700
FXUS61 KPBZ 230348 AAA
AFDPBZ

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
1048 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 /UNTIL 6 AM SATURDAY MORNING/...
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 elsewhere
------------------------------------------------------------------

Late evening update...
Updated to cancel the Winter Storm Warning for the higher
elevations of Westmoreland county, as precip has diminished.
While some additional light rain or snow is possible tonight,
the potential for significant snow accumulation has ended.

Evening update...
PoPs were modified in line with the latest hires model
guidance. Expect to see a slow decay in the precipitation from
the west as the large upper low finally moves out over the
Atlantic. Temperatures continue to slowly warm from west to east
and this has caused much of the snow now to be confined to the
higher elevations. Temperatures will become steady late tonight
and hold there into Saturday morning. Will allow the advisory
for portions of Indiana county to expire.

Previous discussion...
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 /6 AM SATURDAY MORNING 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 FRIDAY/...
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 /04Z SATURDAY THROUGH WEDNESDAY/...
Light rain continues for most terminals overnight, though
coverage is expected to gradually diminish with waning moisture.
IFR to MVFR ceilings are expected through the overnight with
some brief improvement possible for PIT northeastward. Wind
gusts will diminish overnight with decreased mixing, but will
increase again to around 20kts by noon Saturday.

Large-scale ascent and more organized precipitation will
generally move out of the region near 12z. This should improve Vsby
restrictions with more gradual Cig improvement through the
afternoon. Region-wide MVFR throughout the remainder of the TAF
period remains high confidence.

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 PAZ076.
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...WM/22/Frazier
SHORT TERM...Frazier
LONG TERM...Frazier
AVIATION...Rackley/AK