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000
FXUS61 KCLE 091057
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
657 AM EDT Sun May 9 2021

.SYNOPSIS...
Low pressure over the lower Missouri River Valley will move east
today through through Ohio Valley, reaching the Mid-Atlantic
states tonight. A trough will linger across the eastern Great
Lakes on Monday, followed by a cold front on Tuesday. High
pressure will build into the Great Lakes region for Wednesday
and Thursday.

&&

.NEAR TERM /THROUGH MONDAY/...
Two things with this forecast update this morning. First, have
cancelled the Frost Advisory early for NW PA. Increasing
temperatures, clouds, and winds will preclude any additional
frost formation. Second, have tweaked timing of PoPs this
morning slightly. Rain shield is ebbing ever slowly north this
morning with the first bits of rain just reaching the Ohio
Turnpike in Northwest and North Central Ohio. Rain will take
some additional time to fill in across the forecast area and
have slowed down the timing as appropriate. The biggest change
was in NW PA, where categorical PoPs are delayed until the
afternoon hours.

Previous Discussion...
Rain is beginning to enter the southwest portions of the
forecast area this morning as the 700 mb warm front extends from
central Ohio through central Illinois and back towards the
surface low near the Kansas City metro and the region remains in
the right entrance region of an upper level jet. Rain will
continue to overspread the region today as this front slowly
meanders north and deep moisture enters from the Gulf of Mexico
with the moist, warm flow at 850 mb. The upper level jet will
just pivot across the region today, providing ample upper level
support for precipitation all day. With that, have maintained
100% PoPs for the forecast area. For the QPF, have maintained a
gradient of three-quarters of an inch in NW PA to two inches
across the western and southwestern portions of the forecast
area. This is also well supported by the moderate to heavy rain
found upstream in Indiana that will move into the forecast area
over the next several hours. Also, forecast soundings across the
region support precipitable water values of over one inch,
supporting a reasonably high rainfall forecast. High
temperatures today will largely do nothing. For most, high
temperatures will be achieved right ahead of the rain this
morning and remain in the 40s with the rain.

Rain will clear the area from west to east this evening as the
surface low quickly moves through the Ohio Valley region and
crosses the Appalachians to the Mid-Atlantic states. The low
will drag the low level warm front back south and cooler, drier
air will once again overtake the region and end the rain
threat. Conditions should actually quickly improve and clouds
may even scatter out for some, allowing for temperatures to drop
into the 30s and present a patchy frost threat, if winds can
calm enough. A trough will linger across the eastern Great
Lakes for Monday, but with lack of moisture and upper level
support, this feature will be relatively benign. Temperatures
will recover across the region into the 50s with fair skies.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
Monday night looks to be dry but an upper level trough will be over
the central Great Lakes. Skies should clear enough to assist with
winds decoupling. This will result in frost across inland locations
as lows dip into the lower to mid 30`s.

The upper level trough and its associated cold front will swing
across the region on Tuesday. Diurnal heating combined with cooler
air aloft will help to steepen low level lapse rates. This should be
enough to generate isolated to scattered showers and thunderstorms.
Best chances will be afternoon into early evening. The stronger
convection could contain some small hail. Highs Tuesday afternoon
will range from the upper 40`s across NW PA to the upper 50`s
across NW OH. Winds gradually decrease with the cloud cover Tuesday
night as cooler air settles over the region. If winds decrease as
expected much of inland northern Ohio into NW PA will see a
widespread frost. Lows range from the lower to mid 30`s to near 40
along the lakeshore.

High pressure begins to increase its influence from west to east
Wednesday into Wednesday night. This should provide more sunshine on
Wednesday with highs ranging from the mid 50`s to mid 60`s. Another
chilly night Wednesday night with light winds and clear to partly
cloudy skies. Frost will once again be possible but think it will
mainly occur near and south of a line from Marion to Wattsburg. Lows
should range from the mid 30`s to lower 40`s.

&&

.LONG TERM /THURSDAY THROUGH SATURDAY/...
Models in better agreement in the long term tonight with high
pressure gradually weakening at the surface as it drifts eastward
Thursday into Friday. There is a trough that will move over the the
central Great Lakes Friday into Saturday. Each model has a slightly
different take on how to handle it. In any event there wont be that
much moisture for it to work with so rain chances will remain low.

Warmer each day of the long term. Highs on Thursday mostly in the
60`s, then warming to the mid 60`s to mid 70`s on Saturday. Lows
mostly in the 40`s.

&&

.AVIATION /12Z Sunday THROUGH Thursday/...
Some rain and MVFR conditions are starting to invade the
southwest portions of the airspace this morning, but the bulk of
the area remains VFR. Still expecting rain and non-VFR to fill
in this morning and conditions will fall to MVFR and then IFR
for all terminals. More optimistic on the LIFR potential today
and have removed most of the lower LIFR ceilings this afternoon
with the exception of KFDY. The low driving much of this rain
will pull the front away from the region and improving
conditions are expected tonight with rising ceilings and
scattered clouds by Monday morning. Winds will be south to
southeast to start for most. With the low this afternoon and
evening, winds will favor an east then northeast direction and
wind gusts will increase to 25 knots. Behind the low, winds will
settle on a northwest direction at 10 knots or less.

Outlook...Non-VFR conditions may persist in low ceilings on
Monday morning. Non-VFR possible again in showers on Tuesday.

&&

.MARINE...
Low pressure will track northeastward near the Ohio River Valley
today with east to northeast winds expected on the lake through the
day. Winds look to increase above 20 knots with waves building to at
least 4 to 6 feet at times. Only made minor changes to the small
craft advisory to start the central basin slightly earlier. Will
need to watch water levels across the western basin. Current
thinking is that the northeast flow will not persist long enough to
get it more than 66-70 inches above low water datum at Toledo. These
levels are low enough to limit the concern for any lakeshore
flooding.

As the low passes into PA overnight winds shift around to the north
and northwest then remain that way into Tuesday. There could be
brief periods where winds make it back to the west as a trough
wobbles over the central Great Lakes. However by Tuesday a stronger
frontal boundary will move across the lake with west to northwest
winds increase to 15 to 25 knots, strongest across the east end of
the lake. A small craft advisory is expected to begin Tuesday
morning and continue into into the overnight hours. High pressure
then moves over the lake from the Plains Wednesday into Wednesday
night with winds shifting to the west and decreasing.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...Small Craft Advisory from 4 PM this afternoon to 4 AM EDT
     Monday for LEZ148-149.
     Small Craft Advisory from 10 AM this morning to 10 PM EDT this
     evening for LEZ142-143.
     Small Craft Advisory from 10 AM this morning to 4 AM EDT
     Monday for LEZ144>147.

&&

$$
SYNOPSIS...Sefcovic
NEAR TERM...Sefcovic
SHORT TERM...MM
LONG TERM...MM
AVIATION...Sefcovic
MARINE...MM