Decatur, Illinois Weather Forecast Discussion

409
FXUS63 KILX 052252
AFDILX
Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
552 PM CDT Fri Sep 5 2025
.KEY MESSAGES...
- Below normal temperatures in the 70s will prevail for the next
  few days...before summer-like readings well into the 80s return
  by the middle and end of next week.
&&
.SHORT TERM...(Tonight through Saturday)
Issued at 214 PM CDT Fri Sep 5 2025
18z/1pm surface analysis shows a cold front south of the Ohio
River...while a sprawling ridge of high pressure builds southward
out of the Prairie Provinces of Canada into the Central Plains.
Despite FROPA, frontogenetic forcing within the 700-500mb layer
has yielded a mid-level overcast across much of central Illinois
along/south of a Rushville to Bloomington line early this afternoon.
While radar imagery is showing very weak returns along and south
of the I-72 corridor, the dry boundary layer airmass is preventing
any light precipitation from reaching the ground. Would not be
surprised to perhaps see a couple sprinkles across the southern
two-thirds of the KILX CWA for the balance of the afternoon, but
measurable rainfall is unlikely. As a short-wave trough evident on
latest water vapor imagery over southern Minnesota into South
Dakota pivots southeastward, frontogenetic forcing will increase
along/north of the slow-moving surface front tonight. As a result,
light showers will develop from the Ozarks northeastward into the
Ohio River Valley...with a few showers possible as far north as
I-70. Once the front settles further southward, any showers will
come to an end by dawn Saturday...followed by partly to mostly
sunny skies and pleasant conditions with highs in the lower to
middle 70s.
Barnes
.LONG TERM...(Sunday through Next Friday)
Issued at 214 PM CDT Fri Sep 5 2025
The cool and dry weather will continue for both Sunday and Monday
as afternoon highs remain in the 70s and overnight lows dip into
the lower to middle 40s. After that, the unseasonably deep upper
low centered south of Hudson Bay will weaken and lift northeastward,
allowing upper heights to rise significantly. Models have been
consistently showing a vigorous short-wave digging a trough over
the Pacific Northwest/Northern Rockies...with downstream ridging
over the Midwest by the middle and end of next week. While the
exact details of this major pattern shift will likely change a
bit over the next few model cycles, confidence is growing that a
return to summer-like warmth is in store late in the period. The
current forecast features highs climbing into the middle to upper
80s Wednesday through Friday, but there is a potential for even
warmer temps depending upon the strength of the upper ridge. 12z
Sep 5 NBM shows a low probability (20-30% chance) of temps
exceeding 90 degrees both Thursday and Friday...with even higher
probs of 30-50% by next weekend.
Barnes
&&
.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 552 PM CDT Fri Sep 5 2025
Another weak cool front will cross central IL this evening,
veering winds from west-southwest to west-northwest, generally
under 10 kt. Periodic gusts near 20 kt will develop by late
morning. High clouds will affect the area tonight, clearing
Saturday morning then scattered diurnal cu through afternoon.
25
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$

NWS ILX Office Area Forecast Discussion