911
FXUS61 KCLE 041102
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
702 AM EDT Thu Jul 4 2024

.SYNOPSIS...
A weak cold front will stall near the Ohio River this morning
before lifting back northward tonight and Friday as low pressure
moves into the western Great Lakes. This low will move east
Friday night, dragging a cold front across the region by
Saturday morning. High pressure returns by Sunday and Monday.

&&

.NEAR TERM /THROUGH FRIDAY/...
6:30 AM Update...

Added slight chance PoPs along the lakeshore this morning to
account for a few showers that have developed in the past 2
hours. Forcing is weak, and suspect the diffuse front has not
sagged south as quickly as expected, so carried these PoPs into
mid morning. The rest of the forecast remains on track.

Original Discussion...

A seasonably warm and humid airmass will remain in place for the
4th of July holiday through the end of the week, but the
placement of showers and thunderstorms is low confidence as a
diffuse, quasi-stationary frontal boundary starts to lift back
northward later today and tonight. The overall theme is mainly
dry today as the boundary settles near the Ohio River, with
increasing chances for showers and thunderstorms tonight and
Friday. Now for a little more detail...

Broad mid/upper troughing is seen on water vapor imagery from
the northern Rockies through the northern Great Lakes this
morning with quasi-zonal flow from the central Plains into the
southern Great Lakes. At the surface, weak low pressure is found
over eastern North Dakota with a cold front extending southward
from it across the central and southern Plains while another
weak cold front extends eastward from Kansas into the Ohio
Valley. Several areas of convection and associated MCV`s can be
seen traversing this frontal zone from Kansas into Kentucky this
morning, and outflow boundaries as this activity decays later
this morning will be the main driver for redevelopment today.
Most deterministic guidance is in good agreement that the weak
frontal boundary will sag to near the Ohio River this morning
before becoming quasi-stationary as weak surface ridging noses
southward from the northern Great Lakes. This should keep most
of northern Ohio and western PA dry today as slightly drier air
works southward. However, the emphasis is on should. HREF CAMS
are not in agreement on where showers and thunderstorms will
redevelop due to questions on exactly how far south the front
sags and locations of outflow boundaries. Some show
redevelopment over southern and western areas this afternoon and
evening while others show showers from decaying convection just
moving in from the west while others are dry. The best pool of
instability will be to our south in the Ohio Valley, so kept
PoPs lower than blended guidance today, with the highest chances
near the US 30 corridor.

By tonight, the weak/diffuse frontal boundary will start to lift
back northward in response to a stronger mid/upper shortwave
progressing through the Upper Midwest with the left exit region
of a 95-100 knot H3 jet streak deepening the surface low to near
1000 mb by Friday afternoon as it progresses into northern Lower
Michigan. This will pull northern Ohio and NW PA back into the
warm sector, but before that happens, convection is likely to
accompany the lifting frontal boundary. CAMS are again all over
the place regarding convective development tonight making for a
low confidence POP and QPF forecast, and this is largely due to
a lack of a pronounced low-level jet impinging on the frontal
boundary. There will likely be at least scattered showers and
thunderstorms gradually spreading north/northeastward with the
boundary tonight, but a little more widespread activity could
move in from the west after generating upstream in a more
favorable low-level jet environment. Due to questions on the
coverage, kept PoPs at chance tonight, but gradually expanded
them northward. As the low crosses northern Lower Michigan
Friday, it will become vertically stacked as the mid/upper
shortwave closes off, and this will push a strong cold front
through the area in the afternoon and evening. This will be the
best opportunity for more widespread showers and thunderstorms
as the right entrance region of the upper jet interacts with a
moderately unstable airmass. HREF guidance and NAM and RAP
forecast soundings suggest 1000-1500 J/Kg of SBCAPE along with
impressive deep layer (0-6 Km) bulk shear of 40-50 knots. This
along with mid-level dry air and associated inverted-V soundings
could support damaging winds with bowing clusters, but again,
the amount of instability will be a determining factor for the
degree of the threat. There will likely be a lot of debris
clouds and outflow boundaries from prior convection, and this
could temper the already only modest instability or cause new
convection to develop largely east of the area. The SWODY2
marginal risk looks reasonable, and the forecast will continue
to be monitored

