Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 160206

Area Forecast Discussion
National Weather Service Lincoln IL
806 PM CST Fri Dec 15 2017

Issued at 805 PM CST Fri Dec 15 2017

Earlier batch of altocumulus is exiting the northeast fringes of
the forecast area this evening. More expansive area of mid and
high clouds, currently to our northwest, has begun to spill into
central Illinois. Latest humidity progs off the RAP model suggests
this overspreading areas along and north of I-72 past midnight,
but shifting eastward with time and moving out before sunrise.
With southwest winds averaging around 10 mph overnight, not a lot
of additional temperature dropoff is expected. Going forecast had
a good handle on this, and only needed some minor adjustments to
reflect latest trends.


.SHORT TERM...(This evening through Saturday)
ISSUED AT 255 PM CST Fri Dec 15 2017

A weak disturbance will bringing another batch of stratocumulus
clouds (ceilings 4-6k ft) se into central IL and along and
Champaign to Taylorville line at 230 pm. An area of light snow and
flurries was over ne IL and skirting far ne CWA along and ne of a
Henry to Chenoa to Hoopeston line. 1002 mb surface low pressure
was over eastern upper MI and will track to along the southern
Quebec and Ontario province line this evening, taking its light
snow/flurries out of area late today. Low clouds will decrease
early this evening though mid level clouds to continue into
this evening and decrease during overnight. Clouds along with sw
winds 8-13 mph to keep temps from falling too much tonight, with
lows in the upper 20s to around 30F.

A nice day ahead on Saturday with a fair amount of sunshine and sw
winds 10-15 mph and gusts to 20 mph bringing milder temperatures.
Highs range from the upper 40s to around 50F along and ne of I-74
to the mid 50s from Springfield sw.

.LONG TERM...(Saturday night through Friday)
ISSUED AT 255 PM CST Fri Dec 15 2017

Dry weather continues Saturday night as clouds increase by overnight
ahead of wx system taking shape in the southwest states. Lows in the
low to mid 30s, coolest along and ne of I-74. Weak surface low
pressure to eject ne from the southern plains and into nw IL
Sunday afternoon. Precipitation to spread quickly ne across
central IL during Sunday morning and could start as a mix along
and north of I-74 early Sunday morning before becoming all rain.
This system is a quick mover and precipitation already
diminishing from the sw later Sunday afternoon, with rainfall
amounts only up to a tenth inch possible. Highs Sunday in the mid
to upper 40s but these readings still a good 10 degrees above
normal for mid December. A weaker disturbance ejects ne and
brings small chances of light rain showers overnight Sunday night
into Monday morning. Lows Sunday night in the mid to upper 30s.
Highs Monday in the upper 40s north of Peoria and mid 50s by

A dry stretch of weather expected from Monday afternoon through
Thu morning across CWA as storm tracks will be across the Great
Lakes and over the southeast states by a frontal boundary. Above
normal temps continue with highs 45-55 Tue thru Thu. Latest ECMWF
model now showing surface low pressure tracking into the mid MS
river valley by Wed afternoon and brings qpf into southern half of
IL Wed and Wed evening. This will need to be watched but for now
we stayed with consensus of a dry forecast during that time which
GFS and GEM show. A deepening upper level trof over the Rockies by
Thu to eject a weather system into the upper Midwest late Thu and
deepen surface low pressure ne into the southeast Great Lakes Fri
afternoon. Continued small chances of rain showers over IL river
valley late THu afternoon, then spread chances of precipitation
se across CWA during Thu night with rain turning to snow showers as
colder air usher in. Temps cool back closer to normal for next
Friday. 12Z GFS and ECMWF models show an active southern stream
storm track during Christmas weekend and will need to be watched
for holiday travelers. Latest models currently keep precipitation
south of CWA next weekend, but models have not been consistent
from previous runs and also GEM model not in best agreement with
GFS and Ecmwf.


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 520 PM CST Fri Dec 15 2017

Cloud deck around 6,000 feet is pulling eastward and should be out
of the TAF sites in the next few hours. Larger area of mid and
high clouds is streaming southeast and will shift eastward over
central Illinois overnight, but will not pose an aviation impact.
Southwest winds should average around 10 knots throughout the




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