Lake Effect Snow Warning 1, NWS Cleveland, OH

Area Forecast Discussion
National Weather Service Cleveland OH
1244 PM EST Tue Jan 16 2024

.SYNOPSIS...
A surface ridge attempts to reach into Ohio from the southwest
and south through Friday as the polar vortex remains over the
region. Pieces of low pressure will wobble across Ontario and
cross the region today and again Thursday into Friday.

&&

.NEAR TERM /THROUGH WEDNESDAY/...

12:35 PM EST Update...
Most of the forecast remains valid. However, expanded the Winter
WX Advisory to account for trends in the regional radar
network's depiction of the ongoing Lake Erie lake-effect snow
(LES) and webcam imagery since late this morning. The Winter WX
Advisory remains in effect until 7 PM this evening for Lake,
far-northern Ashtabula, and Erie (PA) Counties. Strong low-level
convergence along the LES bands will allow strong/maximized
ascent to be collocated with a cloudy DGZ about 1 km thick at
times. Thus, still expect snowfall rates up to 2" per hour.
Snowfall totals are expected to reach 3-7" in the heaviest,
most-persistent LES, which is expected to be focused along/near
the lakeshore and the I-90 corridor. The LES will continue to
drift N'ward and should become located totally offshore our CWA
by this early evening as the mean low-level flow backs from
W'erly toward SW'erly and a ridge at/near the surface builds
into our region from the southwest. POP's, QPF, SLR's, and
snowfall amounts were updated accordingly for our forecast.

Previous Discussion...
An upper level trough rotating around the polar vortex will
cross the region today. The area of lift ahead of this trough
will produce some light snow for all locations with half an inch
to around an inch possible. The open waters on Lake Erie and
the very cold air in place will allow the lake to contribute
moisture to the lift associated with the trough. This will allow
a heavy band of lake effect snow to develop. We are already
seeing it over the middle of the lake northeastward into western
NY. As the upper level trough crosses the region it will grab
this lake effect snow band and pull it closer to shore. Many of
our hi-resolution models keep this band of snow along the
lakeshore from Ashtabula county into Erie County, PA. There is a
possibility that this band pushes inland enough that we need to
cover all of I-90 in the winter weather advisory. So for this
reason we expanded it into the southern Erie forecast zone. The
heaviest snow (up to 2 inches per hour) looks like it will occur
in an area near and north of a line from Platea to Findley Lake
from 14Z through 19Z then drift back to the north through the
evening as the 925 to 850 mb flow shifts from westerly to
southwesterly. If the higher rates of snow occur longer than
anticipated we may end up needing a short lead time LES warning.
The band will be close to the Ashtabula County lakeshore
forecast zone and will need to be monitored for inclusion in the
advisory. Definitely a very difficult forecast. Just a 10 mile
shift in the band over the lake or onto land will have
significant impacts to snowfall amounts.

Beyond this evening the threat of snow should move back onto the
lake and flow into western NY. In the wake of the upper level
trough winds are expected to increase in our already cold
environment. The lower wind chill values are already impacting
NW OH this morning but will spread eastward during the evening.
All locations will end up with wind chill values of -15 to -20
degrees below zero that persist through Wednesday morning. So
the Wind Chill Advisory will cover the entire region after 7 pm
until it expires at noon Wednesday.

The cold continues today with highs ranging from the upper
single digits across NW OH to the teens across the east. Lows in
the lower single digits tonight as winds increase. Sunshine on
Wednesday should allow for a warming trend. Highs should return
to the teens areawide.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
Active weather is expected for the second half of the work-week.
There are two distinct chances for snow across the entire forecast
area, first Wednesday night into Thursday and then late Thursday
night through Friday. Arctic air filters back in Friday night into
the weekend with lake effect snow lingering.

