CLE issues Area Forecast Discussion (AFD) at Sep 21, 1:23 PM EDT088
FXUS61 KCLE 211751
AFDCLE
Area Forecast Discussion
National Weather Service Cleveland OH
123 PM EDT Sun Sep 21 2025
.SYNOPSIS...
High pressure will move offshore of New England today as low
pressure slowly drifts from the Upper Midwest into the northern
Great Lakes by Monday. This low will drag a cold front slowly
across the region Monday, with the front remaining nearby
through late week as a series of low pressure systems track
along it. High pressure will attempt to return by next weekend.
&&
.NEAR TERM /THROUGH MONDAY/...
Made minor adjustments to the forecast for today. A lot of sun
can be expected this morning with clouds increasing this
afternoon. While it was noted that forcing for convection was
limited, it does look like high resolution models are keying in
on a solid region of moisture and theta-e advection, perhaps
aligned with shortwave energy aloft to kick off convection late
this afternoon. Storm are likely to fill in west of the I-71
corridor late this afternoon and spread northeast through about
the I-77 corridor into this evening. It is less certain how the
morning activity along the Ohio/Indiana state line evolves as
many of the 12Z CAMs did not initialize this activity well.
Expect it to largely lift northeast into Michigan but may clip
counties in NW Ohio first. If this round of rain does not impact
counties along the I-75 corridor then may need to lower pops
for this area this afternoon.
Previous discussion...The well-advertised change to a more
active pattern that will bring opportunities for badly needed
rainfall is occurring this morning. The strong Canadian high at
the surface located over New England this morning will drift
offshore through the day allowing the broad mid/upper low over
the Upper Midwest to slowly drift eastward. This low will reach
the northern Great Lakes by Monday, with the trailing cold front
moving into NW Ohio by Monday morning. The front will then take
its time moving east, and all deterministic and ensemble
guidance continues to slow the passage of the front, which now
looks to be Monday afternoon into Monday night. This all points
to good opportunities for most areas to see measurable rain
between now and Monday evening, but the greatest chances have
shifted to late tonight and Monday, with today trending warmer
and drier.
This does not mean that today will be totally dry. A warm front
extending east from the low is sitting over northern Ohio early
this morning, with a well-defined theta-e and instability
gradient gradually lifting north with the front. This front will
continue to lift north of the region through mid morning,
placing all of northern Ohio and NW PA in the warm sector for
this afternoon. Deep southerly flow and associated warm/moist
advection in the warm sector will support a very warm and humid
day. Forecast soundings show little in the way of capping and
MLCAPE values rising over 1000 J/Kg this afternoon, so widely
scattered convection should develop. The main issue is forcing.
Since the progression of the mid/upper low into the northern
Great Lakes has slowed, the main piece of shortwave energy
rotating around its base across Lower Michigan has also slowed
to late tonight and Monday morning. This does not give much
confidence in seeing anything more than isolated to widely
scattered coverage this afternoon and evening, with coverage
slowly increasing from west to east late tonight. With this in
mind, continued the trend of slowing the timing and coverage of
POPs compared to NBM today and tonight, utilizing a mix of NBM
and other hi-res model guidance. If anything can develop this
afternoon and evening, weak deep layer effective shear of 20-25
knots and some dry mid- level air could lead to locally gusty
winds, so a SWODY1 Marginal Risk remains areawide. The best
chance for this is in NW and north central Ohio.
As the aforementioned shortwave and associated 60-80 knot upper
jet streak lift across Lower Michigan late tonight and Monday,
synoptic forcing beneath the right entrance region of the jet
will strengthen frontogenesis ahead of the slow moving cold
front. This combined with a strengthening low-level jet and
resultant moisture advection will finally allow widespread
showers and embedded convection to move into the region. There
will probably be an initial round late tonight and Monday
morning, then depending on how much sunshine and destabilization
can occur in the afternoon, stronger thunderstorms could develop
for the afternoon and evening. Probabilities for most areas to
see at least one half inch of QPF are over 90% late tonight and
Monday, with some areas likely to see over 1 inch leading to
some drought relief. In terms of any severe weather, the latest
HREF shows increasing probabilities for updraft helicity tracks
Monday afternoon over mainly NE Ohio and NW PA. This makes sense
since shear and forcing will be higher, so depending on the
amount of instability, a few severe storms with strong winds are
possible. PWATs over 1.75 inches also support locally heavy
rainfall, but given the drought, any flooding issues would be
super localized to urban areas.
Highs will warm into the mid/upper 80s today, with upper 70s/low
80s Monday. A very mild night is expected tonight, with lows in
the low/mid 60s.
