CLE issues Area Forecast Discussion (AFD) at Dec 17, 3:24 AM EST916
FXUS61 KCLE 170842
AFDCLE
Area Forecast Discussion
National Weather Service Cleveland OH
324 AM EST Tue Dec 17 2024
.SYNOPSIS...
A ridge builds from the Lower Ohio Valley and vicinity today
before exiting eastward tonight. A cold front is still expected
to sweep eastward through northern Ohio and northwest
Pennsylvania on Wednesday. Behind the cold front, a narrow ridge
builds from the north-central United States through Thursday.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
Fair weather is expected today as stabilizing subsidence
accompanies a narrow ridge at the surface and aloft that
continues to build from the north-central United States, Lower
OH Valley, and vicinity. Highs late this afternoon are expected
to reach the lower to mid 40's as intervals of sunshine result
in daytime warming. However, the daytime warming will be
limited via lingering low-level CAA behind the recent cold front
passage.
The narrow ridge at the surface and aloft exits E'ward tonight as a
trough aloft approaches from the north-central United States, the
attendant cold front approaches from the western Great Lakes region,
and the attendant surface trough overspreads our region from the
west. Farther south along the cold front, a surface low is expected
to develop in vicinity of the Lower MS Valley. The development of
weak low-level WAA and increasing cloud cover via moist isentropic
ascent ahead of the trough axis aloft and the surface low, will
limit nocturnal cooling this evening through daybreak tomorrow. Low
temperatures are expected to reach mainly the upper 20's to lower
30's during the predawn hours of Wednesday morning before readings
moderate by one to three degrees by daybreak in response to the
aforementioned WAA. Fair weather is expected through midnight
tonight. Between midnight and daybreak Wednesday morning, the
aforementioned moist isentropic ascent may allow precip to
overspread our CWA from the south and southwest, and perhaps reach
as far north as a roughly Marion, OH to Warren, OH line by daybreak.
Low-level WAA strengthening with height is expected to allow an
elevated melting layer to develop and eventually become surface-
based as the low-level atmospheric column moderates further.
Accordingly, depending on when exactly precip starts and the
thermodynamic characteristics of the low-level atmospheric column
(e.g. surface air temps and wet-bulb temps), precip may begin as a
light snow/freezing rain mix before changing quickly to plain rain.
Snow accumulations of a trace and ice accumulations of a trace to
0.02" are possible from roughly Marion County to far-southern
Portage County, Mahoning County, and points south. However, this is
a very low confidence forecast regarding wintry precip potential.
For example, some model soundings indicate dry air just above the
surface may result in virga at first. By the time precip reaches the
surface via the wet-bulb effect and moisture advection from the Gulf
of Mexico, the low-level atmospheric column may be warm enough for
plain rain. We will continue to evaluate forecast trends and the
potential need for a Winter WX Advisory for minor ice accumulations.
On Wednesday, the aforementioned trough aloft will begin to
overspread our region from the west. At the surface, the
attendant cold front will sweep E'ward across our CWA from mid-
morning through late afternoon. This timing of the cold front
passage will likely allow the surface low along the front to move
NE'ward through the Lower MS Valley and TN Valley toward the
northeastern United States. Behind the front, a surface ridge builds
from the north-central United States. Additional periods of precip,
mainly in the form of rain, are expected courtesy of moist
isentropic ascent and ascent tied to frontogenetical convergence,
ahead of the trough axis aloft, and via low-level convergence/moist
ascent along the cold front. A very brief period of light
snow/freezing rain may impact interior portions of NE OH and NW PA
shortly after daybreak before the aforementioned WAA allows the low-
level atmospheric column to moderate enough for precip type to
become plain rain. In addition, low-level CAA and the wet-bulb
effect may allow lingering rain associated with the upper-reaches of
the cold front to mix with wet snow. However, precip is expected to
end within several hours after the cold front passage due to
stabilizing subsidence accompanying the aforementioned surface
ridge. Any daytime snow and ice accumulations are expected to be a
trace. Note: It will take some time for cold air to deepen enough
for lake-effect snow to develop over/downwind of ~4C Lake Erie.
Please see the short-term discussion for additional info. Daytime
highs should reach the upper 30's to lower 40's on Wednesday.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
A brief period of lake effect snow is likely across the snowbelt
region of NW PA/NE OH Wednesday night into early Thursday as an
upper trough gradually exits to the east. An inch or two of snow may
manage to accumulate across the higher terrain of NW PA (lower
amounts across the remainder of the snowbelt) before surface high
pressure ushers drier air into the local area Thursday morning and
snow comes to an end. The majority of the area should experience dry
weather for most of Thursday before an Alberta Clipper dives
southeast from the Upper Midwest Thursday night into early Friday.
