PBZ issues Area Forecast Discussion (AFD) at Jan 29, 1:59 PM EST
897
FXUS61 KPBZ 291859
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
159 PM EST Wed Jan 29 2025
.SYNOPSIS...
Snow showers and a few squalls return to the region today with a
crossing cold front. Rain is expected Thursday night and Friday
with crossing low pressure.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
KEY MESSAGES:
- Snow showers with a cold front, with squalls possible this
afternoon across western PA north of PGH.
- Gusty wind continues, strongest in the ridges
----------------------------------------------------------------
Surface low pressure over northern NY state will continue
northeast this afternoon and into the evening. The associated
cold front will continue to sag south across the region before
washing out near the Mason-Dixon line by this evening. Snow
showers will accompany the front, with snow squalls possible
this afternoon, mainly north of PGH based off latest
mesoanalysis. So far today, impacts have been relatively low as
road surface temperatures were previously above freezing, but
behind the front, road temperatures have dropped to below in
some locations, south down to Interstate 80. This trend should
continue the remainder of the afternoon as the front continues
south. For areas south of the Pittsburgh area, moisture in the
dendritic layer looks to be too limited for squalls, despite a
steep low level lapse rate. Temperatures are also likely to be
more marginal for impacts, though conditions will be monitored
through the day.
A tight surface pressure gradient will maintain wind gusts up
to 35 mph for the lower elevations, and the High Wind Warning
remains in effect for eastern Tucker county, where gusts up to
65 mph will be possible.
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
KEY MESSAGES:
- Snow shower chances end
- Wind diminishes this evening
- Dry weather Thursday
- Rain returns Thursday night through Friday
--------------------------------------------------------------------
Snow showers are expected to quickly end this evening as high
pressure begins to build in. Wind will also diminish with as the
pressure gradient relaxes with the building high. Clouds will
also begin to clear overnight, as lows drop to the teens to
lower 20s. Dry weather will continue Thursday as the high tracks
east across the Upper Ohio Valley region. Highs are expected to
be 5 to 10 degrees above average under warm advection.
A central CONUS trough will advance eastward Thursday night, as
a surface low develops across the Midwest. Increasing moisture,
warm-advection ascent, and a crossing surface warm front will
result in increasing rain chances across the region Thursday
night. After initially falling a couple of degrees in the
evening, temperatures should remain steady or slowly rise
overnight, minimizing any freezing rain potential.
Forecast variability in this time range is dominated heavily by
differences in the speed/timing of phasing of a closed low from
the swrn CONUS, with some guidance suggesting a faster phasing
process is possible. The net effect of this quicker process
might suggest faster arrival of warm air and faster onset of
warm advection-driven rain on Thu evening than suggested in the
ensemble mean.
Although there remains some spread in the track of the system's
associated sfc low, general consensus suggests a track across
nrn OH and nwrn PA, eventually pulling a cold front across the
region. With such a track, rain would potentially continue on
Fri/Fri evening, but could be mitigated partly by mid-level
dry-air entrainment. Nevertheless, jet-induced ageostrophic ascent
is also likely on Friday, which could enhance rainfall totals
in a focused area.
Ensemble mean rainfall for Thu night thru Fri suggests is at
1.00" over the upper Mon/Cheat Rivers, with considerable spread
(as high as 1.75" in the WV Ridges) owing to variations in
where the jet enhancement overlaps favorably with synoptic
ascent. With the current water equivalent of snowpack on the
ground in this area, and the potential for higher-than-mean
rainfall in a localized axis across this area, river conditions
are being monitored closely for potential for ice breakup and
related flooding. Temperatures are expected to range in the
lower 40s N to mid 50s south, which should also accelerate any
ice/snow melt.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
KEY MESSAGES:
- Colder but dry Saturday
- Warm up starting Sunday through early next week
- Minimal precipitation chances through the period
-------------------------------------------------------------------
Model ensembles indicate broad troughing will persist across the
eastern CONUS through much of the period as low pressure closes
off in the nwrn CONUS, yielding quasi-zonal flow across much of
the CONUS. Within this flow, ensemble members suggest a number
of low-amplitude shortwave troughs could traverse the nrn CONUS
during the Days 4-7 timeframe.
