391
FXUS61 KCLE 270150
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
950 PM EDT Thu Sep 26 2024

.SYNOPSIS...
After Hurricane Helene makes landfall along the northeastern
Gulf Coast tonight it will lift into the Ohio Valley by Friday
night 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 FRIDAY NIGHT/...
The forecast for tonight remains on track with overcast skies
and mild temperatures. Northeast winds will be on the increase
on Friday with the strongest winds focused across portions of NW
Ohio and along the western lakeshore. Gusts are forecasts to be
30-40 mph during the afternoon while winds top out closer to 30
mph in NE Ohio and Northwest Pennsylvania.

Previous discussion...An active near term forecast period is in
store as the interaction between Hurricane Helene and a non-
tropical closed low over the mid- Mississippi/lower-Ohio Valleys
brings clouds, some rain, and very stiff east-northeast breezes
to the local area. While the weather will be active / unsettled
it will also be relatively low-impact from a hazards
perspective.

Mainly dry weather is expected through tonight as a small ridge axis
aloft briefly builds between the aforementioned closed low to our
southwest and a longwave trough to our northeast. Some weak mid-level
isentropic lift and moisture advection will continue into our far
southern counties tonight, but the lift is overall quite weak so just
carry 20% POPs and no or very minimal QPF from approximately Findlay
to Millersburg points south/west. Farther north it will be mainly
cloudy but should be rain-free outside of perhaps a spotty sprinkle.
Low temperatures tonight will be unseasonably mild, generally in the
low to mid 60s but with a few 50s possible in interior Northwest PA.

It will remain overcast on Friday as Helene becomes entangled with
the closed low to our southwest and accelerates towards the Ohio
Valley. Helene will quickly be weakening and undergoing extra-
tropical transition through Friday. Despite this weakening trend, a
surge of stronger moisture advection and tightening pressure gradient
will bring light rain and increased winds and gusts to the area.
Rain chances will begin quickly increasing from south to north-
northwest after midday Friday, with the most widespread rain
expected during the late afternoon and evening hours. A mid-level
dry slot will begin wrapping in from the south-southeast Friday
night, allowing rain to become much spottier/lighter from the south-
southeast overnight. Have categorical POPs (80-90%) across most of
Northwest and Central OH, dropping off to high-chance to likely
(50-70%) elsewhere. This is a slight increase from the prior
forecast. Essentially all guidance has most or all of the area seeing
a bit of rain, though with light amounts (<0.25") given the ridge
axis aloft persisting ahead of Helene`s remnants and causing the
rain to begin weakening as it spreads in.

A strong low-level jet and tight pressure gradient will lead to gusty
winds across the area, mainly Friday afternoon and evening. Most
models have the tightest gradient and 40-45 knots of 925mb flow
across much of Northwest Ohio, along with across our far southern
counties (i.e. Marion to Knox). In this area, a period of 35-40 MPH
gusts is feasible, with 25-35 MPH peak gusts elsewhere. While the NBM
and HREF actually depict a 30-50% chance of exceeding advisory-
criteria (46 MPH) gusts across this part of our area, widespread
clouds and incoming rain during the period of strongest winds should
limit mixing heights significantly. It also helps that the system
will be quickly weakening as we see our strongest winds. Did add a
Hazardous Wx Outlook mention for wind gusts up to 40 MPH in some of
our western/southwestern counties, but ultimately don`t expect us to
need any wind headlines barring notable changes to the big picture.

It will remain mild on Friday with highs in the mid to upper 70s
ahead of the rain. Lows Friday night will remain in the 60s.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
The remnant of tropical cyclone Helene will meander over the Lower
Ohio Valley this weekend. The center or the low pressure system will
slowly track eastward across the Ohio Valley into the Mid-Atlantic
region through Sunday night. Scattered showers will be likely for
much of the weekend with the greatest rain chances Saturday
afternoon through Sunday afternoon. There could be an isolated
thunderstorm or two but mostly rain showers are expected. Average
QPF this weekend will be between a quarter and a half an inch of
rainfall. The heaviest rainfall with this system will stay south of
our local area. Afternoon high temperatures will be in the 70s this
weekend.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
There will be lingering rain chances into Monday associated with the
remnants of Helene. The higher POPs will be over the eastern CWA. A
quick moving cold front will push through the region on Tuesday with
additional chances for showers. Temperatures for early next week and
ahead of the cold front will be in the 70s for afternoon highs.
Cooler weather will follow behind the cold front by the middle of
next week with highs in the 60s.

&&

.AVIATION /00Z Friday THROUGH Tuesday/...
Overcast skies are in place tonight with a few pockets of MVFR
at 00Z. Generally expecting some improvement with VFR conditions
for most of the night with ceilings lowering to MVFR on Friday.
This is likely to occur in the morning in the western and
southern terminals and later in the day at CLE and possibly not
at all at ERI. Increasing northeast winds during the day on
Friday will be the main concern as the remnants of Helene make
their way into the lower Ohio Valley. Winds are likely to
increase to 15-20 knots with gusts of 30 knots or higher. The
strongest winds are likely at TOL off Lake Erie and possibly
FDY or MFD where gusts may reach 35 knots. Otherwise, rain will
spread north into the area generally between 16-22Z and
restrictions to visibility developing.

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

&&

.MARINE...
Winds will be from the northeast 10 to 15 knots this afternoon
and evening. The low level flow and surface winds will increase
over Lake Erie as Tropical cyclone Helene moves inland along the
Gulf Coast late tonight and move quickly into the southern
Appalachians on Friday. Winds will increase 15 to 20 knots late
tonight and peaking at 25 to 30 knots with gusts to up to 35
knots by Friday afternoon and evening. The highest winds and
waves will be in the western and central basins of the lake
Friday and Friday night. This strong northeasterly flow may
increase water levels Friday evening through Saturday morning.
Northeast winds diminish to 10 to 20 knots Saturday and 10 to 15
knots on Sunday. Small Craft Advisories will be issued for
Friday morning through Saturday morning. The SCA may need to be
locally extended for portions of the western basin of Lake Erie
Saturday into Sunday. Winds will become from the southeast 5 to
10 knots by Monday.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...Beach Hazards Statement from 5 AM EDT Friday through Saturday
     morning for OHZ003-007-009>011.
     Beach Hazards Statement from 8 AM EDT Friday through Saturday
     morning for OHZ012-089.
PA...Beach Hazards Statement from 8 AM EDT Friday through Saturday
     morning for PAZ001.
MARINE...Small Craft Advisory from 5 AM Friday to 8 AM EDT Saturday for
     LEZ142>146.
     Small Craft Advisory from 8 AM Friday to 8 AM EDT Saturday for
     LEZ147>149.

&&

$$

SYNOPSIS...Sullivan
NEAR TERM...KEC/Sullivan
SHORT TERM...Griffin
LONG TERM...Griffin
AVIATION...KEC
MARINE...Griffin