Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 182101

Area Forecast Discussion
National Weather Service Lincoln IL
301 PM CST Mon Dec 18 2017

.SHORT TERM...(This evening through Tuesday)
ISSUED AT 301 PM CST Mon Dec 18 2017

Skies will continue to clear late this afternoon and skies should
be mostly clear through the night and into tomorrow. Could be some
scattered clouds around but not enough to hold temps down. Temps
overnight should remain above freezing tonight and then with
southwesterly winds tomorrow, plenty of WAA and sunshine to allow
temps to climb above 50 across the entire CWA.


.LONG TERM...(Tuesday night through Monday)
ISSUED AT 301 PM CST Mon Dec 18 2017

A weather system is forecast to move across the southern
Mississippi valley mid week but looks like the precip should
remain south of the CWA through the period. This will bring in
some clouds and slightly cooler temps, through still above normal
for middle of Dec. As this moves east, southerly winds will return
with lots of WAA continuing ahead of the next weather system. The
next weather system will bring clouds and precip into the
northwest parts of the CWA beginning Thursday evening. The precip
should remain across the far northern portions of central IL Thur
night. Models then disagree on speed of this system and the
secondary system moving through Fri and Fri night. GFS is quickest
and Canadian is slowest. So prefer the middle ECMWF solution that
has the low pressure area of the system moving into Mich by Fri
evening. Precip is expected with this system with the highest pops
being in the eastern and southeastern part of the CWA Friday
afternoon and evening. P-type will be a mainly rain on Friday,
with a rain/snow mix in the northwest early. By afternoon, it will
be warm enough everywhere that all precip will be liquid. As the
front goes by, colder air is supposed to move into the area. With
the slower ECMWF solution, the rain will change to a mix of rain
and snow, to just all snow Friday night. Temps will be warm
ahead of the system and then get colder after the front moves
through. The timing of this colder air will determine when the
change over to snow occurs, which could be around the time the
precip is ending as well. So, currently not expecting much

Models differ even more for the weekend and after a brief dry
period Sat and Sat night. There might be another system for Sun
and Sun night but the GFS and ECMWF have no precip while the
Canadian has precip. Therefore, will keep low chance pops in
forecast for now. Colder than normal temps are also expected for
the weekend.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1144 AM CST Mon Dec 18 2017

MVFR cigs will be at PIA/BMI/SPI this afternoon and then
clouds/cigs will scatter out and become clear for late afternoon.
DEC and CMI will start at VFR cigs around 3.5kft but drop back
down in an hour or two into MVFR like the others. They will also
scatter out late this afternoon. All sites from late this
afternoon and through the night will remain clear or just have
scattered high clouds this evening/overnight. Clear skies are also
expected tomorrow as high pressure trys to build into the area
behind a weak sfc trough. Winds will be out of the southwest this
afternoon with gusts to around 20-24kts. Winds will decrease this
evening but still remain around 10kts through the night. As sfc
trough moves through the area tomorrow winds will become westerly.




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