Area Forecast Discussion
Issued by NWS Central Illinois

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205
FXUS63 KILX 161154
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
554 AM CST Mon Dec 16 2019

.SYNOPSIS...
Issued at 410 AM CST Mon Dec 16 2019

The first round of snowfall moved out of the region overnight,
leaving behind measurements between 1 to 6 inches. Another round
of snowfall will arrive this morning, and overspread the southern
half of Illinois throughout today. This will bring an additional 1
to 5 inches of snowfall across the region, before exiting the
Midwest overnight. Drier conditions arrive Tuesday, however
temperatures will be chilly through Wednesday.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 410 AM CST Mon Dec 16 2019

Another night of long forecasting, as well as issues with the
forecast due to Prob Ice grids and temperatures creating lower
than expected snowfall totals.

The first round of snowfall exited the region overnight, however
with the low clouds remaining overhead and sufficient moisture at
the surface, light freezing drizzle has developed around the
region this morning. This pattern will continue through the
morning, before the second round of snowfall slides into the area.
Current radar has more precipitation starting to slide across the
Mississippi River north of St Louis, however no reports have been
made about any ground truth of precip. Snowfall is being reported
as far back as eastern Kansas, but with the increased moisture
expecting freezing drizzle or light freezing rain to be the main
impact through the early morning. Temperatures across southern
Illinois remain near freezing, indicating the potential for
additional ice at the sfc this morning, otherwise through the
morning, precip should change to snowfall as ice particles re-
develop in the cloud layer and remain frozen throughout the
transport process to the ground.

This round is not expected to be as widespread as the first wave,
with a northern limit along a Rushville to Bloomington line. Some
light snow, less than 1 inch, could occur north of this line,
however the main concern today will once again fall along and
south of a Jacksonville to Danville line. Some major changes to
the Winter Weather Advisory and Winter Storm Warning were made
with this package, as models honed in on the second convective
band today. Additional snowfall today will range from 1 to 3
inches in the Advisory areas, to upwards of another 5 inches in
the Warned regions between I-72 and I-70.

Walking through the forecast process today was again challenging,
as Prob Ice did not work and hand edits were needed to ensure
proper snow totals and ice accumulations. Also edits to
temperatures to account for the already snow covered ground were
needed, especially for overnight lows Tuesday night when clearing
skies will allow for rapid cooling and winds will help with the
creation of wind chills.

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 410 AM CST Mon Dec 16 2019

Looking ahead to the remainder of the week, not expecting any
major issues. The only big stories will be the colder temperatures
that arrive Tuesday night into Wednesday morning, with wind
chills falling to near 0 in many locations. High pressure will
dominate mid-week holding a dry pattern in place over the central
US. This pattern will continue into the end of the week, when the
High shifts towards the east coast. This will bring southwesterly
winds back to the region, increasing temps once again...as the
roller coaster of this winter continues. Otherwise, dry weather
should prevail through the forecast period.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 546 AM CST Mon Dec 16 2019

Clouds continue to impact the region, with additional low ceilings
beginning to return ahead of the next round of snowfall. This
round is expected to impact the southern TAF sites, while PIA and
BMI will remain dry through most of the period. The only exception
is BMI which starts this period with -FZRA and LIFR ceilings due
to the elevation of the airport. DEC will begin in IFR as
conditions bounce from IFR to low MVFR. Snow showers will begin to
slide into the southern sites late this morning from west to
east, before becoming dominate during the afternoon helping to
reduce visby`s through the afternoon and evening. Ceilings will
begin lifting as this system pulls out of the region late in the
period. Uncertainty remains will exact exit timing of snow from
region overnight, could linger longer than forecast.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until midnight CST tonight for ILZ052-
054>057-061>063-066>068.

Winter Weather Advisory until midnight CST tonight for
ILZ042>051-053-071>073.

&&

$$

SYNOPSIS...Baker
SHORT TERM...Baker
LONG TERM...Baker
AVIATION...Baker



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