Area Forecast Discussion
Issued by NWS Cleveland, OH

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223
FXUS61 KCLE 141356
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
956 AM EDT Sun Jul 14 2024

.SYNOPSIS...
High pressure exits to the southeast today as a frontal boundary
sets up across the Great Lakes. This front will push southeast
across the area as a cold front Tuesday night. High pressure
will build in Wednesday through Saturday.

&&

.NEAR TERM /THROUGH MONDAY/...
930 AM Update...
As of now, there are still two areas of interest: a complex
along and just west of I-75 and an MCS over the Chicago area.
The complex near I-75 will likely continue to weaken since
instability is marginal, which should leave behind some
boundaries for additional convection to develop/strengthen as
the complex near Chicago arrives from the west this afternoon.
There`s still some uncertainty in how well this feature holds
together before it moves into Ohio this afternoon, but currently
thinking it will ride an instability gradient and possibly dive
to the southwest of the CWA or clip southwestern zones. Will
need to see how much clearing occurs between the morning showers
and the MCS; if more clearing occurs, there could be more
destabilization and a better chance of convection. Another MCS
could clip or move across the area overnight tonight, but there
is even more uncertainty with that since it will depend on how
the afternoon and early evening unfold. Regardless, there will
be plenty of moisture and instability to work with in western
and southwestern zones where there will likely be 2000-2500 J/kg
of MLCAPE and at least 2500-3000 J/kg of SBCAPE during peak
heating into this evening. Dew points are also in the mid 60s to
lower 70s with PW values of 1.5-2" expected this afternoon.
Damaging wind gusts will be possible with any thunderstorms that
develop in the area of the higher instability with locally
torrential rainfall likely in any showers/storms. Despite
uncertainty, a Slight Risk has been introduced to southwestern
zones to highlight the area of enhanced instability and elevated
potential for stronger convection if storms occur.

Previous Discussion...
A pair of MCSs are ongoing to our west/northwest at 7 AM, one
approaching I-75 (that is rapidly decaying) and another over WI,
with the WI MCS tied to a convectively-enhanced shortwave. How
these MCSs evolve will heavily dictate our weather today. It is
unclear how far rain with this lead MCS will survive into our
area as it is moving into a dry and stable environment, though
do at the least expect some lighter showers into northwest OH
this morning. By this afternoon, locations west of approximately
I-77 that do not get clouds/rain from this morning`s decaying
MCS will begin destabilizing enough that a combination of any
boundaries left by the MCS and forcing from the convectively-
enhanced shortwave dropping out of the upper Midwest may spark
renewed convective development. This activity would continue
east-southeast through early evening. Isolated strong winds
can`t be ruled out mainly west of I-77 if we do see thunderstorm
development this afternoon, though generally modest
thermodynamics and shear will make it difficult to see any sort
of organized severe threat during the day today.

Ultimately, have chance (40-50%) POPs spreading into the I-75
corridor this morning dropping off to 30-40% farther
east/southeast. Ramp things back up to 50-60% in some of our
southern counties from Marion-Mansfield over towards Akron/
Canton for a few hours this afternoon, where potential for
renewed development seems highest. We will likely see a relative
lull in shower/storm potential later this afternoon into this
evening. Lowered high temperatures a bit for today, especially
across northwest Ohio. Still have most of the area reaching the
upper 80s to near 90 with peak heat index values generally in
the low to mid 90s.

We should start this evening relatively quiet. A bowing MCS is
blasting across SD early this morning and is associated with the
next shortwave that will push across the southern Great Lakes
tonight. While any convective development this afternoon will
have ripple effects on the environment and placement of
boundaries into tonight, leading to uncertainty, there is a
decent likelihood that this next shortwave will spark convection
to our west/northwest by this evening that congeals into an MCS
that spreads east-southeast towards our area late this evening
into the overnight. Placement and intensity of this activity
tonight is quite uncertain due to the aforementioned sources of
uncertainty. However, we will be on the edge of a very unstable
airmass tonight and a strong MCS can locally enhance the shear.
Concern for severe weather, mainly in the form of damaging
winds, is higher tonight than during the day today. Given the
uncertainty the current SPC outlook maintains a Marginal Risk
(risk level 1/5) though do see potential for that to trend up
in future updates, particularly across parts of northwestern
Ohio. Expect muggy lows tonight ranging from the upper 60s in
northwest PA to the low to mid 70s in Ohio.

Showers/thunder may still be ongoing to start Monday,
particularly from eastern OH into PA. Subsidence and a worked
over atmosphere behind any MCS would likely lend to a period of
drier weather for a number of hours on Monday once any morning
activity exits, potentially through most of the afternoon.
Trended POPs down for several hours late Monday morning through
most of the afternoon. The airmass should recover by later
Monday afternoon or evening from the west and southwest, aided
by increasing wind fields and warm air advection ahead of the
next shortwave approaching out of the upper Midwest. The
combination of dew points warming into the 70s, steep mid-level
lapse rates of 6.5-7.5C/km, and hot temperatures should yield
very strong (2000-3000+ J/KG of MLCAPE) with large values of
DCAPE just to our west by Monday afternoon and evening. Lift
associated with the aforementioned shortwave will likely spark
additional convection to our west-northwest Monday afternoon
that spreads towards the upper Ohio Valley late Monday into
Monday night with severe weather potential. Begin ramping POPs
up in our western counties early Monday evening, though the
greatest likelihood for activity will probably come in the
Monday night timeframe.

