907
FXUS61 KCLE 300819
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
419 AM EDT Mon Sep 30 2024

.SYNOPSIS...
A trough lingers across the area today before departing to the
east. A cold front will swing east across the area on Tuesday
and Tuesday night. High pressure builds in on Wednesday and
Thursday with a weak cold front moving across the area on
Friday.

&&

.NEAR TERM /THROUGH TUESDAY/...
An upper-level low that has been influencing our weekend weather
still remains over the Ohio Valley, albeit in a significantly
weaker state. Low-level moisture in the 850-925mb layer is quite
expansive, extending across the entire forecast area, though
deeper moisture to 700-500mb is primarily located east of the
upper-level low trough axis into the far southeast part of our
forecast area (i.e. approximately KGKJ to MNN). We start the
day today with overcast skies areawide and isolated, light rain
showers possible underneath the deeper moisture. Isolated
showers remain possible in our southeast counties through today
and tonight as the upper-level low is very slow to move east,
though overcast conditions should give way to partly to mostly
cloudy skies as some scattering out of the low-level clouds
should occur with some mild daytime heating.

Conditions become favorable for patchy to areas of fog late
tonight into early Tuesday morning west of I-77, especially
closer to the I-75 corridor. Any fog that develops should
dissipate by mid-morning. A cold front approaches from the west,
with sufficient forcing/moisture for a line of showers along and
ahead of this cold front, reaching the I-75 corridor Tuesday
afternoon. Most models have ~500 J/kg MUCAPE so have retained a
slight chance of thunderstorms with this line of showers. It`s
possible there could be a some gusty winds (in the 30-40 mph
range) given deep layer shear of 20-25 knots and marginal
instability, it`s unlikely wind gusts get any stronger than
that.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
A potent shortwave trough aloft moves E`ward through the Lake Erie
region and Upper OH Valley Tuesday night. At the surface, the
accompanying front is expected to be located over central Lake Erie
and near I-71 at sunset. The front will continue to sweep E`ward and
is forecast to exit the rest of our CWA by the wee hours of
Wednesday morning. Behind the front, a ridge builds from the western
Great Lakes. Low-level convergence/moist ascent along the cold front
are expected to trigger scattered showers and isolated thunderstorms
since the ascent should release sufficient, albeit weak boundary
layer CAPE, especially during the evening. Some of the thunderstorms
may be strong given the potential for a moderate deep layer bulk
shear/low CAPE environment in the warm sector. Behind the cold
front, a NW`erly to N`erly mean low-level flow associated with
strong low-level CAA and 850 mb temperatures dropping to near 6C
over ~22C Lake Erie will allow a very brief period of lake-effect
rain showers to occur over and generally southeast and south of the
lake. However, these lake-effect rain showers will likely end by
daybreak Wednesday morning as lake-induced CAPE wanes quickly via a
lowering subsidence inversion and significant low-level dry air
advection accompanying the aforementioned ridge. Lows are still
expected to reach mainly the upper 40`s to mid 50`s around daybreak
Wednesday.

Fair weather is expected Wednesday through Thursday night as
stabilizing subsidence accompanies the aforementioned ridge at the
surface and aloft. This ridge builds from the Upper Midwest on
Wednesday through Wednesday night before it begins to exit E`ward on
Thursday through Thursday night. Late afternoon highs on Wednesday
are still expected to reach the 60`s to near 70F as daytime heating
is limited by net low-level CAA. Mainly clear sky, easing surface
winds, and low humidity at/near the surface are expected to promote
efficient nocturnal cooling Wednesday evening through daybreak
Thursday, when lows are expected to reach mainly the 40`s to lower
50`s. Net low-level WAA begins to affect our CWA on Thursday through
Thursday night as northern OH and NW PA become located along the
western flank of the low-level ridge. Late afternoon highs are
expected to reach the 70`s on Thursday and be followed by overnight
lows reaching mainly the mid 40`s to mid 50`s around daybreak
Friday.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
Another cold front is poised to sweep SE`ward across our CWA on
Friday as another shortwave trough approaches from the Upper Midwest
and vicinity. Isolated rain showers are possible due to low-level
convergence/moist ascent along the front and moist isentropic ascent
aloft, ahead of the shortwave trough axis. Daytime highs should
reach the 70`s before the cold front passage. The shortwave trough
should advance E`ward across the Lake Erie region and Upper OH
Valley Friday night and be followed by a ridge aloft building from
the Upper Midwest and vicinity through Saturday. At the surface, a
ridge builds from the western Great Lakes and vicinity. Periodic
rain showers are possible Friday night due to continued moist
isentropic ascent aloft, ahead of the shortwave trough axis, and the
potential for lake-effect rain showers over and generally south of
Lake Erie due to NW`erly to N`erly mean low-level flow of
sufficiently-cold/moist air behind the shortwave trough axis.
However, any lake-effect rain showers should end by daybreak
Saturday as lake-induced CAPE wanes via significant dry air
advection and a lowering subsidence inversion accompanying the
aforementioned ridge. These same processes are expected to yield
fair weather region-wide during the day on Saturday. Overnight lows
should reach mainly the mid 40`s to mid 50`s around daybreak
Saturday. Late afternoon highs should reach the 60`s to near 70F on
Saturday as net low-level CAA limits daytime heating.

