853
FXUS63 KILX 061035
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
535 AM CDT Mon Apr 6 2026

.KEY MESSAGES...

- Chilly conditions will prevail tonight: however, the risk for
  a hard freeze has decreased substantially due to expected
  cloud cover. Low temperatures will be coldest along the I-74
  corridor where readings will bottom out around 30 degrees.

- An upper disturbance will produce a band of light rain and
  snow along and south of a Macomb...to Decatur...to Mattoon
  line late tonight into early Tuesday morning. Less than 1 inch
  of snow is expected on grassy surfaces.

- Warmer/wetter conditions will return by the end of the week:
  however, severe weather is not anticipated.

&&

.DISCUSSION...
Issued at 247 AM CDT Mon Apr 6 2026

     Cold Tonight...

As has been advertised for the past several days, the coldest
period of the forecast will occur tonight. High pressure
currently extending from Saskatchewan into the Dakotas will
settle southeastward tonight...and is progged to be centered
over Wisconsin by 12z Tue. Meanwhile an upper-level disturbance
tracking out of the Plains will spread clouds across much of
central Illinois tonight. Given the expected cloud cover and
northeasterly winds of 5-10mph on the southern periphery of the
high, radiational cooling will not be ideal. As a result,
several CAMs have trended much warmer...with the 00z Apr 6 RRFS
showing lows staying in the middle 30s along I-74. The HRRR is
not quite that warm, but still only indicates minimum temps
around 30-32 degrees across the N/NE KILX CWA. While sub-freezing
temperatures are still possible, confidence is growing that a
widespread hard freeze with temps dipping into the 20s will not
occur. Will leave the current Freeze Watch in place for
locations along/north of a Macomb to Danville line, but this
will likely be cancelled by later shifts if trends continue. The
latest forecast will feature lows ranging from around 30
degrees along/north of I-74 to the middle to upper 30s south of
I-70.

     Light Rain/Snow Tonight...

As a short-wave trough tracks out of the northern Rockies and
interacts with the trailing end of the departing frontal
boundary, a narrow band of precipitation will develop tonight
into Tuesday morning. 00z Apr 6 models are all in good agreement
concerning the placement of the band from eastern Nebraska
across southern Iowa/northern Missouri into south-central
Illinois. Will need to keep a close eye on later model runs,
because some minor track adjustments are still possible.
Specifically in central Illinois, the latest model consensus
suggests the precip will occur along/south of a
Macomb...to Decatur...to Mattoon line...with the most
significant precip staying along/south of a Rushville to
Springfield line. The NAM shows the strongest frontogenesis
developing within the 800-700mb layer between 06z and 12z, with
the forcing weakening considerably by 15z Tue. While the airmass
will initially be quite dry, the combination of increased
forcing and weak upglide noted on the 300K surface will lead to
the development of light precip primarily after midnight into
early Tuesday morning. The thermal profile will initially be
warm enough to support rain: however, ample evaporative cooling
will allow the precip to mix with and/or change to all snow
overnight. Snowfall will remain light due to the initial mixed
phase of the precip, marginally cold air temperatures, and the
warm ground. 00z Apr 6 HREF mean snowfall is less than 1
inch...while the HREF max features as much as 1-3 inches across
the far SW CWA. At this time, will forecast amounts of less than
1 inch on grassy surfaces along/south of a Rushville to
Springfield line.

     Warmer/Wetter by the End of the Week...

The current northwesterly flow pattern will be replaced by a
flat west-to-east zonal flow by the middle and end of the week.
This will allow temperatures to climb back above normal and also
introduce increased rain chances as a series of disturbances
track across the CONUS. The primary challenge with this type of
scenario is trying to predict exactly where the main baroclinic
zone will lay out. As the first short-wave approaches, it will
drag a cold front toward central Illinois on Thursday...with the
boundary then going parallel to the upper flow and becoming
quasi-stationary after that. Models are showing a good deal of
spread concerning placement of the boundary Friday through
Sunday, so current NBM features daily rain chances through the
period. It will most definitely not rain that entire time, and
PoPs will be adjusted accordingly as details become clearer.

After a chilly day with highs only in the 40s on Tuesday,
readings will climb back into the upper 60s/lower 70s Wednesday
through Friday...then will soar well into the 70s to near 80
degrees by Sunday as the flow becomes more southwesterly.
Tuesday/Wednesday will be dry days...with rain chances north of
I-72 on Thursday, then everywhere Friday through Sunday. While
showers and thunderstorms are in the forecast, the risk for
widespread severe weather will remain low due to marginal
instability and the lack of a strong upper forcing mechanism.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 535 AM CDT Mon Apr 6 2026

VFR conditions will prevail through the entire 12z TAF period.
FEW-SCT mid-level clouds at 10,000-12,000ft will stream across
the sky through early afternoon, then will become BKN-OVC
between 21z and 00z. A weak disturbance is expected to trigger a
band of lower clouds and light precip across northern Missouri
into southwest Illinois late tonight. The exact placement of the
band is still in question: however, it appears it will remain
largely S/SW of the central Illinois terminals. It will come
close enough to warrant VCSH at KSPI after 06z, with dry
conditions elsewhere. Winds will become NW with gusts of 20-25kt
later this morning as a cold front drops through the region.
Winds will decrease to around 10kt by sunset, then will
gradually switch to N/NE after midnight.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Freeze Watch from late tonight through Tuesday morning for
ILZ029-031-036>038-041>046.

&&

$$

KEY MESSAGES...Barnes
DISCUSSION...Barnes
AVIATION...Barnes