CLE issues Area Forecast Discussion (AFD) at Dec 18, 12:36 PM EST499
FXUS61 KCLE 181736
AFDCLE
Area Forecast Discussion
National Weather Service Cleveland OH
1236 PM EST Wed Dec 18 2024
.SYNOPSIS...
A ridge exits eastward early this morning as a low develops in
vicinity of the Lower Ohio Valley. A cold front sweeps eastward
across our region this afternoon through early evening as the
aforementioned low along the front moves northeastward to the
central Appalachians and then toward the New York City region.
Behind the cold front, another ridge builds from the north-
central United States through tonight and continues to impact our
region on Thursday as the ridge begins to exit eastward.
&&
.NEAR TERM /THROUGH THURSDAY/...
12:30 PM EST Update...
Rather dreary conditions continue to impact the CWA with a mix
of fog, rain, and snow showers. Patchy fog is primarily isolated
to NW OH with rain/snow showers impacting areas along and east
of I77. These showers will continue to drift east through the
evening and lake effect is expected to become established on the
back side of the trough. Aside from minor adjustments to timing,
overall forecast through tonight remains the same.
9:30 AM EST Update...
The general forecast remains unchanged with a mix of rain and
snow showers expected across the area through this morning,
tapering from west to east this evening. Biggest adjustment with
this update is the timing of showers as the eastern extent is
much quicker than previously forecast. With current temperatures
hovering right near freezing and dew points generally below
freezing, will continue to monitor for any freezing rain
potential, but given the forecast wet bulb temperatures, not
expected any widespread freezing rain. In addition, opted to
add the potential for lake effect by 00Z Thursday as much colder
850 mb temperatures begin to south southeast across Lake Erie.
Generally still thinking 1-3" are possible across NW PA with
1-2" possible across the OH snowbelt.
6:28 AM EST Update...
Forecast remains valid, overall, per latest trends in obs and
model guidance. Only change was to add patchy fog mention
through late morning since nocturnal cooling and small dew point
depressions have allowed widespread mist to form in northern OH
and NW PA. Some breaks in cloud cover may allow isolated
radiation fog to develop through daybreak. Any fog is expected
to dissipate via limited diurnal convective mixing of the
boundary layer by late morning.
Previous Discussion...
A ridge at the surface and aloft exits E'ward today as a trough
aloft approaches from the north-central United States and begins
to overspread our CWA this afternoon and early evening. The
attendant surface trough will also overspread our region from
the west and a cold front is expected to sweep E'ward through
northern OH and NW PA this afternoon through early evening.
Behind the front, a surface ridge will build from the north-
central United States. Net low-level WAA ahead of the cold front
will contribute to today's highs reaching the mid 30's to lower
40's.
Precip reaching the surface via the wet-bulb effect and low-
level moisture advection from the Gulf of Mexico is expected to
traverse our CWA generally from west to east from about daybreak
this morning through this early evening. The precip, mainly
light in nature, will result from the following: Moist isentropic
ascent ahead of the trough axis aloft, ascent tied to frontogenetical
convergence ahead of the same trough axis, and low-level
convergence/moist ascent along the cold front. A relatively-
shallow surface-based melting layer is expected to exist as
precip reaches the surface in our CWA. Thus, a rain/snow mix is
forecast. Any snow accumulations will likely be a trace. Precip
is expected to end quickly after the surface cold front passage
due to stabilizing subsidence accompanying the aforementioned
surface ridge. Thus, scattered to widespread precip will likely
exit our CWA to the east by sunset this evening.
The above-mentioned trough axis aloft is expected to be located
over NW OH early this evening and exit the rest of our CWA to
the east by the wee hours of Thursday morning. Behind this
trough, the aforementioned surface ridge and attendant ridge
aloft will continue to build from the Upper Midwest and vicinity
through Thursday. Net low-level CAA behind the cold front will
contribute to lows reaching the mid 20's to lower 30's around
daybreak Thursday morning and cooler highs in the lower to mid
30's Thursday afternoon. A lowering and stabilizing subsidence
inversion accompanying the ridge will allow primarily fair
weather to impact our CWA through sunset Thursday evening.
However, 850 mb temperatures dropping to near -11C over ~3C
Lake Erie and a NW'erly mean low-level flow will allow lake-
effect snow showers to impact the snowbelt and vicinity in NE OH
and NW PA late this evening and especially during the morning
hours of Thursday. The aforementioned lowering subsidence
inversion and limited synoptic low-level moisture will limit
the magnitude of lake-induced CAPE and promote primarily light
lake-effect snow (LES). However, some model soundings suggest
periodic bursts of steady to heavy lake-effect graupel are
possible as low-level convergence along the major axes of bands
allows strong/maximized ascent to be collocated with a cloud
temperature of ~-5C, below the mixed phase portion of the lake-
effect cloud layer. The mean low-level flow is expected to back
to W'erly late Thursday morning into the early afternoon.
