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Area Forecast Discussion
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FXUS61 KCLE 252109 AAA

Area Forecast Discussion...UPDATED
National Weather Service Cleveland OH
509 PM EDT Sun Sep 25 2022

A trough will linger across the Great Lakes Region through the first
half of the week bringing a stretch of below normal temperatures.
High pressure will build east across the Great Lakes by Wednesday
and Thursday.


The main focus of the near term forecast will be the potential
for heavy lake effect rainfall downwind of Lake Erie. An upper
level trough has moved over the Great Lakes Region and will
continue to deepen overnight as a secondary piece of energy
slides from the Upper Midwest across Lake Erie. Bands of showers
with a few pockets of thunderstorms continue across the area
this evening but are expected to decrease in coverage with the
loss of daytime heating. As the next trough approaches
overnight, low level flow starts to back with convergence
increasing across the lake once again. This should lead to
renewed lake enhanced rain showers over and downwind of Lake
Erie. There are several factors that will make the environment
more favorable for lake effect rain during the near term. These
include a cooling airmass with 850mb temperatures down to
around 4C by 12Z Monday along with a cold pool aloft and 500mb
temperatures dropping to around -24C. In addition, the lake
remains warm with lake induced CAPE values ranging from
1000-1500 J/kg through Tuesday night. Low level flow backs on
Monday with nearly uni-directional flow through 700mb resulting
in lake effect rain bands developing down the long axis of Lake
Erie. As we already observed this morning, high rainfall rates
of 2+" per hour occurred with thunderstorms in Lake County.
Rainfall is expected to be efficient and heavy at times over the
next 48 hours. The rainfall is expected to become focused
closer to the lakeshore or possible even shift out over Lake
Erie for a time on Monday. A secondary cold front will cross the
lake Monday night shifting heavier rain back a little farther
inland. This veering flow could also result in an increase in
rain back to the west across eastern Cuyahoga and Geauga
Counties on Tuesday.

Due to the potential for heavy rain, a Flood Watch has been
issued for Lake, Ashtabula, and Erie Counties from 4 AM tonight
through 5 AM Wednesday morning. The QPF forecast during this
time is a difficult one in terms of actual amounts given
uncertainty in placement of bands. However given the potential
for high rainfall rates and training of rain/thunderstorms, the
concern is there for the northern portions of any of these
counties to see flooding or flash flooding. High resolution
models are in good agreement in placing 2-4" of rain across the
watch area with some models showing pockets of rainfall in
excess of 6". High rainfall rates can lead to flooding of urban
and poor drainage area as well as rises on area creeks, streams,
and rivers. Can not rule out the need to expand the flood watch
into Cuyahoga or Geauga Counties later in the event depending
on placement of bands but thought that would take some time to
become more of a threat.

Outside of the snowbelt, an uptick in showers is expected across
norther portions of the area on Monday afternoon, then more
focused to the snowbelt/eastern areas on Tuesday. Temperatures
will be below normal through the near term with highs mainly in
the lower 60s except some upper 50s across the snowbelt areas.
West southwest winds will be breezy on Monday with gusts of
25-30 mph ensuring it feels like a fall day.


Aloft, cyclonic W`erly to N`erly flow persists over our CWA
through Wednesday as a deep longwave trough exits slowly
eastward from the Great Lakes and Upper OH Valley, and toward
the Northeast U.S. and Mid-Atlantic states. Simultaneously, a
ridge will build slowly eastward from the Rockies and Great
Plains. At the surface, a reinforcing cold front should sweep
southeast across our CWA Tuesday night through Wednesday morning
as a trough lingers over the Lower Great Lakes and Upper OH
Valley. Multiple bands of lake-effect rain showers and
thunderstorms persist over and generally south of Lake Erie
amidst a NW`erly to N`erly mean low-level flow. This flow will
remain sufficiently-cold and moist across the ~69F lake and
yield moderate to strong lake-induced CAPE. Low-level
convergence along the front should enhance the lake-effect
showers and thunderstorms Tuesday night. Torrential rainfall may
lead to localized flash flooding where rain bands persist the
longest. The best chance for lake-effect precip should be
focused across northeast OH and northwest PA, and in north-
central OH to a lesser extent. Fair weather is likely elsewhere.
Low temperatures should primarily reach the 40`s around
daybreak Wednesday and be followed by highs only in the mid 50`s
to 60F late Wednesday afternoon.

