800
FXUS61 KCLE 150804
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
404 AM EDT Mon Jul 15 2024

.SYNOPSIS...
A frontal boundary will settle across the Great Lakes through
Tuesday before pushing southeast across the area as a cold front
Tuesday night into early Wednesday. High pressure will build in
from the west Wednesday night through the end of the week.

&&

.NEAR TERM /THROUGH TUESDAY/...
Our warm and humid, unsettled pattern continues through the
near term. Forecast uncertainty remains higher than normal due
to the dependence on the evolution of multiple rounds of
convection both overhead and upstream through Tuesday.

A mesoscale convective system (MCS) extends from central lower
MI southwest into central IL as we approach 4 AM and is moving
east. How this MCS holds up into our area is uncertain. The
stronger linear portion of it is diving southeast towards deeper
instability over the Ohio Valley, while a well-defined mesoscale
convective vortex (MCV) is located near Grand Rapids and will
move east from this morning. The portion of the MCS moving
towards our forecast area is relatively weaker and less
organized. With a moderately unstable (1500-2500 J/KG of
MUCAPE) airmass in place will monitor a slightly more organized
segment near Fort Wayne for some continued thunderstorm
generation as it pushing into northwest OH, Lake Erie, and
surrounding areas over the next few hours. Also have a few
showers and storms attempting to develop across parts of
northern OH in modest warm air advection ahead of the MCS and
this may continue this morning too. Ultimately, have a mix of
chance and likely (30-70%, highest across Northwest OH,
Northeast OH, Northwest PA and Lake Erie) spreading in this
morning. The severe weather risk this morning is low given the
lack of current organization to the MCS and weak shear. There`s
enough instability that we can`t entirely rule out any new
updrafts briefly perking up enough for a marginal hail and
perhaps gusty wind potential. Overall though, most or all of the
activity this morning will be non-severe.

We should see lull in activity spread in from the west-
northwest later this morning into this afternoon as we get into
subsidence and a worked over airmass behind the MCS and MCV. The
MCV may pass close to Erie, PA around midday into the early
afternoon and renewed thunderstorm development may begin ahead
of it over Northwest PA before spreading southeast. Farther
west, expect an outflow boundary to settle across our far
southern counties (likely near or south of a Marion-Wooster-
Youngstown-Meadville line) this morning that may be a focus for
isolated to scattered thunderstorm development this afternoon.
Synoptic forcing is weak this afternoon and it`s uncertain how
quickly we`ll recover so confidence in this is low. Overall have
30-60% POPs across our southern/southeastern counties this
afternoon with drier conditions farther north. A strongly
unstable airmass will develop south of the outflow boundary this
afternoon, so if we see re-development across our far
southern/southeastern counties it will carry a conditional risk
for locally damaging winds and perhaps marginally severe hail.
Given clouds/rain this morning and a worked over airmass lowered
high temps a bit today...ranging from the low to mid 80s in
northwest PA to the mid 80s to near 90 in Ohio. Peak heat index
values may still reach the mid to upper 90s (advisory criteria
is 100F) from Toledo to Marion points west with values ranging
from the upper 80s to mid 90s elsewhere.

Any re-development across our far south should exit and leave a
lull for a time this evening. We will (once again) then turn our
attention towards the Chicago area as the next shortwave is
expected to encourage another robust MCS to develop out that
way. Any MCS would spread east-southeast along the instability
axis overnight tonight into early Tuesday. As we saw last night
into this morning, MCSs can weaken quickly once they out-run the
greater forcing and shear, so what state any cluster is in as
it moves into our area overnight tonight or very early Tuesday
is quite uncertain...as illustrated by the SPC Marginal (risk
level 1/5) risk for severe weather. However, there may be some
arguments for any MCS tonight to hold its intensity
longer...there will be a bit more shear, especially upstream,
and less convection over our region during the afternoon and
evening hours than yesterday may allow for more instability to
build in as we will be on the edge of an extremely unstable
airmass. We will as always closely monitor trends both overhead
and to our west today in sizing up our thunderstorm/severe
potential overnight tonight into very early Tuesday, as if we
see a more organized MCS spread in it would carry some form of
wind damage risk. Expect lows tonight to range from the upper
60s to mid 70s. Currently spread 40-60% POPs in after
midnight, though expect refinement in the timing/magnitude.

