Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 151424

Area Forecast Discussion
National Weather Service Lincoln IL
924 AM CDT Sun Apr 15 2018

Issued at 924 AM CDT Sun Apr 15 2018

Large upper low is currently centered just south of Des Moines,
while the surface low near the Indiana/Ohio border has a trough
extending back to a weak low north of Bloomington. Dry slot
continues to work its way across the forecast area, but an
increase in precipitation has been occurring along the Mississippi
River. Highest rain chances continue to be across the northern
CWA, though most areas should at least see scattered showers as
the trough rotates through. Temperatures should only climb a
degree or two at best.

Have sent some updates to adjust the PoP trends for the rest of
the day.


.SHORT TERM...(Today and tonight)
ISSUED AT 340 AM CDT Sun Apr 15 2018

08Z/3 am surface map shows 1004 mb low pressure over west central
IN, with its cold front now east of IL. Temps ranged from the
upper 30s nw of the IL river, to the upper 40s to near 50F from
Rantoul and Champaign to the Mount Carmel airport east. Aloft a
strong 540 dm 500 mb low was along the western IA/MO border. Radar
mosaic shows large area of showers over eastern half of IL
generally along and east of highway 51, with a heavier band of
showers along I-57 and lifting northward. Some patchy fog lingered
over CWA especially at Bloomington and parts of the IL river

Like last night, the HRRR model continues to do well with handling
the showers streaming northward across eastern half of IL early
this morning, and will lean on this model for the forecast today.
This model shows the western/back edge of the showers along I-55
early this morning and shifting eastward toward the Indiana border
by 14Z/9 am, as surface low deepens to 1001 mb to northeast IN and
nw Ohio by 18Z/1 pm today. Meanwhile the strong cutoff upper level
low to move slowly east toward the IA/MO/IL border by early
afternoon. This to likely develop isolated to scattered rain
showers later this morning and early afternoon over central IL and
push se into eastern/se IL during the mid/late afternoon. These
showers to mix with light snow showers nw of the IL river during
the afternoon. The light rain showers then mix with and change to
light snow showers from nw to se across CWA during this evening
and then become more isolated during overnight. Could be some
minor accumulations less than a half inch on grassy surfaces over
northern CWA during this evening. Not much temp rise today, with
highs ranging from the upper 30s/lower 40s over the IL river
valley, to the upper 40s to near 50F in eastern IL. Lows tonight
of 25-30F over central IL and 30-32F in southeast IL and near the
IN border. Will issue a freeze warning overnight until mid
morning Monday for our southeast 8 counties along and south of
I-70 where growing season has commenced.

.LONG TERM...(Monday through Saturday)
ISSUED AT 340 AM CDT Sun Apr 15 2018

Strong cutoff upper level low moves slowly east across central IL
during this evening and into central IN by sunrise Monday. The
large low pressure system then moves into the eastern Great Lakes
by Monday evening. This system will still affect central/se IL on
Monday with a fair amount of low clouds along with isolated light
snow showers in the morning over central and ne CWA. Brunt of
these light showers, possibly back to light rain showers Monday
afternoon mainly from Danville ne then. Highs Monday mostly in the
lower 40s, with areas along and ne of I-74 near 40F. Clouds
decrease late Mon sw CWA and over rest of CWA during Monday night
as low pressure system pulls further away. Another freeze expected
across CWA monday night with lows in the mid to upper 20s in
central IL and around 30F in southeast IL. Will likely need
another freeze warning over southeast 8 counties overnight Monday
night and early Tuesday morning.

Upper level ridge shifts east into the MS river valley by Tue
afternoon and brings mostly sunny skies with milder highs of
55-60F, warmest sw CWA. Increasing clouds Tue night and se winds
to keep it from getting as cold, with lows in the lower 40s from
I-74 ne and mid to upper 40s in sw CWA. Continued slight chance of
showers overnight Tue night along and nw of the IL river, while
any light rain/snow mix will stay north of I-88. 00Z models
continue to bring surface low into western KS by sunset Tue and
passing north of central IL by sunset Wed. This could continue
isolated light rain showers from I-74 north on Wed and Wed evening.
Highs Wed range from upper 50s/lower 60s over the IL river valley,
to the upper 60s to near 70F in southeast IL where more sunshine
expected. Temps cool on Thu with highs mostly in the lower 50s
with dry weather expected Thu thru Fri evening. Highs Fri in the
mid to upper 50s with another upper level ridge moving east into

GFS model continues to be faster than the ECMWF model with
bringing a cutoff upper level low into the southern plains late
this week. Think GFS may be too quick bringing showers into
central IL during Fri night, and think most of our area will stay
dry with maybe isolated rain showers overnight Fri night over the
IL river valley. GFS has widespread rain on Saturday while ECMWF
is still keeping IL dry on Saturday. Stayed close to consensus
which including 20-40% chance of rain showers Saturday into Sunday.
Temps stay below normal (normal highs now are in the mid 60s
central IL and upper 60s in southeast IL). Highs 55-60 on Saturday
again and a bit cooler next Sunday.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 657 AM CDT Sun Apr 15 2018

LIFR conditions will continue at PIA and BMI, with IFR at CMI and
MVFR at DEC, as a surface trough lingers across that area behind
a departing surface low pressure center. Aloft, an upper low
churning to the west of Illinois will slowly progress across
Illinois later today and tonight. Light rain showers today will
mix with and change to snow with time from NW to SE. Little to no
snow accumulation is expected. If any accumulation does occur, it
would be on grassy surfaces, and not on roads.

Cloud cover will prevail throughout the 12z TAF period, with MVFR
eventually becoming the dominant ceiling height later today and
this evening. IFR ceilings are possible later tonight for BMI, and
possibly PIA and CMI.


Freeze Warning from 1 AM to 9 AM CDT Monday for ILZ062-063-



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