PBZ issues Area Forecast Discussion (AFD) at Jan 5, 6:45 AM EST037
FXUS61 KPBZ 051145
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
645 AM EST Sun Jan 5 2025
.SYNOPSIS...
A strong low pressure system will bring widespread snow to the
region late Sunday and Monday, with a wintry mix possible in
some locations south of I-70. Greatest snowfall is expected
south of Pittsburgh.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
KEY MESSAGES:
- Snow showers will diminish near sunrise in the vicinity of
Pittsburgh, early afternoon near I-80
- A large winter system will start to enter the region after
dark
--------------------------------------------------------------------
Brief ridging will build into the region overnight, but a deep,
well-mixed boundary layer, characterized by steep lapse rates,
will persist. Given the infusion of lake moisture into this
environment under northwest flow, snow showers will linger
this morning north of Wheeling due to gravity waves.
Areas in eastern Ohio are experiencing clearing as as low-level
flow shifts from the southwest, temperatures have been adjusted
down to account for radiational cooling. Expected single digits
in locations through 6am. Elsewhere, clouds and lingering precip
will keep temps in the teens.
Strong fetch off of the Great Lakes will likely diminish between
16Z and 18Z and be directed from the west, this will likely end
snow shower activity near I-80.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
KEY MESSAGES:
- Widespread snow returns between 7pm to 11pm tonight: Winter
Storm Warning/Winter Weather Advisory in effect through 7pm
Monday
- Heaviest precipitation expected between 2am and 7am Monday
- Impactful snow accumulations (6-12") is likely south of
Pittsburgh
- Upgrade to Winter Storm Warning for counties under Winter
Weather Advisory is possible
--------------------------------------------------------------------
An advancing low pressure system, which is expected to be center
towards our southwest, will likely make its presence know
between 6pm to 8pm this evening. The leading edge of snow is
expected to advance into eastern Ohio and northern West Virginia
as the center of the low ventures into southern Kentucky/northern
Tennessee.
Snowfall rates are expected to rapidly intensify (0.5 to
1.0"/hr) between 11pm Mon to 1am Tues. This is likely due to an
axis of strong frontogenesis developing south and parallel to
I-70. Probability of occurrence, based on Hi-Res guidance, is
between 60% to 95% in this area.
The axis of heavy snow will be very narrow on the radar, and
may only span 20 to 40 miles from north to south. With recent
Hi-Res model guidance, a slight shift to the north was noted
with the 00Z and 06Z run and additional QPF was added. These two
changes have prompted an upgrade to Winter Storm Warning for
counties that were previously under a Watch. The potential for
at least 3" of snow and morning commute impacts has been issued
for a few counties just north of the Warning. However, it must
be noted, that if guidance continues to shift further north
areas under an Advisory may need upgraded to a Warning
(including the Pittsburgh metro area).
Along with snow, there is the potential for some areas to
experience mixed precipitation (sleet and/or freezing rain) for
a brief period of time. The range of possibilities for 800mb to
825mb temps is -1C to +1C and will heavily determine the precip
type. It could be wet snow, freezing rain, or sleet for areas
south of I-70 at times.
As cold filters in from the north, the potential of mixed
precipitation is expected to end between 12pm to 4pm across the
region and precip type will return to snow. Snow ratios will
rapidly increase as well, from 5:1 to 19:1 by late evening and
snow character will likely be considered 'drier'.
As the trough ventures east late Monday evening/night, mid-
level dry air from a building ridge over the Midwest filters
into the Ohio River Valley. The potential for widespread snow
will diminish. Upsloping, under northwest flow, along the ridges
may prompt an additional 2-3 inches of snow. Therefore, the
Winter Storm Warning will continue through at least 7am Tuesday
morning.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
KEY MESSAGES:
- Periodic snow showers through Thursday
- Below average temperatures continue
- There is the potential for a large-scale weather disturbance
to impact the region Saturday.
--------------------------------------------------------------------.
Upsloping and lake enhancement, within a nw flow pattern,
and will likely sustain snow showers along the ridges and
portions of the region through at least Thurs. However, at this
moment, snow amounts are expected to be low enough (below 3") not
to prompt an advisory.
Confidence continues to remain elevated that below-average
temperature will continue through Fri.
The is the potential for the development of a large-scale
system late week and could impact the region Saturday into
Sunday as a cut-off low forms near southern California mid-week
and tracks east. However, confidence is still low on the overall
track of this noted system. The NBM has a 10-15% chance of 6
inches of snow along the ridges of West Virginia.
&&
.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
Clearing has brought VFR back to our southernmost terminals and
this clearing is advancing NE as expected. MVFR should continue
at the remainder of the TAF sites through early Sunday
morning, before the building high and backing wind result in
the lower level clouds clearing for airports except for FKL and
DUJ (which will likely see this clearing Sunday evening.) Mid
level clouds will quickly increase Sunday ahead of low pressure
approaching from the MS Valley region.
Snow and IFR conditions are expected to overspread the region
from SW-NE Sunday night with the approaching low ZZV should see
these conditions begin around 01Z. PIT should see snow by 06Z.
LIFR is expected along and south of a ZZV to PIT to LBE line
overnight, as the heaviest snow occurs overnight into Monday
morning. Current guidance indicates one inch per hour rates are
likely from near ZZV-HLG-MGW. A brief period of fzra is
possible at MGW, though confidence in occurrence was too low
for a TAF mention at this time.
Outlook...
Widespread IFR restrictions in snow are expected to continue
Monday as the low crosses the Ohio Valley region. The Upper OH
Valley region will then be in a cold NW flow pattern, under
broad upper troughing. Scattered snow showers and periodic
restrictions are expected.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Winter Weather Advisory from 7 PM this evening to 7 PM EST
Monday for PAZ021-077-078.
Winter Storm Warning from 7 PM this evening to 7 PM EST Monday
for PAZ029-031-073>076.
OH...Winter Weather Advisory from 7 PM this evening to 7 PM EST
Monday for OHZ039-048>050.
Winter Storm Warning from 7 PM this evening to 7 PM EST Monday
for OHZ057>059-068-069.
WV...Winter Weather Advisory from 7 PM this evening to 7 PM EST
Monday for WVZ001-002.
Winter Storm Warning from 7 PM this evening to 7 PM EST Monday
for WVZ003-004-012-021-509>511.
Winter Storm Warning from 7 PM this evening to 7 AM EST
Tuesday for WVZ512>514.
&&
$$
SYNOPSIS...Hefferan
NEAR TERM...Hefferan
SHORT TERM...Hefferan
LONG TERM...Hefferan
AVIATION...WM/AK
Source:
PBZ issues Area Forecast Discussion (AFD) at Jan 5, 6:45 AM EST---------------
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