450
FXUS61 KILN 191434
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
934 AM EST Sun Jan 19 2025

.SYNOPSIS...
Snow and some heavier snow showers are expected today ahead of
an arctic front that will sweep through during the afternoon
and evening hours. Bitterly cold conditions will then settle in
tonight through Wednesday morning, with dry conditions expected
through midweek. A slight warming trend is expected by the end
of the workweek, with more seasonable air filtering back into
the Ohio Valley.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Highly amplified mid/upper level flow with ridging along the
west coast and a long wave trof over the eastern CONUS. A
shortwave rounding the base of the digging longwave trof will
continue to pivot east across the southern Ohio Valley this
morning. This has induced a surface low to our southeast with
favorable lift across Northeast KY and south central Ohio. A
band of light accumulating snow will continue to pivot thru this
area. Have adjusted snow totals down slightly - especially
across the northern tier of counties of the winter weather
advisory. Will continue this winter weather advisory thru 1 pm
with up to an inch additional snowfall.

Focus shifts to potential for snow showers/snow squalls this
afternoon into this evening. Strong sharp PV anomaly pivots
across the area during this timeframe with steep low level
lapse rates developing. This coincides with good saturation and
lift in the DGZ zone with a good signal pointing to widespread
snow shower activity this afternoon into the evening. Mesoscale
models showing several focused N-S oriented bands of snow
showers moving east thru area. Given the intensity will likely
observe some snow squalls this afternoon into the evening. Low
level temperatures will support efficient snow accumulation on
roads. Rapid change in visibility and road conditions will be
possible and therefore have continued highlighting this message
in the HWO and with an SPS.

Temperature will range from the lower 20s northwest to the
upper 20s southeast, with a only a small diurnal rise for most
locations. Gusty northwest winds to 25-30 MPH are expected to
develop late afternoon with wind chills dropping thru the teens
into the single digits.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
For tonight, after the evening SHSN/squall activity pushes to
our E, the arctic air rushes in, bringing air temps close to
zero, or perhaps several degrees below zero, by daybreak Monday.
Steady WNW flow through the night at 12-15 MPH, with gusts to
around 25 MPH, will create wind chill values very close to
warning criteria (-15F near/S of OH Rvr and -20F near/N of I-70)
around 12z Monday.

This being said, probabilities for meeting or exceeding warning
criteria have steadily gone down over the past few fcst cycles,
with the most likely outcome being meeting warning criteria in
any one location for perhaps only an hour or two, if at all.
There is a fairly consistent signal for a slightly warmer setup
Monday night into Tuesday, where some locales may not even reach
advisory (-5F near/S of OH Rvr and -10F near/N of I-70)
criteria. The shrinking timeline requires some sort of
resolution to the ongoing extended Extreme Cold Watch, which
latest guidance suggests the best course of action may be a
Cold Weather Advisory area-wide from tonight through Wednesday
morning, even recognizing there /will likely/ be a few spots
where warning criteria is briefly be met/exceeded both Monday
and Wednesday mornings. Confidence is high that this period will
feature large impacts due to the cold conditions, though
confidence is only medium in specific values -- particularly
when dealing with wind chills due to its dependence on two other
elements (temperatures and wind speeds).

Highs on Monday rebound into the single digits above zero
(near/N of I-70) to the lower/mid teens near/S of the OH Rvr
amidst mostly sunny skies.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
On Monday evening, broad troughing will remain in place across the
eastern two-thirds of the CONUS, with arctic high pressure
stretching from the central plains through the mid-Atlantic region.
The focus for the first half of the week remains on the very cold
weather associated with this arctic air mass. A Cold Weather
Advisory is in effect through the coldest part of the week, ending
on Wednesday morning.

