926
FXUS61 KCLE 091157
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
757 AM EDT Sun Aug 9 2026

.WHAT HAS CHANGED...
A Day 1 SPC Marginal Risk (1 of 5) for severe weather has been
expanded through the entire area tonight, and a Slight Risk (2 of 5)
has been added to NW Ohio. A Day 1 WPC Slight Risk (1 of 4) for
Excessive Rainfall has been slightly expanded into more of NW Ohio
tonight, and a Day 3 Slight Risk for Excessive Rainfall has been
expanded to most of the area Tuesday.

&&

.KEY MESSAGES...
1) Briefly quiet and less humid today followed by multiple rounds of
showers and thunderstorms tonight through Wednesday. Confidence is
low on the timing, location, and intensity of each round of storms,
but rainfall totals could add up in some areas, and some of the
storms could produce severe weather.

2) Turning gradually drier, cooler, and less humid Wednesday night
through Saturday.

&&

.DISCUSSION...
KEY MESSAGE 1...
A weak cold front will continue to settle south
toward the Ohio River this morning as weak surface high pressure
builds across the southern Great Lakes. This will allow dew points
to run about 10 degrees cooler today making for noticeably less
humid conditions, but temperatures will remain very warm with highs
in the mid/upper 80s again.

The well advertised very active pattern will begin tonight as the
surface high drifts east and allows the front to lift back north as
a warm front in response to a mid/upper shortwave dropping into the
Upper Midwest. This shortwave will be one of many that will progress
through a WNW mid/upper flow pattern between a broad ridge
covering the southern Plains and Mid Mississippi Valley and
broad trough over southern Canada and the Great Lakes. Each
shortwave will interact with the frontal boundary as it becomes
quasi-stationary across the southern Great Lakes and Ohio
Valley regions, bringing multiple rounds of convection tonight
through Wednesday. Unfortunately, the forecast has become even
more uncertain in terms of the timing, location, and intensity
of each round of convection since each thunderstorm complex
(MCS) will move the location of the front and also lay down
outflow boundaries which will affect the evolution and track of
future complexes. Despite the high uncertainty and resulting low
confidence forecast, attempted to describe some individual
periods below.

Tonight and Monday morning: This period is trending somewhat
more impactful, and the Day 1 SPC Marginal Risk (1 of 5) for
severe weather has been expanded through the entire area
tonight, and a Slight Risk (2 of 5) has been added to NW Ohio,
along with a small expansion of the WPC Day 1 Slight Risk for
excessive rainfall into more of NW Ohio. The initial shortwave
moving into the Upper Midwest tonight will ignite an MCS over
the western Great Lakes this evening, where a 30-40 knot low-
level jet will focus strong warm/moist/theta e advection into
the frontal boundary. The past few runs of the HREF members and
RRFS have struggled with the evolution and track of this MCS
(and will continue to do so in this entire pattern), but
consensus is becoming more aligned with the idea that it will
move at least into NW Ohio late tonight and possibly roll
through the lakeshore counties in the pre-dawn hours Monday
morning along the retreating frontal boundary. Instability will
be weaker tonight and early Monday morning compared to the
source region for this complex to the west, so the most intense
portion of the system may dive south through Illinois and
Indiana, but slowly increasing low-level moisture and
instability through the night coupled with increasing mid-level
flow ahead of the approaching shortwave should be enough to
support some damaging wind risk, and PWATs rising back to 1.5 to
2 inches definitely support torrential rainfall with any
thunderstorms. So, potential is growing for thunderstorms late
tonight and early Monday morning to have decent organization
and produce some scattered wind damage and heavy rainfall.

