CLE issues Area Forecast Discussion (AFD) at Sep 18, 3:35 PM EDT568
FXUS61 KCLE 181935
AFDCLE
Area Forecast Discussion
National Weather Service Cleveland OH
335 PM EDT Fri Sep 18 2026
.WHAT HAS CHANGED...
No significant changes with this update. Rainfall amounts late
Saturday into Sunday remain similar to the previous forecast.
&&
.KEY MESSAGES...
1) Rain showers will slowly increase Saturday, with periods of
heavy rain possible Saturday night into Sunday morning. The
heaviest rain is expected over the lakeshore counties and also
in NW Ohio where localized flooding is possible.
2) Cool and unsettled weather is expected next week.
&&
.DISCUSSION...
KEY MESSAGE 1...
Canadian high pressure over the northern and central Great Lakes
this afternoon through early tonight will briefly keep the
active frontal boundary to our south near the Ohio River.
However, the current showers and thunderstorms over Illinois and
Wisconsin are a sign of what's to come for the weekend. This
activity is tied to the first in a series of mid/upper shortwave
troughs that will progress across the southern Great Lakes
tonight through Sunday. Increasing isentropic ascent and right
entrance forcing beneath a subtle upper jet streak will generate
showers near Lake Erie and NW Ohio by Saturday morning, but
abundant low-level dry air will likely cause much of this
initial activity to fall apart. Kept chance to slight chance
POPS in the morning and afternoon for low impact, scattered
showers.
Better potential for more of a widespread, heavier rain will
start to arrive Saturday evening and especially Saturday night
through Sunday morning as the next and much stronger mid/upper
shortwave crosses the southern Great Lakes region. An 80+ knot
upper jet streak rounding the base of the shortwave trough and
upper diffluence will aid in a slightly deepening surface low
tracking from NE Iowa Saturday afternoon through southern
Ontario Saturday night/early Sunday. The frontal boundary will
lift back north into the region ahead of this low Saturday
afternoon and Saturday night, likely becoming quasi-stationary
near the south shore of Lake Erie. This will bring the rich
low-level moisture characterized by 70+ F dew points back into
the area. The combination of strong warm/moist advection and
isentropic ascent north of the lifting frontal boundary, upper
diffluence and right entrance forcing south of the
aforementioned jet streak tracking over Lower Michigan, and the
moisture rich airmass will lead to a band of steady rain. There
will be a "sweet spot" where the strongest jet dynamics align to
tighten mid-level frontogenesis, and that is where an embedded
narrower strip of heavier convection is expected to line up.
Most of the region will see 0.50 to 1.00 inch of rain late
Saturday through midday Sunday, but where the embedded band of
heavier convection sets up could see 1-2 inches (locally
higher). PWATs of 1.75 to 2 inches will be in the 90th to 99.5th
percentile of daily climatology, and this combined with deep
warm cloud layers supports efficient rainfall rates. The frontal
boundary will be aligned fairly parallel to the mid/upper flow,
so will need to watch for training convection where this narrow
band sets up. This could lead to rises on area rivers, creeks,
and streams as well as flooding of typical flood prone area. The
WPC Slight Risk for Excessive Rainfall still looks good for
both Saturday and Sunday (Level 2 of 4) in NW Ohio since
consensus among RRFS and HREF CAMS are showing greatest
consistency over that area, but this heavy rain swath could also
extend across the lakeshore counties of NE Ohio and Erie
County, PA. Held off on a Flood Watch because there is still
plenty of time to see future CAMS pinpoint the exact location of
the convective band, but a Watch could be considered in the
next couple of forecast cycles.
The area will dry out from north to south Sunday afternoon and
Sunday night as a strong cold front pushes south of the region
behind the exiting surface low and Canadian high pressure tries
to build in from the northern Great Lakes.
KEY MESSAGE 2...
The first true stretch of Fall weather will arrive Monday and
persist through next week as a broad mid/upper trough across
the Great Lakes becomes blocked to the south of an anomalous
mid/upper ridge building over most of Canada. This will result
in a closed (cut off) low eventually developing and pinwheeling
between the Ohio Valley and Mid Atlantic regions mid to late
week to the south of a strong Canadian high over eastern Canada.
This pattern will result in cool NE low-level flow and breezy
conditions, along with periods of rain showers. Details for each
day are very uncertain at this time, but the main message is
cool with periods of showers all week. Highs will generally be
in the low/upper 60s with lows in the 50s.
&&
.AVIATION /18Z Friday THROUGH Wednesday/...
VFR conditions expected this afternoon and evening with mostly
sunny skies due to high pressure over the Great Lakes region.
Winds will be out of the north around 8-10 knots this afternoon.
Low pressure approaches from the southwest, with a series of mid-
level impulses impacting the region starting Saturday. Showers and
thunderstorms are most likely to impact Northwest Ohio Saturday
morning, with showers and storms potentially getting into north-
central and Northeast Ohio later Saturday afternoon/evening. Non-VFR
visibilities are likely within heavier showers/thunderstorms.
Outlook...Non-VFR possible with showers and occasional
thunderstorms through Tuesday.
&&
.MARINE...
NE winds will remain fairly steady at 10-15 knots through
tonight while gradually becoming E at 10-15 knots late tonight
through Saturday. Winds will quickly veer to S and decrease to
5-10 knots Saturday night and early Sunday then all the way
around back to NE Sunday afternoon. NE winds will increase to
15-25 knots by Sunday evening, with NE winds further increasing
to 20-30 knots Sunday night through Tuesday. This will build
wave heights to over 6 feet at times, with the highest waves in
the western and central basins. Long duration Small Craft
Advisories and Beach Hazards Statements are likely Sunday
afternoon into Wednesday since ENE winds will still be over 20
knots at times by Wednesday.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...None.
&&
$$
DISCUSSION...Garuckas
AVIATION...Saunders
MARINE...Garuckas
Source:
CLE issues Area Forecast Discussion (AFD) at Sep 18, 3:35 PM EDT---------------
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