CLE issues Area Forecast Discussion (AFD) at Jan 4, 3:57 PM EST
416
FXUS61 KCLE 042057
AFDCLE
Area Forecast Discussion
National Weather Service Cleveland OH
357 PM EST Sat Jan 4 2025
.SYNOPSIS...
High pressure gradually builds in from the west tonight and
Sunday. A low pressure system moves across the Lower Ohio Valley
on Sunday night into Monday with a trough lingering across the
Great Lakes region through Thursday.
&&
.NEAR TERM /THROUGH SUNDAY NIGHT/...
Lake effect snow continues downwind of Lake Erie through at
least tonight as the thermodynamic profile remains relatively
unchanged through that time period. An ever so slight uptick in
low-level moisture will result in an uptick in lake effect snow
intensity between ~23-05Z this evening into early tonight,
particularly in Lake, Geauga, and Ashtabula where up to 1"/hr
snowfall rates may be possible. Should see a more noticeable
diminishing of lake effect after 05Z tonight as inversion
heights decrease and dry air is advected in from the west as
high pressure builds in from the west. Additional snow
accumulations of 1-4" is expected, most of which will fall
through tonight.
As far as headlines go, everything is unchanged except the
Winter Weather Advisory for Trumbull County, which was extended
through 7 PM. Cuyahoga and Trumbull (which are both set to
expire at 7 PM) may need to be extended for a few more hours
depending on where lake effect snow sets up this evening into
tonight. The warnings for Erie and Crawford PA will likely be
able to get cancelled early sometime on Sunday (very unlikely
that heavy snow lasts all the way through 7 PM), though kept is
as is for now in case the forecast changes.
An upper-level trough and attendant low pressure system move
across the Tennessee and Ohio Valleys Sunday afternoon through
Sunday night. Major impacts from the system will largely stay to
the south of our forecast area, though isentropic lift and
associated mid-level frontogenesis will be far enough north
where we should see the northern extent of the precipitation
shield expand into much of the forecast area for at least a
brief time Sunday night into early Monday morning. A good chunk
of the area should see at least a dusting of snow. Where it
gets complicated is the gradient of the higher snowfall amounts
is right along the southern fringes of our forecast area, which
makes headline decisions (i.e. such as Winter Storm Warning or
Winter Weather Advisory) quite challenging. The best chance for
Winter Weather Advisory criteria (i.e. greater than or equal to
4" snow) is the southern part of Marion, Morrow, and Knox
Counties, where model consensus has snow probabilities of
greater than or equal to 4" snow around 30-60%. Usually this is
"close enough", especially given impacts to the Monday morning
commute are probable even with lesser snow amounts. However,
there was enough model guidance on the low end of the forecast
data with only 1 or 2 inches of snow that we opted to wait one
more cycle to make a (hopefully) more accurate final decision.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
The Ohio Valley low will quickly exit across the Mid Atlantic states
Monday, with the associated mid-level deformation axis pulling east
quickly Monday morning. This will allow lingering synoptic snow to
exit the region by early afternoon, however, the mid/upper trough
axis reamplifying in its wake across the Great Lakes and N to NW
boundary layer flow will support another round of multi banded lake-
effect snow. H85 temps cooling to -12 to -15 C Monday afternoon
through Monday night over the still open waters of Lakes Erie and
Huron will generate conditional instability to support the multi
bands, along with the fetch suggesting a Lake Huron connection
starting over the secondary snowbelt than gradually migrating
eastward. NAM forecast soundings and plan views suggest a dry
airmass and marginal EQL's may be a limiting factor to this event,
and this will likely keep accumulations in check. Nevertheless, snow
will fly again across the primary and secondary snowbelts by late
Monday afternoon through Monday night, with at least a few inches of
accumulation, so increased PoPs significantly Monday afternoon
through Monday night.
Surface ridging building into the Ohio Valley Tuesday will lead to
increasing shear, subsidence, and further drying of the airmass.
This along with backing boundary layer flow will weaken the bands
through the day and push them toward NW PA. The break will be short
lived though as another mid-level shortwave rotates through the deep
eastern North American longwave trough. This feature and associated
surface trough look to drop across the southern Great Lakes Tuesday
night into early Wednesday, with the increasing synoptic moisture
and lift regenerating lake-effect snow showers and squalls. The
boundary layer flow becoming aligned from the N and NW again will
lead to another multi band event across the primary and secondary
snowbelts as H85 temps further cool to -15 to -18 C by early
Wednesday. Raised PoPs significantly once again Tuesday night into
Wednesday for these areas.
