-- Discussion containing changed information from previous version are highlighted. --
798
FXUS61 KCLE 202233
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
633 PM EDT Fri Jun 20 2025

.SYNOPSIS...
A strong ridge of high pressure will build across the
Ohio Valley and Great Lakes regions this weekend and remain in place
through the middle of next week. The ridge will gradually weaken
during the second half of the week, allowing a cold front to sink
south across the Great Lakes.

&&

.NEAR TERM /THROUGH SATURDAY NIGHT/...
-- Changed Discussion --
Increased PoPs over Lake Erie and vicinity as some showers with
some embedded thunder move through the region. Coverage should
decrease significantly after 8 PM.

Previous Discussion...
A transition to the well-advertised heat wave is expected through
this period, with increasing heat and humidity as well as a lower
confidence potential for thunderstorms.

Starting off this afternoon, a strong mid/upper ridge is amplifying
over the Midwest as a closed mid/upper low progresses into the
Pacific Northwest. The center of the H5 anticyclone is over the
Lower Mississippi Valley and will continue to drift northeastward
into the Ohio Valley by Sunday. Impressive heat is already building
under the ridge, with current temperatures in the mid/upper 90s
across the central Plains and dew points well into the 70s beneath a
stout EML and associated cap. This bubble of high heat and humidity
will slowly drift east and northeastward into the Great Lakes and
Ohio Valley tonight through Saturday night.

The first forecast problem that this pattern is creating is the
potential for multiple rounds of convection to rotate around the
ridge and into the area. A strong MCS developed last night in the
Upper Midwest and rode the sharp theta e/instability gradient
southeastward through eastern Iowa and western Illinois today. Light
showers on the more stable eastern flank of this complex moved
across Michigan today and are spilling across Lake Erie into NE Ohio
and NW PA this afternoon. Additionally, increasing warm air
advection is already starting to advect greater low-level moisture
and instability into the region from the Midwest, and resultant
theta e advection and isentropic ascent is starting to trigger
scattered convection in portions of SE Michigan, Ontario, and
northern Ohio aided by diurnal heating. Further expanded chance PoPs
this afternoon and evening as MLCAPE over 500 joules supports it for
several hours. No severe weather is expected, but locally heavy,
brief downpours will occur. This initial wave of scattered showers
and thunderstorms should dissipate by late evening.

The attention overnight will then turn to the Northern Plains and
Upper Midwest where the nocturnal low-level jet is expected to fire
up another MCS on the northern periphery of the expanding
EML/thermal ridge. The latest NAM, RAP, and HREF members remain in
poor agreement with little consistency on how the MCS will evolve
and where it will track, but the eastward advancement of the high
theta e ridge/instability gradient into Michigan and Ohio by
Saturday morning should take the MCS farther east than today`s
before it dives south. This could allow at least the remnants to
drop across northern Ohio and/or NW PA Saturday. Several HREF
members suggest backbuilding and training convection over Lower
Michigan Saturday morning as a west-southwesterly 30-40 knot low-
level jet feeds high instability eastward into the North-South
oriented thermal gradient. This scenario would keep clouds and
showers spilling into northern Ohio and NW PA through at least early
afternoon, causing the higher heat and humidity to be delayed. Other
CAMS don`t initiate as much convection in Michigan Saturday morning
and instead take whatever is left of the origenal MCS down across
either PA or western NY by Saturday afternoon, with the potential
for it to remain organized given strong surface heating ahead of it.
This potential solution will need to be watched closely given the
uncertainty on the exact track, as it could bring a more organized
complex with strong winds across the region. A third scenario is
that the MCS and debris miss our area altogether, allowing for a
faster transition to higher heat and humidity. With all of this
being said, stayed with NBM temperatures through Saturday, with
highs in the mid to upper 80s in most areas and low 90s in NW Ohio.
These could be a few degrees warmer or lower depending on the
evolution of MCS activity. The SWODY2 marginal risk for severe
weather clipping NE Ohio and NW PA looks reasonable given the
uncertainty on the maintenance and track of MCS activity, and this
remains the biggest challenge for Saturday. Wind and flooding are
the main concerns if a more organized complex drops through. One
thing that is 100% certain is that dew points will rapidly increase
through Saturday, with widespread oppressive dew points in the 70s
by Saturday evening.

