724
FXUS61 KCLE 070912
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
512 AM EDT Tue May 7 2024

.SYNOPSIS...
A frontal system moves through the region today and tonight.
Brief high pressure Wednesday followed by another low pressure
system Wednesday night into Thursday.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
515 AM Update...
No changes this morning.

Previous Discussion...
Stationary boundary that is stalled over the Ohio Valley will begin
its push back northward in response to an upper level closed low
slowly ejecting from the intermountain west into the northern plains
region. This upper low and the associated surface system will be
occluding, but that will not completely stifle the eastward progress
of the frontal system. This synoptic scale regime sets the stage for
a potential severe weather threat for much of the forecast area
today into early tonight. A couple of things will need to happen
first, however. First there needs to be a push of low level moisture
into the region as the column RH is on the lower side as we start
out. This moisture flux will occur once the low level flow becomes
southerly and increases, after 16Z today. Will also see a pronounced
increase in the low level flow into western Ohio after 18Z spreading
eastward, just a few hours later. One thing to watch for with the
warm front is the northward extent that it can track, possibly held
up by an onshore ENE wind from the position of a weak high pressure
system over eastern Lake Ontario and upstate New York. This could be
a tricky boundary. For one, it is a place for surface convergence,
but the immediate near surface air over the lake is more stable.
That said, elevated convection could still fire with some backing of
the surface wind, and in the near saturated inversion over the lake,
it could lower the LCLs in that area. Otherwise, expect
destabilization across the area to occur aided by heating today,
setting up vertical profiles in the afternoon for the western half
of the CWA that are characteristic of high CAPE above the boundary
layer, some drying above 600mb or so, a 75mb thick inverted V
boundary layer, increasing low/mid level flows, and around 50-80
degrees of veering of the winds with height through the mid levels.
In the end, a pretty good severe risk today into early tonight given
all of these factors coming into play. Current expansive line of
convection that is moving into the Mississippi Valley extending from
Minnesota back southward through Missouri and then southwestward
into Oklahoma will push into the CWA around 18Z or so. This should
be just prior to the aforementioned low level moisture influx and
shear increases, and expect this to decay as it moves eastward
without much low/mid level support yet. The better threat comes from
the next complex forming in its wake. Will need to watch to see if
the atmosphere can recover, which it should do so from a dynamic
standpoint, but always need to be wary of lingering convective
debris. Cold front moves through west to east 03-09Z Wednesday with
high pressure influences from the south moving in for tomorrow, and
a dry forecast largely after 10Z. Temperatures mainly in the 70s
both today and Wednesday, with perhaps a few low 80s over the
southern zones Wednesday.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
Surface troughing is expected to reside over/near our CWA Wednesday
night as a trough aloft approaches from the north-central U.S. and
Upper Great Lakes. The attendant surface low should advance E`ward
from near central IL to near the border of central IN/OH. Most of
our area should reside in the cold sector, but the west-to-east-
oriented front preceding the surface low should remain nearly-
stationary across central OH, south of the U.S. Route 30 corridor.
Convergence/associated moist ascent along the surface front should
release weak boundary layer instability and moist isentropic ascent
along the upper-reaches of the front should release weak elevated
instability, leading to periods of scattered rain showers. Isolated
general thunderstorms are possible, but despite the expectation of
moderate deep layer bulk shear, the concern for severe thunderstorms
is continuing to decrease given a relative dearth of MUCAPE forecast
in/near our CWA. Overnight lows should reach the 50`s to lower 60`s
around daybreak Thursday. The warmest lows are expected south of the
surface front.