This part of the forecast will focus on temperature and wind chill
conditions on Tuesday and Wednesday mornings. Getting into the
details, one separate section of the surface high will be in place
Monday, moving eastward by Tuesday morning as a weak trough or
frontal boundary moves through the area. A second surface high will
then re-establish itself across the Ohio Valley later Tuesday into
Wednesday morning. It is interesting that on Tuesday morning, ahead
of the surface trough, boundary layer flow will briefly shift to the
southwest -- providing a period of weak warm advection that will
result in Tuesday AM temperatures being a little warmer than Monday
or Wednesday. With that said, temperatures Tuesday morning will
still be in the single digits to near zero. Wind chill values
ranging from 0F to -10F on Tuesday morning may be just shy of the
product criteria for a Cold Weather Advisory, but based on the
continued cold conditions through the daytime hours and then the
expectation of colder temperatures Tuesday night into Wednesday
morning, the advisory will continue through this entire time span.

The coldest raw temperatures of the week will likely occur Wednesday
morning, with lighter winds and mostly clear skies leading to ideal
radiational cooling conditions. Temperatures on Wednesday morning
look to be below zero for the vast majority of the forecast area,
with some values approaching -10F in central Ohio. Despite the
lighter winds, wind chills may again approach -20F in the northern
parts of the ILN forecast area. Exact wind chill values may vary a
bit from place to place, as small changes in winds (which may range
from calm to around 5mph) can change the wind chill calculation by
several degrees. Local geography and any leftover snow pack can also
lead to variance in min temps under favorable radiational cooling
conditions. So, while specific min temps and wind chill values
Wednesday morning may vary from place to play, the overall message
regarding the dangerously cold temperatures remains valid.

As of now, it appears that a very slight warm up could occur for the
end of the week. By later on Wednesday, the surface high will move
to the east, with flow over the Ohio Valley turning to the south. A
stronger signal for warm advection is showing up for Thursday, when
temperatures should be able to get back into the 20s and 30s.
Finally, as another trough moves through the region near the end of
the week, a slight chance of snow has been introduced to the
forecast for Friday.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
MVFR CIGs remain blanketed across the region and expect this to
remain the case through the majority, if not all, of the TAF
period. There is an indication for some clearing and lifting to
VFR toward 06z Monday and beyond, which will move in from the
W, allowing for scattering out of clouds progressively between
06z-12z.

The main item of interest through the TAF period is going to be
the SN, the first opportunity of which will pivot N into far
srn stretches of the area through 18z. Right now, most of this
should miss the local TAF sites to the S, except for KCVG/KLUK,
where a VCSH has been maintained through 16z. Even these sites
should be on the nrn fringe of the steadiest/most widespread
SN, so there is not a ton of confidence regarding VSBYs given
they should be very close to the nrn edge of the SN band during
this stretch. But there is some signal that KCVG/KLUK may only
see a few flurries through the morning opposed to SN that
produces MVFR/IFR VSBYs.

After the banded SN pivots E past 18z, the main item of interest
is going to be the development of scattered to numerous SHSN,
including possible SN squalls, from 18z through 02z. This
activity will progress W to E through the afternoon into early
evening, potentially impacting anywhere with brief squall
conditions of sudden reductions in VSBYs and gusty winds. The
impact would likely be fairly brief in nature, but potentially
somewhat intense. Have included a broad-brushed VCSH for now
given uncertainties regarding specific timing for any one
location.

Steady N winds on the order of 10-12kts will go more out of the
NW at 15-18kts, with gusts to around 25kts, with the arrival of
the arctic front (20z-00z from W to E). Winds will subside
subtly toward 06z and beyond, going more out of the WNW at
around 10-12kts.


OUTLOOK...MVFR ceilings may linger into early Monday morning.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Cold Weather Advisory from 1 AM Monday to 10 AM EST Wednesday
     for OHZ026-034-035-042>046-051>056-060>065-070>074-
     077>082-088.
     Winter Weather Advisory until 1 PM EST this afternoon for
     OHZ073-074-079-081-082-088.
KY...Cold Weather Advisory from 1 AM Monday to 10 AM EST Wednesday
     for KYZ089>100.
     Winter Weather Advisory until 1 PM EST this afternoon for
     KYZ089-090-094>100.
IN...Cold Weather Advisory from 1 AM Monday to 10 AM EST Wednesday
     for INZ050-058-059-066-073>075-080.

&&

$$

SYNOPSIS...AR
NEAR TERM...AR
SHORT TERM...KC
LONG TERM...Hatzos
AVIATION...KC