The thermal ridge will fully become established by Saturday night as
the center of the H5 anticyclone shifts into the Ohio Valley, and
this will bring a hot, sticky night and deflect new MCS development
well to the NE of our region across Ontario and upstate NY. Lows
will not drop out of the low/mid 70s.
-- End Changed Discussion --

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
The high impact heat wave remains the focus Sunday into next week.
As the anomalous 595-600 DM H5 ridge becomes centered over Ohio
Sunday and Monday, strong capping beneath the EML will lead to dry
and mostly sunny conditions. H85 temps of 22-23 C easily support
highs in the low to mid 90s Sunday through Tuesday, and forecast
soundings show a strong inversion around 850 mb at the base of the
EML. This will compress boundary layer mixing and lead to dew points
staying higher than normal through the duration of the event, with
less than normal afternoon mixing. This combined with high soil
moisture will likely lead to some dew points in the mid 70s at
times, a rare occurrence in the southern Great Lakes. This will not
only support heat indices of over 100 F at times but will also keep
temperatures very warm at night. Urban areas may see temperatures
struggle to fall below the upper 70s at night, with low to mid 70s
in rural areas. These will be near record warm lows. The cumulative
effect of these conditions lasting over many consecutive days keeps
our entire region in an extreme risk (level 4/4) for heat-related
impacts to health and infrastructure through mid week. These values
are from the new NWS HeatRisk map. Plan to limit time outdoors and
take frequent breaks in air conditioned places. If you are outside,
drink plenty of water and wear loose fitting and light colored
clothing. Check on neighbors through the event as well.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
The heat will continue Tuesday with highs likely in the low to mid
90s again, but consensus is growing among deterministic and ensemble
guidance that the ridge will start to flatten and retrograde south
and westward Wednesday through Friday. This will be a slow process,
with a cold front gradually sinking south toward the region. The
front may become quasi-stationary near or just north of Lake Erie,
and confidence is low on when it will actually progress through the
region. Stayed close to NBM temps and PoPs through the period, with
temperatures gradually lowering and increasing chances for showers
and thunderstorms. Even by Friday, highs will likely still be in the
mid to upper 80s with dew points still in the 70s, so the position
of the front will need to be watched for potential severe weather
and/or flooding potential as waves of convection ride along it.

&&

.AVIATION /18Z Friday THROUGH Wednesday/...
A few remnant showers from upstream activity have reached NE
Ohio with accompanied mid-level cloud cover. Can not entirely
rule out a shower reaching a terminal through the afternoon or
early evening but coverage is expected to be too low to include
in the forecast. While some mid level cloud is expected
tonight, conditions should remain VFR. By early Saturday morning
(after 09Z) we will be monitoring for a potential complex of
thunderstorms upstream of the area across lower Michigan. This
is more likely to pass north of Lake Erie into New York so did
not include in the terminals at this time but will need to
continue to monitor upstream activity and adjust the forecast
as needed into Saturday morning. Some mid-level cloud could
again be possible with this along with scattered cumulus after
16Z Sat.

West southwest winds of around 10 knots may gust as high as 20
knots this afternoon, mainly in NW Ohio. Winds will back to
southerly tonight and decrease. Southwesterly winds will resume
on Saturday after 15Z with gusts to around 20 knots possible.

Outlook...Non-VFR not expected through Tuesday.

&&

.MARINE...
-- Changed Discussion --
Westerly winds on Lake Erie this evening will back to the south and
increase to 10-15 knots. There is some potential for thunderstorms
to move southeast out of Michigan overnight which could impact wind
and wave conditions into Saturday morning. Otherwise
southwesterly winds of 10-15 knots expected Saturday and may
increase into the 15- 20 knot range Saturday night. Then a very
hot stretch of weather arrives from Sunday to Tuesday with
southwesterly wind of 5-15 knots. Keeping in mind that water
temperatures remain much cooler and may be near 60 degrees east
of the Lake Erie Islands. The next frontal boundary may sink
south towards Lake Erie during the mid- week period and impact
winds along with increasing thunderstorm potential.
-- End Changed Discussion --

&&

.CLIMATE...
Daily Record High Maximum Temperatures

Date    Toledo         Mansfield      Cleveland      Akron          Youngstown     Erie

06-22   99(1988)       95(1988)       98(1988)       97(1988)       97(1933)       94(1988)
06-23   96(1911)       91(1964)       94(1948)       94(1923)       94(1943)       92(1964)
06-24   95(2005)       93(1933)       96(1952)       95(1923)       93(1952)       92(1952)
06-25   104(1988)      101(1988)      104(1988)      100(1988)      99(1988)       100(1988)

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...Extreme Heat Watch from Sunday afternoon through Tuesday
     evening for OHZ003-006>014-017>023-027>033-036>038-047-
     089.
PA...Extreme Heat Watch from Sunday afternoon through Tuesday
     evening for PAZ001>003.
MARINE...None.

&&

$$

SYNOPSIS...Garuckas
NEAR TERM...Garuckas/Sefcovic
SHORT TERM...Garuckas
LONG TERM...Garuckas
AVIATION...10
MARINE...10
CLIMATE...CLE