Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 212136

Area Forecast Discussion
National Weather Service Lincoln IL
336 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


.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 18Z TAFS through 18Z Thursday afternoon)
Issued at 1141 AM CST Wed Feb 21 2018

MVFR conditions dominate this morning with cigs below 1500 ft this
morning. Northerly winds and unrestricted visibility. High res
models attempt to slowly burn through the lower cigs and redevelop
a stratocu layer around 3000-3500ft. Some clearing started to the
NW, so going to keep that trend in the forecast for now. Big issue
for the forecast is the precip starting after midnight. Will
likely start as snow for PIA and BMI, but risk the chances for a
rapid turn to freezing rain after the start of it and into the
early morning hours. The temperatures lingering within a degree or
so of the freezing mark is the concern. Last night, some ice was
mitigated by warmer ground temperatures. With a day sitting at
29-35 degrees...will be that much easier to be a problem later.




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