CLE issues Area Forecast Discussion (AFD) at Dec 19, 6:53 AM EST116
FXUS61 KCLE 191153
AFDCLE
Area Forecast Discussion
National Weather Service Cleveland OH
653 AM EST Thu Dec 19 2024
.SYNOPSIS...
High pressure will build east across the Great Lakes Region today. A
weak clipper system will move southeast across the area on Friday.
Lake effect snows will return Friday night into Saturday as a trough
lingers across the eastern Great Lakes Region.
&&
.NEAR TERM /THROUGH FRIDAY/...
Forecast this morning remains on track. Slightly raised pops for
western portions of the area with the clipper system late
tonight into Friday.
Previous discussion...
Scattered light snow showers are still ongoing across far Northeast
Ohio and Northwest Pennsylvania within the northwest flow and
shallow moisture depth of only 6-7K feet. Any additional
accumulations will be light and mainly confined to inland portions
of Erie County PA. This snow is expected to diminish this morning as
high pressure continues to build eastward and low level flow veers
from northwesterly around to the east northeast. Despite the
building high, moisture is expected to be trapped beneath an
inversion around 4K feet with mostly cloudy skies today.
Temperatures have been slow to fall overnight given the cloud cover
and expect to have a limited rise during the daytime hours with
highs in the low to mid 30s.
By tonight a weak clipper system will track from near Chicago
towards southern Ohio. This occurs as a 150 knot upper level jet
digs across the Plains with the trough aloft extending to the
southeastern United States. The clipper will weaken as it passes to
our south on Friday before being absorbed into a stronger area of
low pressure moving north off the East Coast of the United States.
In terms of impacts to the area, light snow will move into Northwest
Ohio after 3-4 AM with lift in the 925-700mb layer. By Friday
morning some mid-level dry air wraps into the system from the south
which could lead to breaks in the precipitation. At the same time a
cold pool with around -29C at 500mb passes overhead and expect snow
showers to continue off and on for much of the day on Friday.
On the north side of the 700mb low we expect to see a swath of
locally heavier snow where the frontogenetic forcing is
stronger. This looks most likely to line up across southwest
Ohio and expect accumulations in our area to generally be around
an inch. If this axis sets up farther north then we may need to
trend the snowfall forecast up. Surface temperatures in the low
30s are marginal for accumulating snow but expect temperatures
may cool slightly in snow showers given the cold pool aloft.
Accumulations will be highest on grassy or elevated surfaces.
Trended temperatures down slightly on Friday and removed any
mention of rain as snow should be the primary weather type.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
Cyclonic NW'erly flow aloft and embedded shortwave disturbances
affect our region Friday night through Saturday as a surface trough
lingers over the eastern Great Lakes and Upper OH Valley. This
weather pattern will allow net low-level CAA to impact our region.
Accordingly, Friday night's lows are expected to reach the upper
teens to mid 20's around daybreak Saturday. Afternoon highs on
Saturday are expected to reach the lower to mid 20's in NW PA and
the mid to upper 20's in northern OH. Initially N'erly mean low-
level flow of sufficiently-cold/moist air over/downwind of ~4C Lake
Erie is expected to back to NNW'erly Friday night as lake-induced
equilibrium levels (EL's) hover near 8kft above lake level.
Accordingly, lake-effect snow (LES) bands will stream generally
S'ward and then SSE'ward from the lake and at least periodically
impact locations from roughly the longitude of the Lake Erie Islands
and farther east. The heaviest LES, associated with an upstream
moisture connection to Lake Huron, is expected to impact the Lake
Erie Islands and points just to the south Friday evening before
shifting E'ward to near the east side of metro Cleveland and Akron
by daybreak Saturday morning as the expected evolution of mean low-
level flow causes the LES bands to pivot E'ward. On Saturday, the
mean low-level flow of sufficiently-cold/moist air is expected to
back from NNW'erly to NW'erly as lake-induced EL's continue to hover
near 8kft above Lake Erie. Accordingly, LES bands will continue to
pivot E'ward and eventually become focused in the snowbelt of NE OH
and NW PA. The heaviest LES associated with the upstream moisture
connection to Lake Huron is expected to be most-persistent across
far-NE OH during the day on Saturday. Model soundings indicate low-
level convergence along the major axis of this band will likely
result in strong/maximized ascent within a cloudy DGZ at least 1 km
thick and promote maximum snowfall rates of 1-2"/hour Friday night
through Saturday.
NW'erly cyclonic flow aloft and embedded shortwave disturbances
continue to affect our CWA Saturday night as a surface ridge begins
to build from the western Great Lakes. A lowering subsidence
inversion and synoptic low-level dry air advection will cause lake-
induced EL's to drop to near 5kft above Lake Erie and LES intensity
to wane. Mean low-level flow remains NW'erly and maintains an
unusually-cold air mass across northern OH and NW PA. Overnight lows
are expected to reach roughly 10F to 20F. LES showers will continue
to impact most of the snowbelt of NE OH and NW PA. The primary LES
band associated with the upstream moisture connection to Lake Huron
is expected to persist in far-NE OH. Snowfall rates may be as high
as 1"/hour within this band, especially during Saturday evening,
since moderate to strong ascent may be maximized in a cloudy DGZ at
least 0.5 km thick. Outside the LES, periodic flurries and trace
snow accumulations are possible Friday night through Saturday night
in association with moist isentropic ascent preceding the axes of
the aforementioned shortwave disturbances.
