559
FXUS61 KCLE 190216
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
1016 PM EDT Sat May 18 2024

.SYNOPSIS...
High pressure slides across the region tonight and Sunday. A
weak cold front approaches from the northwest Sunday night
before lifting well to our north as a warm front on Monday. A
cold front is expected to push through on Wednesday.

&&

.NEAR TERM /THROUGH SUNDAY NIGHT/...
9:30 PM Update...

Convection has completely dissipated, and that will allow for a
dry night as high pressure builds overhead. We just await the
development of radiation fog. Temp/dew point spreads are larger
than last night, and we mixed well this afternoon, so that will
make the fog less dense and less widespread than last night.
However, the latest RAP forecast soundings still show a low-
level inversion late tonight, especially in NE Ohio and NW PA,
and enough low-level moisture lingers to cause at least mist
with pocket of dense fog in the sheltered valleys. For these
reasons, kept patchy fog in most of the area overnight, with
areas of fog in NE Ohio and NW PA, but not enough confidence on
coverage and duration for any special weather statements at this
point. Lakeshore areas near the Islands have the best potential
for locally dense fog outside of NE Ohio and NW PA where light
NE flow will advect some lake moisture below the inversion, so a
fog bank could redevelop on the lake and affect communities
near the western and central basins. Many HREF members show high
probabilities of this, but confidence is still somewhat low due
to the overall environment being a little drier than 24 hours
ago.

6:30 PM Update...

Increased PoPs over an axis from Morrow and Knox Counties
through southern Richland, Ashland, Wayne, and Stark Counties
over the next 1-2 hours. A weak boundary associated with a
lingering mid-level vort max over eastern Ohio is generating
persistent convection along its low-level convergence where
MLCAPE of 500-1000 J/Kg is present. PWATs are only around 1 inch
in that area, but these cells have produced efficient rainfall
rates of 2 inches in 30 to 45 minutes! This is due to training
and very slow movement of around 5 kts or so. Expect this pulse
convection to finally wane after 23Z as the sun angle decreases.
The rest of the forecast remains on track.

Original Discussion...

Relatively benign weather is expected for the remainder of the
weekend. The combination of heating of a somewhat moist low-
level airmass, a subtle vort max overhead, and some low-level
convergence over the Mid Ohio region has allowed isolated
showers and thunder to develop. Expect this activity to
dissipate by around sunset. Weak high pressure then slides
through tonight and Sunday leading to partly to mostly clear
skies and dry conditions for most of the forecast area through
the rest of the near term. A weak cold front will try to
approach Northwest Ohio late Sunday afternoon / evening before
lifting north to start the week. Strong upper ridging will be
in place, though forecast soundings depict modest to moderate
and uncapped instability near Toledo late Sunday afternoon /
evening. Enough hi-res models have isolated to scattered
convection nearing Northwest Ohio late Sunday to maintain some
20-30% POPs to cover the potential. Weak shear and forcing
suggest any storms will be of the single cell or "pulse"
variety. Thermodynamics may be sufficient for a couple of cells
to produce locally gusty winds or small hail in Northwest Ohio
late Sunday, though overall am not too concerned about any kind
of organized strong to severe storm threat. Any storms that
make it into Northwest Ohio should rain themselves out by late
Sunday evening with dry weather for the rest of Sunday night.

Lows tonight will generally settle into the 50s. It will be
quite warm on Sunday, with highs in the low to mid 80s with the
exception of the eastern lakeshore where onshore flow will keep
conditions cooler. Lows Sunday night will be quite mild, ranging
from the mid to upper 50s from far eastern OH into PA to the mid
60s along and west of I-71. Some radiation fog is likely again
late tonight and very early Sunday though coverage should not be
as widespread as Friday night into early this morning. The most
widespread fog with pockets of dense fog will be from interior
eastern OH into western PA, with fog more patchy and generally
not quite as dense farther west.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Mid to upper level ridging will gradually build east during the day
Monday before an upper trough and embedded shortwave clips Northwest
Ohio on Tuesday. For now, have low end PoPs confined to Northwest
Ohio for Monday afternoon and along and west of I-71 Tuesday
afternoon. The upper trough becomes more pronounced Tuesday night as
the surface low moves northeastward while deepening. This low will
swing a cold front toward the Ohio Valley region to end the short
term and begin the long term period.

Temperatures will rise nearly 10-15 degrees above normal Monday and
Tuesday with highs in the mid to upper 80s. Warm overnight lows
Monday and Tuesday night in the mid to upper 60s.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
The aforementioned deepening low pressure will drag a cold front east
across the local area on Wednesday and bring increased shower and
thunderstorm chances to the region. The environment continues to
look favorable for strong to severe storms develop as we`ll remain
in the warm sector with dew points in the low 60s with current
guidance suggesting roughly 1000-1500+ J/kg of MLCAPE to work with.
We will continue to monitor the severe weather potential for
Wednesday as we get more model guidance. Trended drier toward the
end of the week behind the cold front as a brief ridge of high
pressure builds northward for Friday.

Highs top out in the lower 80s ahead of the cold front on Wednesday
before returning to near normal values in the mid 70s Thursday
through Saturday. Overnight lows through the long term settle in the
mid 50s each night.

&&

.AVIATION /00Z Sunday THROUGH Thursday/...
Convection near KMFD is dissipating and should be gone by 00Z.
This will leave VFR at all sites through the evening. The main
question mark for tonight continues to be how much fog will
develop? Most areas mixed well today, so it should be less
widespread than last night. However, another inversion will
develop tonight, so think most areas should go down at least
below 5 miles, with pockets of 1/2 to 1 mile visibility in fog
as temp/dew point depressions remain small. The duration of the
most dense fog should be shorter, but KERI could still have
dense fog much of the night due to added low-level moisture
advection off of Lake Erie. Any fog/mist will gradually
dissipate by mid to late Sunday morning, but it could once again
hang on at KERI into the early afternoon.

Light N to NE winds this evening will turn light and variable
tonight before becoming N at 5-10 knots Sunday.

Outlook...Low risk for isolated thunderstorms in Northwest OH
Monday night. Somewhat greater potential for isolated to
scattered thunderstorms Tuesday afternoon and evening. Scattered
to widespread thunderstorms are likely Wednesday afternoon.
Mainly VFR is expected outside of thunderstorms.

&&

.MARINE...
Satellite imagery and local area webcams of Lake Erie indicate vast
improvement of visibilities and thus the Dense Fog Advisory was
cancelled. Moist low levels under a steep inversion overnight
tonight will likely prompt the issuance of another fog headline over
the lake. Low confidence in exact timing and placement of overnight
fog so opted to hold off on issuing a new Dense Fog Advisory for
overnight tonight with this forecast update.

High pressure persists through the weekend keeping winds light and
variable on the lake through Monday afternoon. Flow turns southerly
over Lake Erie by Monday night generally remaining between 5 and 10
knots. Deepening low pressure centered over the Great Plains will
enter the Great Lakes region by mid week and will allow for
southerly flow to increase to 15-20 knots during the day Wednesday
before a cold front crosses eastward on Wednesday evening. Southwest
flow of 10-15 knots behind the cold front continues into the end of
the week.

&&

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

&&

$$

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