121
FXUS61 KCLE 160148
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
948 PM EDT Thu Aug 15 2024

.SYNOPSIS...
A warm front will lift northeast across the area on Friday as
low pressure slowly approaches from the northwest. This low
pressure will drift east through the weekend, dragging a cold
front across the area Saturday.

&&

.NEAR TERM /THROUGH FRIDAY NIGHT/...
930 PM...Radar returns continue to be apparent across portions
of North and Northwest Ohio this evening, though much of this
activity remains light with the dry low- level air mass in
place. Slightly heavier rain exists just south of the area
across central OH. Otherwise, we`ll be watching how convection
evolves across eastern IA/IL this evening and overnight ahead of
an upper-level trough evident on water vapor imagery. Still
some uncertainty on the eastward extent of this convective
activity, though there exists the potential for a few
thunderstorms Friday morning across Northwest Ohio.

Previous Discussion...
Low pressure currently over Minnesota will drift towards
northern lower Michigan by late Friday night. Ahead of this low
a warm front will lift northeast across the area on Friday. An
initial cold front (with little airmass change) will cross from
west to east Friday night with a shortwave aloft crossing
through the southern Great Lakes Friday afternoon/evening.

Moist isentropic lift ahead of the warm front is supporting
clouds and light rain showers into parts of western Ohio. While
dry low-levels are in place ahead of this light rain, at least
some of it is reaching the ground. Expect thicker clouds and
potential for a few light rain showers to slowly spread east
through tonight, though progress will likely slow for several
hours later this evening into the overnight as the rain will
struggle to push east into the departing high pressure. There
will be another (greater) push of showers as the warm front
lifts in very late tonight into Friday morning from west to
east. We should see a period of relatively drier weather spread
in from the west/southwest behind the warm front into the
afternoon on Friday. By mid to late-afternoon, any heating will
result in some destabilization which should allow showers and
thunderstorms to increase in coverage as the shortwave moves
through the region and adds some large-scale lift. Storms will
be favored across parts of Northeast OH/Northwest PA in
proximity to the warm front, with additional activity trying to
spread in from the west during the late afternoon or evening
ahead of the approaching cold front. Shower and storm chances
will continue to work east across the area Friday night as the
cold front moves through, though the overall coverage and
intensity should gradually diminish after sunset.

The environment will Friday afternoon and evening will feature
relatively skinny CAPE due to weak mid-level lapse rates with
modest wind shear. Overall, about 25 knots of deep-layer shear
and 750-1500 J/KG of MLCAPE can be expected. While a couple of
stronger storms may produce gusty to locally damaging winds
thanks to 700-1000 J/KG of DCAPE and somewhat steep low-level
lapse rates of 7-8C/km, feel like the severe threat is on the
lower end. The SPC has maintained a Day 2 "Marginal Risk" (level
1/5) for severe weather for Friday afternoon-evening. Skinny
instability profiles and precipitable water values climbing to
1.75-2.00" will support efficient rain rates with convection
Friday afternoon and evening, so if some training or back-
building occurs (as the HRRR and ARW hint at) there could be a
localized heavy rain/flooding concern too. Any localized severe
weather or flooding threats will diminish with time after
sunset Friday night.

Lows tonight will be milder than the last several, generally
ranging from the mid 60s to near 70. Highs on Friday will reach
the lower to upper 80s with increasing humidity. The coverage of
clouds and rain with the warm frontal passage will influence
those highs. With muggy dew points, lows will struggle to fall
much below the upper 60s to near 70 Friday night.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
A wet and active pattern will dominate this weekend as a surface low
meanders east across the Great Lakes region. On Saturday, an upper
level trough will continue to dig south across the region as an
occluding low approaches the central Great Lakes. A cold front
associated with this low will depart to the east early Saturday with
some showers and thunderstorms lingering across eastern portions of
the CWA. The aforementioned low will persist over the region,
resulting in winds behind the departing front remaining from the
southwest and continuing to advect moisture and warmer temperatures
into the area.An 850mb LLJ of 20-30 knots and upper level support
from a shortwave moving on the periphery of the trough will enhance
the chance for shower and thunderstorm potential through Saturday
afternoon ahead of a secondary cold front. Daytime heating should
aid in enhancing instability across the area with models generally
suggesting an average of 1500 J/kg by 18Z Saturday with 0-6km bulk
shear of 20-30 knots. These conditions should lead to an increase
risk of severe weather Saturday afternoon into the evening hours
which SPC has highlighted in a Day 3 Marginal with the primary
threat remaining strong winds. There are some potential limiting
factors however that make this forecast less confident, including
how the overnight/morning convection and lingering clouds will
impact the area by increasing stability which will likely be
enhanced if the initial cold front slows at all. The other aspect is
the exact location of the low pressure center over the region. There
remains a bit of a spread in model agreement with some placing the
low closer to Lake Erie while others place it closer to over Lake
Huron which will impact the location of the features described
above. In addition to the severe threat, PWAT values of 1.5-1.8
inches and warm cloud depths greater than 10kft will present another
chance for locally heavy rainfall and potential flooding. As a
result, WPC has placed portions of the area in a Day 3 Marginal ERO.

