terrain
- The rest of the higher terrain will see warning-level snowfall
  accumulation
- Waves of lighter rain showers are more likely elsewhere
------------------------------------------------------------------

A closed low waffling over eastern PA will continue to see
potent embedded shortwaves rounding its western periphery to
support lower elevation rain showers and high elevation snow
through tonight. Strong 850mb flow gaining greater upslope
angling plus mid-level frontogenesis and deep moisture will
support locally heavy snowfall over the higher terrain of WV and
PA where Winter Storm/Blizzard Warning headlines exist.  Up to
2"/hr rates are possible (favoring eastern Tucker and far
eastern Preston counties at 50% probability) that will combine
with gusty wind to support areas of blowing snow and snow drifts
that may further make travel difficult through midnight.
Confidence remains highest in eastern Tucker County (WV) for
Blizzard like conditions as joint probability of 35+ mph gusts
and heavy snow ranges from 70-100%.

In a bit of unusual pattern, warm advection will slowly raise
area temperature tonight into Saturday morning despite flow
becoming northwesterly as the upper low shifts to the Atlantic
Coast. Moisture wrapping around the low will slowly exit as
well and leave weaker vorticity advection over lake waters to
foster residual precipitation activity. The expectation is for
the gradual diminishing of areal coverage and, more notable,
snowfall rates that will reduce accumulating snowfall to all but
the highest peaks by Saturday morning.

&&

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

- Impactful snowfall accumulations will end, transition to a mix
  of rain/snow with lingering showers.
- West to east drying trend likely through Saturday night.
-------------------------------------------------------------------

As the potent upper level low becomes more coalesced off the New
England coastline Saturday, weak vorticity advection within
northwest flow will continue across the Upper Ohio River Valley.
Streaks of rain showers (and higher elevation rain/snow mixes)
will shift southwest to northeast through the day, with minimal
additional snowfall accumulations expected. High pressure
impinging from the west will aide precipitation erosion while
offering some temperature moderation, but sub-inversion layer
moisture is likely to be too entrenched for notable cloud
clearing. Wind will remain elevated through the afternoon with
diurnal mixing and the existing pressure gradient but will offer
more calming heading into Saturday night.

Dry weather with slightly above normal temperature and increased
sunshine is favored Sunday as the region sits of the eastern
edge of a building lower Ohio River Valley ridge. There remains
some lower probabilities for lingering cloud cover and even
light rain over portions of northwest PA Sunday that could limit
the degree of daytime heating (any precipitation would be light
and likely snow).

&&

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

- More transient weather patter favored next week
- This favors periodic but fast moving precipitation systems
  that will drop temperature below daily averages.
-------------------------------------------------------------------

Brief ridging is favored early Monday as the next upper level
trough develops near the western Great Lakes. There is some
uncertainty in the degree of tilt for that system; more positive
tilt will more rapidly return rain shower chances to the region
Monday afternoon while more neutral tilts will slow
precipitation onset and allow for more daytime heating.
Ensembles are in fairly uniform agreement of the low pressure
system crossing Monday night into Tuesday, with rain serving as
the primary precipitation type before changing to snow behind
the front (but with limit in available moisture). Quick
transition to westerly flow Tuesday afternoon will favor a rapid
return to dry weather with any precipitation relegated to lake
enhancement over northwest PA. Cold advection behind the front
will drop area temperature back below normal.

Uncertainty increases thereafter in relation to the degree of
height recoveries behind the Tuesday system as well as how deep
the next upper level low is able to develop over the Great Lakes
region. The general consensus favors trough movement of some
variety that would favor a continuation of below normal
temperature and periodic precipitation chances.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
A large-scale low pressure system will continue to impact the area
throughout the TAF period. Light snow has largely turned over to
rain across the area as surface temperatures have risen. Snow that
is being reported near the terrain at DUJ, LBE and MGW is expected
to begin to mix with rain shortly. As expected, our transition to
rain has yielded improving VIS across the region and probabilities
of IFR VIS has dropped below 20% for all terminals except DUJ, LBE
and MGW. Winds remain elevated across the region with most terminals
gusting between 20-25KTS at this time. Wind gusts are expected to
slacken some overnight with the loss of mixing, but winds can gust
over 18+KTS again tomorrow afternoon.

The axis of best ascent will move SW of FKL and DUJ during the
overnight hours and these terminals could see a break in
precipitation as well as an improvement in CIGs during the 04-08z
time frame. Models are trying to show marked improvement in CIGs but
lingering northwest flow yields low confidence in this.

Large-scale ascent will generally move out of the region near or
shortly after 12z. As such organized precipitation is expected to
begin to wind down and VIS restrictions are expected to break. CIGs
are expected to clear more gradually as probabilities of IFR VIS
remain >50% at all terminals by 12z Saturday. Region-wide MVFR
throughout the remainder of the TAF period remains high confidence
as probabilities of this remain largely >90% through 18z
Saturday.

Outlook...
VFR should return Sunday as high pressure builds in. Restriction
chances return later Monday and into Tuesday as a system drags
a cold front across the region.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Winter Storm Warning until 7 AM EST Saturday for PAZ074-076.
     Winter Weather Advisory until 7 PM EST this evening for PAZ078.
OH...None.
WV...Winter Storm Warning until 7 AM EST Saturday for WVZ510>513.
     Blizzard Warning until 10 AM EST Saturday for WVZ514.

&&

$$

SYNOPSIS...Frazier
NEAR TERM...Frazier
SHORT TERM...Frazier
LONG TERM...Frazier
AVIATION...AK