095
FXUS61 KCLE 071828
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
228 PM 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/...
145 PM EDT Update...
Showers with embedded thunderstorms associated with the warm
front are starting to lift east-northeast into the CWA. As of
now, do not anticipate any severe weather with this initial
round, especially since the lower levels are still quite dry;
the main show is developing over Illinois and will track east
towards the area through this afternoon. Things are trending a
few hours later with the best window of severe weather entering
western zones sometime between 7-8 PM EDT (perhaps even a little
bit later) with storms gradually weakening as they move east
through about midnight tonight. Despite the later timing,
dynamics and instability will still be sufficient for all
hazards of severe weather, especially in the Enhanced Risk where
there will be the longest residence time in the warm sector and
the best opportunity for moisture/warm air advection and
destabilization. Made adjustments to PoPs based on latest runs
of CAMs, but otherwise no changes needed with this update.

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 FRIDAY 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 /SATURDAY 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 /18Z Tuesday THROUGH Sunday/...
VFR is expected through most of this afternoon, but a brief
period of MVFR is possible as a round of showers with isolated
embedded thunderstorms lifts into the western half of the area.
Otherwise, the next opportunity for non-VFR will arrive near 00Z
tonight as more organized convection moves in from the west.
Generally expecting MVFR visibilities, but IFR visibilities and
MVFR ceilings are possible within the more robust thunderstorms.
Storms may be strong to severe with gusts to 50+ knots, large
hail, and tornadoes, but strong storms will be scattered in
nature and there is still uncertainty in whether or not strong
storms will move directly over a TAF site. The greatest
potential for strong wind gusts will be at KTOL/KFDY in addition
to KCLE/KMFD/KCAK. VFR should return to most terminals once
showers/storms end later tonight, but some MVFR may linger at
KERI/KYNG as a cold front crosses the area late tonight into
Wednesday morning.

Winds will be out of the south/southeast at 6 to 12 knots
through early this evening with northeasterly winds expected
near the lakeshore of NE OH/NW PA. Expect flow to shift to the
southwest tonight before becoming more westerly towards the end
of the TAF period.

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

&&

.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...Maines/26
SHORT TERM...Jaszka
LONG TERM...Jaszka
AVIATION...Maines
MARINE...Jaszka