Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 240517

Area Forecast Discussion
National Weather Service Lincoln IL
1117 PM CST Tue Jan 23 2018

Issued at 850 PM CST Tue Jan 23 2018

A few reports of light freezing drizzle have been noted in the
northeastern part of the central IL forecast area in Vermilion and
Champaign counties this evening. This is likely associated with a
loss of cloud depth behind an outgoing upper wave, resulting in
loss of cloud ice and some condensation of remaining low cloud.
This is unlikely to last long given the lack of reports of any
precipitation upstream as well as larger dewpoint depressions.
Have included a few hours of freezing drizzle mention in the
evening update in this area.

Later on tonight, another upper wave currently over western Iowa,
will cross over central IL. Models continue to produce very
paltry and scattered precipitation amounts, but given the potent
signature on satellite, see no reason to drop mention of flurries.
Lows in the mid 20s look on track.


.SHORT TERM...(This evening through Wednesday)
ISSUED AT 235 PM CST Tue Jan 23 2018

A weak mid level trough and associated vort max will move through
the area late tonight and tomorrow morning. Some models are dry
with this trough and some produce very little qpf. However, in
this kind of environment in the winter, weak troughs with a mid
level vort max, and some lower level cloud cover can easily wring
out some scattered flurries. Since it`s already in the grids, will
be leaving in for late tonight and tomorrow morning, and will just
refine it`s location from northwest to southeast through morning.

Temps will be around normal through the period.

.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 235 PM CST Tue Jan 23 2018

Behind the trough, ridging will begin to build back into the area
and bring dry weather for Wed night through Friday. A weather
system will develop and move across the area Friday night through
Sat night. Models differ on what the surface features will look
like and still differ on timing of the precip. Either way, some
showers/rain will move across the area Friday night and Sat. As
cooler air advects into the area, the rain with become mixed with
snow and possibly change to all snow as the precip is ending,
which should be sometime Sat night. Beyond this system, dry
weather returns for the rest of the weekend and into the beginning
of the following week.

Temps through the period will be warming as the ridge builds back
into the area. Then things cool again back to normal behind the
Sat system on Sunday, then begins to moderate back up some by
Tuesday of next week.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1117 PM CST Tue Jan 23 2018

Fairly uniform MVFR cigs around 2000 ft AGL cover central IL and
surrounding areas this evening with upstream observations
indicating this cloud coverage continuing until around 18Z. An
upper level wave may help produce a few snow flurries late tonight
into Wednesday morning and have included VCSH in TAFs
accordingly, although visibilities will remain above 6SM through
the forecast period. Some potential for IFR cigs looks to
accompany the upper wave according to upstream observations,
however have not included in TAFs at this time as guidance
suggests it will remain MVFR in central IL. Improvement to VFR
cigs looks likely starting 18-22Z as an upper level ridge begins
to build into the region. Winds generally WNW 5-12 kts until 21Z,
with a gradual decreasing trend. Lighter and more variable winds
developing 21Z-06Z.




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