114
FXUS61 KCLE 041804
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
204 PM 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/...
9:40 AM Update:
A somewhat messy forecast today and tonight as we deal with a
humid and modestly unstable airmass, with a nearby front and
weak convectively-enhanced shortwaves providing some lift at
times. There is still broad convergence across northern OH
inland from the lakeshore this morning as the diffuse frontal
boundary has not completely cleared the area. The humid and
weakly unstable airmass is already contributing to a few showers
within the broad convergence axis across northern OH.

Heating will result in approximately 1000 J/KG of skinny MLCAPE
developing south of the front by this afternoon, so a few
showers (and storms by this afternoon) may continue percolating
along the diffuse frontal boundary across parts of
northern/central OH through the afternoon. Outside of these few
showers/storms, most of the area will be rain-free into this
afternoon. There appears to be one convectively aided wave over
southern IN this morning that will spread in later this
afternoon with another, better defined wave currently getting
ready to cross the Mississippi near the IA/MO border that will
move through tonight. Both waves will add a bit of lift and
bring increased potential for showers/thunder, especially south
of the front. Activity will mainly be focused across the
southern half of our area through most of today before shifting
northeast into tonight. Skinny and modest instability profiles
will generally make it difficult to see severe weather, though
with 30-40 knots of deep-layer shear in place will need to
monitor any storms that ride along the front for a bit more
organization and intensity this afternoon or evening. Rain
rates will be efficient today and tonight, though storm motions
should keep total rain amounts (and flooding concerns) in check
unless any training occurs.

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 /18Z Thursday THROUGH Tuesday/...
A batch of rain with isolated embedded thunder is pushing in
from the southwest, currently impacting FDY. This batch of rain
is weakening as it moves in but should at least reach MFD over
the next 30-60 minutes. Elsewhere it`s uncertain if the rain
will make it in, though some scattered convective showers have
developed across inland northern OH, so handled with a few other
VCSH mentions. Another surge of showers/thunder is expected this
evening from west to east, with the greatest thunder potential
at FDY, MFD and CAK but potentially spreading as far north and
east as CLE and YNG too. Attempted to time as best as possible.
Future adjustments are possible, as the evening round of storms
has yet to develop to our west and may be influenced by the
afternoon showers/thunder moving through now. We should see a
lull in precipitation late tonight into Friday morning, though
with the humid airmass and light winds in place some non-VFR
ceilings and visibility may develop for a few hours early
Friday. Isolated to scattered convection likely re-develops
Friday afternoon, though that`s largely past the end of the TAF
period and confidence in coverage/timing is low.

Winds are light, though range from northerly near Lake Erie to
southerly inland this afternoon. Winds turn light and variable
tonight, before shifting southwest at 4 to 10 knots Friday.

Outlook...Non-VFR possible in showers and thunderstorms late
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/Sullivan
SHORT TERM...Sefcovic
LONG TERM...Sefcovic
AVIATION...Sullivan
MARINE...Sefcovic