Highs today and Friday will range from the mid to upper 80s
with continued muggy conditions. Lows tonight will only fall
into the upper 60s/low 70s.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
A surface cold front will be moving through the forecast area on
Friday night and surface low pressure north of the area will
continue departing to the northeast into Canada. The bulk of any
shower and storm chances on Friday night will be east of the cold
front, which should be somewhere along the I-71 corridor at 00z/Sat.
The above conditional severe threat will likely apply for the first
part of the short term period, but loss of diurnal heating and
limited area ahead of the cold front will make the threat very
short. An upper trough will still be present in the Great Lakes
region on Saturday, which would normally be a concern for generating
additional convection in the region. However, drier air will be
surging into the area with low 60s dew points by mid-day Saturday,
so will keep a dry forecast, but this is the time frame that could
see some change. High pressure will build from the southwest for
Saturday night through Sunday night and dry conditions are expected.
Temperatures through the period will be seasonable.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
The long term forecast period will trend back toward an unsettled
weather pattern for next week. However, the forecast trend for
Monday has actually improved in recent forecast cycles as the upper
trough is a bit slower to progress toward the region and the surface
cold front may not enter the area until late Monday night into
Tuesday. Therefore, have a slower PoP progression on Monday and
slightly warmer temperatures with highs in the upper 80s to near 90
degrees. The upper trough and cold front combo will be solidly into
the area on Tuesday and have the highest PoPs for the long term
period during the daytime hours on Tuesday. There will likely be
enough instability ahead of the front to allow for good thunder
chances and potentially even some stronger storms. The front will
cross the region by Wednesday, but have some lingering PoPs during
the daytime hours for mainly the timing differences in the models at
this time. Temperatures will be in the low to mid 80s on Tuesday and
Wednesday with convection in the region and behind the cold
front.

&&

.AVIATION /12Z Thursday THROUGH Monday/...
A few showers have developed near the lakeshore early this
morning, and these could impact KCLE and KERI at times, but
expect conditions to mainly stay VFR. Fog and mist inland
affecting KMFD, KCAK, and KYNG should burn off in the next hour
or two. This will leave mainly dry and VFR conditions the rest
of today. The front will begin to lift back northward as a warm
front tonight, and this will spread showers and thunderstorms
back into the region from SW to NE. Feel that the activity will
still be scattered, so kept the mentions to VCSH and VCTS, but
brief MVFR is possible in any heavier downpours. There is
another good signal for patchy fog in the same inland areas
tonight, so added that to KMFD, KCAK, and KYNG.

Light S to SW winds early this morning will turn more W to NW
later this morning and this afternoon and increase to 5-10 knots
before becoming E to SE tonight as the front lifts northward.


Outlook...Non-VFR possible in showers and thunderstorms Friday
into Friday night.

&&

.MARINE...
A front will settle across the Ohio River Valley today and allow for
light and variable flow to develop across the lake with some lake
breeze components expected. Some remnant showers and storms could
enter the region tonight and winds may try to favor a southerly
direction. The front across southern Ohio will lift back north as a
warm front on Friday and southeast flow will be favored. A surface
low will move north of the lake Friday night into Saturday and
enhanced southwest flow will develop across the lake and a Small
Craft Advisory headline will be possible. The low will depart the
region on Saturday night and high pressure will build from the
southwest, reducing the southwest flow on the lake. The surface high
will move east for Sunday and southerly flow will be favored across
the lake through Monday. The pressure gradient will be light enough
on both Sunday and Monday to allow for some lake breezes to
form.

&&

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

&&

$$

SYNOPSIS...Garuckas
NEAR TERM...Garuckas
SHORT TERM...Sefcovic
LONG TERM...Sefcovic
AVIATION...Garuckas
MARINE...Sefcovic