The stronger the low in the nwrn CONUS, the greater the
amplitude of the downstream flow and greater the potential for
these disturbances to eject. The ern- CONUS low is widely
expected to shift ewd toward mid-week while the nwrn-CONUS low
evolves slowly, maintaining a multi-day stretch of wly to wnwly
flow aloft across the nrn CONUS.
Above average temperatures are featured in the most-likely
forecast scenario Sun and Mon, with readings on Tue likely to be
much closer to seasonal average.
The potential tracks of low pressure through this period could
spell occasional gusty days, especially Sun, but at this time,
the spread of potential outcomes in the probability space
suggests a limited risk of headline-worthy gusts.
&&
.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
MVFR stratocu and temporary IFR vis restrictions this afternoon
at KFKL and KDUJ will accompany a weakening front, but latest
soundings show low VFR being maintained farther south as the
front washes out. Snow showers should dissipate late in the
afternoon and during the evening.
Strong winds will diminish overnight.
Outlook... Widespread VFR returns Thursday under high pressure.
Restriction and rain chances return Friday with low pressure. A
warm front returns restriction potential on Saturday.
&&
.HYDROLOGY...
Rainfall amounts between 0.75-1.50 inches falling on a melting
snowpack could contribute to significant rises on area rivers,
especially in the Mon, Yough and Cheat basins. These rises will
certainly disturb areal river ice and could create ice jam
flooding. At this time multiple forecast points are forecast to
hit action stage but none are currently forecast to hit minor
flood stage.
Mon, Yough and Cheat Basins:
These basins are grouped together because their anticipated rain
totals, snowpack and ice coverage are expected to create similar
issues.
Rises on the Upper Mon and Cheat rivers are expected to on the
order of 6-12 feet. These rises will certainly disturb any river
ice and can exacerbate issues seen across these basins. At this
time there are several locations in these basins forecast to reach
action stage.
Rises on the Lower Mon are expected to be on the order of 10-20
feet. This is expected to take all forecast points on the Lower
Mon to action, but not to minor flood.
Rises on the Yough are expected to be on the order of 3-6 feet.
These rises will certainly disturb thick river ice observed along
the river. At this time no points are forecast to reach action
stage but issues due to ice jams can bring flood concerns anyway.
Allegheny, Ohio and Musk Basins:
Upcoming rainfall and current snowpack are lighter in these
basins. However, rain on rotting snow, river ice and the heating
induced snowmelt are likely to cause rises over the next several
days.
Rises on the Allegheny are expected to be on the order of 1-3
feet. These rises could be enough to disturb the current ice
coverage on the river and lead to ice jam flooding. At this time
no points in the Allegheny Basin are expected to reach action
stage.
Rises on the Ohio are expected to be on the order of 5-10 feet.
At this time no points are forecast to move to action stage but
the disturbance of ice may cause issues.
Rises on the Beaver, Muskingum and Tuscarawas rivers are expected
to be on the order of 1-3 feet. At this time no points are
expected to move to action stage. However, these rises are
sufficient to disturb plentiful areal ice coverage and cause
issues.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch from late Thursday night through Saturday
afternoon for PAZ073>076.
OH...None.
WV...Flood Watch from late Thursday night through Saturday
afternoon for WVZ509>514.
High Wind Warning until 1 AM EST Thursday for WVZ514.
&&
$$
SYNOPSIS...WM/88
NEAR TERM...WM/88
SHORT TERM...Kramar/WM/88
LONG TERM...Kramar/WM/88
AVIATION...22/88
HYDROLOGY...AK
Source: PBZ issues Area Forecast Discussion (AFD) at Jan 29, 1:59 PM EST (https://mesonet.agron.iastate.edu/p.php?pid=202501291859-KPBZ-FXUS61-AFDPBZ)
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