Decatur, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

807
FXUS63 KILX 061750
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1250 PM CDT Tue Oct 6 2026

.KEY MESSAGES...

- No significant weather is expected across central Illinois
  through early next week. Low chances of showers (20-30%) in
  southeast IL overnight Saturday night and Sunday.

- Due to dry fuels and low afternoon relative humidity values,
  there is an elevated risk for agricultural field fires through
  Saturday especially southeast of the IL river where afternoon
  humidity levels will likely reach 30% or less.

&&

.DISCUSSION...
Issued at 315 AM CDT Tue Oct 6 2026

Large surface high pressure over southeast Ontario peninsula
and eastern Great Lakes region was still ridging sw into
central/se IL. Meanwhile a 999 mb low pressure over northern
Manitoba Province has a frontal boundary extending through
eastern ND, central SD and nw Nebraska. Nearby high pressure
ridge continue clear skies with light to calm winds over
central/se IL. Seasonably cool temperatures were in the mid to
upper 40s, ranging from 42F at NWS office on east side of
Lincoln to 50F at the Bloomington and Peoria airports. Very
patchy shallow ground fog was near rivers/waterways with
Robinson airport having dense fog (vsby less than 1/4 miles),
and Jacksonville airport vsby 1.5 miles. Added patchy fog early
this morning in southeast IL especially near the Wabash river
valley and over the middle/lower IL river valley. HRRR model has
been more aggressive than other CAMs with showing patchy dense
fog in southeast IL (generally se of a Paris to Shelbyville
line) drifting sw and lifting by 8 am.

High pressure to settle near the mid Atlantic coast by sunset
while ridging into the mid MS river valley and continue ample
sunshine over CWA again today. A cold front to push into
southern WI and northern Iowa by sunrise Wed and into central
IL during Wed afternoon. Will see light to calm winds early this
morning becoming southerly and increase to a bit breezier
levels by afternoon with gusts up to 20 mph north of I-72. Mild
highs today in the mid to upper 70s, warmest from Springfield
sw. Fair tonight with some increasing high clouds from the nw, with
lows in the low to mid 50s. Cooler lows in the upper 40s near
the Wabash river valley where patchy shallow ground fog could
develop overnight, with upper 50s over west central IL near MS
river valley. SW winds 5-15 mph Wed morning to turn west to nw
during Wed afternoon as weak cold front passes through dry. Warm
highs in the low to mid 80s on Wed, warmest from I-72 south.

Weak 1020 mb high pressure settles se into the Midwest and IL
during Thu with north to nw winds around 10 mph or less and
mostly sunny skies. Highs Thu range from the lower 70s from
Canton to Normal north with upper 70s to around 80F from
Springfield and Paris south. High pressure strengthens as it
settles eastward over the mid Atlantic States on Friday with
return light SE flow setting up over IL. Temps on Friday near
or just above Thursday`s levels in mid 70s to around 80F.
Warmer highs in the low to mid 80s on Saturday as strong
mid/upper level ridge builds into IL and southerly flow
increases.

The National hurricane Center (NHC) has an 80% chance of a
tropical cyclone development next 48 hours over the sw Gulf of
America. This system will likely spread deeper gulf moisture
northward across the Southeast States during this weekend as low
pressure lifts into the lower MS river valley during Sat night.
Big question will be how far north it is able to spread its
moisture into IL and current NBM keep 20-30% pops in southeast
IL overnight Sat night into Sunday. The earlier runs of the
extended models mostly brushed se IL with some qpf overnight Sat
night and Sunday with heavier qpf and stronger winds from Ohio
river se. Latest Ecmwf has shift low track northward to near
Paducah by midday Sunday with qpf overspreading much of CWA
during overnight Sat night into Sunday while GFS and GEM models
keep brunt of QPF se of CWA. We need to monitor this tropical
system. Temps to likely be cooler Sunday with more clouds and
possible showers around especially in southeast IL. Extended
models build another strong mid/upper level ridge into IL early
next work week with warm temps likely Mon/Tue

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1250 PM CDT Tue Oct 6 2026

VFR conditions are forecast to persist through 18z Wednesday.
Surface wind gusts up to around 20 kt may occasionally occur
through this afternoon. Forecast soundings indicate the
potential for a few clouds near 5 kft after 06z on Wednesday
morning, with ceilings highly unlikely. A weak boundary moving
into the region after 12z Wednesday will veer surface winds to
the west.


&&

.FIRE WEATHER...
Issued at 343 AM CDT Tue Oct 6 2026

Given the prolonged stretch of dry weather especially south of
I-72, and RH values routinely dropping to 30% or less southeast
of the IL river during the afternoons especially today and
Thursday through Saturday, a heightened risk for agricultural
field fires exists through Saturday. Though fairly light ambient
winds this week will limit widespread fire weather concerns.
Boundary layer moisture will be on the increase by Sunday as
tropical moisture flows northward from the Gulf of America, and
this should lessen fire wx concerns. Around 36% of corn and 31%
of soybeans have been harvested in Illinois as of Oct 4th and
we are in peak harvest season during the month of October.

&&

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

&&

$$

KEY MESSAGES...07
DISCUSSION...07
AVIATION...AAT
FIRE WEATHER...07