786
FXUS61 KCLE 031051
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
651 AM EDT Mon Jun 3 2024

.SYNOPSIS...
High pressure builds in today before departing to the east
tonight. A warm front will lift north across the area tonight.
A cold front extending from low pressure north of the Great
Lakes will move east across the area late Wednesday followed by
a trough lingering across the region trough the weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
6:30 AM Update...
The entire region has been engulfed in low stratus and patchy
fog. The most persistent dense fog has been along and south of
US-30 and in parts of North-central and Northwest Ohio near
Lake Erie, though there have been patchy 1/4SM obs elsewhere. A
special weather statement was issued earlier for area generally
along and west of I-71 where patchy dense fog was observed
earlier. Patchy dense fog elsewhere shouldn`t last much longer
now that sunrise has occurred, maybe through 12-13Z or so.

Previous Discussion...
Light and variable winds along with decent low- level moisture
has allowed for a variable combination of low stratus and areas
of fog (locally dense) across the area. Dense fog has been most
persistent in the southern part of the forecast area south of
US-30 in central Ohio. Elsewhere, visibility has been more
variable. Consideration will be made over the next hour or two
to determine the need for a dense fog advisory and/or a special
weather statement to cover the fog.

Fog will last through about 12-14Z before quickly dissipating,
giving way to a scattered cumulus field through the early
afternoon, before this cumulus field also dissipates (by mid-
late afternoon) as the boundary layer mixes into the dryer air
aloft. With high pressure overhead and temperatures warming into
the low 80s, a lake breeze is likely to develop, which may
actually make some decent inland progress due to weak
environmental background pressure gradient.

High pressure departs to the east by tonight, with southerly
flow developing on the backside. This should warm temperatures
into the mid-upper 80s by Tuesday afternoon. Dew points in the
low to mid 60s will support some marginal instability, though
dry air aloft and modest MLCIN should prevent any convection
from developing, though can`t completely rule it out. Currently
have ~20% PoPs west of I-77 after 21Z, though this area of PoPs
is very low confidence.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
We`ll start the short term with a ridge over the eastern US and a
trough beginning to dig into the Plains Tuesday night. By Thursday
and Thursday night this trough will amplify and shift east, with
good agreement that a deep and closed-off trough will be sitting
over the Great Lakes to end the week. At the surface, respectably
deep low pressure (near or a bit deeper than 990mb) will drift from
Saskatchewan into Ontario through the period. A re-enforcing warm
front will lift across the area Tuesday night into early Wednesday,
with a strong cold front pushing across the local area late
Wednesday or Wednesday night.

In terms of sensible weather, some showers or thunder are possible
Tuesday night and early Wednesday in association with the re-
enforcing warm front and a weak shortwave. This activity will be
moving through at a diurnally unfavorable time and forcing isn`t
especially strong, so it should be on a weakening trend if it makes
it in Tuesday night. Do have some chance POPs generally west of I-77
for Tuesday night with slight chances farther east. POPs continue to
expand east and increase on Wednesday. The main cold front is not
expected to swing through until the afternoon and evening hours,
though a moist airmass and generally increasing forcing for ascent
ahead of the digging upper-level trough may support some pre-frontal
showers and storms, perhaps a continuation of whatever activity
begins drifting in from the west Tuesday night. Have the highest
POPs (categorical/80%+ area-wide) focused on Wednesday afternoon and
evening with the main cold frontal passage. There should be a period
of drier weather immediately behind the front Wednesday night into
early Thursday, though scattered showers and storms will quickly
return to the forecast off and on beginning on Thursday due to a
combination of weak instability beneath cold air aloft and a series
of shortwaves rotating around the larger upper trough.

Lows Tuesday night will generally stay well into the 60s with
a few spots struggling to cool below 70. Highs on Wednesday have
been lowered a touch from the prior forecast due to uncertainty
regarding pre-frontal showers and storms, though still are near or a
bit better than 80 degrees with a muggy airmass expected to be in
place. Lows Wednesday night will generally settle into the low to
mid 60s, with highs on Thursday likely capped in the mid to upper
70s as dew points cool into the 50s. Most of the area should dip
into the 50s Thursday night.

