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430
FXUS63 KILX 200900
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
400 AM CDT Fri Sep 20 2024

.KEY MESSAGES...

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- Chance of showers and isolated thunderstorms today over central
  IL, with a few strong to locally severe storms east of I-55 from
  mid afternoon into mid evening.

- Very warm and rather humid today and Saturday with highs in the
  upper 80s to around 90 with afternoon heat indices in the low to
  mid 90s.

- More widespread showers and chance of thunderstorms expected
  overnight Saturday night through Monday. There is a 50-60%
  chance of seeing 1-2 inches of rain over central IL with highest
  amounts north of I-70 where locally over 2 inches possible.
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&&

.DISCUSSION...
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Issued at 345 AM CDT Fri Sep 20 2024

Early morning surface map shows a cold front from western WI into
far eastern Iowa and nw MO. Isolated showers had recently develop
nw of Lincoln while more widespread showers and a few
thunderstorms were over southeast WI and northern IL, mainly north
of I-88 and supported by a 25-30 kt sw 850 mb jet. Variable sky
cover over CWA, with less clouds in eastcentral and southeast IL
and more clouds over western/sw CWA. Temps ranged from 58F in
Danville to 75 in Springfield, while more moist dewpoints were in
the low to mid 60s, except mid to upper 50s from Rantoul to Terre
Haute east. Aloft a strong 592 dm 500 mb high was over central
Texas and ridging ne into IL and the central and eastern Great
Lakes. A strong 553 dm 500 mb low was over east central Manitoba
with a 567 dm 500 mb low off the southern CA coast.

Latest CAMs push cold front se across the IL river valley late
this morning and thru rest of central IL during this afternoon
before stalling in southeast IL this evening. Isolated to
scattered showers and isolated thunderstorms possible into mid
morning over central IL, then a lull late morning and mid day,
before more isolated to scattered convection develops along and
ahead of se moving cold front in east central IL during mid/late
afternoon and moving into southeast IL during this evening. SPC
day1 outlook continues marginal risk of severe storms from
Kankakee to Decatur to Taylorville and East St Louis east from mid
afternoon (after 19Z/2 pm) into mid evening. There is 5% risk of
damaging winds and large hail. Wind shear is 30-35 kts in east
central IL and 25-30 kts in southeast IL, while MLCAPEs peak at
1-2k j/kg by late afternoon. Upper level ridging over IL keeps low
lapse rates and limiting factor for more widespread strong to
severe storms. Much of area should be dry overnight into Saturday
with slight chances of convection Saturday afternoon west of
Springfield and Peoria as warm front lifts back north/ne over
central IL on Saturday.

Very warm and rather humid conditions prevail today and Saturday
with highs in the upper 80s to around 90F, with afternoon heat
indicies in the low to mid 90s today and upper 80s and lower 90s
Sat (mid 90s southeast of I-70 Saturday afternoon). A stronger
cold front to move se into nw IL by dawn Sunday and more
widespread convection to spread over central IL during overnight
Sat night into Sunday morning. Fairly high chances of showers and
thunderstorms expected to continue Sunday through Monday night
with frontal boundary over central IL and moving into southeast IL
Monday night. Rainfall amounts from overnight Sat night through
Monday of 1-2 inches likely with locally high amounts nw of I-70
possible. Cooler highs Sunday in the mid to upper 70s in central
IL and lower 80s in southeast IL. A few degrees cooler Monday with
highs in the lower to mid 70s in central IL and around 80F in
southeast IL.

Larger model spread during middle and later part of next week and
stayed close to model blend with generally dry conditions Tue thru
Friday and highs in the 70s with lows in the low to mid 50s
Tue night thru Thu night.

07
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&&

.AVIATION...  (For the 06z TAFs through 06z Friday Night)
Issued at 1153 PM CDT Thu Sep 19 2024

Scattered thunderstorms have developed across portions of central
and southwest Iowa this evening, but has been very isolated so far
further east. Latest guidance has backed off on storms moving
into central Illinois late tonight into Friday morning, but a few
weakening showers may still reach this far east. Have removed the
tempo for precip owing to the lower confidence in showers/storms
reaching central Illinois but maintain a VCSH mention for some
isolated activity. Otherwise, expect south winds overnight to veer
to the SSW Friday ahead of an approaching cold front, then to the
NW Friday afternoon and evening behind the front. Winds will
continue to veer to the N/NE Friday evening as high pressure
builds across the region.

Deubelbeiss

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$