341
FXUS61 KCLE 221940
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
340 PM EDT Sun Sep 22 2024

.SYNOPSIS...
A warm front continues to lift northeast across the area this
afternoon before an associated cold front pushes east tonight
into Monday. Additional disturbances will impact the area
through Wednesday before high pressure returns for the end of
the week.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
A weak low pressure centered over Michigan continues to move a
warm front northeast across the area this afternoon. Behind this
front, increased WAA and predominately clear skies has allowed
temperatures to surge into the mid to upper 80s for much of the
area. The exception to this is near the lakeshore that is being
impacted by a lake breeze and in far northwest Pennsylvania.
Upstream of the CWA, showers and thunderstorms have become more
widespread ahead of an approaching cold front. There are weak
reflectivities over the western tier of counties, however with
limited low level moisture (dewpoints in the 50s) all of this
precipitation is evaporating before reaching the surface. It
will take a bit for the column to become saturated, allowing for
showers to truly initiate in the area closer to 21Z. There
remains a potential of a few thunderstorms across western
counties, but given the dry and fairly stable antecedent
conditions, not expecting anything widespread. In any
thunderstorms that develop, the primary concern will be gusty
winds at the surface with locally heavy rainfall. Overnight lows
will remain mild, dropping into the mid-60s.

Showers will gradually diminish from west to east late tonight
into Monday as a cold front moves east across the area. On that
back end of the low, northwest flow across Lake Erie will result
in the potential for scattered, light lake enhanced showers
across the snowbelt areas, but with marginal 850-mb temperatures
confidence is low on timing and extent. Highs on Monday will be
much cooler than recent days, only climbing into then low to
mid 70s with widespread cloud cover expected.

Another low pressure system will begin to impact the area at the
tale end of this period. Showers will initially impact the
southwestern tier of counties, gradually spreading northeast
late Monday into early Tuesday. Not expecting any thunder with
these showers given the diurnally unfavorable environment, but
cannot rule out a few locally heavy showers. Monday night lows
will drop into the low to mid 60s with the warmest temperatures
isolated to the lakeshore.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Unsettled but relatively low-impact weather is expected this period.
A weakening shortwave and associated surface low will lift northeast
into the Great Lakes Tuesday and Tuesday night. This will first lift
a warm front across the area Tuesday morning into the early
afternoon. The low`s trailing cold front will start pushing into
northwestern Ohio Tuesday evening, though with the low lifting
northeast while weakening this front will be weakening as it pushes
east. The front will likely still be slowly working east-southeast
across the area on Wednesday before clearing by Wednesday night.

There will be opportunities for showers and thunderstorms Tuesday
into Tuesday night, both with the lifting warm front and along and
ahead of the approaching cold front. There is some disagreement
regarding how quickly the surface low will begin to weaken and fill,
with the European model on the stronger side of the envelope and the
NAM on the weaker side. While the NAM appears to be an outlier among
the operational models there are some ensemble members that also
have a weaker system with less QPF. This leads to enough uncertainty
to keep peak POPs for Tuesday and Tuesday night in the 70-80% range
for now (as opposed to continuing to push up towards 100%). Also
went with a blended approach for QPF Tuesday and Tuesday night with
generally 0.40-0.80" of QPF in the forecast for that period, highest
across parts of northeastern Ohio. There is some room for both POPs
and QPF to trend up if we see increasing confidence in a stronger
solution ala the 12z European model. We should see a general lull in
activity overnight Tuesday night into Wednesday morning, though with
the cold front still working through the area some hit or miss
shower activity may persist. Expect to see some increase in coverage
of showers (and possibly a bit of thunder) across our southeastern
counties along/ahead of the cold front with heating Wednesday
afternoon, though forcing will be weak so coverage should have a
hard time increasing beyond "scattered". The front should take any
showers with it as it exist southeast into Wednesday night.

In terms of potential hazards with any of the thunderstorms Tuesday
into Tuesday evening, forecast soundings may support localized
training of heavy rainfall with unidirectional deep-layer flow,
seasonably high precipitable water values, and humid profiles with
tall/skinny instability. However, we need the rain so suspect it
will mainly be beneficial with just a low probability for a
localized flooding issue if training occurs over an especially prone
(i.e. urban) area. With questionable amounts of heating and weak mid-
level lapse rates, most guidance suggests it will be difficult to
see more than about 1000 J/KG of MUCAPE with MLCAPE values
struggling to exceed 500-750 J/KG. While effective deep-layer shear
of 25-35 knots could support organized convection, the poor
thermodynamics are expected to limit or preclude severe potential.