Due to potential for an extensively worked-over airmass and
lingering clouds behind any MCS earlier Monday, lowered high
temperatures and dew points a bit for Monday. Still have highs
ranging from the mid 80s in northwest PA to the lower 90s in our
western counties. Peak forecast heat index values range from
the mid 90s to near 100 west of I-77 (greatest potential for
near 100 from Toledo to Marion points southwest) to the upper
80s/lower 90s in extreme northeast OH and northwest PA. A Heat
Advisory may be needed for western portions of the area on
Monday but confidence is low.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
Won`t restate a lot of the details from the near term discussion,
but the general large-scale pattern and environment remains
unchanged into Monday night (northwest flow aloft, lots of
instability, marginal deep-layer shear). The evolution (timing and
areal coverage) of a potential MCS moving east-southeast across the
area Monday night is quite uncertain and is largely dependent on
what happens with convection Sunday through Monday. Currently, most
model guidance has a convectively-enhanced shortwave trough
moving across the area with an MCS some time Monday night. If an
MCS does move through, the environment would support a marginal
severe weather threat, despite the unfavorable diurnal timing.
Strong to damaging winds would be the primary weather hazard.

By Tuesday, a large upper-level trough digs down into the Great
Lakes region with a surface cold front sagging down just north of
the forecast area (from southern Ontario southwest across lower
Michigan, northern Indiana, etc). A very moist airmass (dew points
in the low 70s) will contribute to moderate to high instability
across the forecast area by Tuesday afternoon with model guidance
generally forecast MUCAPE exceeding 2000 J/kg (but possibly as high
as 4000 J/kg). Synoptic-scale forcing from the approaching upper-
level trough and surface cold front will likely lead to convective
development sometime Tuesday afternoon through late Tuesday night.
Deep-layer shear is expected to be somewhat marginal (20-30 kts) but
sufficient for organized severe convection. Damaging winds is once
again likely to be the primary weather hazard.

The approaching front might stall or slow down a bit as the opposing
low-level jet strengthens Tuesday evening. Continued synoptic-scale
forcing and cloud-layer winds parallel to the front could lead to
backbuilding and training of thunderstorms. Combined with very high
PWAT (ensemble mean of 1.9 inches, which is very high for an
ensemble mean), flash flooding is going to be possible Tuesday
afternoon through Tuesday night. This is supported by the
continuation of the slight risk ERO centered on our forecast area.
Added heavy rain to the forecast to account for this threat.

Eventually, the front makes southward progress, clearing the
forecast area by Wednesday afternoon. Until thing, lingering
isolated thunderstorms could be possible Wednesday morning to early
Wednesday afternoon, mainly for the southern portion of our forecast
area.

Heat indices on Tuesday are expected to be in the mid to upper 90s
before thunderstorms develop. Post-frontal, cooler temperatures are
expected on Saturday, with highs down into the low 80s.

&&

.LONG TERM /THURSDAY THROUGH SATURDAY/...
High pressure builds in behind the departing cold front, ushering in
a cooler, dryer airmass. Temperatures likely to remain in the 70s on
Thursday before a gradual rebound to the low to mid 80s on Friday
and Saturday. No precipitation expected in the long term period.

&&

.AVIATION /12Z Sunday THROUGH Thursday/...
Limited patchy fog will quickly lift through 13z. Otherwise
mainly VFR through this evening with the main concern being
timing and intensity of showers/storms. A weakening cluster of
rain (no lightning) is approaching TOL and FDY and may bring
some showers with few or no restrictions this morning. Some
isolated to scattered showers and thunder may re-develop
farther east/southeast this afternoon, especially in the
vicinity of MFD, CAK, and perhaps FDY, YNG, and CLE. Confidence
in how much thunder this activity has is low and coverage will
likely be isolated to scattered, meaning odds of hitting a given
terminal are low. Given all of this, handled with VCSH
mentions, though it is possible AMDs or the next full cycle
needs to hit this afternoon`s convection a bit harder at a
couple of TAF sites. Generally then expect a lull in activity
into this evening before another potential cluster of showers
and storms spreads in from the west later this evening. Have
broad windows for showers with vicinity thunder and MVFR vsby
late this evening into the overnight at all sites except for
ERI. Future cycles will almost certainly need to refine the
timing and potential restrictions with this activity.

Light southerly winds turn more south-southwest at 6 to 12
knots with a few 15-20 knot gusts this afternoon. Winds remain
generally south- southwest but subside to 4 to 8 knots outside
of any thunderstorms tonight.

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

&&

.MARINE...
Southwest winds will be on the increase today, generally in the 10-
15 knot range through at least Tuesday night. There could be brief
periods of stronger southwest winds to 20 knots. Latest model
guidance suggests the best chance of this occurring would be Monday
night into Tuesday, though there is very low confidence in this
right now, and would likely depend on the evolution of thunderstorms
over the next couple days. A cold front moves south across Lake Erie
late Tuesday night into Wednesday morning with winds becoming
north to northwest Wednesday through Friday.

&&

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

&&

$$

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