587
FXUS61 KCLE 240608
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
208 AM EDT Tue Sep 24 2024

.SYNOPSIS...
Low pressure will lift out of the Mid Mississippi Valley
tonight and through the southern Great Lakes late Tuesday and
Tuesday night. This will lift a warm front through the region
Tuesday morning before a cold front sweeps through Tuesday
night. A trough will linger across the region Wednesday before
high pressure builds in from the north Thursday into Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
900 PM Update...
Warm front/surface low pressure continues to push northeastward
from the mid Mississippi Valley with mid level isentropic lift
bringing the next round of rain in to the CWA. POPs ramp up
overnight, temperatures to the upper 50s/lower 60s. Should be
another round of decent soaking rain for the area in the next
24 hours.

Previous Discussion...
Unsettled weather will continue into mid week bringing pockets of
beneficial rainfall to the region along with abundant cloud cover.

The latest visible satellite loops show the spin associated with
weak surface low pressure lingering over eastern Lake Erie near
Buffalo, NY. Light northerly flow on the backside of this low across
the unseasonably warm lake (water temps in the mid 70s F) combined
with wraparound moisture and weak PVA is generating persistent light
showers and drizzle. This is mainly occurring from north central
Ohio and the central highlands through NE Ohio and NW PA where
upsloping is locally enhancing the showers. QPF through early
evening will only be a trace to few hundredths of an inch, but the
dreary skies and damp conditions will continue. A break in the
showers/drizzle is expected from mid evening through the first half
of the night as the surface low drifts slightly farther east and
becomes absorbed by a newly developing surface low lifting out of
the Mid Mississippi Valley. Weak mid/upper shortwave ridging
building across the southern Great Lakes region early tonight ahead
of this system combined with weak surface ridging from the north
will bring mainly dry conditions for the 00-06Z time period before
the next system moves in. More on that below.

Late tonight and Tuesday, the mid/upper shortwave trough over the
Mississippi Valley driving the aforementioned surface cyclogenesis
will phase with a stronger mid/upper trough dropping through the
Plains and Upper Midwest. This will result in a deep mid/upper
trough axis pushing into the western Great Lakes Tuesday and Tuesday
night, with a slightly deepening surface low lifting from the St.
Louis, MO region Tuesday morning through SE Lower Michigan and SW
Ontario by Tuesday night. As this developing surface low organizes,
a warm front will lift north across the region late tonight and
Tuesday morning. Warm/moist advection and isentropic ascent driven
by a developing 20-30 knot low-level jet will generate widespread
showers spreading from SW to NE in the pre-dawn hours Tuesday, so
have PoPs quickly increasing after 06Z tonight. That is where the
forecast becomes challenging. Yes, everyone will see rain late
tonight and Tuesday morning, but as the surface low lifts toward SE
Lower Michigan in the afternoon and evening, redevelopment of
showers and thunderstorms will occur ahead of the trailing cold
front as the left exit of a 70-90 knot H3 jet streak impinges on the
region and aids with increased frontogenetic forcing. HREF CAMS
continue to show great variability the past two runs with how long
of a dry slot there will be Tuesday afternoon behind the warm front,
and that affects how much heating and destabilization can occur. The
theme seems to be that at least scattered showers and widespread
clouds will stick around through mid afternoon, and with the low
late September sun angle, that makes us believe that instability
will be greatly limited. The NAM only suggests 400 to 700 joules of
surface based CAPE in the afternoon with HREF suggesting less,
especially if the showers hang around through mid afternoon. The
best chance for sunshine and higher CAPE appears to be south of the
region. Nevertheless, with the surface low passing near the region
and the aforementioned jet streak, shear will be sufficient for
isolated strong to severe storms in the late afternoon and early
evening before sunset. Deep layer shear looks to average 30-40
knots, and this could lead to gusty winds if any organized cores can
develop. Low-level shear nearing 20 knots along with veering with
height as the surface low passes nearby and low LCL heights of 500-
1000m could also support a brief spin up tornado. Mid-level lapse
rates will be fairly flat (5.5 to 6 C/Km), so do not expect hail.
Any severe weather would be gusty winds and/or a brief tornado, and
again, this is a very marginal, conditional threat depending on how
much of a dry slot develops. If there is a severe storm, areas along
and south of the US 30 corridor have the best potential since that
area has a greater chance at a longer dry slot/sunshine. Will keep a
mention in the HWO. Showers will gradually end from west to east
Tuesday night as the cold front sweeps east across the region.

