Towanda, Illinois Weather Forecast Discussion

467
FXUS63 KILX 230218
AFDILX
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
918 PM CDT Mon Sep 22 2025
.KEY MESSAGES...
- The unsettled pattern will continue with daily rain chances
  through at least Thursday. The best chance of rain is Tuesday
  night and Wednesday (60-80% southeast of the IL river). New
  rainfall amounts of over 2" are possible, with the best chance
  being southeast of I-70 (30-45%).
- Fog development, some of which could be dense, is likely
  overnight into the Tuesday morning commute. The best chance for
  visibility below a half mile is from I-55 southeast (50-70%).
&&
.UPDATE...
Issued at 918 PM CDT Mon Sep 22 2025
Clear skies, light winds, and lots of low level moisture are all
key ingredients for potential of dense fog overnight. Some
uncertainty for how wide spread it could become but all HiRes
guidance shows any dense fog that develops will remain south of
I-72. Like that idea given that was the location were lower clouds
continued for most of the day and low level moisture likely did
not mix out this afternoon. Have updated grids and wx to reflect
the fog development into areas and widespread...thinking
widespread is where the dense fog will occur. If dense fog becomes
more widespread...then additional counties will liklely get added
overnight. Updated zfp will be out shortly. Dense fog advisory
already issued.
Auten
&&
.DISCUSSION...
Issued at 245 PM CDT Mon Sep 22 2025
Radar mosaic shows the main area of showers and isolated
thunderstorms had passed east and south of IL with scattered
convection in far southeast/southern IL, se of a Bloomington IN
to Marion IL line. A few isolated light showers were east of I-55,
otherwise much of CWA is now dry. Some sunshine was appearing
through the low/mid clouds nw of a Taylorville to Decatur to
Champaign while nearly overcast MVFR clouds 1-2k ft lingered in
southeast IL.
Isolated showers possible into early evening in eastern IL and
late tonight north of a Galesburg to Lacon line as convection
chances increase over northern IL during tonight. Latest CAMs show
fog developing in southeast IL early overnight and spreading
northward into central IL during the overnight and lingering into
mid Tue morning. RAP and HRRR show more widespread fog by late
tonight from I-72 south and HREF has 50-70% chance of vsbys below
1/2 mile in this area, so dense fog is looking more likely over
southern half of cWA. May eventually need a dense fog advisory
from I-72 south. Also seeing patchy fog developing up the IL
river valley late tonight/early Tue morning, though mid and high
clouds increasing over northern/nw CWA toward dawn may limit
extent of fog. Lows overnight in the lower 60s, with mid 60s se of
I-70.
A developing upper level low near the CO/KS border late Tue to
have some short waves ejecting eastward into central IL late Tue
afternoon and Tue night and will see increasing chances of
convection over area later Tue into Tue night. Also an outflow
boundary from convection in southern WI to move into northern CWA
and could develop its own convection during Tue afternoon and a
few cells could become strong. SPC day2 outlook does not have a
marginal risk of severe storms over central/se IL though will need
to monitor northern CWA for Tue afternoon into early Tue evening.
Warmer highs Tue in the lower 80s and still muggy with dewpoints
in the upper 60s.
The cutoff low and trof to move into MO by late Wed and bringing
our best chances of more widespread showers and a few
thunderstorms Tue night and Wed with pops of 60-80% se of the IL
river. The heaviest rains appears to set up over southern cWA Wed
into Thu evening when 1-2 more inches of rain possible. Areas
south of I-70 have a 30-45% chance of seeing over 2 inches of
rain. As been the case the past few days, a few spots could see
locally 3-5 inches over southern CWA but this will be more
isolated if it occurs. WPC has much of central and se CWA in
marginal risk of excessive rainfall Wed and Wed night (and over
southern CWA Tue night). Cooler highs in the mid 70s Wed and mid
to upper 70s Thu. Surface low appears to pass south of CWA WEd and
Wed night near or just north of the Ohio river while upper level
trof axis moves east of IL during Thu afternoon. Have chances of
showers Thu with highest pops 30-40% in eastern IL and qpf
amounts to be lighter.
Models have trended quickly with moving upper level trof east of
IL late this work week and much of area appears drier Thu night
and Fri as upper level ridge building into the central Rockies and
Central Plains. We kept slight chance of showers in eastern IL
Thu evening. Cutoff low still forecast to be over the gulf coast
and southeast Atlantic States this weekend with upper level
ridging into IL, keeping us dry and warmer. Highs in the low to
mid 80s Saturday through Monday.
The Climate Prediction Center (CPC) 8-14 Day Outlook for Sep 30
through Oct 6 has 55-60% chance of above normal temperatures over
central and southeast IL. Precipitation trending near normal or
slightly below normal over far ne and east central IL.
07
&&
.AVIATION...  (For the 00z TAFs through 00z Tuesday Evening)
Issued at 641 PM CDT Mon Sep 22 2025
All sites will start as VFR with very few clouds present on
satellite loops. However, with mostly clear skies and light winds,
expected fog to develop across the southeast parts of the CWA and
then spread north and northwest, reaching SPI, DEC, and CMI
overnight/toward morning. Cigs and vis will drop into IFR
categories for several hours, but LIFR as well for a short amount
of time as vis lowers to below 1sm and cigs below 1kft. Conditions
improve later in the morning bu cigs will be MVFR into the
afternoon. Also expected more storms to develop tomorrow afternoon
across the area as another wave drops into the area. Will have
prob30, but storms should be possible at PIA and BMI first, and
then at SPI, DEC, CMI for last part of afternoon. Winds will be
light through the period.
Auten
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory from 3 AM to 9 AM CDT Tuesday for ILZ054>057-
061>063-066>068-071>073.
&&
$$

NWS ILX Office Area Forecast Discussion