687
FXUS61 KCLE 010136
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
936 PM EDT Tue Apr 30 2024

.SYNOPSIS...
High pressure will build over the Central Great Lakes tonight. A
warm front extending from low pressure over Lake Superior will lift
north across the area Wednesday morning, followed by a weakening
cold front settling south Wednesday night. High pressure will build
east across the Great Lakes Region on Thursday.

&&

.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
9:35 PM Update...
No changes needed to the forecast with this update. Overnight
low temperatures dip into the upper 40s to lower 50s.

Previous discussion...
Satellite imagery shows a thicker cloud field from near Youngstown
into Crawford County Pennsylvania. Can not rule out a sprinkle
or light shower in these far eastern areas before subsidence
wins out by 5 PM. Beyond that, high pressure builds into the
area tonight with skies clearing. Drier air will arrive across
the region but still some potential for patchy fog in the
eastern counties where there will be less time to mix out
dewpoints with nearly calm winds and good radiational cooling.
Lows tonight will be 6-10 degrees cooler than last night.

Upper level shortwave trough will lift into the Upper Midwest
tonight, then round the ridge across the Upper Great Lakes on
Wednesday. At the surface, a warm front will lift across the area as
low pressure reaches Lake Superior by Wednesday morning. Warm
advection driven by breezy southwest winds will boost temperatures
back into the upper 70s to near 80 degrees. The breezy
conditions will slow the rise in dewpoints ahead of the cold
front approaching for the afternoon. Some theta-e advection does
occur but mid-level moisture out paces low level moisture and
expect a capping inversion to develop and limit thunderstorms
from developing. Some mid-level cloud during the morning will be
replaced by a scattered cu field during the afternoon. The best
chance for an isolated shower would be across far Northeast
Ohio or Northwest Pennsylvania heading into Wednesday evening
but the potential for this still looks too low to include in the
forecast. Record high temperatures for the first of May are in
the mid to upper 80s and do not expect to approach those. We dry
out again behind this weakening cold front on Wednesday night
with lows in the lower 50s.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
The axis of a mid/upper ridge will significantly sharpen across the
Great Lakes Thursday in response to a mid/upper shortwave trough
ejecting from the northern Rockies into the Northern Plains before
closing off into a vertically stacked low in the vicinity of
northern Minnesota by Friday. This will set up persistent southwest
flow and resultant warm/moist advection as elongated surface high
pressure over the eastern Great Lakes Thursday gradually moves east
allowing the associated cold front to slowly progress into the area
from the west late Friday and Friday night. Thursday will be dry and
very warm with temperatures continuing in the upper 70s/low 80s, but
the combination of the surface high over the eastern Great Lakes and
weak pressure gradient will cause an afternoon lake breeze to
develop, so expect cooler conditions near the lakeshore. Deepening
moisture and the slow approach of the cold front will start to
gradually bring in chances for showers and thunderstorms Thursday
night and Friday from west to east, but it still looks like most of
the precip will hold off until Friday night due to little in the way
of forcing until the front arrives. Given the strong mid/upper ridge
over the eastern CONUS ahead of a low which is closing off and
lifting well NW of the area into Minnesota and Canada, feel that the
cold front will be very slow to move through and will likely even
become quasi-stationary over eastern Ohio and western PA by
Saturday. This gives confidence in the highest coverage of showers
and thunderstorms occurring Friday night and Saturday.

In terms of severe potential Friday and Friday night, it will be
very limited. As mentioned, there is little in the way of forcing
for widespread, organized convection Friday, so expecting coverage
to be scattered and mainly garden variety Friday afternoon and
evening. Forcing increases as the front moves in Friday night, but
the best jet dynamics lag well to the NW, and we are also dealing
with waning overnight instability (marginal thermodynamics). This
environment of weak shear and weak CAPE supports mainly general,
garden variety showers and thunderstorms Friday night, although
coverage will be greater. Cannot rule out an isolated stronger storm
with gusty winds and small hail, but it won`t be the norm. If
anything, the bigger concern will be locally heavy rainfall from
slow moving/training convection. Deep layer flow will be
parallel to the gradually pivoting NE to SW oriented cold
front, and with seasonably high PWATs and persistent warm/moist
advection, will need to watch for localized flooding. The good
news is that most areas outside of NW Ohio have dried out over
the past 2 weeks, so flash flood guidance is higher.

Highs Friday will warm into the low/mid 80s in most areas with dew
points in the low 60s, so it will be quite humid. Lows Thursday
night will range from the mid 50s to around 60, with upper 50s to
low 60s Friday night.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As mentioned above, the cold front is looking increasingly likely to
become quasi-stationary over eastern Ohio and western PA Saturday as
the associated stacked/closed low lifts well into Canada west of
James Bay, displacing the support well to the NW, and the front also
runs into the persistent ridging over the East Coast. This will
keep fairly widespread clouds and showers/thunderstorms over
the area Saturday, especially in areas east of I-77. Again, will
need to watch for localized heavy rainfall and flooding from
slow moving or training convection, but widespread impacts are
not expected other than it not being the nicest day Saturday.
Uncertainty then increases Sunday into early next week regarding
the coverage of convection. A somewhat deeper shortwave trough
may swing through the Great Lakes by Sunday with surface ridging
trying to build into the Great Lakes late Sunday and Sunday
night. This would force the old frontal boundary farther east
and bring drier conditions, but there is uncertainty in the
pattern evolution among guidance. At this time, have gradually
decreasing PoPs Saturday night through Sunday night. What is
more clear cut is that heights will quickly start to rebound
Monday and Tuesday as broad mid/upper ridging develops over the
central and eastern CONUS ahead of broad troughing carving out
over the western CONUS. This will lead to an increase in
warm/humid conditions again (after a small airmass change this
weekend), with increasing chances for convection as an active
baroclinic zone sets up nearby.

Highs ranging from the low to upper 70s Saturday and Sunday will
warm into the mid/upper 70s Monday and upper 70s/low 80s Tuesday.

&&

.AVIATION /00Z Wednesday THROUGH Sunday/...
VFR under a clear sky this evening across all terminals. A few
higher wind speeds (10+ knots) will last for the next hour or
two before diminishing to light and variable overnight tonight.
VFR will persist through the TAF period, but can`t rule out
patchy fog across Northwest Pennsylvania dropping visibilities
to MVFR.

Light and variable winds overnight tonight become southwesterly
and increase by tomorrow afternoon. Expect southwest winds
between 10-15 knots with gusts to 20-25 knots tomorrow
afternoon.

Outlook...Non-VFR may return in showers and thunderstorms
Thursday night through Saturday.

&&

.MARINE...
Quiet weather is still expected on the lake through the next 5 days
outside of any thunderstorms as the pressure gradients remain weak.
Light and variable winds tonight will turn WSW at 10-15 knots
Wednesday before turning light and variable again Wednesday night.
ENE winds then develop Thursday with speeds of 5-15 knots in
response to stronger high pressure over the eastern Great Lakes
before turning E to SE Thursday night and Friday. Winds should
fluctuate between ENE and ESE Friday night and Saturday with speeds
of 5-15 knots before finally turning back to SW at 5-10 knots late
Saturday night and Sunday.

&&

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

&&

$$

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