The aforementioned trough aloft and embedded shortwave disturbances
are expected to shift slowly from the western Great Lakes and
vicinity to the eastern Great Lakes and Upper OH Valley on Thursday
through Friday. Simultaneously, the attendant surface low is
expected to continue to move generally E`ward and then ENE`ward
along the preceding surface front (i.e the low should advance from
near the border of central IN/OH around daybreak Thursday morning to
near the Gulf of Maine by nightfall Friday evening. In the wake of
the low, a much colder air mass is expected to overspread our CWA
from the north and west, and a surface trough will linger over/near
the eastern Great Lakes and stem from expansion of relatively-warm
lake-modified air as the unusually-cold air mass for May 9th-10th
advances across the lakes. Additional periods of scattered rain
showers and isolated thunderstorms remain possible on Thursday
through Friday due in part to the following: Moist isentropic ascent
releasing weak elevated instability ahead of shortwave trough axes,
self-destructive sunshine during the afternoon through early evening
hours of both days, and the potential for lake-enhanced precip over
and generally south or southeast of Lake Erie Thursday night into
Friday morning amidst weak lake-induced instability over ~55F Lake
Erie, a sufficiently-cold/moist low/mid-level atmospheric column,
and the seeder-feeder process. A net low-level CAA regime should
contribute to daytime highs reaching mainly the upper 50`s to upper
60`s on Thursday and the mid 50`s to lower 60`s on Friday after
morning lows in the mid 40`s to lower 50`s.

Odds favor fair weather Friday night as the aforementioned trough at
the surface and aloft exits E`ward, a narrow ridge at the surface
and aloft builds E`ward, and stabilizing subsidence accompanies the
ridge. Overnight lows should reach 40F to 50F around daybreak
Saturday as the unusually-cold air mass remains entrenched across
our CWA.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Behind the above-mentioned ridge, cyclonic W`erly to NW`erly flow
aloft and embedded shortwave disturbances are expected to become
established over the eastern Great Lakes and Upper OH Valley this
weekend through Monday, which will allow net surface troughing to
impact our CWA and vicinity. Periodic showers/thunderstorms,
isolated to scattered in coverage, are expected, especially during
the afternoon and early evening hours given the typical diurnal
cycle in boundary layer temperatures and instability is forecast.
Afternoon highs should reach the 60`s this weekend. Monday`s
afternoon highs should reach the mid 60`s to lower 70`s, when a
warmer low-level air mass should overspread our CWA from the
southwest, ahead of a stronger shortwave disturbance. Overnight lows
should reach the 40`s to lower 50`s around daybreak Sunday and
Monday mornings.

&&

.AVIATION /06Z Tuesday THROUGH Saturday/...
Already lifting the MVFR ceilings back to VFR thresholds above
3kft and expect this to continue through the early morning
hours. Winds become southerly this afternoon 10-15kts with gusts
15-20kts in the wake of a warm front moving northward through
the area and ahead of a cold front slated to come through 03-09Z
Wednesday. Showers and thunderstorms expected this afternoon
into early tonight. TEMPOs used to to time line of convection
expected to form and move through the area. Gusty winds should
be expected in any storms, and hail and isolated tornadoes
cannot be ruled out.

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

&&

.MARINE...
Winds around 5 to 15 knots and waves of 3 feet or less are expected
through Wednesday night. Winds trend NE`erly to E`erly today as a
ridge exits slowly NE`ward and a warm front approaches Lake Erie
from the southwest. NE`erly to SE`erly winds veer to SW`erly tonight
as the warm front sweeps NE`ward across Lake Erie. Winds attempt to
veer from SW`erly to W`erly on Wednesday as a cold front sweeps
E`ward across the lake. Variable winds Wednesday evening become
NE`erly to E`erly overnight as a ridge builds from northern ON and
vicinity.

NE`erly to E`erly winds around 10 to 20 knots back gradually to
NW`erly on Thursday through Friday as a frontal low moves generally
ENE`ward from near the border of central IN/OH to near the Gulf of
Maine and extends a trough over the eastern Great Lakes. Waves of 1
to 3 feet with occasional 4 footers are expected and a Small Craft
Advisory may be needed, especially Thursday night into Friday. A
narrow ridge should build E`ward across Lake Erie Friday night and
cause NW`erly winds to ease to 5 to 15 knots and back to SW`erly.
Waves are forecast to subside to 3 feet or less. SW`erly winds
around 5 to 15 knots and waves of 3 feet or less should persist on
Saturday as a trough begins to overspread Lake Erie from the western
Great Lakes.

&&

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

&&

$$

SYNOPSIS...26
NEAR TERM...26
SHORT TERM...Jaszka
LONG TERM...Jaszka
AVIATION...26
MARINE...Jaszka