Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 201735
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1135 AM CST Fri Jan 20 2017

.UPDATE...
Issued at 947 AM CST Fri Jan 20 2017

Fog has been lifting over much of central Illinois this morning,
with some patches of 1/4 to 1/2 mile visibility lingering. General
trend continues with slow improvement, and am anticipating letting
the advisory expire at 10 am.

Warm front will continue to sharpen near the I-72 corridor today,
lifting northward through the forecast area by late evening. Short
range models continue to suggest some light rain/drizzle
development very late this afternoon, increasing a bit this
evening. South of the front, temperatures already in the lower 50s
near Lawrenceville/Flora, and still going with highs near 50 as
far north as Havana and Bloomington. With the front going well
north of us, not too much of a dropoff with temperatures tonight.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 333 AM CST Fri Jan 20 2017

Upper wave lifting NE across central IL this morning producing
widespread rain over the northeast corner of the forecast area while
saturated conditions behind this feature leaving patchy to
widespread fog throughout the remainder of the area. Dense fog
advisory now in effect to 10 a.m. roughly west of I-57 as short term
models indicate visibility improving around this time as daytime
warming and southerly flow taking shape behind a warm front crossing
the area. Tonight another disturbance lifting NE through Iowa may
bring another chance for precipitation however given model vertical
profiles of shallow saturation, warm conditions, and low QPF think
this will be mainly drizzle with more patchy fog. Temperatures today
should be upper 40s and lower 50s most of the area to mid 50s south
of I-70. Mild lows tonight with the southerly flow behind the warm
front only mid to upper 40s in general.

.LONG TERM...(Saturday through Thursday)
ISSUED AT 333 AM CST Fri Jan 20 2017

Very mild air will surge into Illinois for the start of the extended
forecast on Saturday, as a warm front pushes north of Illinois. Due
to the closer proximity of the warm front just to our north at
sunrise, we expect some lingering light fog in the morning, with
even some patchy drizzle even possible north of I-74. As the day
progresses, south winds will increase to 15 to 25 mph, bringing
increasing moisture and warm air. Even without much in the way of
sunshine, high temps look to top out very close to record
temperatures for Jan 21, with readings ranging from the upper 50s N
of I-74 to the lower 60s S of I-72. Rain chances will increase east
of I-57 later in the afternoon, with elevated instability providing
support for isolated thunderstorms S of I-70. Shower and storm
chances expand westward to the I-55 corridor Saturday evening, then
shift back east after midnight.

While light rain chances will linger Sunday morning in eastern
Illinois, rain chances look to ramp up again Sunday afternoon and
Sunday night as a southern stream low pressure system passes by to
the south of Illinois. A closed 500mb low and occluded surface low
will progress from Arkansas at 12z Sunday to eastern Tennessee/E
Kentucky by 06z/Midnight Sunday night. A cold frontal passage, as
well as shortwaves of energy rotating around that expansive low
pressure will trigger rain chances mainly east of I-57 from
Sunday afternoon through Sunday night. As the cold front and low
pressure system drift off to the east, a brief period of ridging
at the surface and aloft will provide a break in the rain chances
for Monday into Tuesday. Colder air will limit highs to the 40s on
Monday and Tuesday, which are still above normal.

The next surface low will eject from the central Plains toward
Illinois on Tuesday, with the surface and 500 mb lows passing across
far NW IL Tuesday night. Rain chances will increase Tuesday
afternoon north of a line from Canton to Peoria to Bloomington, and
expand southward toward I-72 Tuesday evening coinciding with the
closest passage of the low pressure system. Precip chances will
retreat back north of Peoria again later Tuesday night and
Wednesday morning as the low pulls away into the Great Lakes. A
brief surge of warm air on Tuesday ahead of the low will help high
temps climb 3 to 4 degrees warmer than Monday but still mainly in
the 40s.

A cooling trend is then expected Wednesday and Thursday as a long
wave upper trough with cooler Canadian air shifts east from the
Rockies toward the Mississippi River Valley. Slight chances of rain
or snow will linger north of Lincoln on Wednesday, but dry
conditions should be seen on Thursday. High temperatures will
decrease a few degrees each day, with Thursday`s highs ranging from
35 near Galesburg to 40 near Lawrenceville.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1134 AM CST Fri Jan 20 2017

Large expanse of IFR/LIFR ceilings continue at midday, although
visibilities have improved at TAF sites to at least a few miles.
Ceilings coming up some to our south and this is advecting
northeast, but the question is how far north it makes it. May see
MVFR ceilings reach KSPI, but have kept the remaining sites at IFR
levels for now. More substantial improvements likely holding off
until late in the night, as a warm front continues to push north
out of central Illinois. However, it will take until mid-late
morning before any widespread VFR conditions return.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Geelhart
SHORT TERM...37
LONG TERM...Shimon
AVIATION...Geelhart



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