Normal, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

475
FXUS63 KILX 042017
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
Issued by National Weather Service St Louis MO
317 PM CDT Wed Jun 4 2025

.KEY MESSAGES...

- Near daily chances for rain will result in above-normal
  rainfall and below-normal temperatures through the middle
  of next week. The exception will be near and north of the
  Illinois River Valley where guidance is trending drier than
  normal.

- There is a low probability for damaging thunderstorm winds
  and/or flash flooding each day through Friday. Otherwise, a
  low- impact weather forecast is in store for central and
  southeast Illinois through the middle of next week, &&

.DISCUSSION...
Issued at 258 AM CDT Wed Jun 4 2025

.Discussion (through next Wednesday)...

Periods of rain will continue to develop near and east of I-55
this evening through Thursday afternoon as multiple shortwave
impulses and attendant surface low pressure ride along a slow-moving
baroclinic zone. Rain may be heavy at times. Model soundings
certainly point to efficient rainfall, as indicated by: a long,
skinny CAPE profile (< 1000 J/kg); deep warm cloud layer (> 10
kft); moist vertical profile (low- and mid-level RH > 70%); and
anomalous PWATS (> 95%). Flash flooding due to repeated storms
is a possibility, though back-building/training could be limited
by fast cloud layer winds (LCL-EL flow > 10 kts) and quick
Corfidi up/down shear vectors (> 15 kts). Still, several of the
CAMs are offering pockets of 2-5 over the next 24-hrs across
portions of central and east-central Illinois. This would
certainly result in ponding across urban or poor-drainage areas.
And, if we experience a few convectively-enhanced showers that
exceed 2-3 in less than 3-hrs, we could be dealing with
isolated cases of flash flooding through midday Thursday.

A marginal threat for severe storms still exists over the next
4-6 hours for portions of southeast Illinois, namely counties
near and south of I-70 where surface heating and rich dewpoints
pooling ahead of the surface front have buoyed MLCAPE values
(>1500 J/kg). While the shear profiles are fairly meager this
afternoon, an incoming shortwave/speedmax will increase mass in
the 850-700mb layer and potentially increase shear into the
30-40 kt range and aid in precip loading. Therefore, an isolated
downburst or two could result in a brief damaging wind risk
before sunset.

After a lull in the precip Thursday evening, another round of
showers and storms returns Friday afternoon as a shortwave trough
and attendant surface low moves along the I-70 corridor. The
Friday airmass does not appear to be as unstable or moisture-
laden as it currently is, and so the severe weather and flash
flood risks are not as apparent. The coverage of showers ought
not be as great either.

Guidance is still pointing toward a drier but not dry narrative
for Saturday as yet another shortwave pushes across the region,
though available moisture will be fleeting. The better chance
for widespread rain this weekend will come Sunday when a cold
front pushes across the region. The CAPE/Shear profiles over the
weekend do not look robust enough to support a severe weather
risk, and marginal moisture profiles and/or faster mid-level
flow should preclude any flash flood risk.

An upper-level low will descend into the Great Lakes region by
early next week, continuing the prospect for diurnally-driven,
strato-cu type showers. Temperatures will be seasonally cool
Monday and Tuesday (mid 70s) in the vicinity of the upper low.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1227 PM CDT Wed Jun 4 2025

-Mostly dry conditions with seasonable temperatures are forecast
this weekend.

-Temperatures will warm into early next week with highs in the
mid to upper 80s Monday and Tuesday expected.

-Chances for showers and thunderstorms return Tuesday and continue
through the end of the work week.

A slow-moving cold front will finally begin to progress
southeastward through the region today. This morning and early
afternoon rainfall should help reinforce the surface boundary
slightly further south, accompanied by increasing chances for
thunderstorms. The best potential lines up roughly along and
southeast of I-72, where instability has time to recover to some
degree before the front clears the area. The greatest aviation
impacts will stem from IFR/LIFR ceilings, visibility
restrictions within thunderstorms, and localized gusty winds in
and around more intense thunderstorms.

IFR/MVFR ceilings linger over parts of the area through
Thursday morning before skies very gradually break from
northwest to southeast. Surface winds briefly go light/variable
during frontal passage (outside of thunderstorms), then turn
out of the northeast Thursday. A majority of the area improves
to VFR between 18z-00z Thursday, just beyond the current TAF
package.

&&

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

&&

$$

DISCUSSION...MJA
AVIATION...WFO ILX