815
FXUS61 KCLE 051035
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
635 AM EDT Wed Jun 5 2024

.SYNOPSIS...
A warm front will move north across the area this morning
followed by a cold front this evening. A surface trough will
build in on Thursday, lingering over the area through the
weekend.

&&

.NEAR TERM /THROUGH THURSDAY/...
As expected, showers did become more developed along the warm
front, so increased PoPs along this line by another 10-20% now
that these showers are more observable. Will have to monitor
trends in upstream convection over Illinois and southern
Missouri as that is likely to become the "main show" for our
marginal severe weather setup for later this afternoon/evening.

Previous Discussion...
A deep upper-level trough digs down into the Upper Midwest this
morning, which is very apparent in water vapor imagery. A warm
front extending from a secondary low located over the northern
Great Lakes is moving northeastward across the forecast area
this morning. A few weak reflectivity returns are noted on radar
but have yet to see any weather stations report precipitation,
so there`s a good chance nothing is reaching the surface just
yet. However, CAMs do have rain showers becoming more developed
later this morning, especially along and east of I-77. These
showers could linger from Youngstown to Erie, PA (and vicinity)
through the early afternoon hours, something the HRRR has been
persistent on occurring with each run.

Moisture advection with increasing southerly winds today will
bring dew points into at least the mid to upper 60s, with some
pockets of around 70 by this afternoon/evening. A dry slot is
already observed within the warm sector across portions of
Illinois/Indiana, which will propagate into our western CWA
today. This should allow for a sizable break in cloud cover and
decent confidence in sufficient heating into the low to mid
80s, contributing to MLCAPE of 1000-1250 J/kg, mainly west of
I-77 and especially near the I-75 corridor. Lingering clouds and
showers may limit heating and instability east of I-77. As the
upper-level trough and associated belt of mid-level
southwesterly winds moves in, deep-layer shear of around 25-30
knots should be sufficient for organized convection and a low
chance of severe weather. For this reason, a marginal risk
(level 1 of 5) of severe thunderstorms is forecast for today.

A line of convection is observed on radar to our west extending
from the Chicago area southeastward down to Texas. This
convection will likely weaken some as it encounters a weakly
unstable environment this morning before becoming reinvigorated
(or redeveloping along its outflow boundary if it completely
dissipates) by this afternoon as instablilty increases ahead of
it. A linear storm mode is favored, though isolated
cells/clusters could develop out ahead of the main line (which
is hinted at by a few CAMs). Damaging winds is likely to be the
primary threat. The tornado threat has lowered substantially
from the previous forecasts as forecast low-level shear/helicity
has decreased quite a bit. Localized flooding with heavy rain
remains a possibility as just about every "flooding"
environmental parameter (PWAT, warm cloud layer, etc.) reveals
high water content throughout and expected efficient rainfall.
The likelihood of flooding would be especially possible if
storms could develop ahead of the "main line" of storms, or if
we observe backbuilding (Corfidi vectors this afternoon are
very favorable for flash flooding if this were to occur).
Limiting factors for flooding include dry antecedent conditions
and progressive nature of a linear system.

Convection is likely to exit the forecast area shortly after
midnight. The upper-level trough becomes a closed low as it
builds southeast into the Great Lakes region, with a secondary
cold front bringing isolated to scattered rain showers to the
area on Thursday. Cooler temperatures are expected with highs in
the upper 70s.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
A cooler than normal and unsettled period of weather is still
expected to end the week and start the weekend thanks to an
unseasonably deep closed upper-level trough/low spinning over the
Great Lakes. Various smaller shortwaves and surface trough axes will
rotating through the larger trough, focusing occasional shower
chances. Daytime heating will also act to encourage an increase in
shower coverage each afternoon. At night, chilly air flowing over
the relatively milder Lake Erie waters may enhance showers east of
the lake...particularly late Thursday night into Friday morning and
again Friday night into early Saturday morning. Guidance is trying
to key on a couple of small shortwaves and associated surface
troughs dropping through between late Thursday night and Friday
evening. Agreement decreases farther out, though there are hints
that there will be another one or two shortwaves rotating through
between early Saturday morning and late Saturday night. We are not
looking at a washout for this forecast period though there will
likely be scattered to numerous showers around at times...especially
when subtle shortwaves work through and when and where lake
enhancement occurs in far Northeast OH and into Northwest PA. Can`t
rule out a bit of thunder each afternoon given cold air aloft aiding
in modest destabilization, though in general we`ll just see showers.
Overall QPF amounts will be light outside of lake enhancement, where
more frequent showers may add up a bit over a long period of time.

Highs will generally range from the mid 60s to mid 70s Friday and
Saturday (coolest far Northeast OH and Northwest PA, warmest along
the I-75 corridor) with overnight lows in the 50s.

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
We remain under the influence of the trough centered over the Great
Lakes/Northeast/southeastern Canada through Sunday night. The trough
should gradually shifting east Monday and Tuesday, though guidance
doesn`t agree on exactly how quickly that will happen. Our cool,
somewhat showery pattern will gradually moderate and dry out once
the trough decides to exit. Highs in the 70s and lows in the 50s
should generally rule the Sunday - Tuesday period, though with a
gradual moderating trend in afternoon highs starting by Tuesday.

&&

.AVIATION /12Z Wednesday THROUGH Sunday/...
Largely VFR conditions expected through the morning hours
today, although could be brief drops in visibility with rain
showers this morning, possibly at KERI and KYNG. Rain showers
could persist longer farther east (e.g. near KERI and KYNG),
even into the early afternoon.

A line of thunderstorms is expected to develop in western
Indiana and move east across the region early this afternoon,
and traverse the region through Wednesday afternoon and
Wednesday evening. Some of these storms could be strong to
severe, mainly west of I-77. Best chance for strongest
thunderstorms will be along the I-75 corridor. Confidence is
high in a period of lower visibilities with thunderstorms. Storms
will likely be in a weakening state the farther east they
progress, so lower confidence in lower visibilities and coverage
of thunderstorms. MVFR ceilings may build in behind
thunderstorms late tonight, mainly east of I-77 before VFR
conditions build back in with scattered clouds.

Southerly winds increase to 10-15 knots with some gusts to 20
knots (potentially to 25 knots west of I-77). Winds weaken and
become southwest and then west behind the main line of storms
late tonight.

Outlook...Non-VFR will be possible with scattered rain showers
and isolated afternoon thunderstorms Thursday through Sunday.

&&

.MARINE...
A cold front will sweep across Lake Erie this evening and tonight.
Southerly winds to around 15 knots are expected ahead of the front.
Thunderstorms are likely over the lake this afternoon and evening,
with a few stronger storms possible. Winds shift west-southwest
behind the front tonight and more west-northwest Thursday night into
Friday, generally remaining west to northwest through early next
week. Winds will generally range from 10 to 20 knots through Sunday
before gradually relaxing into early next week. A couple of periods
of winds to around or slightly greater than 20 knots are possible...
mainly Thursday evening through early Friday behind a re-enforcing
trough axis and perhaps again at some point between Friday night and
early Sunday. Guidance still disagrees on the smaller trough
passages that will briefly enhance winds this weekend. Overall, the
lake will be somewhat agitated through the weekend with a couple
windows in which Small Craft Advisories / Beach Hazard Statements
could well be needed for the central/eastern nearshore zones.

&&

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

&&

$$

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