Area Forecast Discussion
Issued by NWS Wilmington, OH

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FXUS61 KILN 251721

National Weather Service Wilmington OH
121 PM EDT Sun Oct 25 2020

Weak mid level disturbances will move across the region to begin
the week. A somewhat stronger system will move through Monday
night. The remnants of a tropical system may impact the region
Wednesday night into Thursday night.


Weak warm air advection aloft (around 850 hPa) will continue all day
today leading to persistent cloud cover and light shower activity.
Temperatures at the surface remain on the cooler side, near 50, as
weak northerly flow and thick cloud cover limit daytime heating.


Weak forcing regime continues through the short term. Surface
front will remain south and east of the forecast area. It does
appear that a weak wave will track along the boundary tonight
which will shift winds to a more northerly direction. And that
wave could result in some additional light showers, mainly for
eastern counties.

While shallow cold air will remain in place through Monday, an
approaching weak low tracking along a front aloft will increase
convergence along the boundary and result in some showers
developing into northwest counties later Monday afternoon.

Persistent cloud cover with no change in airmass will result in
a continuation of narrow diurnal ranges with not much variation
in temperatures from night to night and day to day.


Monday night into Tuesday morning, favorable jet dynamics in the
form of the right entrance region of a 140kt+ jet streak will be
providing showers across the region. Guidance has been consistent
with this feature, and now focus likely PoPs between roughly
midnight and mid-morning as the precipitation shifts from northwest
to southeast. Since this will occur entirely in the cold sector,
temperatures will remain below normal with highs on Tuesday in the
upper 40s north to mid 50s south.

A short period of dry weather and near normal temperatures follow
Tuesday night through most of Wednesday as surface high pressure
builds across the Ohio Valley. Low level moisture lingers, so
considerable cloudiness will likely hang around on Wednesday as
well. High pressure exits to the east Wednesday evening.

While guidance shows significant variation in track and timing, all
models depict the potential for tropical remnants to impact the Ohio
Valley starting Wednesday night into Thursday night. The ECMWF and
its ensemble mean are slow and further north with its heavy rain
swath, while the GFS and its ensemble mean are quicker and further
south. Will need to focus the timing, location, and rainfall amounts
as the event draws nearer and the tropical system develops; but for
now, have a broad area of PoPs Wednesday night through Friday
morning as the tropical remnants are followed by a closed mid-level
low ejecting from the southern Plains.

Conditions dry out late Friday into the start of the weekend as a
large area of high pressure builds in. Temperatures will be below
seasonal norms.


Warm air advection aloft if leading to persistent cloud cover over
the terminals this afternoon. Surface observations reveal that
ceilings are lowest at the southern TAF sites (KCVG, KLUK, and
KILN). The MVFR ceilings observed at the southern sites will spread
north this afternoon and reach KDAY, KCMH, and KLCK around 0000Z.
MVFR ceilings then will continue lowering below 2000 ft AGL this
evening into Monday morning while warm air advection continues over
the Ohio Valley. There is also a small chance for a brief, light
shower throughout the TAF period.

Winds will remain northeasterly until after 0000Z. Winds will then
back and become northerly overnight into Monday morning. Overall,
wind speeds are expected to remain below 10 knots.

OUTLOOK... MVFR to IFR ceilings and visibilities likely Monday
night into Tuesday and then again Wednesday night into Thursday.




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