ILN issues Area Forecast Discussion (AFD) at Dec 20, 6:14 AM EST
611
FXUS61 KILN 201114
AFDILN
Area Forecast Discussion
National Weather Service Wilmington OH
614 AM EST Fri Dec 20 2024
.SYNOPSIS...
Low pressure will move southeast across the middle Ohio Valley
today, bringing rain and snow. Colder air associated with a high
pressure system will move in behind the low for the weekend,
resulting in below than normal temperatures. Warmer conditions
are expected next week, with precipitation chances returning by
Monday night.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Low pressure near northwest Indiana early this morning is
forecast to track southeast across the middle Ohio Valley today.
Dynamic lift with an upper level short wave will combine with
low level convergence associated with the attendent cold front
to produce a shield of precipitation.
Main concern this morning is the potential for a period of snow
to affect parts of east central Indiana and
western/southwestern Ohio and northern Kentucky (this includes
the Cincinnati and Dayton metro areas). Models continue to show
that precipitation may form into a band due to strong low level
convergence. Precipitation may initially mix with rain at the
onset, then with fairly strong vertical motion, surface
temperatures will cool to near freezing, and the atmospheric
sounding will be cold enough to produce a period of snow. Snow
is expected to accumulate mainly on elevated and grassy
surfaces. However, with temperatures hovering near freezing and
pavement temperatures hovering near freezing as well, a period
of moderate snow could result in a quick covering on roads,
producing slick spots, especially the vulnerable bridges and
overpasses. Snow accumulations will vary between a half inch to
up to 2 inches in this region. Elsewhere, forcing will be
weaker, and with some slight warming occurring ahead of the
front, precipitation should fall as rain/snow or just plain
rain. A Special Weather Statement will be issued to cover the
potential impacts this morning in the aforementioned region.
For this afternoon, the low will exit to the southeast toward
West Virginia. Some wrap around precipitation is expected, but
this will be lighter in nature than this mornings activity.
Slightly warmer air will wrap around the low before much colder
air arrives tonight. Thus, rain/snow or just plain rain, are
forecast for the remainder of the afternoon hours. Highs will
range from the lower to mid 30s west to the upper 30s east.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
For tonight, in the CAA pattern, clouds will linger, especially
south and east. Some patches of light snow may also linger in
the east, but should exit out after midnight. It will be colder
as locally gusty north winds funnel the colder air southward.
Lows will range from near 20 north to the upper 20s along and
south of the Ohio River.
On Saturday, surface high pressure centered over the upper
Mississippi River Valley/western Great Lakes, will build
southeast toward our region. It will remain cold under partly
cloudy skies. Highs will range from the upper 20s north to the
lower 30s south.
&&
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Deep northwest flow will pull in the coldest air of the
forecast with Sunday morning lows generally between 15 and 20
degrees as a ridge of high pressure settles over the CWA. As the
axis of the ridge moves east, return flow will set up on
Sunday. Temperatures will only be marginally warmer than
Saturday's with a continuation of the deep and cool northwest
flow aloft.
A weak mid-level ridge will pass over Sunday night and lows
Monday morning will be marginally warmer in the lower 20s. On
Monday, southerly flow will pick up ahead of an approaching cold
front behind a mid-level shortwave. Winds will turn more
southwest and usher in warmer temperatures in the low to mid
40s.
As the front continues to approach, rain is expected to begin
in the northwest in the late day, spread southward in the
evening, and end overnight for most if not all of the CWA. The
cold front is expected to stretch out over the CWA and weaken
during the day Tuesday.
Models diverge from this point onward, with the GFS showing a
returning warm front lifting ne, followed by s/w energy
triggering showers Thursday and overnight. Friday shows deep sw
flow and a sw- ne area of rain impacting the CWA from s-n. The
footprint of this rain potential does not seem to be plausible
without a surface low/front that is not indicated at this time.
The European and Canadian models also diverge significantly,
most notably with a dry forecast beyond Tuesday.
&&
.AVIATION /11Z FRIDAY THROUGH TUESDAY/...
A clipper system with its center of low pressure over north
central Indiana this morning will track east/southeast across
the middle Ohio Valley today.
Upper level dynamic lift coupled with low level convergence
associated with the low and its attendent cold front will bring
a shield of precipitation to much of the area today, with the
highest chances occurring between 12Z and 18Z. Conditions will
be the worst at KDAY/KILN followed by KLUK/KCVG. KCMH/KLCK
conditions should not be as bad as lighter precipitation in the
form of mainly rain is expected there. Otherwise, the other
terminals will see a period of snow, or rain/snow mixed during
the 12Z to 18Z time frame. Conditions will drop into the
IFR/LIFR categories, with MVFR/IFR expected farther northeast
near KCMH/KLCK. Winds will shift with the low passage and front,
so aviators can expected varied wind changes until the low
passes by and the flow becomes more northerly and gusty.
For tonight, there may be some areas of light snow lingering
east, otherwise skies will range from partly to mostly cloudy.
Ceilings will gradually climb back to the MVFR category and
visibilities will improve back to VFR. There could be some wind
gusts between up to 25 knots with the northerly flow through
early morning.
OUTLOOK...MVFR ceilings to linger into Saturday. MVFR/IFR
conditions likely at times Tuesday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...Hickman
NEAR TERM...Hickman
SHORT TERM...Hickman
LONG TERM...Franks
AVIATION...Hickman
Source: ILN issues Area Forecast Discussion (AFD) at Dec 20, 6:14 AM EST (https://mesonet.agron.iastate.edu/p.php?pid=202412201114-KILN-FXUS61-AFDILN)
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