Decatur, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

624
FXUS63 KILX 302119
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
419 PM CDT Sun Mar 30 2025

.KEY MESSAGES...

- The severe storms are expected to be out of the area by 7pm this
  evening.

- Overnight Tuesday into Wednesday bring the best chances for the
  next round of severe weather. Outlooks from the SPC have a
  slight risk (level 2 of 5) for Tuesday night`s activity and an
  enhanced (level 3 of 5) for Wednesday.

- Gusty winds return Wednesday, with gusts around 30-35 knots
  during the day.

- Multiple round of precipitation are possible through the
  weekend for southeastern IL.

&&

.MESOSCALE...
Issued at 417 PM CDT Sun Mar 30 2025

Key Messages...
Severe threat has shifted to portions of southeast Illinois south
of I-70. There is growing concern for some flooding as multiple
rounds of storms train over the same areas.

Technical Discussion...
Severe threat has shifted into our counties south of I-70 as of 4
pm this afternoon. Environment ahead of the storms remains
favorable to support continued severe thunderstorms with moderate
instability and strong shear. Latest SPC meso-analysis indicates a
corridor of 1500+ J/kg MLCAPE in place ahead of the line while
deep layer shear largely parallel to the line is between 40 and 50
kt. These storms have been transitioning from discrete supercell
to a more linear/QLCS mode and the wind threat will increase while
hail threat tapers some accordingly. There remains a threat for
mesovorticies spinning up within the line, especially for any
eastward bowing segments. Meanwhile, 850-300mb heights are
parallel to the ongoing line of storms resulting in training. MRMS
1-hour QPE estimate shows a narrow ribbon of 1.50-1.75 inches has
fallen while 3-hour estimate show upwards of 2.6 inches in
pockets upstream. Both of these numbers are closing in on the 1-hr
and 3-hr RFC flash flood guidance so will need to keep a close
eye on hydro concerns over the next couple hours.

Deubelbeiss

&&

.DISCUSSION...
Issued at 125 PM CDT Sun Mar 30 2025

The line of storms we have been outlooking have fired and are moving
eastward across the southern half of IL this afternoon. We are
expecting these storms to be out of the CWA by 00z -- exiting out of
southeastern IL. All hazards are still expected throughout the event
and a Tornado Watch (#70) is in effect through 00z.

Monday will be a relaxed day compared to what has been going on.
Highs will be in the upper 40s to low 50s, with low temperatures
around 30 degrees. Temperatures will rebound by Wednesday back into
the 70s.

After today`s severe weather, we are watching Tuesday night into
Wednesday for the next decent chance for severe weather. SPC has us
outlooked for a slight risk (level 2 of 5) Tuesday (Day 3) and an
enhanced risk (level 3 of 5) Wednesday (Day 4). Thinking is the
outlook for Tuesday is for overnight Tuesday into early Wednesday
morning, as there looks to potentially be two rounds of severe
weather. The overnight round (associated with a warm front)
currently doesn`t look as impressive as the daytime convection
Wednesday. The second round will be firing along the passing cold
front and looks to be in the afternoon into the evening. Outside of
the storms, Wednesday looks to be another windy one (gusts around 30-
35 knots).

Overall the extended will be an active and wet period and start to
April, especially for southeastern IL. Several rounds of
precipitation look possible for southeastern IL over the weekend,
including a slight risk for excessive rainfall on Wednesday and
Thursday. Highs will be in the 60s for the entire CWA through the
weekend.

Copple

&&

.AVIATION...  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1225 PM CDT Sun Mar 30 2025

A line of storms are moving through central IL this afternoon,
primarily impacting DEC and CMI into the evening. PIA may see
some light showers this afternoon. Ceilings will drop tonight to
MVFR ~1-2kft. By late morning tomorrow, ceilings will rise back to
VFR for all sites. Winds will be gusty up to 30-35kt.
Southwesterly winds will rotate out of the northwest by this
evening behind the cold front.

Copple

&&

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

$$