161
FXUS61 KCLE 030133
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
933 PM EDT Thu May 2 2024

.SYNOPSIS...
A warm front will lift north across the area tonight into
Friday, followed by a cold front late Friday into Saturday.
Another cold front will move east across the area on Sunday,
then stall across the southern Ohio Valley on Monday.

&&

.NEAR TERM /THROUGH FRIDAY NIGHT/...
9:33 PM EDT Update...
The forecast remains valid per latest trends in obs and model
guidance. Most showers and thunderstorms have dissipated soon
after entering our CWA from the southwest this evening due to
much less elevated instability toward the northeast and boundary
layer stabilization via nocturnal cooling. However, isentropic
ascent along the upper-reaches of the warm front is expected to
tap into additional moisture from the southern Gulf Stream and
Gulf of Mexico, and destabilize overnight tonight through early
tomorrow afternoon. As a result, expect isolated showers and
thunderstorms to become more prevalent over our CWA, especially
after midnight tonight. See discussions below for further
details.

7:50 PM EDT Update...
Most of the forecast remains valid. However, freshened POP`s,
QPF, and sensible WX grids through early Friday afternoon. These
changes are based on latest trends in obs and model guidance.
The surface warm front is beginning to drift NE`ward into far-
southwestern parts of our CWA. The warm front will drift NE`ward
across the rest of our CWA through early Friday afternoon.
Isolated showers and thunderstorms are expected to accompany the
warm front passage due to the following: Moist isentropic
ascent releasing weak, yet sufficient elevated CAPE along the
upper-reaches of the front and convergence/associated moist
ascent along the surface warm front releasing sufficient CAPE
amidst a surface-based effective inflow layer through this early
evening and again late tomorrow morning through early afternoon
given an expected typical diurnal cycle in boundary layer
temperatures, CIN, and CAPE. At this time, the upcoming cold
front is expected to drift E`ward through our CWA late tomorrow
morning through early evening. Additional and scattered
showers/thunderstorms are expected amidst a favorable thermodynamic
environment along and ahead of the cold front. See discussion
below for further details.

Previous Discussion...
An active short term period is in store with widespread showers
and thunderstorms expected Friday afternoon and evening.
Severe weather chances remain very low, although can`t rule out
a strong storm or two, especially east of the I-71 corridor
Friday afternoon and evening. Heavy rain may also accompany any
stronger storms.

For this evening and overnight, starting to see signs of the
warm front across the Ohio Valley, evident by a well-defined cu
field surging north. Have kept the chance for an isolated
shower/storm later this evening across NW OH as the interaction
between the Lake Erie lake breeze front and warm front could
result in increased convergence and lift. As we head overnight
into Friday, a cold front will begin to approach the area from
the west, with shower and thunderstorm coverage expected to
increase across portions of southern Michigan, Indiana, and
eventually into Northwest Ohio. Will need to monitor outflow
patterns from this overnight convection as these boundaries
appear to be driving the shower/thunderstorm initiation for
Friday afternoon and evening.

The updated SPC SWODY2 keeps much of the area in a general
thunder risk for Friday. This appears reasonable given weak
MLCAPE of 500 J/kg or less in addition to bulk shear less than
30 knots. However, still can`t rule out a stronger storm or two
with wind being the primary risk as low-level lapse rates remain
elevated, especially east of the I-71 corridor ahead of the
pre-frontal nocturnal convection. Would typically also be
concerned about heavy rainfall given slow storm motions, but
seasonable PWATs less than 1.50 inches should limit the overall
flash flooding threat, especially as current FFGs are hovering
around 2" in 3 hours.

Only big change to the temperature forecast on Friday was to
utilize the 25% NBM which increased highs out east ahead of the
convection, and lowered highs out west where
showers/thunderstorms are expected to linger.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
The weekend will start off unsettled as a weak stationary front will
be draped in the vicinity of eastern Ohio, western PA, and the
northern Appalachians Saturday due to rather strong mid/upper
ridging holding over the eastern CONUS and the upper support lifting
well to the NW over James Bay. The front will essentially be washed
out and only serve as a weak wind shift, but pooling low-level
moisture near and along it combined with weak upper level diffluence
will keep showers and a few thunderstorms going, especially over
areas east of I-77. The coverage of the precip is uncertain though
because there is no real forcing other than moisture pooling and
weak diffluence, and cloud cover will hold down instability, with
only a few hundred joules of SBCAPE projected by HREF guidance. This
may lead to a lot of drizzle and low clouds, with the heavier
showers and thunderstorms more limited. Nevertheless, since forcing
is weak, the flow through the column will be weak leading to slow
moving showers/storms which could lead to localized flooding,
especially in areas that see heavy rain Friday night. Deep layer
flow parallel to the stalled front supports this potential with any
deeper convection that manages to develop, but PWATs will not be
especially high (averaging 1.50 inches which is climatologically
normal). This will truly keep the flood threat localized, with most
areas just seeing some beneficial rain.

