Area Forecast Discussion
Issued by NWS Cleveland, OH

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FXUS61 KCLE 080844
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
344 AM EST Wed Dec 8 2021

.SYNOPSIS...
A surface trough will affect east central Ohio this morning
before high pressure builds into the Ohio Valley later today
through much of Thursday. A warm front will lift through the
region Thursday night followed by a deep low pressure system
that will progress through the Great Lakes late Friday into
Saturday pulling a strong cold front through Saturday morning.


&&

.NEAR TERM /THROUGH THURSDAY/...
A well defined mid/upper shortwave seen on water vapor loops is
crossing the Ohio Valley early this morning. A weak 1013 mb surface
low in response to the right entrance of a 120-130 knot 300 mb jet
is crossing the southern Appalachians with an inverted trough
extending north from the low into east central Ohio. This surface
trough is focusing some light snow across the southern and eastern
counties this morning beneath mid-level moisture advection and
isentropic ascent. RAP BUFKIT soundings show only weak omega within
the DGZ around CAK, YNG, and ERI from now through sunrise before
rapidly exiting. In addition, a lot of low-level dry air is
depicted. This all points to a very light, quick hitting snow event
from CAK and Mt Vernon NE through YNG and ERI with a trace to 0.5
inches possible. Elsewhere, the drier air should win out with
largely virga expected.

The shortwave and associated surface low will progress through the
Mid Atlantic today and redevelop off the coast. This will reinforce
longwave troughing across the Great Lakes and Ohio Valley with cold
air advection dropping 850 mb temps back to -10 to -11 C. This
airmass moving across Lake Erie water temps averaging in the low
40`s F will lead to moderate instability developing by this
afternoon with BUFKIT forecast soundings depicting lake induced CAPE
values above 300 J/Kg. The boundary layer flow will be SW until late
afternoon when a weak surface trough will pass through and veer the
flow to westerly allowing snow showers to move into Lake, northern
Geauga, Ashtabula, Erie, and perhaps northern Crawford Counties.
This is however not a lake-effect event to get excited about by any
means. Both RAP and NAM BUFKIT soundings show a serious lack of
Omega within the DGZ with nearly all of the lift occurring below 800
mb. A decent amount of shear is also shown from the surface through
about 700 mb. In terms of moisture, it is relatively shallow mostly
confined below 800 mb. However, with the inversion rising to around
7000 feet and equilibrium levels rising to around 9000 feet from mid
afternoon into the evening combined with the long westerly fetch,
believe a weak band will impact parts of the above mentioned areas
at times. HREF guidance gives confidence on some weak lake-effect
too. Accumulations will generally be under an inch, but could
see 1 to 1.5 inches in eastern Erie County where the band could
pivot the longest. Boundary layer flow will veer more
northwesterly in the 00- 06Z timeframe allowing scattered snow
showers to push farther inland, but at the same time, drier air
and a rapidly falling inversion will shut down the activity.
Have all areas dry the second half of tonight. Outside of the
lake-effect areas, some clearing will occur across the western
and southern half of the CWA this afternoon into tonight. Highs
today will remain on the cold side in the low/mid 30`s, except
upper 20`s/low 30`s in NW PA. Will see lows in the low/mid 20`s
tonight with the coldest readings west and south where skies
clear.

The pattern begins to change Thursday as ridging at the surface and
aloft slides over the Ohio Valley and lower Great Lakes ahead of
deepening troughing moving out of the Rockies/High Plains. The
increasing southerly flow will boost highs in the low/mid 40`s with
increasing clouds as mid-level moisture advection and isentropic
ascent begins ahead of a warm front. An isolated rain/snow shower is
possible by evening, but most areas will stay dry.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
An active short term period is in store across the region as a
strong low pressure system develops across the central Plains on
Friday, moving northeast into the Great Lakes region by Saturday.
This system will extend a strong cold front east across the region
on Saturday.

The main impacts from this system could be an isolated severe
threat, especially from US-30 and south, Friday evening and
overnight, as well as another chance for gusty winds behind
the cold front Saturday afternoon and evening. The severe threat
will be contingent upon how much instability can be realized in the
upper OH Valley. As of now, forecast MLCAPE in northern OH is in the
100 to 200 J/kg range with increasing instability located across
central and southern OH, coincident with the northern extent of the
SPC SWODY3.

Gusty winds may also be impactful behind the cold front Saturday
afternoon and evening. Most recent model runs suggest an elevated
period of wind gusts perhaps in the 45 to 55 mph range with
the ECMWF being the strongest. And while the GFS and NAM are
slightly lower, they both still suggest Wind Advisories may be
needed. As of now, our forecast calls for the highest wind
gusts of 35 to 40 mph generally along and west of the I-71 corridor
Saturday afternoon and evening. We will continue to ramp up winds as
needed over the next couple of days. Stay tuned for updates.

Total rain amounts from this system will be around an inch, with the
heaviest rainfall expected Friday night into Saturday morning.
Thunder is also possible, though the extent will be contingent on
available elevated instability, as described above. Not anticipating
much in the way of lake effect snow behind the cold front Saturday
night with marginal 850mb temps and with a quickly-building ridge
set to arrive Sunday morning.

Temperatures will generally be above average in the short term
period, with temperatures peaking in the lower 60s with the strong
warm air advection Friday night into Saturday morning. Temperatures
will sharply drop behind the cold front throughout Saturday, with
widespread 30s likely by Saturday evening.

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
A quiet long term period is expected with above normal temperatures
and relatively dry weather. Temperatures will rise a few degrees each
day from Sunday through Tuesday, with widespread 50s expected by
Tuesday. Mostly sunny skies are also expected during this period,
resulting in pleasant conditions for early December.

&&

.AVIATION /06Z Wednesday THROUGH Sunday/...
Mainly VFR is expected at all TAF sites through this morning,
but periodic light snow could lead to brief MVFR vis at CAK,
YNG, and ERI early this morning. Confidence is medium on this.
For this afternoon and tonight, VFR is generally expected to
prevail as high pressure builds in, but lake-effect clouds and
possibly a stray snow shower could bring periods of MVFR to YNG
and ERI early to mid afternoon before going VFR tonight.

Outlook...Non-VFR possible with periods of snow and/or rain
through this weekend.

&&

.MARINE...
A relatively quiet first half of the marine period is expected with
likely no marine headlines until sometime on Saturday. By Saturday
into Sunday, marine headlines are likely, including the potential
for Gales.

A weak trough will cross the lake this afternoon, resulting in west
to northwest winds of 15 to 20 knots. Waves will peak around 3 to 4
feet, but the period and time of the year preclude need for a Small
Craft Advisory at this time. Southerly winds will pick up again on
Thursday afternoon, 15 to 20 knots and will continue into Friday. By
Friday night, southerly winds increase around 20 knots, though the
offshore flow should preclude need for a Small Craft Advisory. A
cold front will move east across the region on Saturday, shifting
winds more west, southwesterly, first increasing into the 20 to 25
knot range, then to 25 to 30 knots and perhaps higher by Saturday
afternoon and evening. We will need to monitor the potential for
Gales during this time period over the next couple of days. Winds
will shift westerly by Saturday night, remaining elevated in the 20
to 25 knot range. Westerly winds of 15 to 20 knots may persist into
Sunday.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...None.

&&

$$
SYNOPSIS...Garuckas
NEAR TERM...Garuckas
SHORT TERM...Kahn
LONG TERM...Kahn
AVIATION...Garuckas
MARINE...Kahn


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