Highs on Tuesday will range from the upper 60s across interior
northwest PA to the low to mid 70s across most of northern OH. Lows
Tuesday night will struggle to dip below 60 in the relatively humid
airmass. Highs will be in the 70s on Wednesday, with lows Wednesday
night expected to range from the mid 50s to lower 60s.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
A somewhat uncertain long term forecast as the local area will be
beneath a small ridge axis aloft between a cut-off low over the
south-central CONUS and a longwave trough over the northeast. The
ridge axis will generally encourage drier weather, though guidance
disagrees on whether or not the cut-off to our southwest can try
drifting east through the weekend. There`s enough uncertainty that
we carry some low-chance (30%) POPs across our southwestern zones at
times at the end of this week into the weekend, with silent 20% POPs
elsewhere. Temperatures will continue to lean milder than average
for this period unless the forecast trends rainier.

&&

.AVIATION /18Z Sunday THROUGH Friday/...
VFR conditions are expected to continue into the evening hours
before the chance of showers begins to spread west to east ahead
of an approaching cold front tonight. Surface conditions across
the area will start out rather dry, making it difficult for
visibilities and ceilings to diminish below VFR conditions.
However, once showers become well established and low level
moisten, expect ceilings and visibilities to drop to MVFR,
possibly IFR in the heaviest showers. Along the cold front
moving east Monday morning, ceilings are forecast to fall to
high-end IFR for many of the terminals. Thunder cannot be ruled
out, especially for western terminals, but given the diurnally
unfavorable environment, opted to only include VCTS to western
terminals. Conditions will gradually dry out behind the cold
front, but ceilings of 1500-2500 feet are expected to linger
through the period.

Winds this afternoon west of I71 are from the southwest at 5-10
knots as a warm front lifts north of the area, with light and
variable winds elsewhere. A lake breeze is trying to become
established in areas of weaker winds along and east of I71,
likely impacting KCLE and KERI in the coming hours. Tonight,
winds become light and variable. These winds will gradually
become northwesterly at 5-10 knots on Monday behind the cold
front moving across the area.

Outlook...Non-VFR possible in scattered showers and
thunderstorms and low ceilings tonight into Monday. Non- VFR
likely Monday night through Tuesday in showers and thunderstorms
and low ceilings. Non-VFR conditions may linger through
Wednesday.

&&

.MARINE...
A small area of low pressure will pass near or over Lake Erie on
Monday. A warm front will lift across the lake ahead of it tonight
into early Monday, shifting east winds to the south at 10-15 knots.
Winds will quickly turn more north-northwesterly from west to east
on Monday behind the passage of the low, with speeds of 10-15 knots
continuing. Another low will lift out of the lower Ohio Valley and
into the central Great Lakes Tuesday into Tuesday night. A warm
front will lift across the lake on Tuesday, shifting winds to an
easterly and then southeasterly direction ahead of the low. Speeds
will increase to 10-15 knots with the warm frontal passage, with
some brief 15-20 knot speeds possible east of Conneaut. Winds will
gradually turn west-northwesterly Wednesday and Wednesday night as
the trailing cold front moves through, though with the system
generally weakening am not expected much of a push of wind with the
cold front. Winds turn turn east-northeast Thursday into the weekend
as the lake becomes situated between a cut-off low well to our
southwest and high pressure to the north. Speeds should remain
modest through Thursday night. A period of 15-20 knot east-northeast
flow is in the forecast Friday into Saturday, with a brief period of
stronger flow possible depending on the intensity of the cut-off
low. Overall, it will be choppy at times through midweek but
conditions should remain below small craft criteria. There is
some potential for small craft headlines around the end the
week.

&&

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

&&

$$

SYNOPSIS...Campbell
NEAR TERM...Campbell
SHORT TERM...Sullivan
LONG TERM...Sullivan
AVIATION...Campbell
MARINE...Sullivan