903
FXUS61 KCLE 170008
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
808 PM EDT Tue Jul 16 2024

.SYNOPSIS...
A ridge exits southeastward from our region as a weak cold front
drifts southeastward across northern Ohio and northwest
Pennsylvania this evening through late Wednesday morning. Behind
the front, another ridge builds slowly from the north-central
United States and vicinity through the end of this week.

&&

.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
Finally starting to see some lightning with scattered showers
filling south of a line from Findlay to Mansfield. This activity
has been limited thus far by warm air near 600mb which is
limiting updrafts. However it does look like slightly higher
dewpoints may advect in ahead of the front along with low level theta-e
advection below 850mb so some expansion in thunderstorms is
possible into this evening but do not expect them to intensify.
Otherwise may see additional activity overnight develop ahead
of the front across the north and eventually settling southeast
towards Youngstown.

Previous discussion...
Cyclonic W`erly flow aloft and embedded shortwave disturbances
affect our CWA through Wednesday night as a mid/upper-level low
wobbles southeastward from northern ON to southwestern QC. At
the surface, a ridge exits SE`ward as a weak cold front drifts
SE`ward through our region from around sunset this evening
through late Wednesday morning. Behind the front, another ridge
builds slowly from the north-central United States and vicinity
through Wednesday night. However, subtle trough axes associated
with the aforementioned shortwave disturbances will also
traverse our region generally from northwest to southeast on
Wednesday. Overnight lows tonight are expected to reach the mid
60`s to lower 70`s around daybreak Wednesday morning. Late
afternoon highs are forecast to reach the upper 70`s to lower
80`s on Wednesday as intervals of sunshine and daytime heating
are partially-offset by net low-level CAA behind the weak cold
front. Overnight lows are expected to reach the upper 50`s to
mid 60`s around daybreak Thursday morning as a cooler/drier air
mass associated with the aforementioned surface ridge continues
to overspread our region.

Primarily fair weather is expected. However, isolated showers
and thunderstorms are possible through this early evening,
roughly south of U.S. Route 30. This is where CAM`s continue to
suggest residual differential heating-related mesoscale fronts
may act as a focus for convection initiation amidst weak to
moderate boundary layer CAPE, moderate DCAPE around 500 to 900
J/kg, steep low-level lapse rates, and moderate effective bulk
shear. If storms develop in this area, they may produce a few
damaging convective gusts. Additional isolated showers and
thunderstorms are possible along/just ahead of the cold front
this evening through late Wednesday morning as the front
encounters a warm/moist sector comprised of weak to moderate
boundary layer CAPE and moderate effective bulk shear. Severe
thunderstorms are unlikely to accompany the front given
continued weak mid-level lapse rates and weakening DCAPE/low-
level lapse rates via nocturnal cooling. Behind the cold front,
isolated showers/thunderstorms remain possible through the
early evening hours of Wednesday as the aforementioned surface
trough axes encounter moderate effective bulk shear and a "cool
sector" boundary layer comprised of surface dew points mainly
in the 60`s and weak to moderate CAPE. However, model soundings
suggest that low-level CAA partially offsetting daytime heating
and abundant cloud cover will limit the magnitude of DCAPE/low-
level lapse rates as mid-level lapse rates remain poor. As a
result, severe thunderstorms are not a concern on Wednesday, but
trends in forecast model data will continue to be monitored.
Fair weather is expected CWA-wide later Wednesday evening
through daybreak Thursday due, in part to a lowering/stabilizing
subsidence inversion accompanying the surface ridge.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
The pattern change will be fully in place by Thursday signaling the
beginning of a period of spectacular weather that will last through
the weekend. A deep mid/upper trough axis across the central Great
Lakes and Ohio Valley will gradually shift east Thursday night and
Friday, however, broad longwave mid/upper troughing and associated
NW flow will persist across the Great Lakes and Northeast US into
the weekend downstream of a strengthening mid/upper ridge (heat
dome) over the Intermountain West. This mid/upper level pattern will
allow strong surface Canadian high pressure to drift from the Upper
Midwest Thursday to over the central Great Lakes and Ohio Valley by
Friday night.