The ridge aloft continues building eastward Wednesday night,
allowing the accompanying surface ridge to build from the western
Great Lakes. Lingering and tapering lake-effect rain showers
streaming generally SSE`ward Wednesday evening should end by the wee
hours of Thursday morning as lake-induced CAPE wanes via a lowering
subsidence inversion and low-level dry air advection. Otherwise fair
weather is expected. Lows should reach mainly the 40`s around
daybreak Thursday morning.


At this point, primarily fair weather is expected through the period
as the building ridge aloft eventually crests eastward over our CWA
and the surface ridge continues to influence our region. However, TC
Ian should make landfall along the Gulf Coast of the FL Panhandle on
Friday. Its eventual remnant low should then track generally
NNE`ward toward the Mid-Atlantic region through this weekend. Weak
and moist isentropic ascent aloft accompanying the low may allow
isolated to scattered rain showers to affect our CWA Saturday into
Sunday, but major impacts are not expected at this time. Daily
afternoon highs should mainly reach the 50`s Thursday and the 60`s
to near 70F Friday through this weekend. Overnight lows should
mainly reach the 40`s, but mid to upper 30`s are forecast in
interior northwest PA Thursday night. This is where patchy frost is
possible around daybreak Friday morning.


.AVIATION /18Z Sunday THROUGH Friday/...
Bands of showers with a few thunderstorms are filling in across
the area this afternoon and could impact any terminal. Best
focus for thunderstorms is along the cold front extending from
near Youngstown to Canton with a chance of thunderstorms at
CAK/YNG, mainly through 20Z. Aviation conditions may briefly
drop to MVFR in heavier showers this afternoon. Otherwise the
trend will be towards VFR heading into tonight, except with
MVFR downwind of Lake Erie at ERI/YNG. Main challenge tonight
into Monday will be timing lake enhanced rain showers. These are
expected to fill in and become more steady after 10Z at ERI and
could be accompanied by thunderstorms. Passing showers will also
be possible at CLE and YNG heading into Monday. Winds are
veering to west or northwest behind the cold front with gusts to
around 20 knots this afternoon. Winds are expected to back to
southwesterly at many sites tonight and Monday as a trough
resides over Lake Erie. Winds will be breezy again on Monday
with gusts of 20-25 knots.

Outlook...Non-VFR possible in isolated to scattered showers and
thunderstorms through Wednesday. The most-persistent showers and
storms are expected to generally impact ERI, though could see
fringe sites like CLE/YNG experience some impacts as well.


In short, the first half of the week will not be conducive for
recreational marine activities on Lake Erie. The combination of a
deep upper trough and strong low pressure system across the region
will support elevated westerly flow through Tuesday and will
continue the Small Craft Advisory and Beach Hazards Statements, as
is, this afternoon. The trough and low combination along with some
cold, Autumn air will allow for continued showers and perhaps
thunderstorm activity across the lake through Tuesday. The
combination of these organized lake enhanced showers and good lake-
induced instability will allow for a chance for waterspouts through
Wednesday night. However, a strengthening low-level jet on Monday
may allow for too strong of a wind field to support waterspout
development. With the jet on Monday, there will a window with higher
winds on the lake as the jet will mix down to the warm lake and
suspect winds will reach 30 knots. There is a non-zero gale chance
on the lake, but the forecast is on the higher end of guidance at
the moment and will defer on a gale headline for now.

The surface low will exit to the east on Tuesday night into
Wednesday and a residual trough will remain across the lake. Flow
will shift more northwesterly and weaken. However, enough onshore
flow will be present where a marine headline will be needed for the
eastern half of the lake for Tuesday night into perhaps Wednesday.
High pressure will build across the lake by Wednesday night. Light
northerly to easterly flow will take hold through Friday with waves
subsiding to 3 feet or less.


OH...Beach Hazards Statement through Tuesday evening for OHZ007-009.
     Beach Hazards Statement through Wednesday morning for
     Flood Watch from 4 AM EDT Monday through late Tuesday night
     for OHZ012-014-089.
PA...Beach Hazards Statement through Wednesday morning for PAZ001.
     Flood Watch from 4 AM EDT Monday through late Tuesday night
     for PAZ001-002.
MARINE...Small Craft Advisory until 8 PM EDT Tuesday for LEZ142>144.
     Small Craft Advisory until 8 AM EDT Wednesday for LEZ145>149.


LONG TERM...Jaszka

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  • Page last modified: Sep 6th, 2022 18:00 UTC