Current odds favor fair weather Saturday night through Sunday as the
ridge at the surface and aloft crests E`ward over the Lake Erie
region and Upper OH Valley Saturday night and then begins to exit
E`ward on Sunday. However, a few rain showers are possible west of I-
71 Sunday afternoon through early evening as a trough at the surface
and aloft approaches from the Upper Midwest and vicinity, and moist
isentropic ascent aloft precedes the trough axis. Mainly clear sky,
weak surface winds, and low humidity at/near the surface should
permit efficient nocturnal cooling to occur Saturday evening through
daybreak Sunday, when lows should reach mainly the 40`s to lower
50`s. Net low-level WAA along the western flank of the surface ridge
and daytime heating should allow late afternoon highs to reach the
upper 60`s to mid 70`s on Sunday.

&&

.AVIATION /06Z Monday THROUGH Friday/...
Fairly low confidence forecast is laid before us as rain showers
are largely dissipated, leaving us with a cloud deck with
variable ceilings. In the broader sense, current observations
show IFR conditions to the south, with gradually improving
ceilings to MVFR and VFR farther to the north. For the most
part, conditions should remain relatively steady-state through
the pre-dawn hours. However, model guidance show some low-
level drying occurring in western Pennsylvania and should
expect that to move in from the east and southeast through this
morning, so KYNG and KCAK may improve before 12Z. Areawide
though, should see IFR improve to MVFR, with ceilings
1500-2500ft during the late morning to mid-afternoon hours. Most
of the area should lose their ceiling and scatter our between
21-03Z this evening into tonight, with most of the area starting
off the night with VFR expected. Conditions become favorable
for fog development, especially across Northwest Ohio and
central Ohio, so we might see that starting to develop right at
the end of the TAF period.

East winds of 6-11 knots are expected through the day day
before dropping off quickly after sunset, becoming light and
variable.

Outlook...Periods of non-VFR possible through Monday, becoming
more scattered on Tuesday, then expanding again Tuesday night.

&&

.MARINE...
Helene`s remnant low moves generally E`ward from central KY toward
the Mid-Atlantic states before dissipating tonight. Simultaneously,
a trough lingers over Lake Erie and a warm front is still expected
to sweep generally N`ward across the lake tonight through Tuesday
morning. Waves of 3 feet or less are expected in U.S. waters through
Tuesday morning. NE`erly to E`erly winds around 5 to 15 knots
through this early evening veer to S`erly tonight through Tuesday
morning with the warm front passage. A cold front is still expected
to sweep E`ward across Lake Erie Tuesday afternoon through the wee
hours of Wednesday morning. S`erly to SW`erly winds around 5 to 15
knots ahead of the cold front veer to NW`erly and freshen to 15 to
nearly 25 knots behind the front. Waves of 3 feet or less ahead of
the cold front build to as large as 3 to 6 feet behind the front.
Another Small Craft Advisory will likely be needed, especially east
of The Islands.

Behind the cold front, a ridge builds from the Upper Midwest and
vicinity through Wednesday. As a result, NW`erly to N`erly winds
around 15 to nearly 25 knots during the wee hours of Wednesday
morning ease to 10 knots or less by midday. By sunset Wednesday
evening, winds are expected to become variable in direction and ease
further to around 5 knots. Accordingly, waves are expected to
subside steadily to one foot or less by nightfall Wednesday evening.
The light and variable winds become S`erly to SW`erly and freshen to
around 5 to 10 knots Wednesday night through Thursday night as the
ridge exits toward the Mid-Atlantic states. Waves of 3 feet or less
are expected. Another cold front is forecast to sweep SE`ward across
Lake Erie on Friday and cause the S`erly to SW`erly winds around 5
to 10 knots to veer to NW`erly to N`erly and freshen to around 10 to
15 knots. Waves are forecast to remain 3 feet or less.

&&

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

&&

$$

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