A low-amplitude shortwave will zip across the northern Ohio Valley
on Thursday. A combination of jet support from the right-entrance
quadrant of an upper-level jet streak, mid-level warm air and
moisture advection, and a tightening mid-level thermal gradient/
perhaps some modest frontogenesis at times will drive periodic light
snow across the forecast area ahead of this shortwave. Expect snow
chances to begin ramping up Wednesday night and continue through
much of Thursday, with the snow initially favoring our northern
counties and gradually settling south/southeast by Thursday evening.
The lift with this system will generally be modest but it will
intersect with a rather deep dendritic growth zone between 600-750mb
at times, likely leading to a rather efficient / high-ratio snow.
Pursuing the 0z ensembles, nearly all members have light QPF across
our entire forecast area with this system suggesting that there's
high likelihood that everyone gets at least a light amount of snow.

Our current forecast generally lies between 1-3" across the whole
CWA from Wednesday night through Thursday (a long window), with
closer to 1-2" across Northwest Ohio and Central Ohio and closer to
2-3" elsewhere. Latest probabilistic snowfall guidance from the
Weather Prediction Center (WPC) depicts a 50-90% chance of at least
1" of snow across our entire forecast area Wednesday night through
Thursday afternoon, closer to 50/50 Northwest and Central Ohio and
highest across Northeast Ohio into Northwest Pennsylvania. The 90th
percentile values (aka the "reasonable worst case") range from about
2" across our extreme southern counties to 2-4" elsewhere, with up
to 5" across parts of Northeast OH and Northwest PA. So while there
is slight potential to over-achieve a bit if we see some banded snow
given the 90th percentile numbers, this will overall be a light snow
event. Given cold road temperatures the snow will stick, so minor
travel impacts are possible Wednesday night into Thursday. It
generally looks like lake effect snow will stay out over the lake in
this window, though we'll keep an eye on the eastern lakeshore.

After a brief lull in snow Thursday evening into Thursday night,
chances quickly ramp back up late Thursday night into Friday morning
across the entire forecast area. A lobe of the tropospheric polar
vortex will drop into the Great Lakes Friday into Saturday, bringing
Arctic air back to the area. Ahead of this feature, a rather potent
shortwave/clipper will zip across the Ohio Valley Thursday night
into Friday. Yesterday it was mentioned it was somewhat uncertain
how much this system would be able to amplify ahead of the incoming
Arctic air, leading to a low-confidence forecast regarding snow
potential. Since yesterday guidance has generally trended more
amplified with the shortwave, with some models (such as the
Canadian, but with some ensemble support from the GFS and Euro
ensembles) even showing this shortwave phasing with some energy in
the sub-tropical jet stream, yielding a more notable synoptic snow.

Confidence is increasing in at least a light snow area-wide late
Thursday night into Friday following by lake effect snow later
Friday into the weekend. There is some potential for a more notable
synoptic snow if the more amplified solution with Friday's system
proves correct, though that widespread snowier outcome is still on
the "less likely" side. Regardless, the set-up looks favorable for
notable lake enhanced/effect snow Friday into Friday night from the
Cleveland metro area into both the primary and secondary snowbelt
with a north-northwest flow. While growing ice in the western and
perhaps central basins may be a small negative, there should still
be enough open water for a robust lake response. Ice needs to be
thick and locked in to really limit that. Models indicate plenty of
synoptic moisture, strong and deep lake-induced instability beneath
very cold air aloft, a connection to Lake Huron, and fairly modest
winds which will maximize heat and moisture fluxes off of the lake.
From a probabilistic standpoint, the odds of over 1" of snow are 40-
70% across Northwest and Central Ohio and >70% across all of
Northeast Ohio and Northwest Pennsylvania so a widespread, light
accumulation is likely at a minimum. 90th percentile (reasonable
worst case) values range from 3-5" across Northwest and North
Central Ohio to 5-8" across much of North Central/Northeast Ohio
into Northwest Pennsylvania, highest across the snowbelt. This set-
up has some upside and could certainly prompt winter weather
headlines, especially where the lake gets involved.

Lows Wednesday night will generally range from the mid 10s to near
20, with slightly milder highs on Thursday in the mid to upper 20s.
Lows Thursday night generally fall to 15 to 20, with modest rebound
into the low to mid 20s on Friday. Friday night will see single
digits return out west, with low 10s farther east. Wind Chills may
approach -10F Friday night in our western counties.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
A cold weekend is expected with some lingering lake effect. By
Saturday synoptic moisture and support start departing, though
impactful accumulations may occur within any lingering Lake Huron
connection into extreme Northeast Ohio or Northwest Pennsylvania.
Ridging really builds in Saturday night into Sunday, which should
cause lake effect to continue inching northeast while loosing
steam. Moisture return begins on Monday, though notable precip
potential (quite possibly in the form of rain) holds off until
Monday night or Tuesday. It remains very cold through Saturday night
with highs struggling to reach 20 and lows in the single digits or
lower 10s, with a bit of improvement Sunday. Highs appear poised to
finally rise above freezing for most of the area on Monday.

