Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 220004
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
604 PM CST Wed Feb 21 2018

.SHORT TERM...(This evening through Thursday)
ISSUED AT 306 PM CST Wed Feb 21 2018
Cold front responsible for the drop in temps yesterday and today
has sagged south of the Ohio River Valley this afternoon as high
pressure dominates the Midwest on the CONUS surface map. Not a
classic high pressure weather day, however, as moisture trapped in
the boundary layer from the abundant precip from the past few days
has kept the region cloudy throughout the day. Northerly winds
trying to push drier air into Central IL... but dewpoints south of
Interstate 70 remain near the freezing mark. Precip just behind
the boundary south of I70 is expected to continue, albeit light
through the early evening. The first in a series of waves moving
along the southwesterly flow aloft will spread the precip
northward tonight after 00z. A warm nose in the forecast
soundings at midlevels indicate any ice that is introduced into
the layer will melt...and a wintry mix will become an issue for
Central Illinois. Temperatures hovering near freezing may result
in light glazing early on elevated surfaces. Unlike yesterday, the
ground has not gotten as warm today...and the expected sunshine
was limited by a more persistent cloud cover. Concerned that the
temps will have the chance to fall closer to the freezing mark a
little quicker after sunset. Have issued a Winter Weather Advisory
for the areas north of Interstate 70 for a wintry mix as the
precip spreads northward. Have segmented the advisory with an
after midnight start time in the northern portions of the forecast
area. The precip is expected to redevelop along another wave
moving into the region after midnight. Again, little more than a
glaze is anticipated in much of Central IL, but accumulations of
up of a few hundredths are possible south and west of a line from
Decatur to Galesburg. The morning commute may be somewhat
problematic in the morning, especially on bridges and untreated
roads. Temperatures hovering near the freezing mark, there will be
a quick shift back to rain in the morning hours for the southern
segment of the advisory... and by noon for areas along Interstate
74.

.LONG TERM...(Thursday night through Wednesday)
ISSUED AT 306 PM CST Wed Feb 21 2018
Next wave has been delayed until after 00Z Thursday night...
ending by Friday midday. Temperatures are expected to remain warm
enough to keep the precip as rain... back to lows in the upper
30s/40s... and highs in the upper 40s/low 50s on Friday.

The next, and stronger system lifts into the region on Friday
night...spreading more precip northward. Significant precipitation
will be expected with this storm. With the saturated ground
already ahead of this system, flooding concerns will linger into
the weekend. Heaviest rainfall will be anticipated south and east
of Interstate 55 through Saturday night. Forecast dries out on the
other side of the cold front Saturday night. Temps are cooler but
still above normal for the first half of the work week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 604 PM CST Wed Feb 21 2018

Steady northeast winds will continue tonight as a stalled cold
front lingers just south of the Ohio River Valley. A baroclinic
zone extending across southeastern IL is continuing to be a focal
point for rain showers. Warm air overrunning the low level cold
dome will fuel rain or freezing rain, possibly mixed with sleet.
That precip should be mainly along and south of I-72 this evening,
before the initial wave of precip shifts east into Indiana. Late
tonight, another surge of precip is forecast to push into our
west-central counties, and affect mainly SPI, PIA, and BMI. That
precip could start as FZRA or snow/sleet, then warming temps will
change that precip to rain after 15z or so.

Travel surfaces could see a light glaze of ice tonight, due to
colder ambient ground temps than last night.

Wind speeds will remain 10-15kt for most of the next 24 hours,
with wind directions shifting from NE to East tomorrow afternoon.
Precip should diminish or end by afternoon as well.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from midnight tonight to noon CST
Thursday for ILZ027>031-036>038-040>043-047-048.

Winter Weather Advisory until 9 AM CST Thursday for ILZ044>046-
049>057-061.

&&

$$

SHORT TERM...HJS
LONG TERM...HJS
AVIATION...Shimon



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