Highs will remain in the mid 20s to around 30 Monday, with low to
mid 20s Tuesday as the arctic air further deepens across the region.
Lows Monday night and Tuesday night will fall into the mid/upper
teens.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
A mid-winter pattern will continue through the weekend and beyond as
a coupled +PNA, -AO, and -NAO will cause a western North American
ridge, eastern North American trough to persist. This will support
continued shots of arctic air and well below normal temperatures,
along with frequent lake-effect snow showers. Lake-effect snow
showers will be ongoing Wednesday into Thursday across the primary
and secondary snowbelts with continued well-aligned NW flow and H85
temps of -15 to -18 C. Sufficient synoptic moisture and persistent
upsloping could lead to significant accumulations over a couple of
days, so headlines are once again possible for the primary and
secondary snowbelts in the mid to late week period.
Shortwave ridging building into the area Thursday night into Friday
will finally shut down the lingering lake-effect snow showers, but
attention will then turn to a southern stream storm system Friday
night into next weekend that will attempt to phase with the northern
stream trough. Consensus and pattern recognition track the low well
to our south again before a mid-Atlantic coastal low takes over, but
there is a great deal of uncertainty 7 days out on whether we see
any snow from this system. Kept chance PoPs Friday night into
Saturday at this time. Highs will remain in the low to mid 20s
through the period. Wind chill values could dip into the -5 F range
Wednesday and Thursday nights.
&&
.AVIATION /18Z Saturday THROUGH Thursday/...
Lake effect snow continues downwind of Lake Erie for much of
Northeast Ohio and Northwest Pennsylvania with variable
conditions being observed. MVFR will be the most prevalent
condition, though periods of lower conditions are expected with
visibility wherever snow bands develop and persist. Outside of
the snowbelt, isolated to scattered snow showers with OVC/BKN
MVFR ceilings are expected. Lake effect snow and cloud cover
gradually dissipates as high pressure gradually builds in from
the west tonight and Sunday.
Winds 12 to 15 knots with gusts up to 20 to 25 knots are
expected through this evening before gradually dissipating
tonight and Sunday. Gusts may approach 30 knots near the
lakeshore this afternoon.
Outlook...Non-VFR expected in periodic snow and low ceilings
Sunday night through Tuesday. Non-VFR will be possible
thereafter through Thursday with lake effect clouds and snow.
&&
.MARINE...
Brisk W to NW winds will continue on the lake tonight into Sunday,
so extended the Small Craft Advisory from the far western basin to
Vermilion through 09Z Sunday morning. It will still take until
Sunday afternoon for the winds and waves to subside on the central
and eastern basins, so left those Small Craft headlines as is.
W winds will decrease to 5-10 knots by Sunday evening before turning
NE and increasing to 15-25 knots by Monday afternoon, so Small Craft
Advisories will be needed again. Winds will gradually back to NW
through Tuesday with speeds staying in the 15-20 knot range,
occasionally up to 25 knots, so headlines will continue. NW winds of
15-25 knots will then continue Tuesday night through Thursday. Along
with the elevated waves will come freezing spray Monday night
through much of the week. Confidence in how much freezing spray will
occur is somewhat low at this time, but added it to the forecast.
Ice will likely start to form on the western basin by the end of the
week given the sustained arctic airmass.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...Lake Effect Snow Warning until 7 PM EST this evening for
OHZ011-020>022.
Lake Effect Snow Warning until 7 AM EST Sunday for OHZ012>014-
089.
Winter Weather Advisory until 7 PM EST this evening for OHZ023.
PA...Lake Effect Snow Warning until 7 PM EST Sunday for PAZ001>003.
MARINE...Small Craft Advisory until 4 AM EST tonight for
LEZ142>144.
Small Craft Advisory until 4 PM EST Sunday for LEZ145>149.
&&
$$
SYNOPSIS...Saunders
NEAR TERM...Saunders
SHORT TERM...Garuckas
LONG TERM...Garuckas
AVIATION...Saunders
MARINE...Garuckas
Source: CLE issues Area Forecast Discussion (AFD) at Jan 4, 3:57 PM EST (https://mesonet.agron.iastate.edu/p.php?pid=202501042057-KCLE-FXUS61-AFDCLE)
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