Simultaneously, low-level dry air advection and continued
lowering of the subsidence inversion will likely allow lingering
LES in/near the primary snowbelt to end by early afternoon as
lake-induced CAPE wanes significantly. Total snow accumulations
are expected to reach one to three inches in the most-persistent
LES. These greater accumulations are expected to be focused in
the higher terrain of Geauga County, southern Erie County, PA
and northern Crawford County, PA, where LES is expected to be
enhanced by upslope flow and upstream moisture connections to
Lakes St. Clair and Huron. Snow accumulations will likely total
one inch or less in the rest of the LES footprint.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
Clipper system will push southeast from the Upper Great Lakes late
Thursday night into Friday, which will deliver widespread show
showers to the local area for the start of the short term period.
Most locations have a shot at picking up an inch or two of snow
Friday morning and possibly Friday afternoon.
Although the clipper will exit the area by Friday evening, an upper
trough will settle over the eastern United States through remainder
of the short term period with a series of shortwaves pivoting across
the CWA. Lake effect snow showers are likely across the snowbelt
region of NE OH/NW PA Friday night through much of Saturday.
Moisture and upper level support appear to be most optimal Friday
night into early Saturday which will likely be the time period for
the most widespread snow showers and precipitation efficiency. A few
inches of (but likely sub-advisory) snow may accumulate in the
higher terrain of NW PA with lower amounts possible elsewhere. Snow
coverage and snowfall rates will begin to wane on Saturday, but
longer range deterministic guidance is hinting at a band of snow
associated with upstream moisture from Lake Huron developing just
east of The Islands early Saturday and pivoting east into the NE OH
snowbelt by the afternoon as winds shift from the north to the
northwest. This could produce additional snow accumulation, but
still far too much uncertainty in moisture and timing of the
shortwave in addition to the exact placement/overall probability of
the snow band to have a clear idea on specific accumulation. Either
way, snow showers will continue to diminish Saturday night as high
pressure builds in from the northwest.
Friday's highs won't differ too much from Thursday's with maximum
temperatures in the low to mid 30s expected. By Saturday, highs will
drop into the mid to upper 20s. Overnight lows will fall as well;
lows in the mid to upper 20s Thursday night will give way to minimum
temps in the teens by Saturday night.
&&
.LONG TERM /SUNDAY THROUGH TUESDAY/...
High pressure will build over the region Sunday and any remaining
lake effect snow showers should come to an end by the afternoon. Dry
weather will continue through the daytime hours Monday as the high
drifts east, but the next chance of precip could arrive as early as
Monday night as a warm front lifts into the region. Guidance
diverges quite a bit as an upper low or trough crosses the Great
Lakes late Monday into Christmas Eve, but as of now there is a
chance of showers (likely starting as snow Monday night and
transitioning to rain/snow mix as warm air advection develops behind
the warm front Christmas Eve) across the entire area. Will continue
to update the forecast for Christmas Eve and message any travel
impacts if the need arises.
Temps will remain in the 20s during the day Sunday before gradually
moderating through the remainder of the period. Highs should be in
the mid to upper 30s by Christmas Eve.
&&
.AVIATION /18Z Wednesday THROUGH Monday/...
Diminished aviation conditions are expected to continue through
this evening for all terminals across the area. Currently, the
most improved conditions are limited to the western terminals
with KTOL and KFDY rebounding to MVFR visibilities and ceilings
with patchy fog lingering. These terminals should rebound to VFR
overnight tonight. Elsewhere, conditions generally are IFR to
LIFR as rain/snow showers push east. These terminals will likely
remain at least MVFR, if not more diminished, through the entire
period. This initial round of showers moving through the area
this afternoon will depart this evening with lake effect snow
beginning around 00Z for the snowbelt counties. Overall set up
for lake effect is rather marginal and may result in quick
bursts of heavy snow at KYNG and KERI but totals should remain
less than 3 inches.
Winds today will remain from the north-northwest at 5-10 knots
before becoming light and variable by Thursday morning.
Outlook...Non-VFR expected in periodic snow Thursday through
this Sunday morning.
&&
.MARINE...
Winds will be out of the west or northwest and remain under 10 knots
through most of this afternoon before shifting to the northwest and
increasing to 15 to 20 knots tonight into early Thursday. Winds will
be marginal, but waves will build to 3 to 5 feet in nearshore zones
from Vermilion east so have issued Small Craft Advisories that will
gradually expire as winds decrease and waves subside starting early
Thursday morning.
Winds will variable and remain under 10 knots late Thursday morning
through the afternoon, but flow will shift to the southwest with
winds increasing to 10 to 15 knots Thursday night into Friday. The
next Small Craft Advisories will likely be needed starting Friday
afternoon as winds shift to the north/northwest and increase to 15
to 25 knots. Advisories will likely persist in at least the central
basin through Saturday evening or Saturday night before winds
diminish below 15 knots Sunday.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...Small Craft Advisory from 7 PM this evening to 4 AM EST
Thursday for LEZ145.
Small Craft Advisory from 7 PM this evening to 7 AM EST
Thursday for LEZ146-147.
Small Craft Advisory from 7 PM this evening to 10 AM EST
Thursday for LEZ148-149.
&&
$$
SYNOPSIS...Jaszka
NEAR TERM...Campbell/Jaszka
SHORT TERM...Maines
LONG TERM...Maines
AVIATION...Campbell
MARINE...Maines
Source:
CLE issues Area Forecast Discussion (AFD) at Dec 18, 12:36 PM EST---------------
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