Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 120309
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
909 PM CST Thu Jan 11 2018

.UPDATE...
Issued at 909 PM CST Thu Jan 11 2018

Wintery precip and other conditions are progressing eastward as
forecast. Still see light freezing rain occurring in eastern IL
and now moving into southeast IL after the front has moved
through. Have seen several reports of UP in observations and
wondering if it sleet, considering SWOMCD sent out by SPC little
while ago. Definitely possible given the very shallow cold air
that has been pouring in 1-2hrs behind the front. Front has pushed
through LWV this hour and below freezing air is not far behind.
Believe FZRA and sleet is likely in parts of eastern and southeast
IL, roughly along and east of I-57. Advisory will cont through the
rest of the night. Have already cancelled advisory west of I-55
and updated forecast. However, have made some tweaks to overnight
lows looking to go little lower in the northwest and adjusted pops
and wx remainder of the night. Therefore will send another update
shortly.

&&

.SHORT TERM...(This evening through Friday)
ISSUED AT 309 PM CST Thu Jan 11 2018

20z/2pm surface analysis shows a sharp cold front between the
Illinois River and the I-55 corridor. Unseasonable warmth
continues ahead of the front, with readings in the upper 50s and
lower 60s across the eastern half of the KILX CWA. Once the front
passes, temps have been dropping 20-25 degrees in about 2
hours...resulting in current readings only in the middle 20s west
of the Illinois River. A band of rain accompanies the front, but
only very light precip is noted behind the boundary. With
temperatures rapidly falling late this afternoon and evening, a
period of very light freezing rain will be likely. Based on
expected hourly temps, the leading edge of any icing concerns will
reach I-55 by 00z/6pm...a Champaign to Shelbyville line by
03z/9pm...and the far SE around Lawrenceville by around midnight.
As the depth of the cold airmass increases, the precip will end as
a brief period of light snow from west to east late this evening
into the overnight hours. The boundary is expected to slow its
eastward progress late tonight, resulting in a more prolonged
episode of freezing precip along/southeast of the I-57 corridor.
In fact, light snow is expected to linger across the E/SE into
Friday morning. Once the system pushes further east and all precip
comes to an end by midday Friday, the greatest snow and ice
accumulations will be noted near the Indiana border. Around 1 inch
of snow will fall along I-57...with as much as 1-2 inches
along/east of a Paris to Flora line. Ice accumulations will be
less than one tenth of an inch across most of central
Illinois...with amounts close to one tenth of an inch across the
far E/SE. While ice and snow totals will remain minor with this
system, slick roadways and hazardous travel conditions are
expected this evening into Friday morning. As a result, the Winter
Weather Advisory will continue unaltered.

.LONG TERM...(Friday night through Thursday)
ISSUED AT 309 PM CST Thu Jan 11 2018

A much colder airmass will settle into the Midwest behind the
departing front on Friday, with highs ranging from around 20 far
northwest at Galesburg...to the upper 20s far southeast near
Lawrenceville. Once the cold weather arrives, it appears it will
be locked into place through the balance of the extended courtesy
of a persistent northwesterly flow pattern. Several weak impulses
will track through the region during this time, with the strongest
and most consistent feature slated to arrive Sunday night into
Monday. Early indications suggest a light accumulation of
snow...perhaps on the order of 1 to 2 inches. These totals will
likely be adjusted in both magnitude and area over the next couple
of forecast runs...so please monitor future forecasts for updates.
After that, cold and dry weather will prevail through Thursday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 544 PM CST Thu Jan 11 2018

Cold front is quickly moving through the area and has passed all
sites except for CMI, but should be past CMI at issue time. Cold
air is lagging behind some so precip will be ra initially at CMI
but then become FZRA about an hour later. Cigs drop behind the
front as well to below 1kft with BMI below 500ft. This will
continue for several hours at most sites but then rise into the
MVFR levels. However, CMI should see IFR cigs longer since things
will linger in that area this evening. Cigs will continue to rise
overnight and tomorrow morning as the cold front continues to move
east. Will have VCSH at all sites this evening and sites in the
east overnight, but precip type will be scattered fzra. Have added
tempo group at all sites for 4hrs of 5sm -FZRA to account for
scattered precip in cold air behind front. Could be some light
snow as well this evening, but main issue is the freezing rain.
Winds will be northwest through the period, then become northerly
tomorrow morning. Gusty winds will continue as well.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM CST Friday for ILZ038-042>046-
051>057-061>063-066>068-071>073.

&&

$$

UPDATE...Auten
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Auten



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