Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 181151
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
551 AM CST Sat Jan 18 2020

.SYNOPSIS...
Issued at 226 AM CST Sat Jan 18 2020

Moderate to at times heavy rain will continue until midday today
across central Illinois. Temperatures start the day relatively
mild in the 30s and 40s, but a cold front will drive in much
colder temperatures this afternoon and evening. Temps will fall
into the single digits and teens overnight with wind chills of
zero to 20 below. Expect cloudy skies and continued cold and
breezy conditions on Sunday. Temperatures will not warm much
across the region with highs only in the single digits and teens.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 226 AM CST Sat Jan 18 2020

Early this morning, water vapor imagery reveals a strong shortwave
shifting east across the mid Missouri Valley while a strong low
level jet in advance of the wave is advecting another unseasonably
moist air mass across central Illinois. PWats in excess of an
inch, 1.13 inches as sampled upstream earlier by KSGF 00Z raob,
are being advected across portions of the Midwest early this
morning resulting in moderate to heavy rain across the region. As
of 08Z obs, surface temps and dew points have risen to or above
freezing across the entire forecast area, and a slow upward trend
should continue indicating we are past the worst of the freezing
rain potential. Plan to allow the southern portion of the Winter
Weather Advisory to expire at 09Z, and will keep the northern
portion going until 12Z just in case a few elevated surfaces or
cold spots persist, though the threat for ice does appear to be
lowering from this point. Main concern now will be rain rates and
potential flooding. 3-hour flash flood guidance generally ranges
between 1.5 and 2.0 inches while 6-hour guidance is around 2.0 to
2.5, though some areas south of I-70 are under two inches. Axis of
heaviest rain will fall either side of a line from Taylorville to
Danville where three quarters to 1.5 inches of additional
rainfall appears possible through midday. A Flash Flood Watch will
continue until the threat for heavy rain ends by early this
afternoon.

Once precip ends around midday with passage of a cold front,
strong gusty winds and falling temps will be the main story.
West to northwest winds are expected to gust into the 30 to 40 mph
range this afternoon and evening. Cold advection will drive
temperatures down into the teens north of I-72 early this
evening. Temps fall into the single digits and teens overnight
area wide, which coupled with the continued breezy winds will
contribute to wind chills of zero to 20 below across central
Illinois. A Wind Chill Advisory will likely be needed for portions
of the area, particularly along and north of a Cuba to
Bloomington line where wind chills of 15 to 20 below are expected.
Will wait until ongoing headlines are over before issuing
additional advisories.

.LONG TERM...(Sunday through Friday)
ISSUED AT 226 AM CST Sat Jan 18 2020

Expect dry weather Sunday into the middle of the week, but
temperatures start off quite cold during this stretch. Cloudy
skies and continued gusty northwest winds on the nose of a
strong 1045mb Canadian high pressure inching towards the area will
not allow temperatures to recover much from overnight lows,
perhaps only a few degrees. Winds chills near or below zero are
likely much of the day. The high will build across the mid
Missouri Valley Sunday night into Monday morning maintain at least
a modest gradient across central Illinois. Wind chills of zero to
15 below are expected by early Monday, and could be flirting with
advisory criteria northwest of the Illinois River Valley where
air temperatures fall near zero. Temperatures remain well below
normal during the day Monday, but could see a few peeks of
sunshine during the afternoon. Temperatures begin to moderate in
earnest Tuesday into Wednesday as the high shifts east allowing
return flow into the Midwest.

A couple upper level disturbances will bring renewed chances for
precip late next week, but details remain uncertain at this
distance with continued poor model agreement. The GFS maintains a
deeper system with the possibility of another heavy rain event,
while the ECMWF continues to carry a pair of lower amplitude
systems. Will have to continue to keep an eye on model trends to
get a better handle, but for now the forecast will call for broad-
brushed PoPs across the area to account for this system.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 550 AM CST Sat Jan 18 2020

Light rain showers will diminish eastward through mid morning
over central IL and continued MVFR vsbys and possibly down to 2
miles along I-74 airports. Also continued LLWS into mid morning
with 2k ft sw winds of 40-50 kts. Deepening 1006 mb low pressure
along the WI/IA border at dawn had a cold front just west of IL.
Strong cold front to sweep eastward across central IL during
mid/late morning. South to SSW winds of 10-15 kts and gusts 18-25
kts early this morning to switch west to WNW and increase to 18-23
kts and gusts of 28-35 kts by midday and continue thru this
evening. Brisk WNW winds continue overnight at 15-19 kts and
gusts in the 20s. Stratus clouds with ceilings of 200-700 ft this
morning to increase to MVFR during mid to late afternoon and
likely continue thru tonight.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Flood Watch until noon CST today for ILZ042>057-061>063-066>068-
071>073.

Winter Weather Advisory until 6 AM CST early this morning for
ILZ027>031-036>038.

&&

$$

SYNOPSIS...Deubelbeiss
SHORT TERM...Deubelbeiss
LONG TERM...Deubelbeiss
AVIATION...07


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