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000
FXUS63 KILX 052356
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
556 PM CST Thu Dec 5 2013

.DISCUSSION...
ISSUED 331 PM CST Thu Dec 5 2013

Main concerns this package revolve around the winter storm for
tonight through tomorrow and then another chance of snow for
Sunday through Sun night. GFS/ECMWF/GEM look to be in fairly good
agreement all around, while the NAM-WRF looks ok but spreads too
much pcpn further north tonight and tomorrow. Temp profiles in the
models look ok too, so current pcpn type forecast for tonight
looks ok. Most models with weekend system look ok, again except
for the NAM having too little pcpn at the onset. So, overall,
prefer the GFS/ECMWF/GEM solution.

Long term models look in fairly good agreement and
using the blended model forecast looks good for now sine main
focus is in the shortly term.

SHORT TERM...Tonight through Sunday night

Precip occurring across mainly southeast IL at the moment and pcpn
type is a mix of snow and sleet, with some freezing rain. This
will likely continue for next 5-6 hours. Then as temps in the
lower layers cool after sunset, pcpn type will change to all snow,
likely by 8-9pm. Snowfall amounts by morning should reach to
around 3 inches in the extreme southeast, where the warning will
remain. Further north, amounts will be less, to where there will
be just a dusting along I-72. Tomorrow, snow will continue across
the southeast with another 3-4 inches possible. Winter storm
warning will then remain until 6pm tomorrow night. North of I-70,
2-4 inches is expected through tomorrow, so the advisory will
continue as well.

There will be a break in the pcpn as a very cold high pressure
area moves into the midwest. As the high pressure shifts to the
east another weather system will develop in the plains and spread
more pcpn across the area Sunday through Sunday night. Temps will
be quite cold through the period so pcpn type should be all snow.
However, there is a concern as to the pcpn type during the
afternoon. Model soundings in the southeast suggest that pcpn
could be falling as liquid given the warm air advection sounding
and that temps will be just below freezing in the cloud layer. So
have included a mix of freezing rain with the snow in the
southeast during the afternoon. Remainder of the area should be
all snow.

Temps will get very cold as the first real Arctic blast comes into
the area. Temps are expected to remain below freezing through the
period with coldest lows being early Sat morning; where temps will
be in the single digits. Wind chills through the period will also
be below zero as winds will be out of the north at 10-15mph.

LONG TERM...Monday through Thursday

Dry weather is expected through the extended period as a large
high pressure area drops into the area and sits over most of the
US through next Thursday. The upper level trough that finally
moves across the area this weekend will become more zonal for next
week. Very cold temperatures are expected through the extended
period with some possible warming toward the end of next week. So,
expect lows in the single digits Mon night through Wed night and
highs remaining below freezing.

Auten

&&

.AVIATION...
ISSUED 555 PM CST Thu Dec 5 2013

Brunt of accumulating snows along with mixed precipitation with
winter storm to stay southeast of central IL airports next 24
hours closer to a frontal boundary over southeast parts of KY/TN
into central MS. VFR conditions expected this evening with MVFR
vsbys developing with light snow along I-72 overnight into Friday
with ceilings of 5-10k ft tonight lowering to 2-3k ft along I-72
Friday morning with vsbys as low as 2-4 miles Friday as short wave
riding ne along the frontal boundary tugs the light snow further
nw into parts of central IL, especially along I-72 on Friday. IFR
conditions should stay se of SPI/DEC/CMI tonight and Friday. NW
winds around 10 kts tonight to turn nnw 10-13 kts on Friday.

07

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING until 6 PM CST Friday FOR ILZ067-068-
071>073.

WINTER WEATHER ADVISORY until 6 PM CST Friday FOR ILZ056-057-
061>063-066.

&&

$$