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Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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230 FXUS63 KILX 141044 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 544 AM CDT Wed Aug 14 2024 .KEY MESSAGES... - Showers and thunderstorms will track across central Illinois early Thursday morning. Severe weather is not expected, although some of the cells may produce small hail and heavy downpours. - Scattered strong to severe thunderstorms will develop along a cold front Thursday evening. Damaging wind gusts of around 60mph and hail larger than quarters will be possible. - Once the cold front passes, mild and dry weather is on tap for the upcoming weekend. && .SHORT TERM...(Today through Thursday) Issued at 337 AM CDT Wed Aug 14 2024 08z/3am surface analysis shows a 1021mb high anchored over the Great Lakes...while a stationary frontal boundary extends from the lee of the Rockies southeastward into the Deep South. A large cluster of thunderstorms has developed north of the boundary on the nose of a 40-50kt 850mb jet streak across Nebraska. These storms will eventually outrun their energy source and will dissipate as they push further eastward toward the drier/subsident environment across Illinois. CAMs continue to suggest a dry morning, followed by perhaps a few showers reaching the Illinois River Valley toward midday. Have included slight chance PoPs along/west of a Galesburg to Springfield line this afternoon accordingly, although it appears most areas will remain dry. After a sunny start to the day, clouds will be on the increase from west to east as the day progresses. High temperatures will be a couple of degrees warmer than yesterday in the middle 80s. As upper ridging builds over the Plains, the frontal boundary will get nudged E/NE later today into tonight. Models depict the nocturnal low-level jet once again strengthening to 40-50kt tonight, but this time orienting from Oklahoma northeastward into Iowa. As such, am expecting thunderstorms to initiate west of the Mississippi River by late evening...with the activity spilling eastward into central Illinois late tonight into Thursday morning. Based on 00z Aug 14 models, have focused likely to categorical PoPs along/west of I-55 after midnight...then further east to the Indiana border Thursday morning. SBCAPEs will be minimal during this time frame, so the storms are expected to be elevated in nature. Given a narrow corridor of MUCAPEs of 1500-2500J/kg, think some of the stronger cells will be capable of producing small hail and locally heavy downpours...although the severe weather risk will remain quite low. The showers/storms will exit into Indiana toward midday, followed by a period of warm and dry conditions for the afternoon. With boundary layer flow veering from SE to S/SW upon passage of the warm front, higher surface dewpoints in the lower to middle 70s will contribute to a strongly unstable environment with SBCAPEs greater than 2500J/kg. In addition, an approaching short-wave trough will create increasing deep-layer shear as depicted by NAM 0-6km bulk shear values exceeding 40kt by evening. While all the ingredients will be in place for widespread severe weather, convergence along the front will not be that strong. As a result, areal coverage of convection along the cold front may be somewhat lacking. Think scattered strong to severe storms will form along the front across eastern Iowa/northern Missouri by late afternoon...then will push eastward into central Illinois during the evening. The primary hazards will be damaging wind gusts of around 60mph and hail larger than quarters between 7pm and 1am. Barnes .LONG TERM...(Friday through Tuesday) Issued at 337 AM CDT Wed Aug 14 2024 As surface low pressure tracks from Iowa into the Great Lakes, it will drag the cold front across central Illinois late Thursday night into Friday. There is still some potential for strong thunderstorms along the front by peak heating Friday: however, latest guidance suggests this may occur a bit further east into Indiana. Have maintained low chance PoPs for thunder during the day Friday until the front passes. After that, a return to mild and dry weather is anticipated Saturday through Tuesday with high temperatures remaining slightly below normal for this time of year in the lower 80s. Barnes && .AVIATION... (For the 12z TAFs through 12z Thursday Morning) Issued at 544 AM CDT Wed Aug 14 2024 Skies will initially be mostly clear early this morning: however, mid/high clouds will steadily increase from west to east as the day progresses with all terminals becoming BKN-OVC during the afternoon. Convection is expected to develop across Iowa and northern Missouri this evening, then track eastward into central Illinois overnight. Exact timing is still somewhat in question: however, confidence is growing that thunderstorms will reach at least the western terminals prior to 12z Thu. As a result, have added predominant thunder and a low VFR ceiling at KPIA after 09z and at KBMI/KSPI after 10z. Further east, opted to not mention thunder at either KDEC or KCMI. Winds will be E/NE at around 5kt early, then will veer to SE and increase to 8-12kt from late morning through the remainder of the 12z TAF period. Barnes && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$