081
FXUS63 KILX 081736
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1136 AM CST Wed Jan 8 2025

.KEY MESSAGES...

- The coldest weather of the entire forecast period is on tap for
  tonight when lows drop into the single digits across much of the
  area. Even colder readings near or slightly below zero will
  occur along and south of a Paris to Taylorville line.

- A storm system passing well south of the region will spread snow
  into central Illinois Thursday night into Friday. Probabilities
  for an inch or more of snow continue to increase: however, the
  heaviest amounts will remain well to the south across Arkansas
  and Tennessee.

&&

.UPDATE...
Issued at 1050 AM CST Wed Jan 8 2025

Skies are clear over most of the area except for the southeast.
Southeast clouds will clear out to the south within the next
couple of hours. Light northwest winds will maintain cold air
advection over the area so thinking only warmth will come from the
sun today. Current forecast does look ok, but the Bloomington
local effect is occurring again today, giving much warmer temp at
BMI. Will adjust for this in an update to the forecast...which
will be out shortly.

Auten

&&

.SHORT TERM...(Today through Thursday)
Issued at 343 AM CST Wed Jan 8 2025

Persistent cloud cover has prevented temperatures from cratering
over the fresh snow cover early this morning as 09z/3am readings
are mostly in the teens. Based on satellite trends, am expecting
the clouds to thin along/north of a Rushville to Bloomington line
over the next couple of hours...so temps will likely fall into the
single digits or lower teens across this area. Further southeast,
the clouds will hold firm and keep readings nearly steady through
daybreak. The clouds will steadily erode from NW to SE across the
area this morning, with mostly sunny skies across the board by
early afternoon. Despite the sunshine, highs will remain below
normal for this time of year in the lower to middle 20s. As high
pressure builds into the region tonight, skies will remain mostly
clear and winds will become very light. This will allow excellent
radiational cooling to develop and overnight lows to plunge toward
zero. Given the expected position of the high by 12z Thu, it
appears winds will be nearly calm across the southern half of the
KILX CWA. As a result, think the coldest readings at or slightly
below zero will be focused along and south of a Paris to
Taylorville line. Partly to mostly sunny conditions will be
observed on Thursday with chilly afternoon highs in the middle to
upper 20s.

Barnes

.LONG TERM...(Friday through Tuesday)
Issued at 343 AM CST Wed Jan 8 2025

The next storm system slated to impact central Illinois will come
into the picture Thursday night into Friday as a southern-stream
wave over northern Mexico and a northern-stream wave skirting
across the Northern Plains gradually phase over the Midwest/Ohio
River Valley. As has been seen by the past several model cycles,
the latest suite continues to indicate the southern wave will be
the dominant feature...with its corresponding surface low tracking
along the Gulf Coast. A separate low will form much further north
and push into the Great Lakes. Between the two features, general
synoptic lift associated with the phasing upper waves interacting
with increasing moisture from the Gulf of Mexico will produce a
period of light snow across central Illinois Thursday night into
Friday. With NAM precipitable water values increasing to around
0.50 and temperatures climbing into the middle to upper 20s, think
snow-to-liquid ratios of 13:1-14:1 look reasonable for this
event. The 00z Jan 8 LREF shows a greater than 40% chance for
snowfall of 1 inch or more along/southeast of a Peoria to Quincy
line...and a greater than 40% chance for more than 2 inches of
snow along/southeast of I-70. At this time, think most of central
Illinois east of the Illinois River will see around 1 inch of
snow...with a few pockets of up to 2 inches were mesoscale banding
can develop. Areas south of I-70 see the best shot at potentially
exceeding 2 inches as that area will be closest to the low track.
Meanwhile much further south, the latest indications suggest a
major snowfall in excess of 6 inches from Little Rock, Arkansas to
Nashville, Tennessee.

Once the wave passes, light snow will come to an end Friday
evening...followed by a return to cool/dry weather for Saturday
with highs in the middle to upper 20s. Temperatures may make a run
at the freezing mark by Sunday as SW winds in advance of another
weak northern-stream short-wave boost highs into the lower 30s.
This feature may bring another period of very light snow Sunday
afternoon and night before quickly exiting into the Ohio River
Valley. After that, northerly flow on the back side of the
departing wave will drop temps back into the lower to middle 20s
for Monday/Tuesday.

Barnes

&&

.AVIATION...  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1136 AM CST Wed Jan 8 2025

Mostly clear skies continue across central IL this afternoon,
with northwest winds picking up to around 5-10 kt. These will ease
and back to southerly this evening through tonight, as a warm
front lifts north and brings mid to high clouds into the area. One
thing to note: HREF suggests a 10-30% chance of visibilities less
than 1/2 mile near and east of the I-55 corridor between roughly
5am and 9am (11z and 15z), mainly driven by one model - the HRRR.
This was not added to the TAFs due to low confidence, however the
potential for advection fog by southerly winds over the snow pack
will be reassessed in future shifts to determine whether its
inclusion in the TAFs could be warranted.

Bumgardner

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$