&&
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
Coverage of showers and thunderstorms will decrease Monday night
with loss of daytime heating and as the shortwave and associated
forcing lift out of the region. However, the cold front is
likely to stall over or just SE of the region by Tuesday in
response to a second mid/upper closed low tracking from the
Rockies into the Plains and eventually phasing with the remnants
of the Great Lakes mid/upper low by Wednesday. Guidance is
finally coming into somewhat better agreement on this pattern
evolution, with a broad closed low meandering around the Midwest
and OH/TN Valley regions for the second half of the week. This
will keep an active and moist SW flow in place over the Ohio
Valley and southern Great Lakes regions, with multiple pieces of
shortwave energy traversing the frontal boundary. The main
message with this is that additional rounds of showers and
thunderstorms will occur Tuesday through Wednesday night, but
timing and placement of the heaviest axis of QPF is more
uncertain. The 00Z NAM suggests a strong surface wave rippling
up the front late Tuesday into Wednesday, but this may be
convective feedback. Given the uncertainty with timing the
individual shortwaves and exact placement of the boundary, kept
NBM POPS through the period, with the highest chances gradually
shifting south and eastward by Wednesday and Wednesday night.
The additional rains will bring drought relief Tuesday into
Wednesday, but they will not be all day rains, with plenty of
dry time as well.
Highs in the low/mid 70s Tuesday will cool into mainly the low
70s Wednesday. Lows in the low/mid 60s Monday night will cool
into the upper 50s/low 60s Tuesday night and mainly mid/upper
50s Wednesday night.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
Confidence further decreases in the extended given uncertainty
with how the big closed low will eventually eject which affects
how soon the frontal boundary will push away from the region.
Stayed with NBM POPS and temperatures Thursday through Saturday,
with the idea of a slow drying trend. A deepening northern
stream mid/upper trough diving into the Great Lakes next weekend
may finally kick the old system out, but this may not occur
until Sunday. Highs will generally be in the low 70s with lows
in the low/mid 50s.
&&
.AVIATION /18Z Sunday THROUGH Thursday/...
Cyclonic SW'erly flow aloft and embedded/subtle disturbances
affect our region through 18Z/Mon. At the surface, a front has
stalled in vicinity of the southern shore of Lake Erie as a
ridge lingers over the lake and points farther to the north and
east. The front will finally move N'ward across Lake Erie as a
warm front this evening through the first hour or two of Monday
morning as the ridge exits to the north and east. Behind the
warm front, a separate ridge centered near the southern
Appalachians builds into our region through 18Z/Mon, yet subtle
surface trough axes accompanying the disturbances aloft will
sweep NE'ward through northern OH and NW PA.
Ahead of the front, surface winds trend SE'erly to SSE'erly,
while S'erly to SW'erly winds are expected behind the front.
Our regional surface wind speeds will be around 5 to 15 knots
and gusts up to 20 to 25 knots are expected at times, especially
through ~00Z/Mon and in NE OH and NW PA. Primarily VFR are
expected the rest of this afternoon. Cloud cover will increase
and mid/upper-level ceilings will develop and lower gradually
from the south and west the rest of this afternoon through
evening. Ceilings will then linger and continue to lower Monday
morning through 18Z/Mon. In fact, ceilings near 2.5kft to 5kft AGL
are expected to overspread our region from the south and west
between ~10Z/Mon and ~15Z/Mon.
At 17:10Z/Sun, rain showers were impacting KTOL and vicinity.
These showers are expected to exit NW OH to the northeast by
~17:30Z/Sun. Otherwise, very isolated showers and thunderstorms are
possible through 21Z/Sun. Thereafter, scattered showers and isolated
to scattered thunderstorms are expected to develop and overspread
our region from the southwest, generally, through ~04Z/Mon. Periodic
showers and storms should then continue to impact our region through
18Z/Mon. Brief MVFR to LIFR are possible with showers and especially
thunderstorms. Thunderstorms may produce brief/erratic surface wind
gusts up to 30 to 40 knots, especially through 01Z/Mon and after
16Z/Mon.
Outlook...Periodic non-VFR are expected with scattered showers
and thunderstorms through Thursday.
&&
.MARINE...
Southerly flow is expected today, generally in the 10-15 knot range.
A brief period of 20 knot flow is possible in the eastern basin late
this evening into early tonight. Will have to keep an eye on this
for a potential short duration small craft advisory. Winds tend to
be southwest around 5 to 15 knots Monday through Tuesday before a
cold front crosses Lake Erie Tuesday night. Winds veer to out of the
east-northeast Wednesday and Thursday. Wind speeds are currently
forecast to be around 15 knots though there are low probabilities
for 20 knots and 3-5 ft waves at times, especially in the central
basin.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...None.
&&
$$
SYNOPSIS...Garuckas
NEAR TERM...10/Garuckas
SHORT TERM...Garuckas
LONG TERM...Garuckas
AVIATION...Jaszka
MARINE...Saunders
Source:
CLE issues Area Forecast Discussion (AFD) at Sep 21, 1:23 PM EDT---------------
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