Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 180947

Area Forecast Discussion
National Weather Service Lincoln IL
347 AM CST Thu Jan 18 2018

.SHORT TERM...(Today and tonight)
ISSUED AT 345 AM CST Thu Jan 18 2018

The 09Z/3 am surface analysis shows 1038 mb polar high pressure
near the LA/MS/AR border and ridging into the TN and southern OH
river valley. This was providing clear skies over IL. Temperatures
were nearly steady in the teens, with Lawrenceville at 9F. But SW
winds of 8-18 mph and few gusts of 18-26 mph was giving wind
chills ranging from below zero to 10 above. Up north a 1004 mb
surface low (compact 535 dm 500 mb low) was just north of MN and
giving a swirl of mid/high clouds spreading se toward nw and into
nw WI.

High pressure to gradually weaken to 1030 mb by early evening as
it sprawls across the southeast states and continues a breezy sw
flow over central/se IL. 00Z models weaken compact clipper low
just north of the gopher state as it tracks to northern Lake
Superior by early evening, keeping it light snows over the
northern and eastern great lakes. Few cirrus clouds could move
into central/northern CWA midday into afternoon but still expect
another sunny day. Breezy sw winds of 10-18 mph and gusts in the
20s to bring milder temperatures closer to normal today, with
snow melt beginning this afternoon. Highs in the lower 30s over
deeper snow pack (2-4 inches) in eastern IL and upper 30s over 1
inch snow pack from Canton and Springfield sw.

High pressure will remained anchored across the southeast states
tonight with IL staying clear and in a sw wind flow. Lows tonight
of 18-23F, coolest the the Wabash river valley.


.LONG TERM...(Friday through Wednesday)
ISSUED AT 345 AM CST Thu Jan 18 2018

High pressure camped out again over the southeast states on Friday
to bring ample sunshine to IL again with breezy ssw winds giving
milder highs in the low to mid 40s, with coolest readings along
the IN border. Mostly clear skies Friday night with with some
cirrus clouds and lows of 27-32F. A weak cutoff upper level low
moving into the southern TN river valley during Friday night to
keep its clouds and moisture south of IL.

00Z forecast models continue to dig a strong upper level trof over
the western states late this week and surface low pressure
ejecting into OK panhandle and sw KS by dawn Sunday. Saturday
should still remain dry with some increasing low clouds giving
mostly cloudy skies during the afternoon. Highs in the mid to
upper 40s Saturday, mildest from Jacksonville sw where temps
approach 50F. Increased low level moisture from surface to 825 mb
to give isolated light rain showers Sat evening and 20-30% chance
of light rain showers overnight Sat night. Patchy fog could
develop during Sat night into Sunday morning especially over
northern CWA. With models continuing to trend slower with storm
system this weekend, chances of rain showers stay in the 20-30%
range on Sunday with mostly cloudy to overcast skies. This
appears to be the mildest day of the next 7 despite the clouds,
with highs in the low to mid 50s.

Low pressure deepens as it eject ne into southeast IA by midday
Monday and pushes cold front east across IL around Monday
morning. GFS model appears too fast with this storm system.
Showers likely Sunday night and a good chance of showers on
Monday, with likely pops in eastern IL Monday morning. Thunder
chances looks best in southern IL Sunday night but could be very
isolated chances of elevated thunderstorms into southeast IL as
CAPES reach 75-125 J/kg. Lows Sunday night in the low to mid 40s.
Highs Monday in the mid to upper 40s, with Lawrenceville up to
50F. Could be a mix of light snow with light rain nw of IL river
late Monday afternoon as cooler air arrives behind the cold front.
A strong upper level trof over IL Monday evening lingers chances
of light rain changing to light snow showers, especially north of
I-70, with all light snow showers overnight Monday night from I-72

Temperatures cool back to normal Tue with highs in the mid to
upper 30s, lower 40s along highway 50 in southeast IL. Could be
isolated light snow showers or flurries ne of I-74 early Tue
morning, then dry with skies becoming partly sunny toward Tue
afternoon. Similar highs on Wed as what we see on Tuesday, then in
the upper 30s/lower 40s on Thu. Generally dry conditions expected
Tue night into Thursday, with next storm system coming out of sw
upper level flow around next Fri/Sat Jan 26-27th, and looks mostly
like rain showers.

Climate Prediction Center`s (CPC) 8-14 Day Outlook for Jan 25-31
continues to trend toward a milder and wetter wx pattern. CPC has
a 40-45% chance of above normal temperatures and a 35-45% chance
of above normal precipitation over central and southeast IL during
the last week of January. This may offset bitter cold conditions
that we have experienced much of the past 3.5 weeks since
Christmas eve. Temperatures in Lincoln IL have average 14 degrees
below normal in the past 25 days since Dec 24th.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1149 PM CST Wed Jan 17 2018

Main issue in the early portion of the 06z TAFs is the LLWS
potential, especially for our northern terminals closer to the
Low Level Jet of 40-50kt. The southern extent of the 40KT contour
seems to mainly affect PIA and BMI, while CMI, DEC, and SPI are
mostly in the 35-37KT peak LLJ winds. Decided to include LLWS
through 15z in all TAFs, with PIA and BMI having the higher wind

Wind gust will quickly increase tomorrow morning, by 15z or so,
with gusts toward 25KT at times. Wind direction should generally
remain SW, but a brief shift to the W could occur later tonight
into tomorrow morning.

No clouds of significance are expected for the 06Z TAF period.




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