717
FXUS61 KCLE 240002
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
702 PM EST Sat Nov 23 2024

.SYNOPSIS...
Low pressure off the New England coast will slowly pull away
tonight as weak high pressure slides across the Ohio Valley. The
high will drift into the Mid Atlantic Sunday night as low
pressure develops in the Mississippi Valley and lifts through
the Great Lakes Monday. This system will push a cold front
through the region Monday night into Tuesday.

&&

.NEAR TERM /THROUGH SUNDAY NIGHT/...
630 PM...Increased cloud cover across the region, with overcast
skies expected to remain in place through much of Sunday
underneath a ridging regime amidst weak low-level flow.
Beginning to see increased coverage of radar returns across SE
MI this evening, though any precipitation that falls later this
evening and overnight across the eastern half of the area is
expected to be light.

Previous Discussion...
The stubborn upper low is slowly losing influence on the region
allowing for a change in the weather pattern tonight and Sunday,
however, prospects for seeing the sun are not good as the next
system quickly approaches for Monday.

Starting off this afternoon, the closed upper low is drifting
east off the New England coast while the associated mid/upper
trough lingers over the eastern Great Lakes. The continued
cyclonic northwesterly flow on the backside of this system is
still driving lake-effect rain showers over NE Ohio and NW PA,
especially in favored upslope areas. HREF guidance still shows
the boundary layer flow steadily backing to WSW by late tonight
and Sunday morning as weak surface high pressure slides across
the Lower Ohio Valley. Current radar loops support this backing,
with the bands of showers already shifting east. Dry air
advection and a lowering inversion will allow these lake-effect
bands to remain light this evening and overnight as they
eventually become focused over far NE Ohio and NW PA, but
increasing low-level convergence along the south shore may lead
to an uptick in organization for a few hours early Sunday
morning, so have briefly higher PoPs in the primary snowbelt of
far NE Ohio and NW PA. By Sunday afternoon, the drier air will
win out to allow for dry conditions areawide, with any lingering
showers shifting into the Buffalo area.

The dry weather Sunday afternoon (and maybe a brief peak or two
of sunshine) will not last long as warm air advection and
isentropic ascent north of a warm front gradually spreads
showers back into the region Sunday night. This is in response
to a northern stream mid/upper trough digging into the northern
Plains Sunday night and supporting weak surface cyclogenesis in
the Mid Mississippi Valley beneath the right entrance of a
95-100 knot H3 jet streak. Have chance PoPs returning from west
to east Sunday night. It is officially our cloudy season!

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Upper-level trough located over the western CONUS today will reach
the Upper Midwest by Monday. This trough deepens as it moves
eastward across the Great Lakes and Ohio Valley regions, with a
surface low in the vicinity of southern Lake Michigan on 12Z/Mon
moving to near Lake Erie by 06/Tue. Areawide precipitation is
expected with the PoP forecast increasing to the 80-90% range,
though overall QPF is expected to be rather modest (0.15-0.25"
generally). Warm air advection should keep temperatures in the 50s
during the daytime hours on Tuesday. Cool air aloft (850mb
temperatures down to as low as -3 or -4 C) should lead to at least
some modest lake effect/enhanced precipitation Monday night into
Tuesday, possibly lingering into Tuesday night for mainly Northwest
Pennsylvania. This should mainly fall as rain, though maybe a few
flakes fly if it lingers into Tuesday night.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
On Wednesday, high pressure briefly with temperatures on the chilly
side, maybe just briefly eclipsing 40 in the afternoon. Although
this will feel warm compared to the upcoming weekend...

After Wednesday is when the weather really starts to get
interesting. We start with an upper-level trough over the central
Great Plains on Wednesday moving to the Ohio Valley region by mid-
day Thanksgiving. Surface low generally followed a similar drop just
ahead of the trough. An expansive precipitation shield is generally
expected well north of low pressure center and while there is decent
spread in low track, most models have precipitation entering our
forecast area at times Wednesday night into Thursday, so have
increased PoPs to the 50-60% range.

So a few thoughts on this system:
*There is still quite a bit of spread on the low pressure
track/strength, though ensembles generally fall into a couple
different categories: 1. somewhat weaker/faster trough/low that
results in a further south track and less precip, 2. a
stronger/slower low that tracks further north (closer to our CWA),
with more precipitation, 3. somewhere in between.
*There is some uncertainty with how cold the airmass will be
wrapping in behind the low. This will affect precipitation type.
Rain and snow are both possible with snow most likely Wednesday
night into Thursday morning then rain most likely during daytime
Thursday. Snow is most likely on the backside of the low as cold air
wraps in.
*All of this adds up to great deal of uncertainty with the snowfall
potential. The possible outcomes range from all rain for the
duration of this low (with no snow) to several inches of areawide
snow accumulations Wednesday night and Thursday. The ECWMF leans
towards a snowy solution, GEFS towards rain, GEPS somewhere in
between.
*While uncertainty exists, there are some trends we can glean from
the 12z model guidance. In comparison to the 00Z data, all three
major model ensemble guidance have trended towards a deeper, more
amplified upper-level trough, which suggests better potential for
stronger low and greater/larger precipitation shield.

Friday onward, the coldest airmass of the season is expected with
potential for lows down into the teens. There`s pretty good agreement
for 850mb temperatures down into the -10 to -12 C range with all
three models guidance trending colder by several degrees compared to
the 00Z. We`re becoming increasingly confident that there will be
accumulating lake effect snowfall for much of the snowbelt region,
through most of the weekend with ensemble probabilities suggesting a
reasonable shot at significant snowfall accumulations.

&&

.AVIATION /00Z Sunday THROUGH Thursday/...
MVFR across the TAF sites this evening with deterioration to IFR
and perhaps brief pockets of LIFR possible late tonight into
Sunday. Recent satellite imagery reveals a large area of MVFR
ceilings across the Ohio Valley this evening. Already seeing
some IFR pockets embedded within this large area of MVFR
ceilings. Think vsbys should remain VFR for the most part as
west to southwest winds remain elevated in the 5 to 10 knot
range, limiting the fog potential. With little in the way of
low-level flow on Sunday, there is potential for the low IFR and
MVFR ceilings to persist through much of the day and have
reflected this in the recent TAF update.

Lower confidence in IFR ceilings exist at CLE and ERI as
southwest winds may favor a slight downslope component. Thus, have
maintained MVFR ceilings at this time.

Outlook...Non-VFR likely in rain and low ceilings Monday into
Tuesday. Non-VFR possible again in rain and/or snow Wednesday
night through Thursday.

&&

.MARINE...
West-northwest flow of 15-20 knots through this evening and tonight.
Model guidance suggests stronger winds hanging on a bit longer than
expected, so extended the small craft advisory by a few hours. Winds
weaken and becoming southerly Sunday night and Monday. A low
pressure system moves across southern Ontario Monday
afternoon/evening with a cold front moving across Lake Erie. Strong
westerly winds are expected with and behind the cold front with wind
speeds of 25-30 knots. These strong winds continue through Tuesday
night with periods of near gale-force winds possible, especially
late Monday night through Tuesday afternoon. High pressure builds in
by Wednesday.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...Small Craft Advisory until 7 PM EST this evening for LEZ143.
     Small Craft Advisory until 10 AM EST Sunday for LEZ144>147.
     Small Craft Advisory until 4 PM EST Sunday for LEZ148-149.

&&

$$

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