Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 181727

Area Forecast Discussion
National Weather Service Lincoln IL
1227 PM CDT Thu May 18 2017

Issued at 1006 AM CDT Thu May 18 2017

Temperatures rising quickly this morning and have already reached
the lower 80s around Springfield and Champaign. Some adjustments
were made to the hourly temperature grids, but kept highs largely
in the mid 80s over most of central and southeast Illinois ahead
of the incoming frontal boundary, with upper 70s to the northwest.
Initial band of showers and storms has pushed south of the Ohio
River. High-res short-range models continue to focus on some
convective development just ahead of the front along roughly the
I-72 corridor by mid afternoon, where some initial bands of
cumulus are starting to develop. Have also tweaked the hourly
PoP trends to account for this as well.


.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

.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 18Z TAFS through 18Z Friday afternoon)
Issued at 1223 PM CDT Thu May 18 2017

Isolated convection possible this afternoon ahead of a slow moving
cold front. Have only included a VCTS mention at KCMI for now as
they seem to have slightly better chances, but can`t rule out a
stray storm near KSPI/KCMI. A few showers will linger into the
evening as the front becomes stationary from KSPI-KCMI, but main
focus for steadier rains will be after about 09Z as a wave of
energy starts moving in from the southwest.

Gusty southwest winds ahead of the front will diminish late this
afternoon. Winds will then be trending northerly this evening and
then to the northeast or east, where they will remain the
remainder of the forecast period.




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