On Sunday through Sunday night, the aforementioned ridge at the
surface and aloft will continue to build from the western Great
Lakes and vicinity as an unusually-cold air mass persists in our
region. Afternoon highs are expected to reach the upper teens to
upper 20's on Sunday and be followed by overnight lows near 5F to
15F in NW PA and mainly 10F to 15F in northern OH around daybreak
Monday. LES, mainly light in nature, should continue to stream
generally SE'ward from Lake Erie and impact the snowbelt before it
ends during Sunday afternoon as lake-induced CAPE and EL's decrease
significantly via continued low-level dry air advection and a
lowering subsidence inversion accompanying the ridge. Otherwise fair
weather is expected due to the stabilizing subsidence inversion. Our
updated official forecast depicts lake-effect snowfall totals of 4-
8" in the heaviest and most-persistent snow across far-NE OH, with
lesser snow accumulations expected elsewhere in the LES footprint
Friday night through Sunday. However, this snowfall forecast may be
conservative, especially for the aforementioned primary LES band.
The HWO has been updated to highlight increasing concerns regarding
an impactful LES event. Stay tuned to forecast updates and possible
issuance of Winter WX alerts.
&&
.LONG TERM /MONDAY THROUGH WEDNESDAY/...
Current odds favor fair weather this Monday as the above-mentioned
ridge at the surface and aloft exits E'ward. Net WAA along the
western flank of the low-level portion of the ridge will contribute
to afternoon highs reaching the upper 20's to lower 30's in NW PA
and the lower to mid 30's in northern OH.
The general weather pattern on Monday night through Wednesday is
expected to feature our CWA remaining along the western flank of the
ridge at the surface and aloft while troughing aloft tends to be
focused in vicinity of the Upper and Mid MS Valley. This pattern
will allow net low-level WAA to persist. Highs should reach the mid
30's to lower 40's on Christmas Eve and Day, respectively. Lows
should reach the lower 20's to lower 30's around daybreak on
Christmas Eve and the upper 20's to mid 30's around daybreak on
Christmas Day. Shortwave disturbances should eject generally E'ward
from the aforementioned trough aloft and traverse our area while
being accompanied by surface trough axes on Monday night through
Christmas Day. Periods of precip are expected due to moist
isentropic ascent ahead of the shortwave trough axes aloft and via
low-level convergence/moist ascent along the attendant surface
trough axes. Given the projected diurnal cycle in temperatures and
wet-bulb temperatures at/near the surface, a mix of rain and snow is
anticipated, with the best potential for snow each night through
the following mid-morning hours.
&&
.AVIATION /12Z Thursday THROUGH Monday/...
Flurries and a few light snow showers continue to fall in far
Northeast Ohio and Northwest Pennsylvania. Precipitation will
end this morning as high pressure continues to expand overhead.
Overcast skies will continue and will be on the fringe of
2500-3500 feet. Expect the trend to be more into the MVFR range
today as inversion heights gradually lower.
A weak clipper system will move southeast tonight from near
Chicago across southern Ohio. Light snow is possible across the
area beginning after 06Z in the west and continuing at times
through the end of the TAF period. Brought declining
visibilities down to IFR after 09Z tonight with snow showers
beginning at CLE and CAK at 11Z . MVFR to IFR
Winds will start off light out of the northwest, veering to
northeast and eventually easterly. Aside from a few gusts to 20
knots at ERI, winds will tend to be 10 knots or less.
Outlook...Non-VFR expected in periodic snow late Thursday night
through Friday night, then continuing in the snowbelt into
Sunday morning.
&&
.MARINE...
A ridge builds from the western Great Lakes through this early
afternoon before exiting E'ward later today through tonight. A low
tracks SE'ward from the north-central United States to the
southwestern Great Lakes region through daybreak Friday morning.
This weather pattern evolution will allow NW'erly winds around 10 to
15 knots early this morning to become light and variable late this
morning through afternoon. During this evening and overnight
tonight, winds will trend E'erly to SE'erly around 5 to 15 knots.
Waves will be 3 feet or less.
On Friday, the aforementioned low in vicinity of the southwestern
Great Lakes is expected to be absorbed by a deepening coastal low
expected to move NE'ward from near Cape Hatteras to near Nova
Scotia. Accordingly, a residual trough will linger over Lake Erie on
Friday through Saturday. This will cause initially E'erly to SE'erly
winds around 5 to 15 knots Friday morning to back to N'erly and
freshen to 15 to 20 knots by sunset Friday evening. Waves of 3 feet
or less will build to as large as 4 to 5 feet, especially east of
The Islands. Another Small Craft Advisory will likely be needed.
N'erly to NW'erly winds around 10 to 20 knots and waves as large as
3 to 5 feet are expected Friday night through Saturday. N'erly to
NW'erly winds ease to 5 to 15 knots Saturday night, which will allow
waves to subside to 3 feet or less by daybreak Sunday morning.
A ridge builds from the western Great Lakes on Sunday and exits
E'ward on Monday. Winds become variable in direction and ease to
around 5 to 10 knots on Sunday. Winds then become SE'erly around 5
to 15 knots Sunday night into Monday. A warm front will sweep N'ward
across Lake Erie Monday evening, which will cause SE'erly winds to
veer to S'erly and freshen to 10 to nearly 20 knots. Waves are
expected to be 3 feet or less in U.S. waters on Sunday through
Monday.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...None.
&&
$$
SYNOPSIS...KEC
NEAR TERM...KEC
SHORT TERM...Jaszka
LONG TERM...Jaszka
AVIATION...KEC
MARINE...Jaszka
Source:
CLE issues Area Forecast Discussion (AFD) at Dec 19, 6:53 AM EST---------------
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