Monday afternoon and Monday night: This period is trending drier
since the greater coverage and organization of the convection
early Monday morning should push the boundary back southwest and
also lay down outflow boundaries. This will likely cause new
convection to initiate farther southwest Monday evening and
Monday night. The shortwave will continue to progress through
the central Great Lakes Monday afternoon and evening, with a
30-40 knot low-level jet response focusing warm/moist/theta e
advection into the front and outflow boundaries. This will
ignite another MCS Monday evening or early Monday night, but
consensus is growing that the bulk of the activity will be
confined to areas along and south of a Findlay to Mount Vernon
line, and some HREF members even have it entirely southwest of
our CWA. While the threat of organized convection is decreasing
for most of our area Monday evening through Monday night,
noteworthy deep layer effective shear of 35-40 knots along with
the low-level jet aligned increasingly parallel to the main
boundary supports both severe weather (mainly damaging winds but
a couple of tornadoes) and torrential rainfall/flash flooding
from backbuilding convection wherever it develops and tracks. It
will be important to continue to check the latest forecast for
Monday evening and Monday night since the convection will be
significant wherever it ends up being.

Tuesday and Tuesday night: Uncertainty becomes really high by
the time we get to this period of the forecast, but the synoptic
frontal boundary remaining quasi-stationary and wavering around
the southern Great Lakes and Ohio Valley combined with what
appears to be one or two additional shortwaves will ignite
additional scattered convection during peak heating and MCS
clusters at night. Whether the convection ends up south of our
CWA (possible scenario due to all of the outflow from previous
convection) or into parts of our area, excessive rain totals and
flash flooding will be a growing concern because this will be
the third day of potential heavy rain. The expansion of the WPC Day
3 Slight Risk for excessive rainfall into most of the area
Tuesday and Tuesday night is reasonable based on the uncertainty
in location but potential for rainfall accumulations to be high
by the time this period arrives depending on where all of the
individual rounds end up.

Wednesday and Wednesday night: The shortwave train should
finally flatten the southern CONUS ridge enough by this period
that the trough across the Great Lakes and Northeast CONUS will
finally be able to deepen enough to begin to push the active
boundary south of the area. One more day of convection and heavy
rainfall is possible over or just south of the CWA Wednesday
before the drier air begins to work in Wednesday night.

KEY MESSAGE 2...
The deepening mid/upper trough across the Great Lakes and
Northeast CONUS Wednesday night through the start of the weekend
combined with Canadian high pressure at the surface gradually
sliding down across the Great Lakes and pushing the frontal
boundary into the Ohio River Valley will yield drier, cooler,
and less humid conditions. Highs will be in the mid to upper 70s
by Friday and Saturday with lows in the 50s away from the lake.

&&

.AVIATION /12Z Sunday THROUGH Thursday/...
Outside of some brief fog and mist in NE OH and NW PA,
conditions will trend to clear with high pressure entering the
region. There are some lake clouds in NE OH that will largely
avoid the terminals. Winds will be light and southwest for much
of the day.

After midnight, the first in a series of systems will reach the
area bringing increasing cloudiness before showers and storms
arrive to the region. Have begun to expand mentions of VCTS and
higher impact PROB30s when there could be higher confidence in
impacts due to TS. There is still a fair amount of uncertainty
in the TS potential late tonight into Monday and this time
period may need to be refined further.

Outlook...Periods of non-VFR conditions are expected through
Thursday as several rounds of scattered showers and
thunderstorms move across the airspace. Some storms could be
strong to severe during this timeframe, especially on Monday.

&&

.MARINE...
Northwest flow is present over the lake this morning with a cold
front exiting the region. High pressure will briefly build over
the lake today and flow will shift to the southwest by this
afternoon. For tonight through Wednesday, the weather pattern
appears fairly unsettled with several weak low pressure systems
moving over or just south of the area. These systems will allow
for southwest to west flow to persist through the middle of the
week and will bring periodic shower and storm chances. There may
be some marine headlines needed with the storm chances over the
lake. A cold front will cross the area by Thursday and high
pressure will build into the region toward the end of the week,
allowing for northwest flow to take over. There could be some 2
to 3 ft waves with the cold frontal passage, which may lead to a
brief moderate swimming risk.

&&

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

&&

$$

DISCUSSION...Garuckas
AVIATION...Sefcovic
MARINE...Sefcovic