Decatur, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

351
FXUS63 KILX 260954
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
454 AM CDT Tue May 26 2026

.KEY MESSAGES...

- No major storm systems are expected to impact the region over
  the next week. As a result, the severe weather risk across
  central Illinois will remain very low (less than a 5% chance)
  through next Monday.

&&

.DISCUSSION...
Issued at 341 AM CDT Tue May 26 2026

08z/3am water vapor imagery shows an upper low spinning over the
ArkLaTex region. With deep-layer moisture flowing northward
from the Gulf ahead of this system, showers have spread as far
north as the Ozarks into western/southern Kentucky. As the
precipitation continues to lift slowly northward, it will
eventually encounter synoptic subsidence and a drier airmass
beneath a surface ridge axis across central Indiana/Illinois.
As a result, the northward progress of the rain will be
slow...with most CAMs confining any showers to locations
along/south of I-70 through this afternoon. Further north, am
expecting mostly cloudy and dry conditions. High temperatures
will range from the upper 70s along/south of I-70 to the middle
80s north of the I-72 corridor.

The low will continue its gradual trek northward tonight:
however, it will be weakening as it does so. 00z May 26 models
are all in good agreement concerning the eventual northern
extent of showers tonight into Wednesday...with consensus
placing it near a Rantoul to Jacksonville line. The main
forecast concern is rainfall amounts as a few models indicate
bands of showers blossoming and becoming quasi-stationary
across portions of east-central Illinois late tonight into
Wednesday morning as the low approaches. The 06z HRRR shows a
few amounts over 1 inch from Paris/Marshall southwestward to
near Effingham. Meanwhile the 00z HREF mean QPF features pockets
of 0.75-1.00 across this general area and perhaps as far N/NW
as Tuscola and Shelbyville. The NBM is considerably lighter with
amounts of only around 0.25. At this point, will focus highest
PoPs (40-50% chance) south of a Danville to Shelbyville line
with rainfall of 0.25 to 0.50. Will need to keep a close eye on
future model data in case rainfall needs to be boosted in this
area. Further northwest along/NW of I-55, little to no rain is
expected.

As upper ridging builds over the Upper Midwest, it will shunt
the remnants of the low southward and allow a return to dry
weather across the board Wednesday night through the end of the
week. After that, the synoptic models indicate surface high
pressure over the Great Lakes region will keep central Illinois
dry through early next week as short-wave energy remains S/SW of
the area. Seasonal temperatures in the upper 70s and lower 80s
are anticipated.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 454 AM CDT Tue May 26 2026

VFR conditions will prevail through the entire 12z TAF period. A
high overcast will persist through this afternoon before
ceilings gradually lower to 8000-12000ft this evening. Showers
will develop and lift slowly N/NW toward I-72 late tonight, but
should largely remain SE of the terminals. Have added a PROB30
group for showers at KCMI/KDEC as some models suggest rain will
reach those sites. Winds will initially be E/NE early this
morning, then will become E/SE this afternoon through tonight.

&&

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

&&

$$

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