Severe weather and flooding concerns are not extremely high for the
cold frontal passage Wednesday afternoon/evening but aren`t zero
either. The airmass ahead of the front will be quite humid,
characterized by dew points in the mid to upper 60s and precipitable
water (PWAT) values of 1.60-1.90", which is close to climatological
max values for early June per Wilmington, OH observed sounding
climatology. While shear will not be overwhelmingly strong, guidance
ranges from 25 to nearly 40 knots of effective bulk shear across the
area Wednesday afternoon. This is sufficient for loosely organized
clusters and lines on the lower end and more organized lines/bows
(and perhaps a transient supercell) on the higher end. The main
limiting factor for severe potential will be thermodynamics, with
poor mid-level lapse rates and potential for pre-frontal precip both
making it questionable how much instability we can develop on
Wednesday. If more heating occurs moderate instability would
develop, which would point to at least a marginal wind damage
threat. Regardless, the poor mid-level lapse rates suggest a skinny
CAPE profile, favoring efficient rain rates with any storms. Feel a
marginal risk for excessive rainfall as presented by the WPC is
reasonable, suggesting a bit of potential for localized heavy rain
and flash flooding, with the main concern being in urban areas or if
any spot sees localized training convection. The SPC does not
currently have any severe weather risk areas outlined for Wednesday,
though do believe there`s room for an eventual marginal risk if
sufficient instability develops, as has been consistently shown by
Colorado State machine learning severe weather forecast
guidance.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
General troughing will persist over the Great Lakes and Northeast
through the weekend. Models do not agree on how quickly the core of
the trough shifts east, though cooler than average temperatures
along with occasional chances for scattered showers/storms remaining
in the forecast through the weekend either way. We should see any
washouts in this type of pattern, though any shortwave rotating
through the larger upper-level trough will be a potential focus for
scattered rain chances. Details will be refined as we get
closer.

&&

.AVIATION /12Z Monday THROUGH Friday/...
IFR and lower conditions with FG/BR and low stratus are being
observed across the entire region except the I-75 corridor where
MVFR/VFR conditions persist (despite being surrounded in all
four directions by IFR conditions). Fog has occasionally been
dense in some locations this morning, especially south of US-30
and in some spots near Lake Erie.

Fog should quickly dissipate through 13Z-14Z this morning,
giving way to low IFR/MVFR clouds that should eventually
transition to a scattered cumulus by early afternoon. This
cumulus should also gradually dissipate by mid-late afternoon as
the boundary layer mixes with dry air aloft. Mostly clear skies
with the occasional high cirrus is expected the rest of this
evening and tonight.

Light and variable winds of 5 knots or less generally expected
through the TAF period, except for an afternoon lake breeze for
locations within ~20 miles of Lake Erie where onshore flow of
5-10 knots is expected between approximately 18-23Z.

Outlook...Non-VFR is expected with periods of showers and
thunderstorms Wednesday and Wednesday night. Non-VFR will be
possible with scattered rain showers and isolated afternoon
thunderstorms Thursday through Friday.

&&

.MARINE...
Fairly tranquil marine conditions are expected today and Tuesday.
Onshore winds may reach 10-12 knots for a few hours this afternoon
across the western basin. East-southeast will increase to 10-15
knots for a few hours Tuesday afternoon and evening ahead of a re-
enforcing warm front. Otherwise, winds will be under 10 knots. There
is a low risk for a thunderstorm over the lake Tuesday night.

More active conditions are expected Wednesday through Friday with
gradual improvement this weekend. A cold front will cross the lake
Wednesday afternoon. Scattered storms are likely over the lake along
and ahead of the cold front Wednesday. Winds will turn west-
southwest Wednesday night and Thursday behind the front and west-
northwest Thursday night through Friday night behind a secondary
trough. Winds will increase to 15 or so knots at times Wednesday
night through Friday night. A period or two of 20 knot winds is
likely at some point late Thursday through Friday night, which would
build waves and warrant a Small Craft Advisory. Guidance disagrees
on when exactly the strongest winds will occur so we don`t have any
winds over 20 knots in the forecast yet, though would be surprised
if we don`t need headlines at some point towards the end of the
week, especially across the central and eastern basin. The pressure
gradient should slowly relax this weekend though west winds may
maintain some wave activity, even if sub-headline. A risk for
isolated thunderstorms persists over the lake off and on through the
weekend due to cold air aloft and a series of weak disturbances
rotating through a large upper trough over the region.

&&

.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