Decatur, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

853
FXUS63 KILX 071757
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1257 PM CDT Sat Jun 7 2025

.KEY MESSAGES...

- SPC removed the severe weather risk for today across central and
  southeastern IL. Showers and thunderstorms are expected today,
  with localized heavy rainfall (especially south of I-70).

- Sunday has a marginal risk for the entire CWA with areas west of
  the I-155/I-55 corridor in a slight risk. SPC indicates as the
  storms move further east of the Mississippi River, they will
  lose their severe ability.

- A dry stretch of weather shows its face starting late Monday
  morning into Thursday as a high pressure system settles over the
  Ohio Valley.

&&

.UPDATE...
Issued at 1035 AM CDT Sat Jun 7 2025

Updated the forecast to increase chances of showers and
thunderstorms from sw to ne during the afternoon, and diminishing
from the west during this evening. Also increased QPF amounts per
WPC upgrade to slight risk of excessive rainfall over east central
IL with marginal risk of excessive rainfall over remainder of CWA
this afternoon and evening where some areas could top 1 inch of
rainfall with a few areas reaching 1-2 inches in a few hours. PW
values of 1.5-1.75 inches in sw IL and se MO to advect ne into
CWA during this afternoon, highest in sw CWA and se IL. Highs in
the mid to upper 70s look on track, coolest in sw CWA.

Convective complex currently over nw MO, sw IA into ne KS with
showers as far east as Kirksville MO to track eastward into
central IL during mid afternoon into mid evening. SPC day1 outlook
has extended marginal risk of severe storms for 5% risk of
damaging winds and large hail northward to a Pittsfield to
Litchfield to Olney IL line and including central and sw Clay
county, sw Richland and far sw Lawrence counties for late
afternoon into mid evening time frame. The slight to enhanced risk
of severe storms this afternoon/evening remain south of IL where
much higher instability will be in the warm sector. The RAP13 and
NAM12 show pockets of CAPES from 800-1300 j/kg from mid afternoon
into early evening from the IL river se so could see some pulsey
type stronger cells with gusty winds and possible hail further
north into CWA.

Air Quality Index (AQI) is currently in the orange category
(101-150 unhealthy for sensitive groups) from Lincoln to
Rushville south and yellow category (51-100 moderate category)
rest of CWA at late morning. Forecast shows Air Quality generally
in the moderate category (yellow color) this afternoon and
tonight while northern Indiana gets into the unhealthy for
sensitive groups category (orange color).

07

&&

.DISCUSSION...
Issued at 232 AM CDT Sat Jun 7 2025

This morning is shaping up to be a foggy one for areas near and
south of the I-72 corridor. There is a Dense Fog Advisory out for
the southern half of the CWA this morning, expiring by 14z (9am) as
the sun erodes the fog. We could see some more fog tomorrow morning
as well with the moist grounds and light winds. How dense it gets
will depend on if there are any areas of sky clearing overnight
tonight. Highs today in the mid 70s.

More showers and thunderstorms are forecast to move through central
IL this afternoon, associated with a weak low pressure system. The
low center will progress eastward across southern / southeastern IL.
The SPC has removed the entirety of the CWA out of the marginal risk
for severe weather for today. The thunderstorms this afternoon into
evening should behave themselves. South of I-70 there is around 1000
J/kg of CAPE, little to no CIN, and ~20 knots of bulk shear. The
soundings have the appearance of a heavy rain event, more than a
severe shape. There are values of 1.6-1.8 of PWAT, long skinny CAPE
profile, and slow storm motions (15-30 knots). localized 1 inch
amounts or more are likely in stronger cells. They should exit just
after midnight tonight.

Tomorrow we have even more chances for showers and thunderstorms.
The difference being more of a severe risk with these storms, with
all hazards possible. This round is firing along a cold front that
will move through the CWA from late tomorrow afternoon into Monday
morning. SPC has us in a marginal risk for the entire CWA with
areas west of the I-155/I-55 corridor in a slight risk. SPC
indicates as the storms move further east of the Mississippi
River, they will lose their severe ability.

From Monday morning to early Thursday, a high pressure system
settles into the Ohio Valley. We finally see a period of drier
weather during this period. Temperatures will warm into the 80s
for highs by Wednesday and should stay there into the weekend.
Lows will warm into the mid to upper 60s.

The dry weather won`t stick around long. By Thursday afternoon, more
rain chances enter the forecast again into next weekend as a
disturbance or two traverse the region.

Copple

&&

.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1240 PM CDT Sat Jun 7 2025

An approaching disturbance will bring showers and isolated
thunderstorms to the area later this afternoon into early
evening, with most activity pushing out between 02-04z. Ceilings
will steadily lower this evening, becoming MVFR at all terminals
by 03z, and then IFR by 09z. Winds will remain light and variable
through the period with speeds generally under 10 kts, allowing
for patchy dense fog to re- develop into Sunday morning. VFR
conditions then return to all sites by Sunday afternoon with the
heat of the day.

MJA

&&

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

$$