Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 122120

Area Forecast Discussion
National Weather Service Lincoln IL
320 PM CST Thu Jan 12 2017

.SHORT TERM...(This evening through Friday)
ISSUED AT 319 PM CST Thu Jan 12 2017

A strong cold front has pushed southeast to near the Ohio river at
mid afternoon, taking rain showers southeast of CWA. Northwest winds
of 8-15 mph and few gusts to 20 mph were ushering in colder air to
central and southeast IL today. Mercury levels at mid afternoon
range from 22F at Galesburg to 42F at Lawrenceville and Mount Carmel
airport. Overcast stratus clouds below 1.5k ft over CWA were
breaking up in nw IL closer to 1033 mb arctic high pressure over
western ND and ridging into the central plains.

Latest forecast models take cold front southeast across KY/TN
tonight as arctic high pressure moves into the upper MS river valley
Friday morning. This should decrease clouds from nw to se late today
and into tonight and keeping precipitation south of CWA through
early Fri morning. Lows tonight range from mid teens from IL river
nw to the mid to upper 20s in southeast IL. Overrunning will set up
over southern CWA during Friday with clouds spreading back northward
during Fri morning as skies become mostly cloudy to overcast by
Friday afternoon. Also will see light freezing rain spread into
areas south of a Jacksonville to Mattoon to Robinson line by late
Friday morning and getting as far north as a Lincoln to Danville
line by sunset Friday. Northern fringe of system will also have
chance of sleet while south of I-70 could see light rain as well.
Will continue the winter storm watch for central and southern CWA
starting Friday afternoon, though the wintery mix may not reach
northern part of watch area from I-72 north until late Friday
afternoon. Highs Friday range from upper 20s nw of I-55 to the mid
30s in southeast IL.


.LONG TERM...(Friday night through Thursday)
ISSUED AT 319 PM CST Thu Jan 12 2017

The frontal boundary stalling just southeast of the forecast area
and broad surface high pressure moving eastward through the Great
Lakes Region over the weekend will provide the main ingredients for
winter weather over the weekend into Monday morning as the high
feeds cold surface air into the area from the north/east, and the
frontal boundary allows a couple of disturbances to propagate
northeastward into the area brining precipitation. A persistent warm
layer aloft will cause any precipitation to fall as rain, however
temperatures will be below freezing for the nighttime periods...only
rising to near or a few degrees above freezing in the afternoon.
Highs will potentially get a bit more solidly above freezing south
of I-70 in the upper 30s. Therefore, periods of freezing rain can be
expected through the weekend, especially the nighttime periods.
Total ice accumulations could exceed a quarter inch from roughly I-
72 southward and I-57 westward, although at this point it appears
the breaks in accumulation and the potential melting in the
afternoon periods may prevent any ice buildup over one quarter inch
so have kept the winter storm watch going and have not upgraded any
portion to warning or advisory so far. Also added remaining portions
of northern CWA to the watch starting Midnight Saturday night and
going to Monday morning.

Strong warming expected to take place Monday as a low tracks NW of
the area bringing strong warm advection and heavier rainfall which
could result in rainfall up to an inch Monday through Tuesday.
Precipitation chances taper off through midweek and mainly based on
timing uncertainty with the progression of the early week low. Highs
expected to get to the 40s and 50s Monday through Thursday with lows
mainly 30s, possibly 40s Monday night.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1158 AM CST Thu Jan 12 2017

A strong cold front has recently pushed southeast of Lawrenceville
and Mount Carmel airports with band of rain showers and isolated
thunderstorms also passing southeast of CWA. NW winds of 8-14 kts
and few gusts 15-19 kts over central IL this afternoon will veer
northerly around 10 kts this evening and then NE later tonight
into Friday morning at 8-14 kts. Overcast stratus clouds with IFR
bases of 500 to 900 ft over central IL at midday will gradually
lift to MVFR of 1-2k ft in next few hours. 1033 mb arctic high
pressure near MT/ND border and ridging southward across the great
plains will build into the upper Midwest tonight and Friday
morning brining fair weather to central IL. Drier air advecting
into central IL on nw winds should decrease/scatter out low clouds
during mid/late afternoon happening at PIA 21-22Z and DEC and CMI
at 23-24Z. Broken cirrus clouds 20-25k ft to then occur tonight
into Fri morning with mid level clouds around 15k ft spreading ne
over central IL between 15-18Z Friday. MVFR vsbys of 4-5 miles
with light fog will lift to VFR in next hour or 2 leaving VFR
vsbys rest of taf period. Precipitation should stay south of
central IL through 18Z/noon Friday.


Winter Storm Watch from Friday afternoon through Sunday morning
for ILZ042>057-061>063-066>068-071>073.

Winter Storm Watch from Friday afternoon through late Sunday
night for ILZ040-041.

Winter Storm Watch from late Saturday night through late Sunday
night for ILZ027>031-036>038.



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