Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 271629
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1029 AM CST Fri Jan 27 2023

.SYNOPSIS...
Issued at 1029 AM CST Fri Jan 27 2023

A few rain and snow showers will pass through north-central
Illinois today...primarily along and north of the I-72 corridor.
Southwesterly winds will gust over 30mph at times, which will
boost afternoon high temperatures into the upper 30s and lower
40s.

&&

.UPDATE...
Issued at 1029 AM CST Fri Jan 27 2023

Vigorous short-wave trough evident on 16z/10am water vapor imagery
over eastern Iowa is triggering scattered snow showers across the
northern two-thirds of the KILX CWA this morning. Temperatures are
still near or slightly below freezing across much of the area, but
have climbed into the middle 30s along/southwest of a Jacksonville
to Effingham line. A few scattered slick spots may develop on
untreated and/or secondary roads for the next couple of hours
before readings climb above freezing across the board by midday.
Afternoon highs will range from the upper 30s along/north of I-74
to the middle 40s across the far S/SW CWA. Therefore any lingering
precip will transition to rain showers before ending from west to
east by early evening.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 156 AM CST Fri Jan 27 2023

The main forecasting concerns for today include:

(1) Gusty winds, and
(2) Light wintry precip

-------------------------------------------------------------------
Synoptic Overview
-------------------------------------------------------------------
 A mid-level shortwave trough will continue digging across the
 Upper Midwest today, helping drive a frontal system through the
 region. Surface winds will become backed and quickly increase
 over the next few hours as a warm front lifts through central
 Illinois. Light precip will develop later this morning as the
 nose of the LLJ impinges upon the warm front. P-type will
 initially favor snow before transitioning to rain as temperatures
 warm into the upper 30s by afternoon.

 Precip will shut off by this evening as a dry slot works in
 behind the cold front. Short term model guidance is then in good
 agreement that the front will slow down and stall-out somewhere
 along I-72/Danville as deep zonal flow develops overnight.
--------------------------------------------------------------------

Gusty Winds:
As the surface pressure gradient tightens ahead of the cold front
today, frequent gusts to 30 mph are anticipated. A quick glance at
some regional BUFKIT soundings suggest low stratus could limit
boundary layer mixing, but occasional gusts to 40-45 mph cannot be
ruled out and are actually supported by a few of the HREF progs.
This puts us up near Wind Advisory criteria, and while we might
meet it in a few spots, we`ll hold off on the headline for now --
citing only isolated occurrences.

Light Wintry Precip:
There`s a chance (30-50%) for light snow to develop this morning
as the nose of a LLJ overruns the warm front. The best chances
will be along and north of I-74 where thermal profiles support
snow, and is roughly where the warm front will be positioned when
all the key ingredients come together. Any wintry precip should
then transition to rain by afternoon, perhaps briefly mixing with
freezing rain, as surface temperatures warm into the upper 30s
ahead of the cold front. Little or no impact to travel is
anticipated from today`s precip.

.LONG TERM...(Saturday through Thursday)
ISSUED AT 156 AM CST Fri Jan 27 2023

Another shot for wintry precip arrives Saturday evening as weak
low pressure develops along a stalled-out baroclinic zone. Thermal
profiles across central Illinois will be complex as a plume of
low- level Gulf moisture surges northward and overruns the surface
front. Locations south of this front will receive mostly rain
through the daytime hours before transitioning to freezing rain
and then snow overnight into Sunday as the front sags further
south. As a point of reference, the freezing line (32 degF)
appears to stay north of the Illinois River Valley until about
9-10pm Saturday evening.

The higher QPF will be displaced further north across northern
Illinois and southern Wisconsin where strong f-gen will develop
beneath a flat upper-level jet core. Further south across central
Illinois, amounts generally range between 0.10" - 0.25". These
amounts, while lighter, may still prove to be impactful, but
travel conditions will be much worse north of Interstate 80.
And while we don`t have this forecast nailed-down quite yet
regarding the position of the surface front and the strength of
the warm nose, we are forecasting a few hundredths of ice to
precede light snowfall (< 2") accumulations Saturday night into
Sunday morning.  Roads will become slippery.

Wintry precip tapers off by Sunday afternoon as the polar jet
stream begins to buckle over the northern Rockies. The net effect
will be a drier and colder air mass spilling across the northern
Plains and into the Midwest. This stretch of cold/dry weather,
which will feature overnight wind chill values below zero, will
then continue through the middle of next week before another
winter weather system threatens the region.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 516 AM CST Fri Jan 27 2023

A frontal system will keeps skies murky through much of the TAF
period. While flight conditions will be VFR at the onset, a
lowering to MVFR is plausible as soon as 15z/9am with these lower
ceilings (~3 kft AGL) extending until at least 00z/6pm. Beyond
that time, some forecast uncertainty exists. While short term
forecast models begin to signal a return to VFR ceilings with
clouds gradually lifting and breaking, there is at least some
possibility that low clouds will persist all night as the cold
front stalls- out over central Illinois.

Surface winds will increase later this morning ahead of the cold
front. Winds will gradually veer from south to west through the
TAF period with sustained speeds between 15-20 kts and occasional
gusts to 35 kts, diminishing after sunset and becoming calm beyond
06z/Midnight.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Barnes
SYNOPSIS...Barnes
SHORT TERM...MJA
LONG TERM...MJA
AVIATION...MJA


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