&&

.AVIATION /18Z Tuesday THROUGH Sunday/...
Cyclonic SW'erly to W'erly flow aloft and embedded disturbances
affect our region through 18Z/Wed. At the surface, a trough
lingers over/near the Great Lakes. Simultaneously, a ridge
attempts to build into our area as the core of the ridge moves
from the south-central U.S. toward the TN Valley. Our regional
surface winds trend SW'erly around 10 to 15 knots with gusts up
to 20 to 25 knots at times.

MVFR ceilings are expected to exit our region generally from
west to east through this early evening. Isolated general snow
showers associated with a potent disturbance aloft will exit
far-NE OH and NW PA to the east by about 19Z/Tues. Periodic MVFR
visibility is possible with these snow showers. Lake-effect
snow (LES), heavy at times, streaming eastward across far-NE OH
and far-NW PA, including KERI, will continue to shift northward
and should become located totally offshore our region by
~02Z/Wed. Ceilings and visibility will vary between MVFR and
LIFR in the LES.

Outlook...Periods of non-VFR in snow and low ceilings are
expected through this Sunday.

&&

.MARINE...
Brisk southwest winds develop today, prompting Small Craft
Advisories beginning at 10 AM this morning for all nearshore waters.
Winds will generally be 20 to 28 knots today, building 5 to 9 foot
waves across much of the central and eastern basins. Winds remain
strong tonight and increase further late tonight into Wednesday,
with 25 to 30 knots expected across the western basin and 30 to 35
knots across the central and eastern basins. While it would be a low-
end gale, NBM probabilities for gale-force winds remain 20-40% as
far west as off of Cleveland and increase to 50-70% over the east
end. This is sufficient for a Gale Watch for approximately the
eastern two thirds of the lake for Wednesday. Heavy freezing spray
will also become a concern late tonight into Wednesday across the
central and eastern basins, with low water levels across the western
basin. The plan is to issue any Heavy Freezing Spray or Low Water
headlines when any Gale Warnings are issued, as those hazards will
generally go hand in hand. Flow gradually eases Wednesday evening
allowing the Gale Watch to end, though lingering Small Craft
Advisories can be expected through Wednesday night. A general lull
in winds and waves is expected Thursday and Thursday night. North-
northwest winds will increase to 15-25 knots Friday afternoon
through Saturday, likely causing renewed Small Craft Advisories.

Moderate to rapid ice growth will continue across the western and
central basins through this weekend with some shore ice potentially
forming farther east. Strong southwest winds through Wednesday night
will cause extensive movement of any ice that has already developed.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...Wind Chill Advisory until noon EST Wednesday for OHZ003-006-
     017.
     Wind Chill Advisory from 7 PM this evening to noon EST
     Wednesday for OHZ007>010-018-019-027>030-036-037-047.
     Wind Chill Advisory from 10 PM this evening to noon EST
     Wednesday for OHZ011>014-020>023-031>033-038-089.
     Winter Weather Advisory until 7 PM EST this evening for OHZ012-
     089.
PA...Wind Chill Advisory from 10 PM this evening to noon EST
     Wednesday for PAZ001>003.
     Winter Weather Advisory until 7 PM EST this evening for PAZ001-
     002.
MARINE...Small Craft Advisory until 10 PM EST Wednesday for LEZ142>145.
     Small Craft Advisory until 7 AM EST Wednesday for LEZ146>149.
     Gale Watch from Wednesday morning through Wednesday evening
     for LEZ146>149-166>169.

&&

SYNOPSIS...MM
NEAR TERM...Jaszka/MM
SHORT TERM...Sullivan
LONG TERM...Sullivan
AVIATION...Jaszka
MARINE...Sullivan

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