Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 180846
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
346 AM CDT Thu May 18 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 340 AM CDT Thu May 18 2017

A 996 mb surface low pressure near Eau Claire in west central WI
had a cold front extending through nw Iowa into central KS and
extended to 999 mb surface low in ne NM. Aloft a 590 dm 500 mb
subtropical ridge was off the southeast Atlantic coast while
550 dm 500 mb low near Salt Lake UT and a 554 dm 500 mb low over
the upper MS river valley near MN/WI border.

Skies have temporarily cleared over much of central IL with
clouds in nw IL, and in southeast IL south of I-70. An area of
showers and thunderstorms was over se MO into southern IL south of
I-64 and tracking NE. Some of this convection will track areas
areas se of I-70 this morning. Then expected isolated showers and
thunderstorms to develop in warm/humid airmass along and south of
I-72 this afternoon. Can not rule out a stray shower or
thunderstorm to pop up later this afternoon further north of I-72
as cold front pushes se into the IL river valley late this
afternoon, approaching I-55 by 00Z/7 pm and to I-70 by 06Z/1 am
tonight, then pressing southward across southeast IL overnight.

SPC Day1 Outlook continues a marginal risk of severe storms later
this afternoon and evening over most of CWA with passage of this
cold front. Warm highs in the low to mid 80s today (except upper
70s by Galesburg) with breezy sw winds of 15 to 20 mph and gusts
of 20-30 mph. Cooler lows tonight range from around 50F from
Peoria and Bloomington north, to 60-65 in southeast IL from I-70
south.

&&

.LONG TERM...(Friday through Wednesday)
ISSUED AT 340 AM CDT Thu May 18 2017

Frontal boundary will be south of area on Friday with surface low
pressure moving into the central plains and spreading a good
chance of showers and a few thunderstorms ne back across mainly sw
CWA later tonight and across areas during the day Friday. Highs
Friday contrast from 60F by Galesburg and Lacon, to 75-80F in
southeast IL from I-70 south. SPC day2 outlook as marginal risk of
severe storms for mainly hail across area Friday afternoon into
Friday night, while slight risk of severe storms along and south
of a Rushville to Decatur to Terre Haute line.

Low pressure will eject ne into central IA by midday Saturday and
lift the warm front north of central IL, then cold front to push
east across IL during Sat night. This will likely bring more
showers and thunderstorms and SPC day3 outlook has entire area in
a marginal risk of severe storms especially later Sat afternoon
and Sat evening. Warmer highs in the low to mid 80s Sat with some
upper 70s nw of IL river.

00Z models have trended quicker with moving cold front out of area
on Sunday as surface low moves north of Lake Superior later in the
day. Have 20-40% pops east of i-57 Sunday morning then dry skies
becoming partly to mostly sunny Sunday afternoon. Cooler highs
Sunday in the mid to upper 60s central IL and lower 70s in
southeast IL. Dry weather expected Sunday night and Monday as weak
high pressure settles into the mid MS and OH river valleys. Highs
Monday in the lower 70s with mostly sunny skies.

Large upper level trof digs into the Midwest on Tue and shifts
east into the Ohio river valley on Wed. This to return unsettled
weather with good chance of showers and a few thunderstorms by
overnight Monday night thru Wed. Highs Tue in the upper 60s and
lower 70s, then mid to upper 60s on Wed. Dry Wed night and Thu
over most of area with highs in the upper 60s on Thu. CPC`s 8-14
day outlook from May 25-31 favors below normal temperatures over
IL as upper level trof continues to influence the eastern US.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1259 AM CDT Thu May 18 2017

SW winds 15-25 kts and gusts 25-35 kts early overnight to
gradually diminish. These winds could pick back up for a time Thu
morning before diminishing again during Thu afternoon as low
pressure pulls away from IL. VFR conditions expected to continue
across the central IL airports through 06Z/1 am Thu night.
Isolated showers and thunderstorms have lifting ne of central IL
in northeast IL. Another area of convection was in southeast MO
and lifting ne toward southeast IL and these should stay south of
I-70. Just scattered mid level clouds of 7-12k ft to occur into
the morning, then scattered cumulus clouds with bases of 4-6k ft
appear by afternoon. A 996 mb surface low pressure over southeast
MN near WI border has cold front through nw IA and far southeast
NE. This front to move se to PIA around 22Z and reach CMI and DEC
around 02Z/Thu. Could see broken 5-6k ft clouds behind the front
along with wind shift to north around 10 kts and few higher gusts.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SHORT TERM...07
LONG TERM...07
AVIATION...07



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