656
FXUS61 KCLE 270901
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
501 AM EDT Fri Sep 27 2024

.SYNOPSIS...
The tropical remnants of Helene will lift into the Ohio Valley
by tonight while rapidly weakening. Weak low pressure
associated with the remnants of Helene will then drift across
the Ohio Valley through the weekend before dissipating early
next week.

&&

.NEAR TERM /THROUGH SATURDAY/...
Hurricane Helene currently located over southern Georgia as of
07Z with continue to rapidly dissipate as it moves north across
the state and then northwest towards the Ohio Valley where it
will become "absorbed" into an upper-level low later today and
tonight. This upper-level low is expected to remain across the
Ohio Valley through Saturday (and beyond), and will be the
primary driver for the local weather patten for the time being.

Regional radar observations reveal an expansive area of rain
across the southeast CONUS extending northward into the Ohio
Valley with the northern extent of the precipitation shield
just now entering the southern part of the forecast area (i.e.
Marion to Knox County). This precipitation will make very
minimal northward progress, maybe another tier of counties this
morning before there is a more substantial northward surge of
precipitation later this afternoon through tonight as the
remnants of Helene approach. There should be a fairly expansive
area of rain between 18-22Z before becoming more scattered this
evening into tonight. In addition to the rain, northeast winds
will be on the rise today, peaking during the afternoon/evening
hours. The strongest wind gusts of 35-45 mph are expected in
parts of Northwest Ohio and Central Ohio.

A dry slot wrapped around the upper-low and behind the main
area of moisture associated with Helene will result in a ~12
hour period late tonight into Saturday morning where most areas
become relatively rain-free. However, additional moisture moves
back in with scattered rain showers likely by Saturday
afternoon/evening.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
A trough at the surface and aloft affects our CWA through the short-
term period as the vertically-stacked remnant low of Helene wobbles
ENE`ward from the Lower OH Valley toward the Middle OH Valley
Saturday night through Monday night, In addition, the remnant low is
expected to devolve into a trough at the surface and aloft Monday
night. Simultaneously, a warm front is expected to sweep generally
N`ward through our region Monday night in association with a potent
shortwave trough aloft progged to approach our CWA from the Canadian
Prairies and the northern Great Plains. This weather pattern
evolution will allow moist isentropic ascent aloft to generate
abundant cloud cover and periodic rain showers in northern OH and NW
PA through the short-term period. The moist isentropic ascent may
release enough elevated instability to trigger a few thunderstorms,
especially during the afternoon and evening hours of Sunday and
Monday. Overnight lows are expected to reach mainly the lower to mid
60`s Saturday night and then mainly the mid 50`s to lower 60`s
Sunday night and Monday night, respectively. Daytime highs are
expected to reach the 70`s on Sunday and Monday.

&&

.LONG TERM /TUESDAY THROUGH THURSDAY/...
The aforementioned shortwave trough aloft is expected to approach
from the Upper Midwest on Tuesday and then traverse the Lake Erie
region and Upper OH Valley generally from west to east Tuesday
night. Simultaneously, the attendant surface cold front sweeps
SE`ward through our CWA Tuesday through Tuesday night and will be
followed by a surface ridge building from the north-central U.S.
Scattered showers are expected along and ahead of the cold front
courtesy of low-level convergence/moist ascent along the front and
pre-front low-level moist isentropic ascent aloft. In addition, the
convergence/ascent along the surface cold front may trigger weak,
yet sufficient boundary layer CAPE to trigger a few thunderstorms.
Behind the front Tuesday night, a sufficiently-moist NW`erly to
N`erly mean low-level flow associated with strong CAA and
accompanied by 850 mb temperatures dropping to near 3C over ~22C
Lake Erie will allow scattered lake-effect rain showers to occur
over and generally southeast or south of the lake. Daytime highs are
expected to reach the 70`s on Tuesday, before the cold front
passage. Lows are expected to reach mainly the upper 40`s to mid
50`s around daybreak Wednesday.

High pressure at the surface and aloft is expected to build from the
Upper Midwest and vicinity on Wednesday through Thursday. Low-level
dry air advection and a lowering subsidence inversion accompanying
the ridge are expected to cause lake-induced CAPE to wane and
lingering lake-effect rain showers over/generally southeast or south
of Lake Erie to end by Wednesday evening. Otherwise, fair weather is
expected through Thursday as stabilizing subsidence accompanies the
ridge. Limited daytime heating amidst net low-level CAA will allow
highs to reach the 60`s to near 70F Wednesday. Considerable
clearing, easing surface winds, and low humidity at/near the surface
are expected to allow lows to reach the 40`s to lower 50`s around
daybreak Thursday. During the day on Thursday, our CWA is forecast
to become located along the western flank of the surface ridge and
begin to be impacted by net low-level WAA. This net low-level WAA
regime and daytime heating should allow late afternoon highs to
reach the upper 60`s to mid 70`s.

