Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 170835

Area Forecast Discussion
National Weather Service Lincoln IL
235 AM CST Sun Dec 17 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 235 AM CST Sun Dec 17 2017

Short-wave trough evident on 07z/2am water vapor imagery
extending from Kansas to Louisiana will lift northeastward
today...spreading clouds and light precip into central Illinois.
Latest regional radar mosaic shows a large area of light to
moderate rain across Arkansas into southern Missouri. The leading
edge of the rain has been slowly progressing northward, but it is
battling an unfavorably dry boundary layer to the north. This dry
air will delay precip onset across the KILX CWA until mid to late
morning. Since the upper wave will be weakening as it approaches,
think rainfall amounts will remain light...generally one tenth of
an inch or less. Will carry high chance to likely PoPs for light
rain from late morning through mid-afternoon before the rain
diminishes and pushes further northeast out of the area by the end
of the day. Due to extensive cloud cover and scattered showers,
temperatures will be held down...with afternoon highs mainly in
the lower to middle 40s.

After the upper wave passes, forecast soundings show saturated
boundary layer conditions persisting through tonight and into
Monday morning. Do not see much synoptic lift within the moist
layer: however, several high-res models are hinting at some light
QPF...which is likely due to drizzle in this case. Have therefore
included patchy fog and drizzle in the forecast for
tonight...lingering into Monday morning.


.LONG TERM...(Monday through Saturday)
ISSUED AT 235 AM CST Sun Dec 17 2017

After a dreary Monday morning, skies will be slow to clear...and
in fact, conditions will likely remain overcast until Monday
night. Despite southerly winds, have lowered temps a few degrees
due to expected cloud cover...with Monday afternoon highs in the
upper 40s and lower 50s. Warmest day of the forecast period will
be Tuesday, as skies become mostly sunny and highs climb well
into the 50s. After a cold front passes late Tuesday, temperatures
will cool into the 40s for Wednesday. The next chance for
widespread precipitation will not arrive until Thursday night into
Friday as a stronger cold front pushes into the region. This
system has been delayed by about 6-12 hours, with the 00z Dec 17
GFS now coming into closer agreement with the consistently slower
ECMWF. As a result, mild and dry weather is expected on
Thursday...followed by increasing rain chances Thursday night. As
colder air begins to trickle into the area, the rain may mix with
snow west of the I-55 corridor late Thursday night into Friday
morning. The front will push into Indiana during the day
Friday...with post-frontal precip potentially lingering near the
Indiana border until Saturday morning.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1123 PM CST Sat Dec 16 2017

Ceilings will be steadily lowering through the night, but anything
below 10,000 feet should hold off until Sunday morning. As areas
of rain spread northeast across central Illinois, moistening of
the lower levels will result in continued lowering of ceiling
heights. MVFR conditions will overspread the area during the
afternoon. By evening, there are some indications of potential
ceilings below 1,000 feet. Have included IFR conditions from
KPIA-KCMI late in the period as a result.




LONG TERM...Barnes
AVIATION...Geelhart is the U.S. government's official web portal to all federal, state and local government web resources and services.