Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 161801
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1201 PM CST Sat Dec 16 2017

.UPDATE...
Issued at 1045 AM CST Sat Dec 16 2017

Forecast looks on track today and just a few very minor tweaks on
winds and temperatures, nudging them up a bit. A nice mid
December day unfolding across central and southeast IL with ample
sunshine expected to continue rest of the day. Breezy southwest
winds of 10-20 mph and gusts in the 20s along with sunny skies was
warming temps into the low to mid 40s by 10 am. Late morning
surface analysis shows 1029 mb high pressure sprawled across the
southeast states (centered on the AL/GA line). Meanwhile 1009 mb
low pressure was over ne Iowa with a cold front extending sw thru
se NE and nw KS to deepening 1004 mb low pressure in se CO. Breezy
sw winds between these features will gradually weaken toward
sunset. Some scattered cirrus clouds this afternoon while more
widespread clouds stay north of area through early evening. Highs
of 50-55F look on track, warmest from Springfield sw where mid
50s.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 330 AM CST Sat Dec 16 2017

Breezy and much warmer conditions will be the rule today...as
southwesterly winds increase ahead of the next slowly approaching
cold front. A band of mid-level clouds currently along/north of
the I-74 corridor will quickly lift northward early this morning,
leaving behind mostly sunny skies across the entire KILX CWA for
the balance of the day. Despite full sunshine and brisk
southwesterly winds, warming will be mitigated somewhat by shallow
mixing. Forecast soundings suggest mixing will only take place up
to about 900-950mb, which would yield afternoon high temperatures
in the upper 40s and lower 50s. Skies will remain clear this
evening before clouds rapidly increase from south to north across
the area after midnight as a short-wave trough approaches from the
southwest. Low temperatures will be in the lower to middle 30s.

.LONG TERM...(Sunday through Friday)
ISSUED AT 330 AM CST Sat Dec 16 2017

Precipitation associated with the wave will lift northward tonight
and will be poised just S/SW of the CWA by 12z Sun. Forecast
soundings are initially quite dry, so have delayed the onset of
precip by about 3 hours...with areas along/north of I-74 remaining
dry until the 15z-18z time period. Given the delayed arrival and
the resulting boundary layer warming that will take place, most of
the precip will be in the form of light rain...however enough
evaporational cooling may occur to allow for a brief period of
sleet as the precip commences. Any sleet will be very short-lived
as the precip quickly transitions to light rain. The rain will
come to an end by late Sunday afternoon as high temperatures top
out in the lower to middle 40s.

After that, a period of mild and dry weather will be on tap for
much of the extended...before the next significant system arrives
by the end of next week. 00z Dec 16 models are in relatively good
agreement with this system...with the ECMWF being about 6-12 hours
slower than the GFS. At this point, think a cold front will push
into Illinois Thursday afternoon accompanied by rain showers. As
the front passes and colder air trickles into the region, rain
will change to light snow Thursday night into Friday
morning...with some minor accumulation possible. Will need to keep
an eye on later trends...because if the ECMWF verifies, there
will be more rain and less snow than currently forecast.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1159 AM CST Sat Dec 16 2017

VFR conditions are expected to continue across the central IL
airports through 18Z/noon on Sunday. Scattered cirrus clouds will
occur into this evening, with broken mid/high clouds moving in
from the sw during overnight. Low pressure over se CO will eject
across the central plains overnight and lift ne as a weak 1015 mb
low over nw IL by sunset Sunday. This will spread very light rain
ne across central IL during mid/late Sunday morning with ceilings
lowering to around 5k ft. Breezy sw winds 10-17 kts and gusts of
18-26 kts early this afternoon, will weaken to 4-9 kts by sunset
and veer south. Expect SSW winds of 5-10 kts on Sunday morning.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

UPDATE...07
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...07



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