Decatur, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

127
FXUS63 KILX 142312
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
612 PM CDT Wed May 14 2025

.KEY MESSAGES...

- Record warmth is forecast for Thursday highs and lows.

- A conditional risk for severe weather exists both Thursday and
  Friday. SPC has maintained a slight risk (level 2/5) for
  Thursday and increased to an enhanced risk (level 3/5) on
  Friday.

- After a brief reprieve this weekend, the severe weather
  potential returns early next week.

&&

.DISCUSSION...
Issued at 239 PM CDT Wed May 14 2025

We continue our first taste of summer this week. We are looking at
potentially warmest low temperature records and record highs for
tomorrow (Thursday). Lows tonight are forecast to be around 66-69
degrees and the record is 65-69 degrees for our climate sites. Highs
tomorrow will warm into the low 90s. The record high for tomorrow is
91-93 degrees. Despite Friday also being quite toasty (highs in the
upper 80s), we shouldn`t see any records being broke.

Overnight, as the warm front moves northward across central IL, a
weak line of showers, and maybe some thunderstorms, are to develop.
SPC has thrown a Marginal Risk in for parts of the CWA tonight for
some elevated storms with the threat of large hail. CAMs have these
showers and thunderstorms popping at 01-02z this evening, and
exiting to the north by about 12z tomorrow morning.

Tomorrow, alongside the record warmth, dewpoints will be soupy to
the east of the dryline that will be setting up across the CWA. To
the east of the dryline, Tds will be in the 70s. To the west, Tds
will be in the upper 40s to low 50s. These lowered dewpoints will
increase the fire danger on Thursday. Use caution if burning and
avoid it if you can. We continue to see very impressive
environmental parameters that would support severe storms tomorrow,
but the capping issue remains. This event for tomorrow evening into
the overnight will be a "boom or bust" scenario. IF we can overcome
the residual capping, we will see some severe storms (potentially
supercells) that will have an all hazards risk (damaging winds,
large hail, and tornadoes). However, if we never break through,
tomorrow afternoon could bust, with some isolated showers. SPC has
maintained the marginal/slight risk in our area.

Friday appear to be the better day for us to get severe weather. The
environment looks very similar to Thursday`s, just without the
residual capping problem. Storms won`t have an issue tapping into
the great energy in place. (~3000 J/kg of MLCAPE, 50-70 knots of 0-
6km bulk shear.) The only uncertainty is just how far north the
threat will extend based on the moisture return overnight Thursday
into Friday. Timing Friday looks to be similar to Thursday. Mainly
affecting I-72 and south, it will enter the area by 20z and
exit before 06z Saturday.

After Friday, we return to highs in the 70s and lows in the 50/60s.
Dry weather will hang over for Saturday and Sunday. Monday brings
the next system which will bring its own chances for strong to
potentially severe storms. We will dive deeper into the details as
it moves closer in time.

Copple

&&

.AVIATION...  (For the 00z TAFs through 00z Thursday Evening)
Issued at 612 PM CDT Wed May 14 2025

A line of scattered showers/storms is expected to lift northeast
into central Illinois late this evening, most likely to impact the
KSPI-KCMI corridor in the 03-07Z time frame before fading away.
This may bring brief MVFR visibilities with the heavier showers.
Further into the forecast period, focus turns more toward the
winds, as strong south winds gust from 25-30 knots by midday and
gradually turn more southwest. A few isolated storms can`t be
ruled out toward the end of the forecast period in eastern
Illinois, though it appears more of the threat will be after 00Z.

Geelhart

&&

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

$$