By Saturday night and Sunday, a weak mid/upper shortwave moving
through the central Great Lakes will slowly push a secondary cold
front across the region from NW to SE, which will overtake the old
frontal boundary. This will start to gradually push the best chances
for showers/storms farther SE, so have the highest PoPs gradually
shifting farther SE Saturday night and Sunday. By Sunday night, it
looks like the boundary will finally be far enough away for mostly
dry conditions as surface ridging and associated drier air build in
from the north, so kept PoPs mostly slight chance Sunday night. All
in all, not a washout this weekend by any means, but Sunday will
have less coverage of precip than Saturday.

Highs Saturday will be kept in the low/mid 70s in most areas, with
upper 60s in far eastern Ohio and western PA where clouds and precip
will be greater. Sunday will be slightly warmer with highs in the
low/mid 70s areawide thanks to a bit more sunshine and less precip.
Lows Saturday night will range from the mid 50s to low 60s, with
low/mid 50s Sunday night and decreasing humidity as the drier air
finally works in.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
An active pattern will quickly return next week as a strong
mid/upper shortwave trough moves through the Rockies Monday then
gradually lifts into the Northern Plains and Upper Midwest by
midweek. This will force downstream height rises over the eastern
CONUS, with flat ridging across the Ohio Valley and Mid Atlantic
regions. The frontal boundary from Sunday will start to lift back
north as a warm front in response to the height rises and developing
southerly flow Monday and will then set up as a quasi-stationary
east-west front/baroclinic zone Tuesday through Thursday. Shortwave
impulses ejecting out of the broader upstream trough will traverse
this boundary and interact with increasingly rich low-level moisture
and instability to generate multiple MCS clusters. This could bring
strong to severe storms and heavy rainfall. The overall pattern is
becoming more clear, however, the details are still very uncertain
regarding where this boundary will ultimately set-up. It will likely
waver a bit north and south. As of now, the strongest shortwave
seems to be Tuesday and Tuesday night, so have the highest PoPs at
that time. However, given the uncertainty with this pattern, kept a
broad brushed, blended PoP forecast with at least high chance PoPs
Monday through Thursday. It will definitely not rain all the time,
but again, we could have multiple rounds.

Highs in the upper 60s to low 70s Monday will warm back into the
upper 70s to low 80s Tuesday and Wednesday, then cool slightly into
the mid/upper 70s Thursday.

&&

.AVIATION /00Z Friday THROUGH Tuesday/...
Aloft, a ridge exits E`ward through 06Z/Fri and is followed by
SW`erly flow and embedded disturbances through 00Z/Sat. At the
surface, a ridge exits as a warm front drifts NE`ward through
our region through ~18Z/Fri. Behind the warm front, a cold front
should begin to drift E`ward across our area after 14Z/Fri and
near the longitude of KERI by 00Z/Sat. Our regional surface
winds are expected to be around 5 to 10 knots through the TAF
period. Variable wind direction ahead of the warm front is
expected to become S`erly to SW`erly behind the warm front and
ahead of the cold front. Behind the cold front, regional surface
winds veer to W`erly to NW`erly.

VFR ceilings are expected to overspread our region generally
from southwest to northeast and lower gradually prior to the
surface cold front passage. Behind that front passage, widespread
MVFR ceilings are expected. Isolated showers and thunderstorms
should accompany and precede the NE`ward passage of the surface
warm front through early Friday afternoon. Scattered showers and
thunderstorms are then expected along/ahead of the surface cold
front. Any MVFR ceilings ahead of the cold front should be
isolated and brief. Additional scattered rain showers are
likely for several hours following the passage of the surface
cold front and will be associated with the upper-reaches of the
front. VFR visibility is expected outside precip, while visibility
should be no lower than MVFR in precip.

Outlook...Non-VFR likely with periodic showers and thunderstorms
through this Tuesday.

&&

.MARINE...
Quiet weather will continue on the lake through the period as
pressure gradients remain weak. The only impactful winds and waves
will come from localized stronger thunderstorms. E to NE winds will
decrease to 5-10 knots tonight and Friday, with ENE winds then
increasing back to 10-15 knots Saturday before turning SE at 10-15
knots Saturday night and finally swinging all the way around to W to
NW Sunday while decreasing to 5-10 knots. NE winds will then
redevelop Sunday night and increase to 10-15 knots Monday before
turning SE Monday night and Tuesday.

&&

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

&&

$$

SYNOPSIS...Kahn
NEAR TERM...Jaszka/Kahn
SHORT TERM...Garuckas
LONG TERM...Garuckas
AVIATION...Jaszka
MARINE...Garuckas