073
FXUS61 KCLE 041020
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
620 AM EDT Tue Jun 4 2024

.SYNOPSIS...
A warm front lifts north across the region today and tonight
followed by a cold front on Wednesday night. A trough builds in
on Thursday which will linger across the area through the
weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
High pressure has moved off to the east coast, though near calm
conditions could result in very patchy radiational fog in some
inland valleys east of I-77. Southerly flow develops today,
with temperatures warming into the mid to upper 80s (perhaps
even a couple spots touching 90). Dew points will be manageable
in the low 60s, while partly cloudy skies and at least a light
breeze should minimize heat risk. A light lake breeze develops,
though shouldn`t make too much inland progress due to background
environmental winds out of the south.

A deep upper-level trough begins digging down into the Upper
Midwest late tonight into Wednesday morning, with its associated
occluded low well off to the northwest in Manitoba, Canada. A
cold front will extend southward, bisecting the CONUS in the
vicinity of the Mississippi River by Wednesday morning with a
warm front extending from a triple point area along this cold
front. The warm front lifts northeast across the forecast area
late tonight (boundary is more discernible in dew point or
theta-e fields rather than temperature) with some frontogenesis
in the 925-700mb layer providing a focus for a line of isolated
to scattered rain showers and perhaps an isolated thunderstorm
late tonight through early Wednesday morning. Behind this front,
dew points rise into at least the mid to upper 60s, with
pockets of 70 dew points possible. Surface-level warming will
greatly depend on daytime cloud cover and any morning
convection, though it seems most model guidance is predicting at
least temperatures into the low 80s, which is likely to
contribute to MLCAPE of 1000+ J/kg. As the upper-level trough
and associated belt of mid-level southwesterly winds, deep-layer
shear of around 30 knots should be sufficient for organized
convection and a low chance of severe weather. Convection could
develop along a pre-frontal trough (from decayed convection
from previous day`s system) and/or along the cold front itself
sometime Wednesday afternoon, with shear vectors favoring a
mixed-mode (probably clusters of storms rather than discrete
supercells or a fully developed QLCS). Storms will tend to grow
upscale into a more defined line as they move east across the
area. Development along the cold front would likely have the
best severe weather chances and would likely result in later
timing across the area (west of I-77 4-8 PM, east of I-77 8-11
PM).

Currently SPC has 5% probabilities for damaging winds, which is
expected to be the primary severe weather hazard but would not
be surprised if a 2% tornado outlook was added down the road.
It`s localized, but many models have some clockwise curvature in
forecast hodographs with ~100 0-1km SRH and near 1 STP. Small
hail is possible but large hail is unlikely given poor mid-level
lapse rates and favored linear convective mode.

Localized flooding with heavy rain could be possible primarily
due to the seasonably high environmental moisture content
(characterized by high PWATs, dew points, warm cloud depths,
etc.). Even so, antecedent conditions aren`t concerning (and
actually most of the region is somewhat dry and could use the
rain) and would likely need some convective development ahead of
the "main line".

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
An unseasonably deep closed upper trough will settle into the Great
Lakes this period and won`t be going anywhere fast, bringing a
period of cooler than average temperatures with occasional shower
and storm chances. There may even be some lake enhancement during
the overnight and early morning hours beginning Friday.

A cold front will still be crossing the area Wednesday evening
before exiting east. Showers and storms remain in the forecast along
and ahead of the frontal passage before a brief dry break. By
Thursday and Friday we`ll be beneath the influence of the closed
upper trough settling into the Great Lakes with various smaller
shortwaves and associated surface troughs rotating through the
larger trough. Guidance is beginning to key in on one such feature
dropping through the area Thursday morning and early afternoon...
another late Thursday night or early Friday...and yet another later
Friday evening or Friday night. It`ll be an active pattern. It will
not rain the whole period, though there will be occasional chances
for showers and perhaps an isolated storm beginning early Thursday
through Friday night. Precip chances will largely be focused by the
aforementioned shortwaves and surface troughs rotating around the
large closed upper low, though there will also be a diurnal flavor
with showers generally more numerous during peak daytime heating
hours each day beneath chilly air aloft. The one area that will
likely buck the diurnal trend will be the primary "snowbelt" region
from far Northeast OH into Northwest PA. Lake Erie water
temperatures range from 16-18C east of Cleveland to 18-21C west of
Cleveland, and 850mb temperatures will fall to a 4-7C range by
Friday and Friday night. Diurnal heating on land will tend to
disrupt any lake effect/enhanced processes during the day Friday
with activity becoming more focused away from the lakeshore, though
at night temperatures aloft will be just cold enough to actually
focus/enhance showers east of Lake Erie...especially Friday night.

