694
FXUS61 KCLE 250222
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
922 PM EST Sun Nov 24 2024

.SYNOPSIS...
Weak high pressure will depart through the Mid Atlantic tonight
as low pressure develops in the Mississippi Valley. This low
will lift across Michigan Monday before departing into eastern
Ontario and Quebec by Tuesday, pulling a cold front through the
region Monday night. A trough will linger across the Great Lakes
Tuesday before high pressure attempts to build in Wednesday.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
930 PM...
Quiet weather is expected tonight as a weak ridge gradually
exits east of the region into Monday morning. Light rain will
begin to spread east through the area from west to east through
Monday. Can`t rule out periods of drizzle/patchy fog late Monday
afternoon and evening as low-level moisture continues to
increase throughout the day. Overall, it looks to be another
very dreary, albeit mild, day.

Previous Discussion...
Briefly quieter weather is expected to close out the weekend
this evening into tonight as weak surface high pressure departs
across the Mid Atlantic region. This will set up southerly
return flow and resultant warm air advection. However, this warm
air advection will also lead to showers returning from west to
east late tonight into early Monday morning as isentropic
ascent increases ahead of a lifting warm front, so the quieter
weather will be short lived. This warm front develops in
response to a northern stream mid/upper trough digging into the
Northern Plains supporting surface cyclogenesis over the Mid
Mississippi Valley beneath a bit of a coupled H3 jet structure.
This low will lift northeastward through Lower Michigan Monday
and across Lake Huron Monday night while deepening to around 999
mb, supported by the mid/upper trough axis tilting negative.

Expect the showers to come in two waves with this system. The
first wave will likely be a broken band of showers tied to the
warm air advection/isentropic lift ahead of the warm front late
tonight and Monday morning. Deterministic guidance and HREF
members show these showers staying light and fairly disorganized
since the forcing is relatively weak without a connection to
the Gulf, so kept the highest PoPs within a 2 to 4 hour window
as the band progresses west to east. Precip will be light. The
steadiest showers should exit to the NE of the region by 18Z as
we get into the warm sector, so dropped Monday afternoon PoPs to
chance for several hours until the cold front approaches in the
late afternoon and evening. This will be the second wave of more
organized showers, and expect several hours of steady rain
Monday evening, especially in NE Ohio and NW PA where synoptic forcing
will be maximized near the left exit of a 100-105 knot H3 jet
rounding the base of the digging mid/upper trough. QPF on Monday
should generally range from 0.25 to 0.50 inches, with the most
falling Monday evening.

The mid/upper trough axis will swing into the Great Lakes Monday
night as the cold front exits to the east. This will take the
steadiest rain east of the region, but cold air advection, wrap
around moisture, and the boundary layer flow becoming well
aligned from the WNW with increasing lake induced instability
will lead to lake-effect showers developing in NE Ohio and NW
PA, so kept likely to categorical PoPs in that area. The core of
the coldest air will hang north of the region, so expect p-type
to be all rain through sunrise.

Highs will warm into the low/mid 50s Monday after lows tonight
in the low/upper 30s (coldest in NW PA). Lows Monday night will
range from the mid to upper 30s.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Upper-level trough will be overhead at 12Z/Tue with the associated
surface low and cold front off to the east. Cool air aloft with
850mb temperatures of around -4 to -5 C will be sufficient for some
scattered lake effect showers downwind of Lake Erie in Northeast
Ohio and Northwest Pennsylvania during the day Tuesday before it
winds down Tuesday night as high pressure builds in. Daytime
temperatures around 40 should easily keep precipitation as rain,
with some snow possibly mixing in for whatever showers remain
Tuesday night.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
An upper-level trough and low pressure move across the Ohio Valley
Wednesday night into Thursday. Substantial uncertainty still exists
model guidance present variability in upper-level trough
strength/speed as well as the associated surface low track. In
general, ECWMF ENS have a deepening low tracking across West
Virgina, the GEFS have a weaker low and farther south towards
Tennessee and the Carolinas with little to no precipitation reaching
our forecast, and the GEPS is somewhere in between. Most models do
have some precipitation, so retained 60% PoPs in the forecast,
though the chance for impactful, accumulating snowfall remains the
most uncertain part of the forecast, although probabilities of GTE
1" of snow has been trending downward the past few models runs.

A cold airmass filters in behind the departing low Thursday night
through the weekend with the coldest temperatures of the season with
850 mb temperatures dropping down to around -10 to -13 C and staying
within that range through the weekend. Flow looks to start off out
of the northwest Thursday night into Friday, favoring much of the
typical snowbelt areas in Northeast Ohio and Northwest Pennsylvania
for lake effect precipitation. Precipitation may initially fall as a
mix of rain/snow Thursday evening and early Thursday night but
temperatures should quickly fall to below freezing with all snow
expected by early Friday morning. Lake effect snow is expected
to continue through the weekend as model guidance favors west
flow on Saturday and then southwest flow on Sunday. Snowfall
accumulations are very likely for a good portion of the snowbelt
region but particulars with amounts and locations will greatly
depend on mesoscale details of the bands as well as the
synoptic-scale flow regime. Even so, there is high confidence is
cold air aloft over near record Lake Erie water temperatures
for numerous days, so we`re nearly guaranteeing accumulating
snowfall in the snowbelt region and likely to see significant
snowfall accumulations somewhere in the snowbelt.

&&

.AVIATION /00Z Monday THROUGH Friday/...
Mainly VFR across the TAF sites this evening, with widespread
deterioration to MVFR and IFR once again by Monday. MVFR
ceilings at ERI should briefly improve to VFR by early Monday
morning/late tonight. Another system is expected to move west to
east through the region on Monday, bringing widespread, light
rain across the area. Confidence was too low for inclusion of
IFR ceilings at CLE/ERI as southerly winds of 5 to 10 knots may
limit low- level moisture. Otherwise, widespread IFR ceilings
appear likely across all other TAF sites. Can`t rule out brief
periods of LIFR, though confidence was too low at this time for
inclusion. Mist/drizzle may develop late Monday afternoon and
evening, with MVFR vsbys most likely.

Winds are currently favoring a weak easterly direction, around 5
knots, this evening. Winds will gradually become southeast, then
south through Monday morning and afternoon, increasing to 7 to
10 knots. A cold front will eventually sweep across the area
Monday night which will shift winds towards the west, 10 to 15
knots with gusts up to 20 knots possible. Only site have this
reflected so far is CLE, but anticipate inclusion in the next
update.

Outlook...Non-VFR conditions will linger Monday night into
Tuesday. Non-VFR likely in rain and/or snow Wednesday night
through Thursday, becoming all snow by Thursday night into
Friday.

&&

.MARINE...
Conditions on Lake Erie have improved as high pressure builds in
this afternoon and evening, so have allowed the small craft advisory
to expire. Low pressure will work its way eastward across southern
Ontario with a cold front moving east across Lake Erie Monday night.
Strong westerly winds of 25-30 knots are expected Monday night
through Tuesday, winding down Tuesday night night as high pressure
builds in. Waves of 6-9 feet are expected to build east of the
islands. Low pressure expected to move across the Ohio Valley on
Thursday with some potential for northwest to west winds of 15 to 20
knots winds, perhaps continuing into the weekend.

&&

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

&&

$$

SYNOPSIS...Garuckas
NEAR TERM...Garuckas/Kahn
SHORT TERM...Saunders
LONG TERM...Saunders
AVIATION...Kahn
MARINE...Saunders