-- Discussion containing changed information from previous version are highlighted. --
994
FXUS61 KCLE 291019
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
619 AM EDT Wed May 29 2024

.SYNOPSIS...
A broad area of low pressure will cross the Upper Ohio Valley
today, dragging a cold front through the area. High pressure
will build across the Great Lakes and Ohio Valley tonight and
persist into Saturday. A weak cold front will cross the region
Saturday night into Sunday.

&&

.NEAR TERM /THROUGH THURSDAY/...
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6:30 AM Update...

Moved the categorical PoPs farther north into the NW and north
central Ohio lakeshore areas early this morning based on
current radar, otherwise, expect the showers to slowly pivot
east this morning while still struggling to reach far NE Ohio
and NW PA. The rest of the forecast remains on track.

Original Discussion...

One more day of the cool, showery weather is on tap as a mid-
level vort max and associated surface low, currently located
near southern Lake Michigan, rotates across the area. This will
bring periodic showers today, with embedded thunderstorms this
afternoon due to diurnal heating beneath the large cold pool
aloft. However, precip coverage is somewhat uncertain since
forcing and moisture advection is weak other than lift from the
aforementioned vort max and diurnal instability. We have
underachieved on coverage of the precip and QPF in this pattern
so far, but it should be a bit more widespread today given the
vort max and surface low moving overhead.

In terms of details, a band of showers driven by weak moisture
advection and isentropic ascent ahead of the vort max/surface
low will continue to slowly rotate across north central Ohio and
into interior NE Ohio this morning. Instability has decreased
overnight, so do not expect any thunder through sunrise,
although enough elevated CAPE remains to maintain some embedded
convective cells with locally moderate to heavy downpours. As
the low/vort max rotates into central Ohio by late this morning,
this band of showers will continue to pivot farther east,
although it is looking less likely to reach the lakeshore or
far NE Ohio/NW PA. For this reason, gradually moved the likely
to categorical PoPs east this morning, but kept chance wording
along the lakeshore and in far NE Ohio and NW PA. By this
afternoon, the center of circulation will shift across southern
PA and northern WV taking the steadier precip east, but daytime
heating from the strong May sun beneath the large cold pool
aloft will generate over 1000 joules of SBCAPE as low and mid-
level lapse rates once again steepen to near 7 C/Km. This will
support diurnal convection (scattered thunderstorms) away from
the influence of the lake shadow, so kept elevated PoPs inland
this afternoon. Again, the coverage of precip is low confidence,
but any convection will be slow moving given the weak flow
aloft, and with seasonably high PWATs, could see localized
rainfall amounts of 1-2 inches which is also supported by HREF
ensembles. More areas will stay dry compared to where rain
actually falls though. Additionally, could see small hail and
gusty winds up to 30-40 knots in the strongest cells this
afternoon given the low freezing levels and steep lapse rates.
Non-supercellular funnels cannot be ruled out either due to the
spin from the exiting vort max and surface low, but no severe
weather is expected.

Drier air will work in rather quickly this evening and tonight
as a large surface high builds southeastward from the Upper
Midwest, and this high will become centered over the southern
Great Lakes and Ohio Valley Thursday setting up a picture
perfect day with sunny skies, although still cool as deep
mid/upper troughing remains across the eastern Great Lakes.

Highs today will mostly be in the mid/upper 60s, with low 70s
possible in NW Ohio. Highs Thursday will be about the same with
generally mid/upper 60s, except low 70s in NW Ohio. Lows tonight
will be impressively cold as the high settles overhead, with
low/mid 40s away from the lake and low 50s near the lake.
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&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
A 1024mb area of surface high pressure will be overhead on
Thursday night. This will support good radiational cooling with
clear skies and nearly calm winds. Minimum temperatures are
forecast to be in the low 40s in the east with mid 40s across NW
Ohio Ohio and 50 degrees along the lakeshore. Can not rule out
a few of the cooler locations in the east dipping into the upper
30s but feel the likelihood of frost remains fairly low.

High pressure will maintain dry conditions through at least Friday
night as it builds to the East Coast. Temperatures will gradually
warm with highs back in the upper 70s to near 80 degrees by
Saturday. Forecast uncertainty increases over the weekend as the
strong upper level ridge shifts east and starts to break down. The
00Z/29 Canadian and ECMWF indicate a shortwave will pass near or
north of Lake Erie and result in a chance of showers and
thunderstorms by Saturday night. Meanwhile the GFS favors a closed
upper level circulation moving out of the Mid-Mississippi Valley
into the Ohio Valley which is a little it slower. Given the
uncertainty but signal for returning moisture with some forcing,
will maintain a slight chance of showers in NW Ohio Saturday
afternoon with the chance expanding to all of the forecast area by
Saturday night. Given the preceding dry airmass, instability still
looks to be low by Saturday night so will limit pops to 40 percent.

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
An active pattern looks to continue into the extended periods of the
forecast. An upper level wave opens and lifts into the Ohio Valley
on Sunday. This will maintain a chance of showers and thunderstorms
over the weekend but confidence remains low in timing favored
windows for convection. In additions, several shortwaves are
forecast to move through the flow aloft through the first part of
next week, making timing a challenge at this time scale.
Temperatures will trend warmer each day as the upper level ridge
finally builds with mid-80s expected by Tuesday and Wednesday.

&&

.AVIATION /12Z Wednesday THROUGH Sunday/...
Showers will gradually move eastward early this morning bringing
periods of MVFR, with the best chances in west and southwest
areas like KTOL, KFDY, KMFD, and KCAK. Otherwise, mainly dry and
VFR conditions are expected through sunrise except for KERI
where some lower clouds and mist will occur at times. From mid
morning into the afternoon today, showers and embedded thunder
will expand as an upper low crosses the region combined with
daytime heating. Coverage and timing is again uncertain today,
but most sites will see precip at times, with the greatest
frequency being away from the lake at KFDY, KMFD, KCAK, and
KYNG. Brief drops to MVFR or lower will occur in the heaviest
convective showers, with mainly VFR in between, but these drops
will be tough to time. Drier air will finally work in this
evening as high pressure builds in, leading to VFR areawide
tonight.

Light and variable winds early this morning will turn N and
increase to 10-20 knots later this morning through the
afternoon.

Outlook...Non-VFR may return Saturday night into Sunday in isolated to
scattered showers and thunderstorms.

&&

.MARINE...
Low pressure over eastern Ohio today will move to the Mid-Atlantic
by tonight. North to northeast winds of 5-10 knots today will
increase this evening as a secondary cold front moves south across
Lake Erie. Winds increase to 15 to 20 knots for the Ohio waters and
a Small Craft Advisory has been issued from the Islands to Geneva-on-
the-Lake. Onshore waves build to 3 to 5 feet which will also result
in a high risk of rip currents for those areas. Conditions will
improve quickly on Thursday as high pressure builds over the Central
Great Lakes. Generally good marine conditions will continue Friday
and Saturday as high pressure continues to influence the region while
it builds to the East Coast.

The weather pattern is on track to become more active over the
weekend. Uncertainty exists in timing chances of showers and
thunderstorms so it will be necessary to check back for forecast
updates.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
OH...Beach Hazards Statement from this evening through late tonight
     for OHZ009>012.
PA...None.
NY...None.
MARINE...Small Craft Advisory from 7 PM this evening to 4 AM EDT
     Thursday for LEZ144>147.
-- End Changed Discussion --

&&

$$

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