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000
FXUS61 KILN 060818
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
418 AM EDT Thu May 6 2021

.SYNOPSIS...
High pressure will slide off to the east this morning with Low
pressure tracking into Northwest Ohio late in the day and across
the area tonight. This will bringing a likelihood of showers
and a few thunderstorms late in the day into tonight. Expect
cool temperatures and the threat for showers to continue through
the weekend, especially on Saturday night through Sunday night
when low pressure is forecast to travel across Kentucky.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Amplified mid/upper level flow with a broad mean trof over the
Great Lakes/Ohio Valley. Embedded short wave to drop southeast
through the Upper Mississippi Valley this morning and into the
Great Lakes this aftn. Associated surface low to track into
Northwest Ohio by 00Z Friday with southward trailing cold front
into extreme Western Ohio. Airmass is initially dry with high
and mid level clouds increasing thru the morning into the aftn.
A tongue of low level moisture to advect into the area with
surface dewpoints increasing into the upper 40s ahead of the
approaching front. This low level moisture combined with cooling
aloft will lead to very marginal instability late in the day.
Have showers developing  between 18Z and 21Z in the west and
around 00Z in the far east. Have limited mention of thunder to
slight chance. Cool temperatures to continue with highs from
around 60 northwest to the mid 60s southeast.



&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
A shortwave trough rotating through a mean trof over the Great
Lakes/Ohio Valley will induce a surface low that is forecast to
be located over Northwest Ohio early this evening. This system
is progressive with the low and associated cold front pushing
east and showers diminishing by 06Z in the west and 09Z in the
east. Clouds to linger thru the night Thursday with lows from
the upper 30s far west to the lower/middle 40s east.

Northwest flow pattern with mid level short wave dropping into
the area Friday. Cooling aloft will steepen low level lapse
rates offering marginal instby during the aftn. Have bumped up
pops over the northeast to likely where most favorable
conditions will exist. Have also included a mention of thunder
with marginal instability developing. Temperatures look to be
around 10 degrees below normal Friday with highs from the
upper 50s northwest to the lower 60s southeast.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Summary: A few lingering showers could be ongoing at the start of
the long-term period before surface high pressure noses in from the
northwest Friday night into Saturday morning. Chilly start to the
day on Saturday with attention shifting to the next chance for
precipitation Saturday night and through the rest of the weekend.
Low pressure and a stalled warm front supports the potential for
locally heavy rain and perhaps some river flooding. Drier pattern
returns for early next week before another low pressure moves into
the Ohio midweek.

Details: The onset of the long term period features the chance for
frost as showers and clouds clear with high pressure moving into the
forecast area from the northwest. Highest confidence for frost is
currently located across west-central Ohio where mostly clear skies
has the best chance of occurring. Temperatures are forecast in the
mid 30s elsewhere, so a frost advisory may be needed in future
forecasts.

After a chilly start to the day on Saturday, temperatures do warm up
into the upper 50s and lower 60s, but increasing mid-level clouds
hint that the next weather maker approaches from the west. Most of
Saturday will be rain-free as mid-level dry air delays saturation.
Aided by jet dynamics and low-level frontogenesis, vertical ascent
increases across the Ohio Valley, resulting in widespread rain late
Saturday night. Deeper moisture moves into the Ohio Valley during
the day on Sunday, leading to quite a miserable Mother`s Day. Deep
cloud depths limit surface heating and widespread rain hold maximum
temperatures in the 50s. The only exception could be areas along the
Ohio River where low 60s are forecast closer to the warm front. On
the other hand, some areas, especially across there north, may
struggle to rise to current forecast temperatures. Overall, forecast
soundings indicate moderate to even heavy rain is expected during
the day on Sunday due to the intense vertical lift. This may
eventually lead to areal flooding and increasing river levels,
especially with rainfall amounts between 1-3 inches. There is
continued ensemble support from GEFS/EPS that at least a widespread
area of 1+ inches is very likely across much of the forecast area.
This is supported by WPC`s current Day 4 outlook indicated at least
1 inch across the area. The local axis of maximum rainfall will
continue to shift as model guidance gains a better handle on the
amplification and progressiveness of the trough moving into the
central US. Even with some uncertainty of where the heaviest rain
will fall, the increasing confidence in widespread moderate/heavy
rainfall area wide has been mentioned in the HWO.

Rain chances begin to decrease late Sunday night into Monday morning
as northwesterly mid-level flow ushers in drier air. Cloudy skies
likely linger throughout the day on Monday with below normal
temperatures forecast. Synoptically, the persistent long wave trough
situated over Canada will continue to supply below normal
temperatures and drier conditions across the northern US for the
rest of the forecast period. Small chances for rain are forecast but
much uncertainly exits with the amplification of a shortwave moving
through the mid-level quasi-zonal flow. A shallow/flat shortwave
would likely keep the highest rain chances south of the forecast
area. A more amplified trough would lead to a much more favorable
low pressure track. The current forecast maintains a slight warming
trend through mid-week, however, temperatures are still below
normal. This statement is supported by CPC`s 6-10 day temperature
outlook which shows 70-80% chance for below normal temperatures.

&&

.AVIATION /07Z THURSDAY THROUGH MONDAY/...
Surface high pressure will offer dry weather, light winds and
mainly clear skies this morning. Although the airmass is dry,
the KLUK valley location will likely observe some MVFR vsby
restrictions due to fog this morning.

Fast moving surface low pressure to track from the Middle
Mississippi Valley this morning into Northwest Ohio by evening.
Mid and high level clouds will increase across the area during
the day. As moisture increases showers to develop ahead of an
associated cold front after 21Z at KDAY and KCVG and 00Z at
KCMH/KLCK. Instability is marginal but can not rule out some
embedded thunder -- especially in the western TAFs. Expect
ceilings to drop to MVFR this evening with MVFR vsby
restrictions at times in rain showers. This system is
progressive with rain showers ending in the west by 06Z and
in the eastern TAF by 09Z.

Light and variable winds will become south at less than 10 kts
this aftn and then shift to the northwest around 10 kts with the
frontal passage this evening.


.OUTLOOK...Rain is expected Saturday night through Sunday night
MVFR to IFR ceilings can be expected with LIFR ceilings possible.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.

&&

$$
SYNOPSIS...AR
NEAR TERM...AR
SHORT TERM...AR
LONG TERM...McGinnis
AVIATION...AR