By Saturday night, showers and thunderstorms will linger across the
area, but the severe threat will diminish once the sun goes down.
The aforementioned low will continue to very slowly move east through
Sunday, finally reaching the New England area Sunday night. With the
placement and continued upper level support from a deepening trough,
chances of showers and isolated thunderstorms will persist through
the entire period, gradually tapering from west to east Sunday
night. Less confidence exists for any chance of severe weather or
heavy rainfall on Sunday as the generally flow become northwesterly
and colder air begins to push south. Will need to continue to
monitor the pattern given the uncertainty of the low placement.

High temperatures on Saturday will climb into the upper 70s to low
80s, possibly warming a tad more in areas where there is any cloud
breaks. Once winds shift to northwesterly for Sunday, CAA will
return highs to the mid to upper 70s. Overnight lows through the
period will be in the low 60s.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Lingering showers and storms may persist across the eastern CWA as
the aforementioned low continues to slowly drift northeast towards
Nova Scotia. By Monday evening, high pressure should become dominant
across the entire area and end the potential for precipitation from
Monday night through Thursday. With the presence of a Canadian high
pressure over the area, temperatures will remain a bit cooler Monday
through Wednesday with highs climbing into the low to mid 70s and
then will slightly warm near the end of the period into the upper
70s. Overnight lows will drop into the 50s.

&&

.AVIATION /00Z Friday THROUGH Tuesday/...
VFR across the TAF sites this evening with primarily VFR to
persist through much of the TAF period. Will be primarily dealing
with a lot of light rain showers with minimal impact expected
in the first half of the TAF period. Non- VFR appears more
likely towards the end of the TAF period Friday afternoon and
evening, though confidence remains low on thunderstorm timing
and location. Have added vcts at the central and eastern TAF
sites in this update, excluding TOL/FDY since confidence in
afternoon/evening thunderstorms is lower along the I-75
corridor. Thunderstorms could be strong at times Friday
afternoon and evening, with the primary threat being wind.
Otherwise, ceilings should remain above 3kft for the most part,
though can`t rule out brief drops between 2 to 3kft in any
heavier showers or thunderstorms.

Winds will generally favor a east to southeast direction this
evening and overnight, around 5 knots. Winds will gradually
shift more towards the southeast and eventually south by Friday
afternoon, 10 to 12 knots.

Outlook...Non-VFR possible in periods of showers and
thunderstorms Friday night through Monday, especially in the
afternoon and evening hours. Widespread non-VFR appears most
likely in low ceilings on Sunday into Monday.

&&

.MARINE...
Easterly winds of 5-10 knots this afternoon will gradually become
southeasterly at 10-15 knots by Friday morning. A warm front
associated with a low pressure system over the western Great Lakes
will move north across the lake on Friday resulting in winds
gradually becoming more southerly at 10-15 knots. The aforementioned
low pressure system will slowly drift east across the region,
becoming centered near Lake Erie on Saturday. This will increase the
gradient across Lake Erie and result in winds increasing from the
southwest to 15-20 knots. This flow will keep the largest waves
isolated to the northern lakeshore. As the low shifts towards New
England late Sunday into Monday, a northerly flow will become
established at 15-20 knots with waves building to 4-6 feet along the
near shore. The entire period from Saturday through Monday will
potentially need a Small Craft Advisory. By Tuesday of next week,
high pressure will return to the region, weakening variable winds to
5-10 knots.

&&

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

&&

$$

SYNOPSIS...Sullivan
NEAR TERM...Kahn/Sullivan
SHORT TERM...Campbell
LONG TERM...Campbell
AVIATION...Kahn
MARINE...Campbell