572
FXUS61 KCLE 092048
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
307 PM EST Sat Nov 9 2024

.SYNOPSIS...
A high pressure ridge exits toward New England as a warm front
approaches from the Lower Mississippi Valley. The warm front
will sweep northeastward across our region Sunday morning
through early afternoon and then a cold front will sweep
eastward through our area Sunday night as a low moves from the
north-central United States to southwestern Quebec. Behind the
low, a trough lingers over the eastern Great Lakes and Upper
Ohio Valley on Monday as a secondary cold front sweeps
southeastward through our area.

&&

.NEAR TERM /THROUGH SUNDAY NIGHT/...
A high pressure ridge at the surface and aloft exits toward New
England and the Canadian Maritimes through Sunday as a potent
trough aloft moves from the northern and central Great Plains to
the western Great Lakes. At the surface, the attendant and
occluded low moves NE`ward from the central Great Plains toward
the Upper Peninsula of MI and allows a surface trough to
overspread our CWA generally from the west. In addition, a warm
front is expected to sweep NE`ward through our area late Sunday
morning through early afternoon. Stabilizing subsidence
accompanying the aforementioned ridge will allow fair weather to
persist in our region for the time being. Widespread rain,
heavy at times, will overspread our region from SW to NE during
the wee hours of Sunday morning through the early afternoon as a
return flow of very moist air originating over the southern
Gulf Stream and Gulf of Mexico undergoes isentropic ascent along
the upper-reaches of the warm front and is enhanced by a S`erly
to SW`erly LLJ of about 30 to 45 knots. Following the passage
of the surface warm front, scattered, lighter, and intermittent
rain showers are expected through sunset as weaker moist
isentropic ascent precedes the trough axis aloft that will
approach from the west.

Tonight`s lows are expected to reach the mid 30`s to mid 40`s
in NW PA and the 40`s in northern OH. These lows will likely be
reached late this evening before readings moderate during the
predawn hours of Sunday morning in response to strengthening
low-level WAA ahead of the surface warm front. SE`erly
downslope surface winds are expected to gust up to 30 mph in
far-northern Erie County, PA tonight, especially after
midnight. On Sunday, low-level WAA and limited daytime heating
via a few peeks of sunshine will allow late afternoon highs to
reach the mid 50`s to mid 60`s. Diurnal convective mixing of the
boundary layer tapping into stronger flow just aloft will
likely contribute to S`erly to SW`erly surface wind gusts as
strong as 25 to 35 mph across our CWA, behind the surface warm
front.

Aloft, the potent trough moves from the western Great Lakes to
southern QC and the northeastern United States Sunday night as a
shortwave ridge builds from the Upper Midwest. At the surface,
the occluded low is expected to move from the Upper Peninsula of
MI to southern QC and allow the trailing cold front to sweep
E`ward through our region late Sunday evening through the
predawn hours of Monday morning. Weak/moist isentropic ascent
ahead of the trough axis aloft and low-level convergence/ascent
along the cold front amidst sufficient moisture and potential
instability in the lowest 1 km AGL will allow scattered/light
rain showers to impact our CWA. Behind the front, a lake-induced
thermal surface trough is expected to linger over the
relatively-warm Great Lakes as a surface ridge attempts to build
from the north-central United States. Stabilizing subsidence
accompanying the ridge aloft is expected to promote mainly fair
weather behind the cold front. However, a W`erly mean low-level
flow may be cold and moist enough over and downwind of ~14C Lake
Erie to allow light lake-effect rain showers to impact the
primary snow belt of NE OH/NW PA and vicinity toward daybreak Monday
morning. Rainfall through the near-term is still expected to total
0.50" to 1.00".

Low-level CAA behind the cold front will contribute to lows
reaching the 40`s to lower 50`s around daybreak Monday. Note:
Steepening low-level lapse rates amidst winds and CAA increasing
with height in the low-level atmospheric column will allow
mechanical mixing of the boundary layer to tap into stronger
flow just aloft and generate W`erly surface wind gusts as
strong as 25 to 35 mph behind the cold front. The strongest
gusts are still expected along the lakeshore from downtown
Cleveland through Erie County, PA due in part to less friction
over the relatively-smooth lake surface.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Scattered lake effect rain showers may persist across NE OH and NW
PA through the daytime hours Monday, although 850mb temperatures
will be extremely marginal (2 to 5C) Monday morning and early
afternoon so showers may be hit and miss and/or it could be more of
a lake effect cloud scenario. Opted for chance PoPs (30 to 50
percent) through Monday afternoon, but there`s a chance that Monday
remains dry for most snowbelt locations. It will be quite breezy
Monday with wind gusts to 25 to 30 mph possible areawide during peak
diurnal mixing Monday afternoon and along the lakeshore of NE OH and
NW PA Monday morning through Monday evening.