Showers/storms have a decent likelihood to still be ongoing
across parts of our area Tuesday morning. How quickly this
activity exits will heavily dictate how widespread and intense
thunderstorm development ahead of an approaching cold front is
Tuesday afternoon. Shear and forcing will be a bit stronger over
the local area on Tuesday as the front approaches but
instability may end up being a limiting factor if we are too
worked over from any storms late tonight into Tuesday morning
and struggle to re-cover. Either way, have POPs ramping up to
the 60-70% range for most of the area (a bit lower towards
Toledo) Tuesday afternoon and evening. With a very moist airmass
and storm motions nearly paralleling the approaching cold front
locally heavy rain and flash flood may also be concerns Tuesday
afternoon and early evening. Lowered highs a bit on Tuesday,
now generally ranging from the mid to upper 80s. Dew points in
the 70s may still bring heat index values into the low to mid
90s but advisory criteria values look to be avoided.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
Convection that develops Tuesday afternoon/evening is likely to
persist into Tuesday night. However, despite the cold front
slowing/stalling to just north of our forecast area, a lot of model
guidance is starting to shift south of convection Tuesday night. The
NAM is one model that is still holding onto the idea of persisting
convection and heavy rain through much of Tuesday night, however the
overall trend is a southward shift. This is captured by WPC`s latest
D2 ERO where the slight risk area now only encompasses from
Youngstown to Marion (and points south). The severe risk will likely
be waning through Tuesday night.

The aforementioned cold front moves south across the area early
Wednesday morning through early Wednesday afternoon. Lingering
isolated showers and thunderstorms will be possible ahead of this
cold front. With abundant deep-layer shear, would not be surprised to
see a stronger/spiny storm or two, but the severe risk is
minimal for Wednesday.

High pressure gradually builds in behind this cold front, with dry
weather Wednesday night and onward. The airmass accompanying this
high is cooler as well, with high temperatures in the upper 70s to
low 80s on Wednesday and mid 70s on Thursday (running about 6-10
degrees below normal. Thursday night could even be a touch chilly
for some with overnight lows in the mid to upper 50s.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
High pressure becomes centered over the region by Friday, with the
high remaining steady but gradually weakening through Saturday and
Sunday. A gradual rebound to the temperatures are expected through
the weekend with highs back in the low to mid 80s on Saturday and
Sunday. With no precipitation and low humidity, it should be a
rather pleasant summer weekend.

&&

.AVIATION /06Z Monday THROUGH Friday/...
Another TAF cycle with opportunities for showers and
thunderstorms at several terminals but with relatively low
confidence in the details. A cluster of thunderstorms stretches
from western MI to northern IN to central IL. Guidance not
handling the presentation of this well, though there has been a
bit of a weakening trend recently. Still, expect sufficient
lingering instability ahead of this cluster to encourage at
least some shower and thunder activity to spread in from the
west after 9 or 10z with some scattered activity potentially
developing ahead of it, especially from CLE and CAK points
northeast starting 9-11z. This activity may not exit ERI and
YNG until late morning or around midday, with a lull across most
of the area this afternoon and evening. Some re-development may
occur near or south of MFD, CAK and YNG this afternoon, though
odds appear to favor that activity developing a bit
south/southeast of those terminals. Another cluster of
showers/storms has a chance to spread in from the west late
tonight into early Tuesday, largely after the current TAFs.

Southwest winds 6-10 knots continue this evening and overnight.
Winds turn more southwest while increasing to 8-14 knots with
some gusts 20-25 knots this afternoon. Higher winds and gusts
will occur in any thunderstorms.

Outlook...Mainly VFR outside of occasional thunderstorms through
Tuesday evening.

&&

.MARINE...
Starting off this morning with southwest winds generally in the 10
to 15 knot range. A Mesoscale Convective Vortex (MCV; a low caused a
large cluster of thunderstorms) is expected to move just north of
Lake Erie later today. Latest model guidance suggested a brief
period of 3-6 hours of enhanced wind speeds in the 20-25 knot range
late this morning through the afternoon hours. Confidence is
somewhat low in this occurring but will continue to monitor
observations today to see if this materializes and some sort of
headline needs to be a issued.

By tonight, conditions become a bit quieter (outside of any
thunderstorms that cause issues) with flow of 5-10 knots out of the
south. Southwest winds increase to 10-15 knots out of the southwest
on Tuesday with a possibility for brief periods of 20 knot winds at
times during the day time hours. Winds weaken Tuesday night,
becoming 10-15 knots generally out of the north by Wednesday
afternoon following a cold frontal passage. Winds become light and
variable by Friday as high pressure gradually builds in from the
west.

&&

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

&&

$$

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