Lake-effect clouds will linger from north central Ohio into NW PA
Thursday morning, but increasing amounts of dry air and subsidence
will lead to mostly sunny skies by afternoon, with mostly clear
conditions then lingering through Friday night. The NW flow aloft
and Canadian high pressure will bring below normal temperatures for
a change with highs in the low/mid 70s Thursday and mid 70s to near
80 Friday. Lows Thursday night and Friday night will be impressively
cool due to the clear skies and light winds promoting radiational
cooling. Expect lows in the mid/upper 50s both nights, with some low
50s in sheltered valleys of interior NE Ohio and NW PA and along the
US 30 corridor.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
The relatively cool pattern will continue this weekend, but gradual
warming with an increase in humidity is expected early next week as
the surface high drifts into the eastern Great Lakes Saturday and
Sunday and eventually offshore of the East Coast by Tuesday. This is
in response to rising heights across the Appalachians and Ohio
Valley as the Bermuda High strengthens off the SE coast ahead of
a shortwave gradually progressing out of the Plains early next
week. Deterministic and ensemble guidance are struggling to time
this shortwave as it may evolve into a closed low over the
midsection of the country, and that affects how soon a warm
front and associated warm air advection may set up across our
region. The trends have been slower, so kept dry conditions
through Sunday with increasing clouds, with slight chance PoPs
for isolated showers and thunderstorms reaching the US 30
corridor Monday. The better surge of moisture and greater
chances for diurnal showers/storms will probably be delayed
until Tuesday.

Highs will warm into the low 80s Saturday and low to mid 80s Sunday,
but humidity levels will remain comfortable with dew points in the
50s. Highs in the low to mid 80s are expected Monday and Tuesday
with a noticeable increase in humidity as dew points rise into the
60s.

&&

.AVIATION /00Z Wednesday THROUGH Sunday/...
Scattered showers have developed just south of a line from FDY
to MFD this evening with some low level moisture advection
ahead of a cold front that will settle south across the area
overnight. Any thunderstorm this evening will have brief heavy
rainfall if they hit a terminal with brief IFR possible, but
coverage of thunderstorms is expected to be low. We do expect
scattered showers to also accompany this cold front but
confidence in which terminals may be impacted is low so backed
off from prevailing showers in most cases to tempo for light
rain showers. An expansion of cloud cover is also likely ahead
of the front and may be MVFR for inland locations. It is not out
of the question that a few pockets of IFR are also possible
between 09-12Z, mainly at MFD or CAK.

The front is generally slow to cross the area with a wind shift
to the northwest reaching northern terminals between 7-10Z, and
inland terminals between 12-14Z. Ceilings will improve to VFR by
midday and then scatter out late, except TOL/MFD which will
scatter out during the morning.

Outlook...Non-VFR possible with isolated showers/thunderstorms
Wednesday afternoon through evening.

&&

.MARINE...
The winds and waves have diminished on Lake Erie as the MCV has
moved well to the east, so allowed the headlines to expire at 20Z.
This will leave SW winds of 10-15 knots in place tonight, shifting
to N by Wednesday morning while diminishing to 5-10 knots through
the day as a cold front pushes south of the lake. N winds will
continue Wednesday night and Thursday with an increase to 10-15
knots Thursday before diminishing to 5-10 knots again Thursday night
and Friday. Winds will generally turn light and variable on the lake
this weekend. Overall, very quiet marine conditions are expected,
however, there will be a near 14 C lake to 850 mb temp differential
Thursday morning, so cannot rule out an isolated waterspout or two.
The boundary layer dries quickly, and short fetch N flow is
expected, so will leave this out of the HWO for now, but it`s
something to further investigate.

&&

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

&&

$$

SYNOPSIS...Jaszka
NEAR TERM...KEC/Jaszka
SHORT TERM...Garuckas
LONG TERM...Garuckas
AVIATION...KEC
MARINE...Garuckas