Lows Wednesday night will generally dip into the low to mid 60s,
with highs rebounding into the mid to upper 70s for Thursday as dew
points cool into the 50s. Lows Thursday night will dip into the 50s,
with a somewhat greater airmass change by Friday with highs likely
ranging from the upper 60s in far Northeast OH/Northwest PA to the
low 70s along the I-75 corridor. Rain amounts will generally be
modest with the occasional shower chances Thursday and Friday,
though parts of the primary snowbelt may begin picking up somewhat
more moderate rain amounts due to some added enhancement from the
lake, especially early Friday and again overnight Friday night.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
More of the same through the weekend and likely to start next week,
with the closed upper trough sitting over the Great Lakes and only
very slowly filling through the period. This will lead to a
continuation of cooler than average temperatures and occasional
shower chances, with some lake enhancement to the rain showers
possible during the night and early morning hours east and southeast
of Lake Erie. Guidance has generally trended towards the trough
lifting out even slower than some prior runs depicted, so POPs have
increased a bit in some forecast periods this weekend. Still not
looking at all day washout rains, but it`ll be an unsettled and at
times showery pattern to be sure. There will be a diurnal flavor to
the showers with activity more numerous during peak heating hours,
though various subtle shortwaves and surface troughs rotating
through will also focus rain chances. QPF amounts remain generally
modest through the extended, though depending on the amount of lake
enhancement parts of Northeast OH and Northwest PA could rack up a
bit more rain than the rest of the area through early next week.
Temperatures will begin to slowly moderate by Sunday and Monday,
though highs in the 70s and lows in the 50s will remain common.

&&

.AVIATION /12Z Tuesday THROUGH Saturday/...
VFR conditions are observed and expected to be the predominant
condition through the TAF period. The exception could be some
patchy BR, especially for central and east-central Ohio, early
this morning between 08-12Z. Isolated rain showers might start
moving in from the southwest late tonight along with mid-level
clouds, but this is low confidence. Added some VCSH mention to
account for this.

Winds will be light and variable or from the south tonight under
5 knots. Winds become predominantly out of the south and
strengthen to 5 to 10 knots during the daytime hours today.
Another lake breeze is likely this afternoon, though probably
won`t make as much inland progress as yesterday.

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 Saturday.

&&

.MARINE...
A diffuse warm front will be located near Lake Erie through tonight.
Generally light east-southeast flow will turn east-northeast and
increase to 10-15 knots due to a lake breeze this afternoon,
increasing chop in the nearshore waters. Winds shift south at 10-15
knots overnight tonight into Wednesday. A cold front will cross the
lake Wednesday evening, with cyclonic flow around a relatively large
surface low pressure controlling the winds over Lake Erie Thursday
through much of the weekend. Winds will shift to the west-southwest
behind the front Wednesday night through Thursday. Winds will shift
westerly Thursday night and remain generally westerly through the
weekend. A somewhat tight pressure gradient and cold air advection
will increase winds to 10 to at times 20 knots Wednesday night
through Saturday. Winds should gradually relax later this weekend
into early next week as the low pressure affecting the Great Lakes
slowly weakens and begins exiting to the east. Still believe there
may be one or two windows of Small Craft Advisory conditions in the
central and eastern nearshore waters between Wednesday night and
Saturday as waves will build to 4 or so feet at times in the
nearshore waters when the westerly winds are strongest, though
guidance still disagrees on when windows of stronger winds will be.
Thunderstorms are likely over the lake Wednesday and Wednesday night
ahead of the cold frontal passage, with a low risk for isolated
thunder over the lake Thursday through the weekend.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...Air Quality Alert until midnight EDT tonight for OHZ010>014-
     020>022-089.
PA...None.
NY...None.
MARINE...None.

&&

$$

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