Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 231955

Area Forecast Discussion
National Weather Service Lincoln IL
255 PM CDT Mon Oct 23 2017

.SHORT TERM...(This evening through Tuesday)
ISSUED AT 255 PM CDT Mon Oct 23 2017

Deformation zone precipitation looks to linger through the late
afternoon from near I-57 eastward due to the upper level trough over
IN, lifting northeastward. A much faster moving shortwave,
meanwhile, is approaching from the northwest, currently over IA,
with an associated surface cold front already near the Mississippi
River. Showers associated with this system will move rapidly into
central IL this evening as it moves into an area of richer moisture.
Precipitation amounts will be light overnight, generally around a
tenth of an inch or less. Following tonight`s shortwave and cold
front, a larger scale upper trough will set up over the area with
embedded disturbances keeping showery weather through Tuesday. After
reinforcing cool air behind tonight`s cold front, lows will dip into
the lower 40s tonight, followed by highs only reaching the upper 40s
in most of central IL Tuesday.


.LONG TERM...(Tuesday night through Monday)
ISSUED AT 255 PM CDT Mon Oct 23 2017

Tuesday night, a pocket of -2 C 850 mb temperatures associated with
the trough will move across central IL, producing surface
temperatures approaching the freezing mark. Currently, it looks as
if temperatures will remain just above freezing, with relatively dry
and breezy conditions preventing frost toward Wednesday morning,
however this will need to be watched as conditions are precariously
close to the first freeze of the season.

A shortwave ridge will provide for dry conditions, mostly clear
skies, and milder temperatures climbing well into the 50s (Wed) and
60s (Thu) with lows only reaching the upper 30s to mid 40s.

Good model agreement then presents itself for Friday into the
weekend as all models/ensembles carve out a deep trough roughly
centered over Illinois, with an average 850 mb temperature around -7
C Saturday. This will bring a strong chance for sub-freezing low
temperatures either Friday night, Saturday night, or both. For now,
kept temperatures just below freezing Friday night and Saturday
night although a harder freeze is possible Saturday night, depending
on exact timing of the system. Highs look to range from around the
mid 40s to low 50s over the weekend.  Although temperatures would be
cold enough for a snow shower at times over the weekend, current
chances for any precipitation over central IL are too low to outlook
any snow. A shortwave ridge looks to bring highs back up to the low
and mid 50s Monday.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1242 PM CDT Mon Oct 23 2017

Scattered IFR/MVFR cigs persist from KDEC-KBMI eastward with VFR
to the west. IFR/MVFR will slowly shift east and should clear out
of KCMI around 21Z. Next weather system approaching rapidly from
the NW and should cause scattered showers to develop around 00Z
and persist through the remainder of the forecast period.
Cigs/vsby should slowly trend downward to MVFR by 08-12Z. Winds
WNW 6-12 kts increasing to 10-15 kts with gusts around 25 kts
after 12Z.





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