A secondary cold front will push southeast across the local area
Monday night into early Tuesday morning and there will likely be a
shot of cooler 850mb temps along and just behind the front. With
that being said, there`s still some uncertainty in exactly how cold
850 mb temps get Monday night and how long the coldest temps aloft
persist, which will ultimately affect lake-enhanced precipitation
chances. There`s high confidence that 850mb temps fall to 0 to -3C
Monday night, but would like to see slightly cooler temperatures to
maximize lake-induced instability and precipitation efficiency.
There`s also the possibility of the best forcing (and cooler temps
aloft) remaining to the northeast of the CWA which could throw a
wrench into the precipitation forecast. Regardless, there`s a decent
chance of at least scattered lake-enhanced rain showers across NE
OH/NW PA with the frontal passage, hence likely PoPs from roughly
00Z to 06Z Tuesday. Surface high pressure and an upper ridge quickly
follow the cold front so any precip will taper off by Tuesday
morning with dry weather persisting through the remainder of the
short term period.

The air mass will only modify slightly Monday with highs in the mid
50s to lower 60s likely. Cold air advection behind the cold front
Monday night will allow overnight lows to fall into the mid to upper
30s. Cooler temperatures continue into Tuesday; highs will be in the
upper 40s to lower 50s and minimum temperatures will drop into the
mid to upper 20s in higher elevations and inland locations east of I-
71 and lower 30s elsewhere.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Upper ridge axis/surface warm front will cross the area Wednesday as
an upper-level trough advances east across the Plains. The trough
and its associated cold front will cross the region at some point
Wednesday night into Thursday, although there`s still significant
model spread in the timing and strength of the system. Maintained
broad likely PoPs (around 60 percent) Wednesday night into Thursday,
but refinements are likely as confidence in the synoptic pattern
increases. The highest PoPs will be associated with the
frontal/upper trough passage. Warm air advection will produce high
temps in the 50s and lower 60s Wednesday.

Behind this system, a ridge will begin to build into the eastern
United States, although still a lot to iron out with the placement
of the associated surface high. Either way, drier weather and above
average temperatures are favored Friday through Saturday.

&&

.AVIATION /18Z Saturday THROUGH Thursday/...
Aloft, a ridge builds E`ward across our region through ~00Z/Sun.
Thereafter, the ridge begins to exit E`ward and a trough
approaches from the northern and central Great Plains through
18Z/Sun. At the surface, the ridge exits slowly E`ward as a
warm front approaches our region from the Lower MS Valley and
vicinity. This warm front is expected to begin to sweep NE`ward
across our region after ~12Z/Sun and near KERI and vicinity by
18Z/Sun. Our regional surface winds veer from SE`erly to S`erly
with the passage of the warm front and remain around 10 to 15
knots. Gusts up to 25 knots are expected at times, especially at
KERI and especially from ~05Z/Sun through 18Z/Sun.

Widespread mid/upper-level clouds and associated VFR ceilings
accompanying the warm front and preceding the aforementioned
trough aloft will lower/thicken into low-level clouds from SW
to NE between ~10Z/Sun and 18Z/Sun. The widespread low clouds
are expected to yield MVFR to IFR ceilings. Widespread rain,
heavy at times, is forecast to overspread our region from SW to
NE after ~07Z/Sun. Visibility is expected to vary between VFR
and MVFR in precip.

Outlook...Periodic rain with non-VFR expected through Monday
night. Additional periods of rain with non-VFR are possible this
Wednesday afternoon through Thursday.

&&

.MARINE...
East winds 6 to 12 knots this afternoon and early evening become
southeast and increase to 10 to 15 knots tonight before shifting to
the south and increasing to 15 to 25 knots Sunday morning. A cold
front will cross the lake Sunday night, allowing winds to become
westerly/southwesterly and increase to 20 to 30 knots with the
highest winds anticipated in the open waters of the eastern half of
the lake. Winds are expected to diminish to 15 to 25 knots by Monday
morning with a wind shift to the northwest anticipated as a
secondary cold front crosses the lake Monday night into early
Tuesday.

Small Craft Advisories will most certainly be needed for the
nearshore zones of Lake Erie by no later than Sunday evening, but
advisories may begin as early as mid to late Sunday morning if
offshore winds in the nearshore zones trend higher than the current
forecast (15 to 20 knots). The best opportunity for Small Craft
Advisory conditions ahead of the frontal passage will span from
roughly the eastern fringe of the Lake Erie Islands to Geneva-on-the-
Lake. Small Craft Advisories are expected to persist through Tuesday
morning and will also need to keep an eye on potential for low water
hazards in the western basin of the lake when west/southwest winds
peak late Sunday night into early Monday morning.

Flow should become more northeasterly with winds finally diminishing
to 10 to 15 knots by Tuesday afternoon. Generally expect quiet
marine conditions through the majority of Wednesday before
south/southwest winds increase to 20 to 25 knots ahead of the next
system Wednesday night into Thursday. Additional Small Craft
Advisories will likely be needed for mid to late week.

&&

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

&&

$$

SYNOPSIS...Jaszka
NEAR TERM...Jaszka
SHORT TERM...Maines
LONG TERM...Maines
AVIATION...Jaszka
MARINE...Maines