512 
FXUS61 KCLE 120603
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
203 AM EDT Tue Sep 12 2023

...06z TAF Aviation Forecast Update...

.SYNOPSIS...
Low pressure crossing the central Great Lakes tonight will drag
a strong cold front across the region late tonight and Tuesday.
A trough will persist across the Great Lakes region through
Wednesday before high pressure builds in Thursday and remains in
place into next weekend.

&&

.NEAR TERM /THROUGH TODAY/...
930 PM Update... 

Showers should start moving into NW OH over the next couple of
hours, before making their way into the CWA by late tonight 
into the overnight. No changes needed with the forecast beyond 
making minor adjustments to dew points and temps based on 
current observations. Don't expect much overnight cooling due to
weak warm air advection.

Previous Discussion...

The welcome sunshine this afternoon unfortunately will not last
long as a deep mid/upper trough is already digging into the
Upper Midwest with an associated surface low in the vicinity of
Lake Michigan. This is extending a strong cold front across
Illinois and Indiana through central Missouri. The mid/upper
trough will gradually dig into the western Great Lakes tonight
and into the central Great Lakes and Ohio Valley by late
Tuesday and Tuesday night. As this occurs, a 80-90 knot H3 jet 
streak rounding the base of the digging trough tonight and 
Tuesday will place the lower Great Lakes in the favorable right 
entrance region. This will strengthen frontogenesis along and 
ahead of the cold front as it slowly progresses eastward across 
northern Ohio and NW PA tonight into early Tuesday afternoon. 
This will result in a band of widespread rain moving slowly west
to east across the region. In terms of timing, the rain should 
reach the I-75 corridor in the 03-06Z timeframe, the I-71/I-77 
corridors by 09-11Z, and the OH/PA borders by 13-16Z. The rain 
will last a solid 3 to 4 hours at each location as it moves 
east, so used a narrow swath of likely to categorical PoPs 
progressing west to east tonight and Tuesday. A 20-30 knot low- 
level jet in response to the aforementioned upper forcing will 
advect higher PWAT values into the region tonight and Tuesday 
morning with dew points rising into the low 60s, but PWAT values
capping in the 1 to 1.25 inch range (seasonable for mid 
September based on daily sounding climatology) combined with 
drier conditions over the past 2 weeks will prevent any flooding
risk. Most areas will see 0.50 inch or less of QPF despite the 
band of steadier rain, so soils can easily handle it. Chances 
for thunder are further diminishing based on upstream radar 
trends indicating stratiform rain, and with the overnight timing
and abundant precip around, any thunder will be spotty. 
Nevertheless, the low-level jet will lead to a slight amount of 
elevated instability, so kept slight chances for thunder 
overnight.

The band of steadiest rain will gradually progress east of the
region with the front Tuesday afternoon, but it will take until
mid to late afternoon to clear far eastern Ohio and western
PA. This will allow for gradual drying from west to east. As 
the mid/upper trough axis shifts toward the central Great Lakes
Tuesday evening and Tuesday night, wrap around moisture and an
approaching surface trough from the NW will bring scattered
showers back into the region, so kept chance PoPs in most areas
Tuesday evening into Tuesday night. Increasing cold air
advection across Lake Erie Tuesday night with 850 mb temps
falling to 6 to 7 C, abundant lift/PVA from the trough aloft,
plenty of wrap around moisture and deep cyclonic flow, and lake
temps still in the low 70s F will set up lake-effect rain 
showers. An initial W to WSW boundary layer flow will first 
develop the rain bands up the lakeshore east of Cleveland into
NW PA, but as the aforementioned surface trough crosses the 
lake later Tuesday night, the bands will push inland as the flow
veers. Some of this rain could be moderate to briefly heavy 
given moderate to strong lake induced instability and increased 
low-level convergence along the surface trough. 

