CLE issues Area Forecast Discussion (AFD) at Sep 9, 2:19 PM EDT
870
FXUS61 KCLE 091819
AFDCLE
Area Forecast Discussion
National Weather Service Cleveland OH
219 PM EDT Wed Sep 9 2026
.WHAT HAS CHANGED...
Trends are for multiple rounds of thunderstorms this afternoon
and evening, with scattered storms mainly in NE OH and NW PA
between 2 and 4 PM, then another more widespread round of
thunderstorms crossing west to east between 4 and 8 PM.
&&
.KEY MESSAGES...
1) Scattered thunderstorms will develop and impact NE Ohio and
NW PA between roughly 2 and 4 PM followed by a more widespread
line between 4 and 8 PM. The main hazard is damaging winds, but
isolated tornadoes and localized flooding are possible.
2) Showers linger mainly south of I-80 Thursday before high
pressure brings dry, cooler, and less humid weather the rest of
the week.
3) Warm, humid, and unsettled weather returns Saturday into next
week.
&&
.DISCUSSION...
KEY MESSAGE 1...
Following the theme of summer and now early Meteorological Fall
of 2026, yet another severe weather event is expected across NE
Ohio and NW PA this afternoon and evening. Afternoon visible
satellite and water vapor loops show a strong mid/upper
shortwave trough progressing from the Upper Midwest into the
Great Lakes. This is eroding the northern periphery of an
unseasonably strong mid/upper ridge centered over the SE CONUS.
The surface low associated with the mid/upper shortwave is near
Hudson Bay and will progress east into northern Quebec tonight,
dragging a cold front across our region. Despite the surface low
being displaced so far north, plenty of jet dynamics will
accompany the mid/upper shortwave this evening to enhance height
falls and large scale ascent as well as to increase deep layer
shear. This forcing coupled with moderate instability (MLCAPE of
1000-1500 J/Kg) will support a healthy line of convection.
In terms of timing and details, dying convection from last night
has left a band of showers over Lower Michigan, Indiana, and
extreme NW Ohio early this afternoon. This is setting up a
differential heating boundary/pre-frontal trough over NW Ohio,
which will act as the main trigger to ignite the main line of
convection this evening as the shortwave and associated forcing
overspread the area. Out ahead of this pre-frontal trough, a
lake breeze boundary may set up east of Cleveland this
afternoon. Forecast soundings do not have much of a cap to erode
since mid-level lapse rates are weak ( 5 to 5.5 C/Km) and the
atmosphere is quite warm through the entire boundary layer, so
expect initial scattered convection to develop between 18 and
20Z along the lake breeze and impact NE Ohio and NW PA. A few of
these storms could produce damaging winds since strong surface
heating has created steep low-level lapse rates and resultant
high DCAPE over 800 J/Kg. However, the main show will be with
the line of convection that develops on the pre-frontal trough
this evening. Consensus among HREF CAMS and the RRFS is for this
line to develop from roughly the Lake Erie Islands to Marion
after 20 or 21Z then propagate east through the Cleveland and
Akron areas around 23Z and through NW PA by 01Z. The
aforementioned instability coupled with deep layer effective
shear increasing to 40-50 knots will support bowing segments
capable of damaging winds. Any bowing segments will also need to
be watched for isolated QLCS tornadoes since 0-3 Km shear will
be over 30 knots and will try to orient normal to the line at
times. Surface to 1 Km shear of 20-25 knots also supports the
isolated tornado threat. Finally, storm cell movement will be
fast (generally over 40 knots to the E and SE), but any repeated
rounds of convection could result in locally excessive rainfall
and flash flooding since PWATS are running unseasonably high
(1.7 to 2 inches) and soundings show a deep warm cloud layer.
This will mainly occur if parts of NE Ohio and NW PA see heavy
rain from the initial scattered convection late this afternoon
before the main line crosses the region this evening.
KEY MESSAGE 2...
There will be a break in the rain showers most of tonight behind
the line of convection, but a second mid/upper shortwave will
progress across the Great Lakes and Upper Ohio Valley Thursday.
The right entrance region of the mid/upper jet will lead to a
weak surface wave that will ride along the front, causing the
frontal boundary to briefly stall over northern or central Ohio
Thursday morning. This wave and right entrance ascent should
generate additional showers north of the boundary Thursday
morning into the afternoon, especially along and south of I-80
and I-76. CAMS are in agreement with this, so increase POPS from
12 to 18Z. The front will finally push south behind this wave
late Thursday afternoon and Thursday night allowing a large
Canadian high at the surface to build down across the Great
Lakes. This will bring dry and cooler, much more seasonable
weather for Thursday night and Friday.
KEY MESSAGE 3...
Unfortunately, the more typical mid September weather will not
last long as a warm, humid, and unsettled pattern looks to
quickly return this weekend. A couple of mid/upper troughs and
associated closed lows progressing into the Pacific Northwest
between Saturday and Wednesday will build an elongated mid/upper
ridge across the south central and SE CONUS. This will allow
temperatures well into the 80s and dew points in the upper 60s
to around 70 to build back into the region Saturday and largely
remain through Wednesday. Active quasi-zonal mid/upper flow
across the Great Lakes on the northern periphery of the
elongated ridge will send shortwave energy near or north of the
region at times interacting with a wavering frontal boundary,
and this will lead to at least scattered showers and
thunderstorms. At this time, the greatest chances for rain
appear to be Saturday and Tuesday, but timing individual chances
is low confidence in this pattern, so the main message is very
warm and humid with periodic showers/storms.
&&
.AVIATION /18Z Wednesday THROUGH Monday/...
VFR across the TAF sites at 17z. However, ceiling will lower
from northwest to southeast this afternoon and evening. In
addition, showers and thunderstorms are possible near and round
KTOL and will start this TAF withe a tempo group for TS at 18z
and VCTS KFDY and KMFD this afternoon. Slightly bumped up by an
hour or two for timing for TSRA impacts at TAF sites this
afternoon. Still some uncertainty in TSRA coverage and
intensity today, though strong wind gusts (around 30 knots) are
likely with any storms that impact TAF sites east of KCLE.
Targeted higher wind gusts in the 40 to 50-knot range may be
needed in future amendments if confidence in direct impacts
increases.
Confidence is also increasing for a period of non-VFR
vsbys/ceilings following the convection overnight into Thursday
morning. Have introduced MVFR vsbys/ceilings at most sites in a
tempo group around 12z Thursday.
Winds will generally favor a south to southwest direction
today, increasing into the 10 to 15 knot range with periodic
gusts of 20 to 25 knots possible later this afternoon.
Outlook...Additional scattered showers are possible through
Thursday, generally along and south of the US-30 corridor. Non-
VFR may return for the weekend in isolated to scattered showers
and thunderstorms.
&&
.MARINE...
WSW winds will increase ahead of a cold front this evening and
tonight, and may near Small Craft criteria in the eastern basin
as winds approach 20 knots. The offshore component will build
the highest waves in the open waters, but could see over 3 feet
at times from Conneaut to Ripley. Winds will become NNW and
rapidly decrease to 5-10 knots Thursday morning, with light and
variable winds Thursday night becoming NE at 5-10 knots Friday
as high pressure builds overhead. Variable wind speeds and
directions are then expected Saturday through early next week as
a frontal boundary sets up and wavers near Lake Erie.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...None.
&&
$$
DISCUSSION...Garuckas
AVIATION...FZ
MARINE...Garuckas
Source: CLE issues Area Forecast Discussion (AFD) at Sep 9, 2:19 PM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202609091819-KCLE-FXUS61-AFDCLE)
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