695
FXUS61 KCLE 130808
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
408 AM EDT Sat Jul 13 2024

.SYNOPSIS...
High pressure remains in control of the local weather through
tonight. A warm front lifts across the area on Sunday before
stalling across the central Great Lakes region on Monday and
Tuesday. The front will move southeast across the area as a
cold front Tuesday night or early Wednesday.

&&

.NEAR TERM /THROUGH SUNDAY/...
Warm and mainly dry weather is in store for today with weak
surface high pressure in control. Patchy fog is developing
across a few valleys early this morning but will quickly mix
out after sunrise. Water vapor imagery reveals a weak vort max
over southern Lake Michigan that should move through this
afternoon. Very modest ascent ahead of this feature should
combine with the development of weak to moderate and uncapped
instability to yield a cumulus field and at least a few attempts
at showers or storms this afternoon or early evening. The
greatest potential for activity to pop will be along a lake
breeze that will push inland this afternoon, though hilltop
convergence may contribute as well. The minimal forcing, a warm
layer around 600mb and dry mid-levels will be limiting factors
for shower/storm development today though most hi-res models
manage to develop at least isolated activity. Given this,
maintain the slight chance (20%) POPs that we`ve been carrying
in the forecast away from the lakeshore and a smaller area of
chance POPs from approximately a Medina to Millersburg line
points east-northeast across the Youngstown and Warren area.
Highs today will generally reach the mid to upper 80s with dew
points in the mid to upper 60s.

Given steep lapse rates above 600mb, long/straight hodographs in
the hail growth zone, large amounts of DCAPE and steep low-level
lapse rates there is a low but non-zero pulse severe concern
(marginal hail/downbursts) if one or two cells are able to
punch through the mid-level warm layer and develop stronger
cores aloft. It seems more likely that the warm/dry mid-levels
and minimal forcing keep any cells too weak to realize this
potential, though some hi-res models such as the 0z 3km NAM and
RRFS do have a couple of more robust cells that could realize
such potential. Something small for us to watch for.

Quiet weather is expected tonight with lows generally ranging
from the mid 60s to near 70, though some rural valleys from far
Northeast OH into Northwest PA may get slightly cooler. Patchy
fog is possible again late tonight, though with a weak wind
developing fog should generally be limited to valleys in far
Northeast Ohio and Northwest Pennsylvania.

Sunday will begin a stretch of more active weather, with
generally low predictability of timing/magnitude of rain and
thunderstorm chances due to dependence on upstream convective
evolution over the Upper Midwest and western Great Lakes.
Guidance agrees in a shortwave approaching from the northwest
Sunday morning and moving through Sunday afternoon. Where
guidance disagrees is on whether or not some form of decaying
MCS will accompany this shortwave. Many models show any MCS
falling apart before moving in on Sunday, though some (such as
the 6z run of the HRRR) maintain an MCS through much of our
area Sunday morning/early afternoon. MCS/s have a habit of
occasionally propagating faster and dissipating a bit slower
than models suggest, so do have POPs spreading in from the
northwest Sunday morning/early afternoon. If the MCS falls apart
before making it in or doesn`t arrive until Sunday afternoon,
renewed development or re-intensification would be possible in
the afternoon with a modest severe potential given some
potential increase in instability and shear Sunday afternoon.
However, if the MCS is faster/more robust (such as the
aforementioned 6z HRRR) we`d likely see showers/thunder during
the morning and early afternoon with minimal to no severe risk
given a generally stable/dry environment overhead MCS Sunday
morning. This solution would leave us with a worked over
atmosphere preventing afternoon convection. All this to say that
we have broad 30-50% chance POPs spreading in from the
northwest beginning Sunday morning and continuing through the
afternoon. Lowered highs on Sunday just a bit given potential
for clouds/precip, though still range from the upper 80s to
lower 90s. The POP, QPF, sky, and temperature/heat index
forecasts Sunday remain subject to further adjustment.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
On the synoptic scale, northwest flow continues aloft, with surface
high pressure centered over southern Appalachia, and generally
across much of the southeast CONUS through Monday, before this high
departs to the east over the Atlantic. Broadly, this pattern will
consist of heat and humidity, with thunderstorm chances in each
period.

