Decatur, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

646
FXUS63 KILX 100502
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1202 AM CDT Fri Jul 10 2026

.KEY MESSAGES...

- Rain chances will be highest late this afternoon into early
  evening, then again Friday night. A few of the storms will be
  on the strong side, but the main threat of that will be south
  of I-72.

- Locally heavy rain will result in the potential for areas of
  flooding, with the focus shifting more into areas south of
  I-72 by Friday night.

- Temperatures remain typical for July. While a warming trend
  takes place next week, humidity levels will make it feel less
  oppressive than last week`s heat wave.

&&

.UPDATE...
Issued at 921 PM CDT Thu Jul 9 2026

Showers and storms have quited down for now, but lots of
leftover outflow boundaries in the area. These could be focus
for more showers and storms later tonight as the low level jet
increases during the overnight hours. Believe the main focus
will be along and south of I-72/Danville so have adjusted pops
to reflect that trend. Adjusted pops for tomorrow as well since
any boundaries should be in southeast CWA through the morning.
Things will begin to increase again as the boundary in northern
IL/IA will slide south in our north and could be the focus for
more showers and storms tomorrow afternoon and evening. Update
should be coming shortly.

&&

.DISCUSSION...
Issued at 116 PM CDT Thu Jul 9 2026

Short Term (through Saturday):

Prominent MCV from the decaying convection across Missouri is
about to cross the Mississippi River south of Pittsfield.
Despite a fair amount of cirrus blowoff, MLCAPE`s of 1000-1500
J/kg have allowed scattered storms to develop over the last hour
across eastern Illinois. Recent Day1 convective outlook shifted
the risk areas a little further south and are mainly
concentrated south of I-72. Greatest downdraft CAPE is expected
preceding the anticipated convection across central Illinois,
though there remains some uncertainty with the extent of
strong/severe storms. In general, much of the shower/storm
activity is expected through sunset. While development of
another MCS across Missouri is expected this evening, most of
the high-res guidance keeps this to our southwest.

A front across Iowa and southern Wisconsin is expected to only
slowly drift southward the next couple days. Additional
convective complexes are expected to ride along the boundary
Friday night, and highest rain chances remain over the south
half of the forecast area during this time. East-west upper
troughing will set up during the weekend, keeping the frontal
movement on the slow side. However, by late Saturday night, it
should finally be near the Ohio River, ending the rain threat.


Long Term (Sunday through Thursday):

Little change in the forecast for next week. A sprawling upper
high will dominate a large portion of the CONUS to start the
week, before the ridging amplifies near the Plains by midweek.
This pattern will result in seasonably warm temperatures near 90
degrees in our area, though with the Gulf cut off, humidity
levels should not get as rough as last week`s heat wave. Still,
heat index levels of 95-100 degrees are likely Tuesday-Thursday.

As the upper ridge establishes itself, we`ll be on the periphery
of a northwest flow, which can be favorable for MCS activity.
Right now, that activity looks to be more across the Great Lakes
region, so a dry forecast will be maintained in the extended
period.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1202 AM CDT Fri Jul 10 2026

Areas of MVFR ceiling and visibility are expected to develop
over central IL later tonight, and persist through 13-14z. There
are low probabilities of IFR conditions during this period. The
other aviation issue will be scattered TSRA Friday afternoon and
evening. Due to timing and coverage issues, kept mention to
PROB30 for now. Winds predominantly light/variable through the
forecast.

&&

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

&&

$$

KEY MESSAGES...Geelhart
UPDATE...Auten
DISCUSSION...Geelhart
AVIATION...25