Highs Tuesday will only reach the low 70s with lows in the upper
50s/low 60s tonight and low/mid 50s Tuesday night. NW Ohio could
fall into the upper 40s Tuesday night where skies begin to clear.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...
A deep/expansive trough aloft resides over the Great Lakes, Upper OH 
Valley, and vicinity through Wednesday night as the trough axis 
moves from near central ON and the southwestern Great Lakes toward 
the Upper St. Lawrence River Valley and northeastern U.S. At the 
surface, a trough lingers over/near our CWA as a ridge attempts to 
build from the Upper Midwest. Net low-level CAA causing 850 mb 
temperatures to fall from near 8C to near 5C over ~23C Lake Erie 
combined with abundant/fairly deep moisture and WNW'erly to NW'erly 
mean flow in the low-levels will cause bands of scattered lake-
effect rain showers to occur over/downwind of Lake Erie, especially 
in/near our snowbelt counties. The trough at the surface and aloft 
exits gradually E'ward on Thursday through Thursday night as high 
pressure at the surface and aloft builds from the Upper Midwest and 
vicinity. Lingering lake-effect rain showers amidst primarily 
NW'erly mean low-level flow will weaken and should end by sunset 
Thursday evening as lake-induced CAPE wanes via low-level dry air 
advection and a lowering subsidence inversion accompanying the 
building ridge. Fair weather is likely outside the lake-effect 
precip through the short-term period. An usually-cold air mass is 
forecast to affect our CWA through the short-term period. Daily 
afternoon highs should reach only the 60's. Overnight lows should 
reach mainly the mid 40's to lower 50's around daybreak on Thursday 
and Friday.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Fair weather is expected Friday through Saturday as the stabilizing 
ridge at the surface and aloft builds and eventually crests E'ward 
over our CWA. Net low-level WAA should accompany the ridge and 
contribute to afternoon highs reaching the upper 60's to lower 70's 
on Friday and mainly the lower to mid 70's on Saturday. Overnight 
lows should reach mainly the mid 40's to lower 50's around daybreak 
Saturday morning. Isolated to scattered rain showers are possible 
Saturday night and especially on Sunday through Monday as the ridge 
at the surface and aloft exits E'ward, a trough at the surface and 
aloft overspreads our CWA from the western Great Lakes and vicinity, 
shortwave disturbances ripple generally E'ward through the trough 
aloft and their axes are preceded by moist isentropic ascent, and a 
surface cold front sweeps generally E'ward through our CWA on 
Sunday. Daytime highs should reach the upper 60's to mid 70's on 
Sunday and the mid 60's to lower 70's on Monday in the slightly 
cooler air mass behind the expected cold front. Overnight lows 
should reach mainly the 50F to 55F range around daybreak on Sunday 
and Monday mornings, respectively.

&&

.AVIATION /06Z Tuesday THROUGH Saturday/...
The main weather concerns for aviation with this TAF update will
be ceilings lowering to MVFR and some locations to lower MVFR
later this morning through the afternoon. Clouds are increasing
from west to east through the predawn hours. Scattered light
rain showers will also move in this morning through the 
afternoon as a cold front pushes through the area. Eventually,
we will moisten up enough later this morning through the early
afternoon to have slight visibility reductions dropping to 4sm 
or 5sm due to the light rain showers and misty conditions.

Ceilings and conditions will improve after the frontal passage
today with VFR returning to most sites by this evening or the 
end of the TAF period. Skies will clear out first over northwest
Ohio including FDY and TOL. Overcast ceilings will hold across 
much of NEOH and NWPA through this evening into the overnight 
due to lake effect clouds coming off Lake Erie. YNG and ERI as 
well as much of the Snowbelt areas will stay with MVFR ceilings 
through the overnight. Scattered lake effect rain showers will 
also continue for the Snowbelt TAF sites into the overnight 
hours. 

Winds will be light 5 to 10 knots during the next 24
hours. Light south-southwesterly winds this morning will shift
to more westerly during the day today and eventually becoming
northwesterly by this evening and tonight. 

Outlook...Non-VFR possible in lake effect rain showers, mainly 
for the areas of the Snowbelt downwind of Lake Erie, Tuesday 
night through Wednesday.

&&

.MARINE...
Variable winds around 5 to 10 knots through this early evening are 
followed by primarily southeasterly winds of 5 to 15 knots veering 
to southwesterly tonight as a warm front sweeps northeastward over 
Lake Erie. Winds around 5 to 15 knots then veer to westerly and then 
toward northwesterly on Tuesday as a cold front sweeps generally 
eastward across the lake. Winds remain around 5 to 15 knots as a 
trough lingers over Lake Erie through Wednesday night and a ridge 
begins to build from the western Great Lakes and vicinity on 
Thursday. Of note, waterspouts may accompany showers/storms along 
Tuesday's cold front and then lake-effect rain showers Tuesday night 
through Wednesday night. Waves should trend 3 feet or less, but 
occasional 4 footers are possible on Tuesday through Thursday 
morning. These forecast marginal conditions preclude the issuance of 
a Small Craft Advisory. Variable winds around 5 to 10 knots are then 
expected Thursday night through Saturday as the ridge continues to 
build. Waves should trend 3 feet or less.

&&

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

&&

$$

SYNOPSIS...Garuckas
NEAR TERM...Garuckas/Maines
SHORT TERM...Jaszka
LONG TERM...Jaszka
AVIATION...Griffin
MARINE...Jaszka