There's still some uncertainty in the exact track of this system,
but the center of the low will most likely at least clip the western
half of the local area. GFS suggests that the system will be on the
dry side which would limit PoPs/QPF/snow amounts, but the Canadian
and ECMWF have a bit more moisture and higher QPF. Opted for broad
likely to high-end chance PoPs for the entire area that will be
refined as confidence increases in upcoming updates.
A colder air mass will settle in behind the clipper Friday night and
continued upper troughing will likely result in the development of
lake effect snow showers across the snowbelt region towards the end
of the period.
Below normal temperatures return for the short term period with
highs in the low to mid 30s anticipated for Thursday and Friday.
Overnight lows will gradually decrease late in the workweek with
upper 20s Wednesday night giving way to upper teens to lower 20s by
Friday night.
&&
.LONG TERM /SATURDAY THROUGH MONDAY/...
Upper trough will settle across the eastern CONUS Saturday with a
series of shortwaves pivoting across the area through at least
Saturday afternoon. A colder air mass will remain in place through
the weekend and conditions will be favorable for periodic lake
effect snow showers Saturday with precipitation chances likely
dwindling as early as Saturday night into Sunday as surface high
pressure builds in from the northwest. Any snow accumulation (and
overall precipitation chances) will depend on the timing of
shortwaves/troughs, moisture, and fetch over the lake which remains
a bit murky so still too early to speculate on potential snow
accumulation. Dry weather is favored most of Sunday through Monday.
Expect well below normal temperatures over the weekend with highs in
the 20s and lows in the teens expected. Temperatures will recover
slightly on Monday, but it will still be in the chilly upper 20s to
lower 30s.
&&
.AVIATION /06Z Tuesday THROUGH Saturday/...
At the surface, an E'ward-moving cold front and associated
scattered rain showers were located in vicinity of a KBUF to
KZVV line at 05:40Z/Tues. Therefore, the front and showers were
located east of all of our TAF sites. This front and accompanying
showers will exit far-NE OH and NW PA by 07Z/Tues. Behind the
front, fair weather is expected through 06Z/Wed as a ridge
builds from the north-central United States, Middle MS Valley,
and vicinity.
Ahead of the cold front, SW'erly surface winds around 10 to 20
knots, gusting up to 30 knots, are expected. Behind the front,
our regional surface winds trend SW'erly to W'erly around 5 to
15 knots with gusts up to 20 to 30 knots at times. After
00Z/Wed, surface winds will primarily become light and variable
as a weakening MSLP gradient accompanies the aforementioned
ridge. VFR visibility prevails through the TAF period. Periodic
MVFR ceilings are expected through at least early Tues evening.
Outlook...Non-VFR expected in periodic rain and/or snow this
Wednesday through Saturday.
&&
.MARINE...
Small Craft Advisories remain in effect east of the Islands due to
west/southwest winds to 15 to 30 knots over the lake. The highest
winds close to 30 knots are anticipated in the open waters of the
eastern basin. Winds will gradually diminish from west to east
starting during the predawn hours this morning and west winds should
be 15 knots or less shortly after 00Z this evening. It may take some
time for waves to subside so the easternmost advisory ends at 06Z/1
AM Wednesday. Flow becomes light and variable for a brief period
Wednesday morning before shifting to the northwest and increasing to
15 to 25 knots Wednesday night into Thursday morning, during which
time a Small Craft Advisory will likely be needed at least east of
the Islands. Guidance favors southerly flow 10 to 15 knots Thursday
night into Friday, but winds once again become northwesterly and
increase to 15 to 25 knots in response to the development of cold
air advection late Friday morning or early Friday afternoon; this
will likely necessitate Small Craft Advisories through Saturday.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...Small Craft Advisory until 10 AM EST this morning for LEZ144.
Small Craft Advisory until 7 PM EST this evening for LEZ145-
146.
Small Craft Advisory until 1 AM EST Wednesday for LEZ147>149.
&&
$$
SYNOPSIS...Jaszka
NEAR TERM...Jaszka
SHORT TERM...Maines
LONG TERM...Maines
AVIATION...Jaszka
MARINE...Maines
Source:
CLE issues Area Forecast Discussion (AFD) at Dec 17, 3:24 AM EST---------------
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