&&

.AVIATION /06Z Friday THROUGH Tuesday/...
Overcast skies are observed areawide with mostly high cirrus,
though a few pockets of clouds around 4-7kft. Impacts from the
remnants of Helene will begin to occur later this morning with
low ceilings, rain, and wind. Rain and thickening clouds will
occur from south to north late this morning through the day and
into this evening and tonight. Initially, a steady rainfall is
expected, especially west of I-77 but rain will become more
scattered this evening into tonight. A gradual lowering of
ceilings to the 1-3kft range is expected late this afternoon
into tonight at most TAF sites. Northeast winds will also be on
the rise late this morning, with gusts of 20-30 knots possible
this afternoon through this evening. Strongest wind gusts are
expected towards the south and west (e.g. TAF sites such as
KTOL, KFDY, and KFDY) where gusts of 25-30 knots will be more
persistent and max isolated gusts of 35 knots will be possible.
Winds should gradually subside tonight.

Outlook...Periods of non-VFR are possible with scattered rain
showers and low ceilings through Tuesday.

&&

.MARINE...
The Small Craft Advisory and Beach Hazards Statement from Maumee Bay
to Willowick take effect at 5 AM today, while the Small Craft
Advisory and Beach Hazards Statement from Willowick to Ripley take
effect at 8 AM today. All of these alerts will be in effect until 8
AM EDT Saturday. Fairly-strong ENE`erly winds on Lake Erie may allow
the water level at/near Toledo to peak near 5.5 feet to nearly 6
feet above low water datum late this afternoon through early
evening. Flood stage at Toledo is 6 feet above low water datum. We
will continue to monitor the latest lake level forecast and
observations closely for the potential need for a Lakeshore Flood
Warning.

Helene`s low wobbles generally N`ward and then NW`ward from GA to
the Lower OH Valley through this evening. Thereafter, this low is
expected to remain nearly-stationary through Sunday night before
drifting ENE`ward toward the Middle OH Valley on Monday and weaken
steadily. Simultaneously, a trough extending from Helene`s low is
expected to impact Lake Erie and interact with a high pressure ridge
focused over/near the northern Great Lakes. The interaction between
the trough and ridge will allow NE`erly to E`erly winds around 10 to
20 knots early this morning to freshen to around 20 to 30 knots by
daybreak and remain around 20 to 30 knots through this evening.
Waves of 4 feet or less early this morning build to as large as 5 to
10 feet later this morning through evening. As Helene`s low weakens
steadily and the attendant trough over Lake Erie does the same, the
NE`erly to E`erly winds are expected to ease to around 15 to 25
knots between midnight and daybreak Saturday morning, ease further
to 5 to 15 knots by daybreak Sunday, and then remain around 5 to 15
knots through Monday. Waves are expected to subside to 4 feet or
less by nightfall Saturday evening and to 3 feet or less by daybreak
Sunday. However, occasional 4 footers are possible in open U.S.
waters on Sunday through Monday.

E`erly to SE`erly winds around 5 to 15 knots veer to S`erly Monday
night as Helene`s remnant low dissipates in vicinity of the Middle OH
Valley and a warm front sweeps N`ward across Lake Erie. On Tuesday,
S`erly to SW`erly winds around 10 to 20 knots veer to NW`erly as a
cold front sweeps SE`ward across the lake. Waves are forecast to be
mainly 3 feet or less, but occasional 4 footers are possible and the
cold front passage may yield Small Craft Advisory conditions.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...Beach Hazards Statement through Saturday morning for OHZ003-
     007-009>011.
     Beach Hazards Statement from 8 AM EDT this morning through
     Saturday morning for OHZ012-089.
PA...Beach Hazards Statement from 8 AM EDT this morning through
     Saturday morning for PAZ001.
MARINE...Small Craft Advisory until 8 AM EDT Saturday for LEZ142>146.
     Small Craft Advisory from 8 AM this morning to 8 AM EDT
     Saturday for LEZ147>149.

&&

$$

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