Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 200740

Area Forecast Discussion
National Weather Service Lincoln IL
240 AM CDT THU OCT 20 2016

.SHORT TERM...(Today and tonight)
ISSUED AT 239 AM CDT Thu Oct 20 2016

Scattered showers and isolated thunderstorms continue over about the
southeast half of the forecast area early this morning with the
greater concentration of steadier rains extending along and
southeast of a Champaign to Springfield line. Heaviest rainfall so
far has fallen south of I-72 to the I-70 corridor with areas from
Effingham to near Marshall (Clark county) receiving from 2 to 3
inches so far. Rainfall rates have decreased significantly in these
areas but light to moderate rains with isolated thunder should
continue for the next several hours.

An area of low pressure and frontal boundary over extreme southern
Illinois should begin to shift off to our east and south today but
cyclonic flow around the departing wave and a deepening 500 mb trof
tracking east across the Midwest will keep showers going into at
least the middle of the afternoon for areas east of Interstate 55.
With the cloud cover, scattered showers and gusty northerly winds
today, temperatures will be held down this afternoon with readings
in the upper 50s to lower 60s, coolest in the east and southeast
where the showers will be more persistent today.

The low will continue to move away from our area tonight with
clearing skies and chilly temperatures. High pressure will shift
from the central Plains east to just west of our area by 12z Friday
which should result in the coolest temperatures across the west and
northwest, closest to the ridge axis. We look for lows to drop into
the mid 30s northwest with patchy frost, to the lower 40s southeast.
It still appears the better setup for more widespread frost will
be to our northwest Friday morning, closer to the surface high.


.LONG TERM...(Friday through Wednesday)
ISSUED AT 239 AM CDT Thu Oct 20 2016

Rather quiet period expected during much of this part of the
forecast. Deep upper trough will be swinging into the eastern U.S.
on Friday, allowing for a period of zonal flow this weekend before a
ridge starts to build across the Rockies on Sunday. This ridge will
amplify some early next week and shift toward the Mississippi
Valley. However, a shortwave will be tracking toward the Midwest,
arriving across Illinois on Wednesday. The GFS is stronger with this
wave and quickly pushes a storm system with showers and a few
thunderstorms through on Wednesday. The weaker ECMWF has a warm
front lingering just to our north for a time Tuesday and Tuesday
night, bringing an extended period of showers across the northern
half of the forecast area before the wave pushes through. For now,
will focus on the faster solution and limit the PoP`s to Wednesday.

Coldest part of the forecast will be on Friday, as another surge of
colder air is drawn down behind the departing trough. With 850 mb
temperatures around -2C, highs should only reach the mid 50s in most
areas, and the chilliest temperatures Friday night will be mainly
over the eastern CWA, with a touch of frost possible. After that, a
nice warming trend sets up, and upper 60s/lower 70s should prevail
for highs the first half of next week.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1128 PM CDT Wed Oct 19 2016

Showers have begun to diminish west of PIA to SPI, and that trend
will continue slowly to the east. Low pressure is making its
closest approach to our southeast counties from now through 06z,
then will advance east of Illinois the rest of the night. However,
rain chances for the eastern terminals will continue through
Thursday morning in the wake of the low, as we experience
continued lift in the mid-upper levels ahead of the upper trough
axis. CMI could even see stray showers linger Thursday afternoon.

Instability parameters show low potential for thunderstorms near
any TAF site through tomorrow, so no thunder was included this
TAF issuance.

VFR conditions are expected to prevail throughout the next 24
hours, with brief MVFR cloud conditions possible for DEC and CMI
the rest of the night, per the latest HRRR. Have not included any
MVFR conditions in the 06z TAFs.

Winds will increase toward sunrise from the northeast, into the
10-13kt range. Gusts are expected tomorrow from the north at
12g18kt at times, especially near our eastern terminals. Winds
will subside with sunset tomorrow, as clouds decrease from west to


.ILX Watches/Warnings/Advisories...


LONG TERM...Geelhart
AVIATION...Shimon is the U.S. government's official web portal to all federal, state and local government web resources and services.