364
FXUS61 KCLE 011051
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
651 AM EDT Sat Jun 1 2024

.SYNOPSIS...
High pressure departs east today, with weak low pressure moving
east across the region late tonight and Sunday. High pressure
briefly returns Sunday night and Monday before a warm front
lifts through Monday evening. The area remains in the warm
sector until a cold front crosses Wednesday night or Thursday.

&&

.NEAR TERM /THROUGH SUNDAY/...
After one last chillier start early this morning the atmosphere
will get the memo that it is now "meteorological summer" and
respond accordingly, with a warm and largely dry day on the
backside of departing high pressure. A shortwave and weak
surface low will be lifting out of the mid-Mississippi Valley
today which will cause high clouds to spread in and begin
thickening and lowering late this afternoon into this evening.
However, rain chances don`t begin ramping up until this evening
and tonight. Highs will be near or better than 80 for most.

While the shortwave and surface low are not anything to write
home about from a meteorological perspective, they will bring
enough forcing for ascent that when combined with a seasonably
moist airmass much of the area can expect showers tonight into
Sunday. POPs ramp up from the west starting this evening. Dry
low-levels in place ahead of the rain may eat away at the front
edge just a bit and slowed down the onset of POPs a bit from
the prior forecast. Regardless, by early Sunday showers should
have spread into most of our Ohio counties and will be spreading
into Northwest PA. A modest slowing trend continues with this
system and the whole area will be ahead of the shortwave trough
axis and weak surface low early Sunday, which is where forcing
will generally be maximized in a warm/moist advection regime.
Given this, notably increased POPs area-wide for Sunday morning.
The shortwave trough axis should cross the OH/PA boarder early
to mid-afternoon on Sunday with shower coverage decreasing
behind that trough axis. Held on to "likely" shower wording in
far Northeast OH and Northwest PA into early Sunday afternoon.
Behind the shortwave trough axis POPs do decrease quite a bit,
though modest heating of a moist airmass combined with broad
convergence in the vicinity of remnant surface low will likely
support isolated to scattered shower re-development Sunday
afternoon. Given this, increased POPs some to keep at least a
20-30% type mention in everywhere until Sunday evening.

All in all Sunday will not be a true washout of a day but it
looks showery area-wide out of the gate with fairly numerous
showers not exiting our eastern counties until some point in the
afternoon. At least isolated pop-up activity remains possible
in the afternoon behind the main batch of showers. Area-average
rain amounts of 0.10-0.30" are anticipated with no concern for
flooding. Thunder is appearing unlikely as overall instability
will be quite limited, though did leave a slight thunder mention
in across the southwest Sunday afternoon. Lows tonight generally
remain in the low to mid 60s with a few spots out east slipping
into the 50s. Highs on Sunday have been lowered a bit, ranging
from the upper 60s to mid 70s. Light winds through the period.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
A ridge of high pressure builds in Sunday night, with cloud cover
gradually dissipating from the west. Decreasing cloud cover, nearly
calm conditions, and residual low-level moisture should result in
some patch fog and low clouds late Sunday night into Monday morning,
particularly low-lying areas along and east of I-71.

This surface ridge gradually departs eastward to the east coast
Monday and Monday night. Southerly flow brings temps in the upper
70s and low 80s on Monday and to the mid 80s by Tuesday, with
moisture advection bringing dew points into the low 60s by Tuesday.
Precipitation chances gradually increase from west to east, with
isolated to scattered rain showers and thunderstorms to develop,
mainly during the afternoon on Tuesday when there is likely to be
some marginal uncapped instability (around 1000 J/kg or less).
Currently have PoPs around 30-50% (higher out west such as Northwest
Ohio, lower out east such as Northeast Ohio and Northwest
Pennsylvania). However, some models have a weak shortwave moving
northeast across the area on Tuesday, so it`s possible PoPs could
increase if this shortwave can provide forcing for a more focused
area of convection. Either way, any rain that occurs is likely to be
short-lived, with most of the day being precipitation-free.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
An upper-level negatively-tilted low builds in from the northwest on
Wednesday, with the trough axis likely extending southeastward
across the upper Midwest and mid-Mississippi Valley at the start of
the long term period. A surface low (likely occluded) will be
located way back along the Quebec/Manitoba border in Canada, though
a cold front will bisect the CONUS, extending across much of the
Mississippi Valley to our west. We`ll likely be within the warm
sector and Wednesday will be our best best for modest instability as
dew points are expected to rise into the upper 60s. This cold front
and upper-trough axis should provide sufficient forcing for ascent
and with modest instability forecast, have raise PoPs so that the
entire forecast area has a period of 70-80% chance of precipitation.
It won`t necessarily be an all-day washout (in fact, most of the day
will probably be rain-free) but synoptic-scale forcing is increasing
confidence in a solid period of showers and thunderstorms some time
between Wednesday afternoon through early Wednesday night. There is
a low chance of severe weather with this activity, which is really
dependent on the evolution of the upper-level trough. Some models
have the best mid-level flow (and thus deep-layer shear) lagging
behind, which would inhibit severe convection. Latest CSU-ML
available to us (00Z/31) only shows a 5% chance of severe weather.

The upper-level low continues to build in, likely encompassing much
of the Great Lakes region Thursday through Friday. This will likely
bring cooler temperatures (near normal on Thursday, below normal on
Friday), with scattered rain showers and afternoon isolated
thunderstorms.

&&

.AVIATION /12Z Saturday THROUGH Wednesday/...
VFR through the day today. A weak area of low pressure will
spread showers in from the west starting late this evening and
through tonight. By 12z Sunday, expect all to be raining except
for ERI and perhaps YNG. Dry low-levels ahead of the rain will
likely result in ceilings only slowly lowering. Expect some non-
VFR by later tonight into early Sunday due to lower ceilings
and perhaps some periods of reduced visibility in steadier rain.
Some guidance suggests fairly widespread IFR spreading as far
east at CLE and CAK by 12z Sunday...experience says this is
likely overdone. Did go with IFR at TOL late in the TAF period,
though based on HRRR ceiling forecasts (which tend to be
correctly optimistic in these scenarios) kept all other sites
MVFR or VFR through 12z Sunday with this update.

Winds will shift out of the south-southeast and increase to 6
to 12 knots today. A lake breeze will likely flip winds onshore
for a few hours at ERI this afternoon. Currently think the lake
breeze won`t quite reach CLE though it will be close. Light
south-southeast winds continue tonight.

Outlook...Some non-VFR continues into Sunday morning due to
showers and lower ceilings before gradual improvement Sunday
afternoon and evening. Thunderstorms and associated non-VFR
possible at times Tuesday and Wednesday.

&&

.MARINE...
Conditions are expected to remain quiet with no marine headlines
expected through at least the next few days. High pressure departs
to the east coast today before a weak low moves to the vicinity of
Lake Erie tonight and Sunday, dissipating and filling in as it does
so. This low is replaced by a high pressure ridge that builds across
the Great Lakes region Sunday night and Monday before it departs to
the east coast. Southwest to southeast flow will be the prevailing
winds Tuesday through Wednesday, with a low chance for near 20 knot
winds on Wednesday.

&&

.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