926
FXUS61 KPBZ 031228
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
728 AM EST Tue Dec 3 2024
.SYNOPSIS...
Patchy lake enhanced snow showers will diminish over the course
of the day. More widespread snowfall is expected Wednesday
afternoon into early Friday morning, with greater than six
inches likely along and north of the I 80 corridor. Strong wind
gusts are also expected Wednesday night through Thursday.
&&
.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:
- Lake-enhanced snow showers, primarily north of Pittsburgh,
will diminish through the afternoon.
- Below average temperatures continue.
-------------------------------------------------------------------
Lake-enhanced snow shower coverage is likely to shift farther
north primarily along and north of the I-80 corridor over the
course of the morning as brief surface ridging builds into the
region. Coverage and intensity should gradually taper off
through the afternoon.
Accumulation is expected to be light, an inch or two possible
north of I-80. Probabilities for more than two inches in any 6
hour period remain highest over northern Forest County (around
35%), with a 10-15% chance of greater than one inch for the same
areas. As typical with any lake-enhanced snow setup, local
pockets of higher accumulation are always possible, but at this
time 95th percentile 1 hour totals are largely less than a half
inch any given hour. Mid/late afternoon will be the most ideal
time for accumulating snow north of I-80. Road temperatures,
however, should be between the upper 30s and low 40s during
that timeframe based off of upstream METRo road temperature
forecasts. Lingering snow showers north of I-80 will diminish
early this evening. Overnight lows in the teens and lower 20s
will be around 10 to 15 degrees below normal on average.
&&
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
KEY MESSAGES:
- Winter weather impacts increase late Wednesday with strong
cold front followed by lake effect/enhanced and terrain-forced
snow showers Thursday
- Gusty winds (Advisory-level in the ridges) are expected with
the front Wednesday night and Thursday
- Wind chill values will be below zero in the higher terrain
early Friday morning
-------------------------------------------------------------------
A deep trough will dig across the Upper Midwest and into the
Great Lakes region on Wednesday as a strong surface low crosses
Ontario. Warm advection into the afternoon will boost daily
highs into the mid/upper 30s (though still below average).
As low pressure passes to the north, a cold front will cross the
region Thursday evening into the overnight. Widespread snow
showers are expected by the late afternoon/evening hours,
diminishing early Thursday morning behind the cold front. Winds
will veer northwesterly behind frontal passage with strong cold
advection over the lakes Thursday into Friday. This will present
an optimal situation for heavy lake effect/enhanced snow along
the snow belt/I-80 corridor and terrain-forced upslope snow in
the ridges Thursday.
Between initial synoptic snow Wednesday night and heavy lake
effect through Thursday night, areas north of I-80 have a 50-60%
chance of 6" (Warning criteria) snow, with a 25-75th percentile
range of roughly 4 to 10 inches. Local snow totals in this area
will depend heavily on snow bands, with some locations likely
much closer to 10, and others much closer to 4 inches. In
collaboration with neighboring offices, have issued a Winter
Storm Watch for lake effect snow from Wednesday night through
early Friday morning.
Snowfall immediately south of I-80 and in the ridges, though
lesser than north of I-80, has a 70-85% chance of reaching 3+
inches. A Winter Weather Advisory will likely be needed for
these areas.
A second concern will be strong gradient wind. Gusty wind is
expected as early as Wednesday afternoon ahead of the cold
front and with a strong 50-60kt LLJ, peaking overnight into
Thursday behind the front. Lower terrain probabilities for
advisory level wind gusts (46+ mph) run at 25-50%, and the NBM
mean max gust is 40-45 mph nearly areawide. However, an advisory
is very likely in the ridges where probabilities are greater
than 75% and max gusts above 50 mph are expected. Eastern Tucker
County, WV in particular may need a High Wind Warning as
forecast gusts near 65-70 mph.
Strong wind gusts will further complicate travel in locations
with snowfall, causing snow drifts and reducing visibility. The
Thursday morning commute may be particularly difficult along
the I-80 corridor and in the ridges, where snowfall and wind
will be maximized. Strong winds will also lead to low wind chill
values Thursday morning. The ridges will see single digits wind
chills, with higher peaks possibly dropping below zero.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
KEY MESSAGES:
- Brief break later Friday before snow chances return for the
weekend
-------------------------------------------------------------------
Snow showers are expected to taper off Friday and Friday night
as the trough exits and flow backs to the SW.
There is much higher uncertainty for the weekend, with high
pressure to our south. There is the possibility for another
wave to bring additional precipitation Saturday into Sunday,
but still little agreement on this. However, there is higher
confidence in a more robust system early next week. Regardless,
temperatures will remain below average through the period.
&&
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
Lingering light snow showers can be seen on radar near the
PA/WV border. This acivity is expected to continue to wind down
and move out of the area shortly after sunrise.
The passage of the trough axis and low-level flow backing to SW
will allow for modest improvement of ceilings during the late
morning and afternoon hours Tuesday, with decreasing snow shower
activity. ZZV, MGW, and to some extent, HLG are most likely to
enjoy scattered cloud coverage during much of the day.
A W to WSW wind of up to 10 knots can be expected through the
period, with some gusts near 20kt on Tuesday.
Outlook...
Restriction and snow potential returns late Wednesday with a
warm front. Widespread restrictions, snow showers and gusty
winds are then expected Wednesday night and Thursday with a
cold front and subsequent upper troughing and lake enhancement.
Improvement to VFR is expected from S-N Friday as the wave exits
and wind backs to the SW. Restriction and snow potential returns
Saturday with a warm front.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Winter Storm Watch from Wednesday afternoon through late
Thursday night for PAZ007>009-015-016.
OH...None.
WV...None.
&&
$$
SYNOPSIS...88
NEAR TERM...88
SHORT TERM...Rackley
LONG TERM...Hefferan/Rackley
AVIATION...AK/Shallenberger
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