750
FXUS61 KPBZ 310853
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
353 AM EST Fri Jan 31 2025

.SYNOPSIS...
Rain is expected across the region throughout the day. Well
above normal temperatures today as well. Rain will taper off
late tonight and may end as light snow showers. Cooler but dry
on Saturday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
KEY MESSAGES:

- Widespread rain today. Highest amounts south of I-70
- Temperatures well above normal.

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A weak ridge will rest over the region this morning as an upper
level low digs into the central CONUS and then moves eastward
across the midwest and gulf coast states. Height falls will then
ensue this afternoon as the now open wave rushes eastward. A
surface low will move eastward from western Illinois this
morning reaching central PA sometime early this evening. A plume
of moisture, caught in the southerly flow aloft on the eastern
flank of the trough, will pump deep moisture into the area
throughout the day. A large rain shield will remain parked over
the region today as the surface low moves toward the area.

Blended mean rainfall amounts range from 0.4-1.30 inches today
with the highest amounts generally over northern WV.
Probabilities of > 0.50 inches are above 70% across the entire
forecast area. The highest probs of > 1.00 inches are focused
mainly south of I-70. Probs south of I-70 for > 1.00 inches
range from 30% to 70%, with the highest over Tucker county WV.

Warm air will surge northward today as well. This will push high
temperatures well above seasonal averages. Prob for highs > 50
range from 60%-100% across the southern half of the forecast
area, with 10%-40% across the north.

Rainfall, and the warm temperatures, will continue the snow
melting process. The combination of these will increase the
amount of water into area streams and rivers. One other thing to
consider is that the ground underneath the snow pack is frozen
meaning not much of the rainfall will be absorbed, this will
greatly increase runoff.

Area rivers, particularly those south of PIT, are expected to
rise later today and into Saturday.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
KEY MESSAGES:

- Rain ends tonight
- Dry weather returns Saturday.
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Rain will end from north to south tonight as the trough axis
rushes eastward. Colder and much drier air will fill in behind
the exiting wave. Its not out of the question that a few flakes
could mix in on the northern side of the exiting rain shield.

River rises will continue Saturday.

High pressure will settle in over the area on Saturday as well
as a brief period of cold air advection. Lots of sun on Saturday
with temperatures falling back to near normal values.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
KEY MESSAGES:

- Slight chance for rain with a Monday cold front
- Rain and snow chances return Wednesday with low pressure
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Sunday will feature a return to warm and moist southwest flow
thanks to an eastward migration of the high pressure, though a
clipper system may affect northeast zones with a brief bout of
precipitation late Sunday that is most likely rain with light
accumulations. This forecast if fairly high confidence given low
variability in ensemble clusters.

Model ensembles indicate a general zonal flow is expected across
the CONUS for much of the long term period, as a trough develops
off the Pacific NW coast. A weak cold front embedded in the flow
is progged to cross the Upper Ohio Valley region on Monday, with
only a slight chance of rain expected. Generally dry weather
returns on Tuesday as surface high pressure builds in.

Low pressure is expected to develop along a stalled surface
boundary across the Mississippi Valley region Tuesday night,
approaching the Ohio Valley region on Wednesday, though
clustered variability increases with this. Rain chances return
with the approach of the low. Some snow is also possible,
depending on the exact track of the low and where the surface
boundary sets up. Stayed close to the ensemble blend to smooth
out some of this uncertainty in the forecast. The more
concerning aspect with this secondary system is more potential
for higher QPF and additional river rises. Goal posts are
currently between 0.2" (10th percentile) and 2" (90th
percentile).

Temperatures are expected to average above seasonable levels
through most of the period, with Tuesday being the coldest day
after FROPA.

&&

.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
Restrictions in rain will progress from west to east early this
morning with an advancing low pressure system. Dry slotting may
initially keep rain light and prolong VFR ceilings, but rapid
saturation with strong warm advection should then quickly drop
cigs into low IFR/LIFR over the next several hours. Higher
rainfall intensity will likely remain focused south of PIT, with
highest probabilities between 12Z to 18Z. Periods of fog are
also increasingly likely this morning after sunrise, though this
may be spotty north of PIT.

Cold frontal passage is expected in the 19-23z time range, with
a possible line of showers and briefly gusty winds. Post-frontal
dry advection and increased mixing will ease rain coverage and
improve vsby restrictions near 00z, though lower cigs are likely
to persist through the overnight.

Outlook...
Lingering moisture and delay in the passage of the upper trough
may result in another period of IFR cigs with light rain/drizzle
late Friday night into early Saturday morning. High pressure and
dry advection in northwest flow will end precipitation by 12z
Saturday and aide gradual improvements to VFR by Saturday night
(near 100% probability).

Weak shortwave movement in zonal flow to the north may lead to
a period of MVFR cigs (40-60% probability of occurrence) and
light rain/drizzle Sunday that favors northwest PA. Periods of
gusty wind may also develop as low pressure system cross north
of the region through early next week.

&&

.HYDROLOGY...
Rainfall amounts between 0.60-1.30 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.

Allegheny Basin:
Upcoming rainfall and current snowpack are lighter in the
Allegheny Basin than others. However, rain on rotting snow,
river ice and the heating induced snowmelt are likely to cause
rises this weekend of 1-2 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.

Monongahela, Youghiogheny 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 Monongahela and Cheat rivers are expected between
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 Monongahela are expected to range between 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 Youghiogheny 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.

Ohio and Musk Basins:
Expected rainfall totals and observed snow depth is lesser across
these basins. However ice coverage is plentiful.

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 through Saturday afternoon for PAZ073>076.
OH...None.
WV...Flood Watch through Saturday afternoon for WVZ509>514.

&&

$$

SYNOPSIS...22
NEAR TERM...22
SHORT TERM...22
LONG TERM...WM/Milcarek
AVIATION...Rackley/Frazier
HYDROLOGY...