Sunrise 5:59 AM   Sunset 7:52 PM Moonrise 12:00 AM   Moonset 7:56 AM

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FXUS63 KILX 271059 AFDILX

Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 559 AM CDT Sat Apr 27 2024

KEY MESSAGES

- Warm, breezy and unsettled weather prevails today through Monday over central and southeast IL, with with a couple rounds of showers and thunderstorms expected. Fair weather briefly returns Tue before more chances of showers and thunderstorms Wed into Friday.

- Isolated strong to possibly severe storms possible from mid afternoon into the evening. Best chance for severe weather will focus in the Illinois River Valley tonight, then again west of the I-55 corridor late Sunday afternoon and Sunday evening.

- South to southwest winds could gust 30 to 40 mph at times today and again on Sunday, with breezy southwest winds prevailing Monday.

DISCUSSION
Issued at 400 AM CDT Sat Apr 27 2024

Predawn surface map shows 995 mb low pressure over southwest MN with its warm front extending through northeast IL. Very isolated showers were in southeast IL from Shelbyville to Danville southeast, while a stronger thunderstorm with pea size hail was lifting ne toward Chicago area. Mild temps were 60-65F over much of central IL with upper 60s to 70F from Clay, Richland and Lawrence counties southward. Moist dewpoints in the upper 50s and lower 60s across CWA Breezy south to SSE winds were 10-20 mph with gusts 20 to 26 mph.

Low pressure forecast to weaken as it lifts northeast of Lake Superior by late this afternoon, and pulling a cold front se into central WI/IA. Main focus for severe convection will be nw of central IL this afternoon and evening. Though there is a slight risk of severe storms from the IL river nw with marginal risk as far se as Shelbyville to Danville line. Diurnal heating of unstable air mass with CAPES elevating to 1300-2500 j/kg this afternoon (highest over western/nw CWA) to develop isolated to scattered thunderstorms during mid and late afternoon and continue this evening. Wind shear is 20-30 kts and strongest over western/nw CWA so this area is more favored for severe storms with hail and damaging winds. Also have a 2% to less than 5% risk of tornadoes from I-55 west. Breezy SSW winds gusting 30-35 mph today to bring warmer highs in the upper 70s to around 80F along with moist dewpoints in the 60s. Convection to gradually weaken overnight as instability wanes.

Another surface low pressure along the southern CO/KS border at sunset today to lift ne along the frontal boundary into central IA by sunset Sunday. More convection to develop by Sunday afternoon though mainly over the IL river valley and west and shift eastward into central and southeast IL during Sunday night as cold front moves east toward western IL by dawn Monday. SPC day2 outlook has slight risk of severe storms west of Peoria and Springfield where 2 to less than 5% chance of tornadoes with marginal risk over rest of IL except far eastern IL. Hail and damaging winds are risks over much of CWA late Sunday afternoon and Sunday evening.
South winds gusting 30-40 mph on Sunday brings another warm day in the lower 80s, with mid 80s near the Wabash river valley.

Cold front moves eastward over IL on Monday likely bringing showers and some thunderstorms, though diminishing pops in western CWA after frontal passage. SPC day3 keeps marginal risk of severe storms Monday well south of IL as instability is much weaker.
Highs Monday in the low to mid 70s with breezy sw winds. Chance of showers and isolated thunderstorms could linger in southeast IL Monday evening, otherwise dry weather returns over area overnight Monday night and Tue. Tue looks like a nice day with mostly sunny skies and highs 75 to 80 with south to sw winds only gusting 20-25 mph by Tue afternoon.

A northern stream storm system off the Pacific Northwest tracks eastward over the northern plains and into western Ontario Tue night into Wed, bringing cold front and next chance of showers and isolated thunderstorms into central IL overnight Tue night and Wed. Still warm on Wed ahead of the front with southerly winds bringing highs in the lower 80s. Some instability returns by Wed afternoon and could be a few stronger storms. Yet another wx system ejects out of the central high plains Wed night and Thu likely bringing another round of showers and possible thunderstorms with highs in the 70s Thu. Shower chances could linger into Friday as temps continue to cool a bit more, with highs in the upper 60s/lower 70s (mid 70s southeast of I-70).

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AVIATION
(For the 12z TAFs through 12z Sunday Morning)
Issued at 550 AM CDT Sat Apr 27 2024

A warm front has lifted northeast of the central IL airports early this morning and central IL to remain in the warm sector through Sunday. Leaned on the HRRR model for convection trends through tonight, which shows isolated to scattered showers and thunderstorms developing from 20-24Z with diurnal heating of unstable air mass. More widespread convecting affecting PIA overnight closer to a frontal boundary nearing nw IL. MVFR ceilings could develop at times today and tonight with the convection.
As for winds, continued LLWS until 13-14Z over central IL with 2k ft SSW winds 40-50 kts. SSW to SW surface winds increase to 16-22 kts with gusts 26-33 kts during mid/late morning and diminish some later today. Expect south to SSE winds 12-16 kts tonight with gusts 20-27 kts this evening.

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ILX WATCHES/WARNINGS/ADVISORIES
None.

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