Sunrise 5:59 AM   Sunset 7:52 PM Moonrise 12:00 AM   Moonset 7:55 AM

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FXUS63 KILX 270430 AFDILX

Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 1130 PM CDT Fri Apr 26 2024

KEY MESSAGES

- Warm and unsettled weekend ahead...with a couple rounds of convection expected.

- Best chance for severe weather will focus in the Illinois River Valley Saturday evening...then again west of the I-55 corridor late Sunday afternoon into Sunday evening.

UPDATE
Issued at 808 PM CDT Fri Apr 26 2024

A large area of moderate rain with embedded thunderstorms is spreading northeast across central IL this evening. This is occurring just ahead of a surface warm front, and additional lift provided by a small but impressive 100 kt 300 mb jet streak.
Latest ILX sounding shows the atmosphere has moistened nicely ahead of this wave, as PWATs have risen from 0.80" this morning to 1.23" at 00z. The warm front will lift north of the area later this evening, allowing better instability to spread in (MUCAPEs 500-900 J/kg west of I-55 by midnight). Thus a few stronger storms could develop on the back side of the rain over the western half of the CWA with small hail or an isolated gusty wind report not out of the question. Short range guidance is in good agreement that the back edge of the precipitation will begin to diminish from the southwest around midnight, then exit our eastern CWA by 2-4 am. The moistening airmass will result in an unseasonably warm night with lows in the low to mid 60s.

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SHORT TERM
(Tonight through Saturday)
Issued at 325 PM CDT Fri Apr 26 2024

19z/2pm surface analysis shows a 992mb low over Nebraska with a warm front arcing southeastward into the Ohio River Valley. Much of the KILX CWA remains north of the boundary as evidenced by E/SE winds and temps only in the 50s. Further south closer to the front, SE winds and partial sunshine have boosted readings into the lower 70s along/south of a Flora to Lawrenceville line. After one round of convection this morning that mainly impacted locations along/west of I-55...a second dissipating wave of convection has lifted northeastward out of Missouri this afternoon. Given the stable boundary layer, radar is indicating just light showers between the Illinois River and I-57. This precipitation will continue to diminish over the next few hours, as an overall lull in precip coverage develops across central Illinois. Meanwhile, a third wave of convection currently over the Ozarks will lift into the area later this evening. HRRR/RAP have been consistently tracking showers/storms northeastward...mainly impacting locations east of the Illinois River from mid-evening into the first part of the overnight hours. With NAM MUCAPEs increasing to 1000-1200J/kg as the surface warm front nears, think thunder will become more prevalent. May even see a couple of the stronger cells produce gusty winds and small hail: however, the overall severe risk tonight will remain minimal.

The warm front will lift north of central Illinois on Saturday, resulting in a breezy and much warmer day with afternoon highs soaring into the upper 70s to around 80 degrees. With dewpoints climbing well into the 60s, a moderately unstable environment will develop...with HRRR mean SBCAPEs exceeding 2000J/kg along/west of I-55. Main mitigating factors for severe convection during the day Saturday will be a lack of a forcing mechanism and the overall meager deep-layer shear characterized by 0-6km bulk shear values of just 25-35kt. Am expecting only widely scattered thunderstorms with perhaps one or two cells producing gusty winds/hail. Models have been highlighting areas further northwest across northern Missouri into eastern Iowa for convective development along/ahead of a slowly approaching cold front by late afternoon/evening. Some of this activity will spill into the Illinois River Valley later Saturday evening, bringing a risk for damaging wind gusts, large hail, and isolated tornadoes.

Barnes

LONG TERM
(Sunday through Next Friday)
Issued at 325 PM CDT Fri Apr 26 2024

The most widespread risk for severe weather still appears to be late Sunday afternoon into Sunday evening as the cold front edges eastward toward Illinois. There are still questions concerning the amount of destabilization that will occur within the mostly cloudy and potentially showery airmass ahead of the front: however, upper dynamics and kinematics favor at least a Slight Risk for storms capable of damaging wind gusts/large hail west of the I-55 corridor. Any severe storms that form ahead of the cold front will tend to decrease in intensity further east well after dark, so the risk for severe will decrease rapidly across the E/SE KILX CWA toward midnight.

The cold front will gradually shift eastward through central Illinois on Monday, continuing the chance for showers and thunderstorms. Will need to keep an eye on the far E/SE counties Monday afternoon as a few of the storms could possibly become strong to severe before exiting into Indiana, although the overall risk remains low at this time.

Once the front departs, dry weather will arrive by Tuesday. After that, another cold front will bring scattered showers/thunder Wednesday/Thursday before cooler/drier weather returns by next Friday.

Barnes

AVIATION
(For the 06z TAFs through 06z Saturday Night)
Issued at 1130 PM CDT Fri Apr 26 2024

Scattered TSRA will diminish by 08z over eastern IL, leaving gusty southeast winds and LLWS in place overnight. MVFR ceilings are forecast to develop across all central IL terminals between 12-14z, then scatter out during the afternoon. Isolated to scattered instability TSRA should develop during the late afternoon, and have included PROB30 for a few hours at all sites.
South/southwest winds to gust 20-30 kt through the afternoon then veer south/southeast with reduced speeds during the evening.

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ILX WATCHES/WARNINGS/ADVISORIES
None.

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