Getting into the details, most models have a convectively-induced
shortwave trough overhead with a thunderstorm complex exiting the
area at the start of the short term period Sunday night. Most models
have another convective complex developing upstream and then moving
across the area again very late Sunday night into Monday morning. A
lot of these features are being driven on the mesoscale however, so
very low confidence in this exact setup/scenario because these small
things can change very easily this far out. We`ll have to pay
attention to the mesoscale details upstream over the next couple
days, which can hint at how the forecast could change. Generally
though, the environment will be favorable for severe weather,
particularly damaging winds as surface dew points in the low 70s and
mid-level lapse rates of 6.5-7 C/km result in moderate instability.
Deep layer shear is uncertain, but is in the 20-30 knot range, which
is marginal but sufficient for severe weather, especially if there
is greater instability.

By Monday, uncertainty increases as we continue to depend on
mesoscale features to drive the forecast. Still though, the general
environment will be favorable for severe thunderstorms and
instability is actually expected to increase by Monday. CSU-ML has
its max severe weather probabilities on Monday (15% for entire area
and 30% probabilities touching Northwest Ohio), driven completely by
it`s wind probability forecast. Heat and humidity is expected to
peak Monday, with heat indices in the mid to upper 90s areawide,
with some spots along and west of I-77 touching 100. It`s possible
we may need a heat advisory but this is highly dependent on the
precipitation forecast. By Tuesday, a broad upper-level trough and
associated surface cold front approaches the Great Lakes region from
the northwest, providing some synoptic-scale forcing and greater
confidence in thunderstorm development. Have highest PoPs of the
short term period Tuesday through late Tuesday night with most of
the forecast area up into the 60-70% range. Severe thunderstorm will
be possible again Tuesday and Tuesday night.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
The cold front is expected to cross the region late Tuesday night
into Wednesday morning, ushering in a pattern change to the region
as the high pressure building in will be accompanied by a cooler and
drier airmass. Afternoon temperatures in the upper  70s to low 80s
are expected Wednesday through Friday with no precipitation expected
(outside Wednesday when some lingering showers and thunderstorms
will be possible).

&&

.AVIATION /06Z Saturday THROUGH Wednesday/...
Patchy fog is beginning to develop early this morning. Not
expecting widespread dense fog, though a few terminals may see a
couple or few hours of restrictions. Any fog/mist will mix out
by 12 or 13z. Isolated to widely scattered showers and thunder
will attempt to develop this afternoon away from the Lake Erie
shoreline. Coverage will be low and any thunder or restrictions
will be very hit or miss, so just maintained a VCSH mention at a
few sites. If confidence in thunder or restrictions increases we
may add at a site or two in future cycles. Like Saturday, any
activity should dissipate by 0z this evening.

Winds through the period will be light - largely variable
through morning and favoring north to northwest for Saturday
afternoon.

Outlook...Periodic rounds of showers and thunderstorms with
non-VFR may be possible this Sunday through Tuesday.

&&

.MARINE...
Quiet conditions are expected today and tonight as high pressure
remains over the area, with a weak afternoon lake breeze. As high
pressure departs to the southeast, southwest winds in the 10 to 20
knot range develops on Sunday, lasting through at least Tuesday
evening. Speeds will be variable, with any 20 knots winds expected
to be brief, although can`t necessarily rule out the need for any
short small craft advisories and any point this week. A cold front
moves southeast across the lake Tuesday night with winds veering to
out of the northwest and north Wednesday through Thursday. Current
indications suggest these winds should hold under 20 knots, but
onshore flow will certainly make it choppy despite the otherwise
nice weather these days.

&&

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

&&

$$

SYNOPSIS...Sullivan
NEAR TERM...Sullivan
SHORT TERM...Saunders
LONG TERM...Saunders
AVIATION...Sullivan
MARINE...Saunders