Lewistown, Illinois Weather Forecast Discussion

795
FXUS63 KILX 102325
AFDILX
Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
625 PM CDT Wed Sep 10 2025
.KEY MESSAGES...
- An extended period of above normal temperatures continues
  through at least the middle of next week, if not longer.
- Little to no precipitation is expected during the next 7 days,
  introducing the risk for flash drought conditions through mid
  September.
&&
.DISCUSSION...
Issued at 245 PM CDT Wed Sep 10 2025
Mid afternoon surface analysis shows a frontal boundary near the
WI/IL border and extending into central parts of Iowa and SD. A
1025-1027 mb Canadian high pressure was over Hudson Bay into
central Ontario and ridging into the upper MS river valley. Aloft
a mid/upper level trof was over eastern Canada into the Great
Lakes and OH/TN river valleys. A stronger upper level low/trof was
over the Pacific states (568 dm 500 mb low in northern CA) while
upper level ridging in between over the Great Plains. Scattered to
broken hi base cumulus clouds (bases 6-8k ft) was from I-72 south
and from the Quad Cities to Lacon north. Sunny to mostly sunny
skies in between over much of central IL. Temps at 230 pm were in
the low to mid 80s with Taylorville and Effingham the hot spots at
88F. Comfortable dewpoints in the low to mid 50s over central IL
and mid 50s to around 60F in southeast IL with light to calm winds
across the area.
A weak short wave trof to track se across central and southeast IL
into early evening. Latest CAMS continue to keep isolated
convection se of Lawrence county through early evening but may be
close to southeast Lawrence county by Wabash river early this
evening. Patchy fog appears to stay se of the Wabash river as well
overnight. Otherwise a weakening front to push se into central IL
this evening and shift winds east to NE during tonight and stay
around 5 kts or less. Lows overnight in the upper 50s to around
60F with mid 50s by Galesburg and Macomb.
Not much change in the weather for Thu with surface high pressure
ridging down from the north and upper level ridge slowly shifting
eastward into the Central and Eastern Plains. A few to scattered
cumulus clouds from midday into afternoon. Warm highs in the mid
to upper 80s again with comfortable dewpoints in the 50s and light
winds. Lows Thu night in the upper 50s with fair skies.
Upper level ridge builds more into IL on Friday as 500 mb heights
rise above 588 decameters. Winds turn southerly on Fri as surface
high pressure ridge shifts eastward. Dewpoints come up a bit but
still mid to upper 50s east of the IL river and lower 60s west.
The main story will be the heat building this weekend. Highs
in the lower 90s Fri (around 90F in eastern IL). An extended
period of hot temperatures expected Friday through middle of next
week with highs in the lower 90s Friday through Wed (warmest on
Sat/Sunday with mid 90s more common). Similar to previous
forecasts, blended in the NBM 50th percentile with the raw NBM
output to bring some of these higher end max temps down from
Friday through early next week.
A short wave ridging over top of the upper level ridge Fri night
may bring isolated convection northern CWA. The 12Z GFS model is
further south with qpf over much of CWA from Fri night into Sunday
but have followed the blended forecast (NBM) which keeps pops
below 20%, with slight pops ne CWA Sat night and nw CWA Sunday
night. A strong subtropical ridge is forecast to influence
central/southeast IL into the middle of next week, keeping above
normal temps and below normal precipitation going.
The Climate Prediction Center (CPC) 8-14 Day Outlook for Sep 18-24
has 60-70% chance of above normal temperatures over central and
southeast IL with near normal precipitation in eastern IL and
trending slightly above normal pcpn (33-40%) west of I-57. CPC
8-14 Day US Hazards Outlook has Rapid Onset of Drought conditions
from I-72 south.
07
&&
.AVIATION...  (For the 00z TAFs through 00z Thursday Evening)
Issued at 624 PM CDT Wed Sep 10 2025
High pressure centered near Hudson Bay will drift slowly eastward
tonight into Thursday resulting in very light winds across central
Illinois favoring a northeasterly direction, but variable at
times. Some patchy fog is possible late tonight into Thursday
morning across east central Illinois, but the chance is too low at
DEC/CMI to include in the TAF. Otherwise, VFR conditions are
expected through the period.
Deubelbeiss
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$

NWS ILX Office Area Forecast Discussion