ILN issues Area Forecast Discussion (AFD) at Jan 21, 2:35 AM EST871
FXUS61 KILN 210735
AFDILN
Area Forecast Discussion
National Weather Service Wilmington OH
235 AM EST Tue Jan 21 2025
.SYNOPSIS...
Bitterly cold conditions will persist through Wednesday,
with mainly dry conditions expected through midweek. There will
be a few chances for patchy light snow showers Tuesday and again
Thursday into Friday, but precipitation should be isolated and
very light in nature. A slight warming trend is expected by the
end of the workweek, with more seasonable air filtering back
into the Ohio Valley as we head into the weekend.
&&
.NEAR TERM /THROUGH TODAY/...
Sfc high pressure centered to the SE of the OH Vly continues to
drift to the E, with return flow briefly setting up on the
backside of the departing high. This is allowing for the earlier
calm winds to gradually shift around to out of the SW at about
5kts or so, reducing the good radiational cooling conditions
that allowed temps to drop so efficiently in the several hours
after sunset. But through the predawn hours, with the arrival of
some better cloud cover as well, expect that temps will largely
plateau across most of the area, with the expectation for even
a several degree rise near/W of I-71 through daybreak.
Although temps dipped below zero for many locales in the late
evening/early overnight hours, winds have largely been very
light or calm. As the winds begin to pick up, so too will the
temps, so the balancing act will result in wind chills generally
staying within the -5F to -15F range through daybreak for most
locations.
For the daytime today, the longwave trof entrenched across the
ern CONUS will dig back into the OH Vly once again by this
afternoon, with much colder air set to filter back into the
region by tonight into Wednesday morning. This disturbance,
given the very cold air already in place, should provide just
enough forcing amidst a meager moisture profile to generate
additional scattered flurry or very light SHSN activity this
morning through the afternoon along the eastward-advancing front.
This will especially be the case across parts of central/south-
central OH and NE KY mid afternoon, where a dusting to perhaps
a few tenths of an inch will be possible. But the sfc high will
quickly build back into the area by this evening, shunting any
light SHSN activity to the E by sunset.
Today is going to be a tricky day from a temp perspective as
the front will already be entering parts of EC IN and WC OH
around sunrise, meaning that temps in these areas may not
rebound much during the day (generally staying in the single
digits above zero). Further to the SE, however, enough diurnal
warming ahead of the FROPA through early afternoon may allow
temps to reach into the upper teens and lower 20s, particularly
across N/NE KY and the lower Scioto Valley. This will make for a
~15 degree gradient across the area by early afternoon before
stronger CAA overspreads the entirety of the area by late in the
day, sending temps downward once again area-wide this evening
into tonight.
&&
.SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/...
Sfc high pressure will build into the srn OH Vly this evening
through early tonight, creating ideal radiational cooling
conditions locally through at least the first half of tonight.
There is a strong signal that the coldest temps of the entire
stretch are expected tonight given the favorable setup, but this
may not necessarily translate into colder wind chills than what
we have already experienced given the light/calm winds.
With the ~1038mb sfc high traversing srn parts of the region,
do think that most, if not all, areas will experience below zero
air temps tonight. In fact, sheltered/low-lying areas will
likely see air temps around/below -5F, with -10F air temps very
possible in rural/sheltered spots in parts of central/south-
central OH. The fly-in-the-ointment, however, is going to be
that as the sfc high pulls E of the region very late tonight
through early Wednesday morning, return flow on the backside
will allow for winds to begin to increase to around 5-10kts
across parts of EC IN and WC OH during the predawn hours. This
may not seem like much, but with air temps between -5 and -10
degrees, any light wind will have a significant impact on the
wind chill. But it may also help nudge the air temp up a few
degrees around daybreak, too. Either way, minimum wind chill
values are going to get very close to warning-level criteria
(-20F N and -15F S) for a large portion of the area late
tonight into Wednesday morning, but there is not /quite/ enough
confidence at this time to support an upgrade to a warning given
the uncertainties in the ever-delicate temp/wind dance that
will unfold late tonight. It is going to be very cold no matter
the circumstances, even if wind chill values stay in advisory
criteria due to lighter wind.
Breezy conditions are expected on Wednesday amidst a tightening
pressure gradient, with temps rebounding rather abruptly past
sunrise from the -5 to -10 range into the upper teens to mid
20s by the afternoon. The stiff SW breeze will be in response to
the approach of the next weak system, which may bring additional
low-end light snow chances to the area by Thursday.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
On Wednesday evening, surface high pressure will be moving off the
east coast, as a surface low moves east through the Great Lakes.
Boundary layer flow will be generally southerly, as the period of
very cold temperatures will have come to an end. Attention will then
turn to two shortwaves moving eastward through the generally
westerly flow aloft. Although moisture will be limited, these waves
will be capable of producing flurries or perhaps some very light
accumulations of snow. Confidence, however, is rather low in exact
placement and timing. This forecast will simply carry a slight
chance of snow for sections of the forecast area on Thursday (with
the first wave) and Friday morning (with the second wave). In
between the two, a weak surface boundary will re-establish some
slightly cooler air over the area Thursday night into Friday.
Conditions will change a bit over the weekend, as high pressure sets
up over the southeastern states, leading to deeper and stronger
southwesterly flow into the Ohio Valley. This will bring
temperatures above freezing (lower 30s to lower 40s) for the ILN CWA
on both Saturday and Sunday. At some point over the weekend,
probably heading into Sunday, there has been a fairly consistent
model signal for precipitation. As the surface high drifts a little
further to the southeast, theta-e advection on its western periphery
will develop from the Gulf of Mexico through the middle Mississippi
Valley region, with eventually some theta-e advection aloft reaching
the Ohio Valley as well. While sometimes these types of setups could
produce a risk of freezing rain, the warmer conditions on Saturday
and lack of significant overrunning may help to mitigate this, and
model ensemble probabilities suggest only very low probabilities for
anything other than a mix of rain and snow as of now.
&&
.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
VFR conditions are expected overnight, with mostly clear skies
and light southwest winds.
During the day, some VFR stratocumulus clouds will move into
the area, as southwest winds increase to 10-15 knots. A front
will then move through the area, switching winds to the west,
with a few gusts into the 20-25 knot range. Some very light snow
(mostly just flurries) can also be expected, and this has been
included at KDAY/KILN/KCMH/KLCK. At worst, some brief MVFR
visibilities could occur. There will also likely be a period of
a few hours of MVFR ceilings, which will clear up by late
afternoon or early evening.
Clear skies and light winds are then expected heading into
Wednesday morning.
OUTLOOK...MVFR ceilings are possible Thursday into Friday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Cold Weather Advisory until 10 AM EST Wednesday for OHZ026-034-
035-042>046-051>056-060>065-070>074-077>082-088.
KY...Cold Weather Advisory until 10 AM EST Wednesday for KYZ089>100.
IN...Cold Weather Advisory until 10 AM EST Wednesday for INZ050-058-
059-066-073>075-080.
&&
$$
SYNOPSIS...KC
NEAR TERM...KC
SHORT TERM...KC
LONG TERM...Hatzos
AVIATION...Hatzos
Source:
ILN issues Area Forecast Discussion (AFD) at Jan 21, 2:35 AM EST---------------
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