Highs will range from the mid to upper 70s Tuesday, except upper 60s
to low 70s in NW PA where showers are likely to hang on the longest.
Lows tonight will generally be in the upper 50s to low 60s, with low
to mid 60s Tuesday night.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Showers and thunderstorms will be ongoing in the eastern half of the
CWA throughout the day Wednesday. There is some fair instability on
Wednesday as CAPE values will be approaching 1000j/kg in the
southeast and eastern counties due to diurnal heating. The surface
low will be occluding to the north, and with low lapse rates and
minimal shear in place, only general thunderstorms are expected at
this time. A cold front will push through the region Wednesday night
into Thursday and with that PoPs will decrease. On Thursday a ridge
will build in over the western Great Lakes as a cutoff low moves
south over the mid-Mississippi Valley. Dry weather is expected
through the end of the period as northeasterly flow sets up over the
region.

Highs for Wednesday will be in the mid to upper 70s with overnight
lows down into the upper 50s. For Thursday, highs will reach the
upper 70s and low 80s and lows in the upper 50s, low 60s for the
night.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
PoP chances will increase throughout the day on Friday as a
potential tropical system makes its way north into the region. There
is still some uncertainty as to the northern extent of the system
and how it will interact with the upper-level cutoff low in the mid-
Mississippi Valley. As of now, chance PoPs have been carried over
for the western two-thirds of the CWA for Friday into the weekend.
There will be an tightened pressure gradient as the system moves
northward with winds gusting out of the northeast at 20-30 mph
Friday afternoon into the overnight hours.

Temperatures will be roughly 5 degrees above average through the
weekend with highs in the mid 70s to lower 80s. Lows will be in the
lower 60s before falling into the high 50s to start next week.

&&

.AVIATION /06Z Tuesday THROUGH Saturday/...
A mix of VFR and MVFR ceilings will trend downward through the
morning hours as a warm front will bring additional showers to
the region and bring lower ceilings, largely below 2 kft. There
could be some periods of IFR conditions during the morning
and early afternoon hours, but this may hinge on sustained rain
showers during the first part of the day. There seems to be
consensus on a break in the rain activity during the afternoon
hours. Additional rain and perhaps some TS will develop during
the evening hours and move across the area and have some windows
of VCTS at most terminals. Conditions will try to favor MVFR
through the day but some more IFR could develop with any TS
this evening. Rain should exit toward the end of the TAF period
with MVFR ceilings remaining in the region. Winds will be east
to southeast, shifting to the south through the period. Some
stronger southerlies will develop over NW PA and eastern Lake
Erie and have some gusts in the KERI TAF.

Outlook...Non-VFR conditions may linger Tuesday night into
Wednesday with residual rain and low ceilings in the region.
Strong northeast winds are expected across the region on Friday.

&&

.MARINE...
A northwesterly wind continues over Lake Erie at 10-15 knots with
waves 1 to 3 feet this afternoon. Winds will become light and
variable as a surface low pressure slows across the eastern Great
Lakes overnight into Tuesday. On Tuesday, winds will shift to be out
of the southeast at 10-15 knots as the low moves off eastward.
Tuesday night, winds will increase in the eastern portion of Lake
Erie to 20-25 knots. A Small Craft Advisory will be needed for
Ashtabula, OH east to Ripley, NY for a short period of time during
the overnight hours into Wednesday. Winds will veer to be
southwesterly and lighter at 5-10 knots during the day Wednesday as
a cold front crosses Lake Erie. The winds will start to veer
throughout the day on Thursday ahead of the next low pressure system
before settling in a east-northeasterly at 10-15 knots. The
aforementioned low will approach from the south and winds will
increase as a result to 20-25 knots over the central and western
basins of Lake Erie. As a result, a Small Craft Advisory could be
needed for those areas Friday.

&&

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

&&

$$

SYNOPSIS...Garuckas
NEAR TERM...Garuckas/26
SHORT TERM...Kennedy
LONG TERM...Kennedy
AVIATION...Sefcovic
MARINE...Kennedy