Area Forecast Discussion
Issued by NWS Wilmington, OH

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FXUS61 KILN 312319
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
719 PM EDT Sat Oct 31 2020

.SYNOPSIS...
High pressure will move east tonight while a strong cold front
approaches the region from the west. This strong cold front
will sweep east across the region early Sunday bringing, gusty
winds, scattered showers, and a reinforcing shot of colder air.
A large Canadian high pressure system will bring dry weather for
next week, with much below normal temperatures expected early
in the week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Mid level flow will back southwesterly as a strong shortwave
digs into the Great Lakes. Clear skies thru the evening will
be replaced by increasing clouds as a 45-50 KT southerly low
level jet develops overnight. With the increase in clouds and
with southerly winds increasing to 15 to 20 mph -- temperatures
will hit lows around midnight and then rise slightly, especially
in the northwest counties. Expect milder lows from the upper
30s to the middle 40s.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Digging mid level shortwave to develop into the Great Lakes
Sunday. A strong cold front will sweep east across ILN/s FA
early Sunday morning. Best forcing and moisture across the
north/northeast counties -- where have a couple hours of
categorical pops for showers. With steepening low level lapse
rates a few lingering showers psbl across the north with a
mix of rain and snow possible as colder air advects into the
region.

With the early fropa, expect some drop in temperatures
especially across west central Ohio. Expect early highs from
the upper 40s northwest to the mid 50s southeast. Winds will be
on the increase during the afternoon in the cold advection with
gusts of 35 to 40 mph.

As surface high pressure begins to nose into the area cold
readings are expected by Monday morning. Expect lows in the mid
and upper 20s. Have issued a freeze watch where frost/freeze
program continues across southeast Indiana/northern KY and
Hamilton county Ohio.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
On Monday morning, a very amplified long-wave pattern will be in
place across the CONUS, with a deep trough moving east through New
England, and heights beginning to rise rapidly over the Ohio Valley.
An expansive area of surface high pressure will be centered over
Arkansas, enveloping much of the southern tier of states, and
eventually extending into the Ohio Valley on Monday night. Through
the rest of the week, this pattern will support broad ridging over
the eastern CONUS, with the ILN forecast area either underneath it
or just on the western edge of it. This presents a fairly high
confidence forecast of dry conditions through at least Friday, with
model uncertainty starting to show more uncertainty over the weekend
and beyond. For an overall longwave pattern, this is a fairly long
time range into the future (around 6-7 days) without any significant
model differences (across multiple GFS/ECMWF runs).

From a temperature perspective, there is good confidence in a
gradual warming trend through the period, with Monday -- behind a
cold front -- likely the coolest day of the period. Max temps are
only expected to be in the mid to upper 40s (10-12 degrees below
normal). Temperatures will be back to normal (or even above) by
Wednesday and Thursday, possibly increasing as far as the mid to
upper 60s by the end of the week.

The one weather element worth mentioning through the week is the
wind, with the potential for a few slightly gusty days. On Monday, a
tightening pressure gradient over Great Lakes will lead to some
gusty westerly winds over the northern Ohio Valley region -- perhaps
as high as 30 knots in the northern sections of the ILN forecast
area. Once SSW flow has become established on Wednesday and
Thursday, some gusty conditions will again be possible -- especially
given the expectation for a very dry boundary layer, favorable for
deep mixing.

&&

.AVIATION /23Z SATURDAY THROUGH THURSDAY/...
Clouds and wind will increase tonight ahead of a strong cold
front. A low level jet ahead of front will bring a period of non
convective LLWS generally between 06Z and 12Z.

The cold front will move east across the region on Sunday
morning. A brief period of light showers may occur near
KCMH/KLCK with other locations seeing a chance of light showers.
Ceilings will drop into the MVFR category along and just behind
the cold front. Then ceilings will rise above to VFR during the
afternoon. Winds will shift from the southwest to the
west/northwest with sustained winds between 15 and 25 knots
with gusts between 30 and 35 knots.

High pressure will build into the Ohio Valley Sunday night. The
pressure gradient will gradually relax, and with loss of diurnal
mixing, gustiness will eventually subside overnight.


OUTLOOK...No significant weather expected.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Freeze Watch from Sunday evening through Monday morning for
     OHZ077.
KY...Freeze Watch from Sunday evening through Monday morning for
     KYZ089>100.
IN...Freeze Watch from Sunday evening through Monday morning for
     INZ073>075-080.

&&

$$
SYNOPSIS...AR
NEAR TERM...AR
SHORT TERM...AR
LONG TERM...Hatzos
AVIATION...Hickman



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