Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 151759

Area Forecast Discussion
National Weather Service Lincoln IL
1159 AM CST Fri Dec 15 2017

Issued at 1045 AM CST Fri Dec 15 2017

Updated the forecast today for a few adjustments to the sky cover
and as a clearing slot has worked into portions of central IL by
late morning west of I-55. But another batch of stratocumulus
clouds was pushing se from IA into nw IL approaching Galesburg and
Quincy. This batch of clouds along will drift se across central
IL during the afternoon with ne half of CWA likely seeing more
clouds overall today with flurries/drizzle possible from I-74 ne.
Highs to range from the mid 30s from Bloomington and Champaign
ne, to the lower 40s from Springfield sw by 2-3 pm. WSW winds of
8-16 mph and gusts of 18-24 mph expected to prevail today and veer
more sw toward sunset.


.SHORT TERM...(Today and tonight)
ISSUED AT 327 AM CST Fri Dec 15 2017
Cloudy day is anticipated today for Central Illinois, as a
north/south orientation of upper level flow just to the west puts
the region in the axis of an upper trof. Cyclonic flow will
continue through the day and keep the clouds in place for the most
part. Southwesterly winds at the surface will help with some warm
air advection and bring the temps up into the mid-upper 30s/near
40. Should the southwest clear some of its clouds later in the
day, sunshine could bring up max temps in the southwest and create
an even steeper temp gradient from SW to NE. Those same clouds
anchored over the area tonight will keep the temps from plummeting
too far...with minimums in the upper 20s.

.LONG TERM...(Saturday through Thursday)
ISSUED AT 327 AM CST Fri Dec 15 2017

The remainder of the forecast is centered on the wave currently
moving onto the Pacific coast this morning. This same wave digs
into the western coast of the CONUS, and kicks the upper low
currently in the Gulf of California out and across the southern
tier of the country. That same wave results in a storm system that
pushes rain/precip north of the Ohio River Valley and into Central
IL for Sunday. PoPs have gone back and forth with each run of the
models as there is a lack of continuity as to the track of the
surface system. The wave that replaces it over the desert SW has
alternately split, phased, or become cutoff from the rest of the
country with each run. Models are starting to show some repetition
with shearing out some of the energy and bringing it through the
Midwest as a weak frontal boundary on Monday night with some
precipitation. Just as quickly, the 00Z ECMWF came in with a
slower progression of a more compact wave and passing it to the
south of the area. For now, best chances for precipitation is the
rain on Sunday, should the system take a slightly more northerly
track. Temperatures throughout the extended remain impacted by
the deep trough over the SW keeping the orientation
southwesterly...and slightly above normal highs for the latter
half of December.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1159 AM CST Fri Dec 15 2017

Aside from MVFR ceilings of 2.5-3k ft at CMI during next hour,
VFR conditions are expected across the central IL airports through
18Z/noon Sat. Broken stratocumulus clouds east of I-55 with
ceilings of 2.5-4k ft will scatter out in next hour or 2. However
another batch of stratocumulus clouds with higher ceilings of 4-6k
ft was approaching the IL river at 18Z and will spread se across
rest of central IL between 18-20Z. These low clouds should scatter
out by early evening while mid level clouds also scatter out
between 09-12Z. WNW winds 10-16 kts and gusts 17-22 kts early this
afternoon will veer sw later this afternoon and weaken to around
10 kts early this evening. Expect SSW winds of 10-16 kts on
Saturday morning.





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