Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 171748

Area Forecast Discussion
National Weather Service Lincoln IL
1148 AM CST Sun Dec 17 2017

Issued at 1050 AM CST Sun Dec 17 2017

Late morning surface analysis shows a warm front stretching from
just north of a Galesburg to Pontiac line, and still south of
Lacon in Marshall county where temp was only 34F. Warm front
extended westward to a weakening 1017 mb low pressure south of
Des Moines in south central IA. An area of light rain had lifted
northward across central IL during the morning and was approaching
Peoria at 1045 am. Rainfall amounts have been very light, with
Springfield seeing the most so far with 0.04 inches. Light rain
was already diminishing from Taylorville sw and expect the light
rain to diminish from sw to ne during the afternoon. HRRR model
shows light patches of rain lingering along and north of I-74 at
sunset and this seems reasonable. Cloud decks to lower into this
evening with fog and drizzle developing during tonight across
central IL. Cloud cover and some light rain to keep temperatures
nearly steady in the low to mid 40s today.


.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 18Z TAFS through 18Z Monday afternoon)
Issued at 1148 AM CST Sun Dec 17 2017

Weakening 1017 mb low pressure over south central Iowa with its
warm front extending eastward near I-80, will continue to weaken
as it lifts an area of light rain showers ne of central IL during
mid/late afternoon. VFR ceilings this afternoon ranging from 3.5
to 7k ft will lower to MVFR during this evening and then IFR
likely overnight as stratus, fog and drizzle develop during
tonight. VFR vsbys this afternoon to become MVFR especially
overnight into mid Monday morning as fog develops. Stratus and
fog likely linger into Monday morning with ceilings lifting up to
MVFR between 16-18Z Monday. SW winds 7-14 kts early this afternoon
and few higher gusts along I-74 to veer SSW and weaken to 5-9 kts
by sunset. Winds turn back to sw overnight and increase to 8-13
kts on Monday morning.





LONG TERM...Barnes
AVIATION...07 is the U.S. government's official web portal to all federal, state and local government web resources and services.