PBZ issues Area Forecast Discussion (AFD) at Jan 1, 5:34 AM EST720
FXUS61 KPBZ 011034 AAA
AFDPBZ
Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
534 AM EST Wed Jan 1 2025
.SYNOPSIS...
Rain will continue to change to snow this morning. Gusty wind
and snow showers are then expected today and tonight, with most
of the accumulation north of Interstate 80 and across the
higher terrain. Snow will taper off by Thursday, with more
widespread snow on Friday.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
KEY MESSAGES:
- Rain and snow transitions to snow showers today
- Wind gusts 30-40 mph, with gusts to 50 mph across the WV
higher terrain
--------------------------------------------------------------------
Update...
Most of the precipitation has transitioned to all snow. Updated
weather types for this transition, and POPs over the next
several hours based on radar and near term model data.
Previous discussion...
The latest surface analysis shows low pressure centered across
southern NY, with a cold front trailing south across MD and WV.
Rain continues to transition to snow from W-E in cold advection
behind the front. The stratiform precip should transition to
snow showers later this morning with steepening lapse rates.
The Upper Ohio Valley region will remain under broad upper
troughing today, with a series of crossing vorticity maximums.
The boundary layer flow is also progged to ne WNW most of the
day. The trough, along with lake and terrain enhancement, should
maintain snow showers across the region through the day. Most
areas will see less than an inch of accumulation, though areas
across the higher terrain and N of I 80 have the highest
potential for accumulations today.
850mb temperatures are marginal for lake enhancement during the
day, though moisture and lapse rates in the dendritic growth
zone increase later today. Maintained the current winter
headlines as is, and added Mercer, Venango and Forest counties
to a winter weather advisory with 2-4 inches of total snow
accumulation expected.
Mixing and a strong pressure gradient will result in wind gusts
from 30-40 mph for much of the region today, with gusts up to 50
mph across the highest terrain areas of WV. Expect temperatures
to remain steady through much of the day as well under cold
advection.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
KEY MESSAGES:
- Snow showers continue tonight, especially north of I 80 and in
the ridges
- Gusty wind continues tonight
- More snow Friday
--------------------------------------------------------------------
Broad upper troughing, along with lake and terrain enhancement,
will maintain snow showers across the region tonight. The
heaviest snow is expected this evening into the overnight hours,
with sufficient moisture and a steep lapse rate in the dendritic
growth zone.
The upper trough is progged to shift eastward late tonight. A
subsidence inversion is progged to develop as well, with
decreasing moisture in the dendritic layer. This should result
in a diminishing trend in the snow showers, especially in the
ridges. Areas north of I 80 will still see lake enhancement,
though boundary layer flow should back to the west late. Current
ending times of the winter weather headlines appear reasonable
under this scenario. Wind should also begin to diminish late
tonight, though will stay elevated across the ridges.
The boundary layer flow is progged to back to the WSW on
Thursday, with any remaining snow showers diminishing.
A shortwave trough, and associated cold front, is progged to
track out of the Upper Midwest Thursday night, crossing the
Upper Ohio Valley region on Friday. Snow chances will escalate
again late Thursday night and Friday. As the front crosses on
Friday, NW flow and cold advection will result in additional
lake and terrain enhancement to the snowfall across the area. At
this time, a general inch or two is expected for much of the
area, though the ridges and areas N of I 80 have the potential
to see several inches. Will highlight this potential in the
Hazardous Weather Outlook.
Snow will continue Friday night under cold NW flow, and another
shortwave rotating through the main trough. 850mb temperatures
are expected to drop to around -15 degC by Saturday morning.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
KEY MESSAGES:
- Cold through the period
- Snow chances continue Saturday
- Accumulating snow possible Monday
--------------------------------------------------------------------
Model ensembles indicate the area will be under NW flow and
broad troughing on Saturday, with snow chances continuing.
Sunday should be dry but cold as shortwave ridging briefly
builds in.
Models agree in general on the approach of a central CONUS
trough late Sunday night and Monday. Differences exist on the
resulting development of a surface low, its exact track across
the OH or TN Valley region, and the northern extent of any
associated snowfall. Stayed close to the ensemble blend to
smooth out these differences for the forecast. At this time, NBM
based probabilities for at least 2 inches of snow have increased
especially from PIT southward. Will monitor the trends
regarding this system over the next few days.
Snow chances continue Tuesday under broad upper troughing and
cold NW flow. Temperatures are expected to remain below average
through the period.
&&
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
The cold front is in the process of traversing the forecast area
tonight. Wind shifts to the WNW and NW have begun in OH and will
soon be shifting into eastern OH and PA. This will usher in
colder temperatures and allow the rain to change to snow. The
snow showers will persist on and off through the rest of the
night and even during the day tomorrow. The other impacts will
be the lower cigs through the night and into the coming day at
all the terminals. The NBM probs suggest a 50% to 70% (even
higher for the FKL and DUJ terminals) of IFR and below cigs.
Expect this to continue through the day and although there will
be a chance of some improvement late in the day tomorrow, MVFR
cigs are most likely.
After the winds shift tonight behind the front, they will
increase to around 15 knots with gusts to 30 knots from time to
time through the end of the forecast period. Some of the
ridgetop winds can gust higher through the day.
Outlook...
Lake and terrain enhanced snow showers could result in
restrictions lingering Thursday north of I-80 and along the
ridges, with improvement to VFR possible elsewhere. Snow and
widespread restrictions return Friday with a crossing cold
front, and Saturday under cold NW flow off of the Great Lakes.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Winter Weather Advisory from 10 AM this morning to 7 AM EST
Thursday for PAZ007>009.
Winter Weather Advisory until 4 AM EST Thursday for PAZ074-076.
OH...None.
WV...Winter Weather Advisory until 4 AM EST Thursday for WVZ510-511.
Winter Storm Warning until 4 AM EST Thursday for WVZ512>514.
&&
$$
SYNOPSIS...WM
NEAR TERM...WM
SHORT TERM...WM
LONG TERM...WM
AVIATION...Shallenberger
Source:
PBZ issues Area Forecast Discussion (AFD) at Jan 1, 5:34 AM EST---------------
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