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Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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731 FXUS63 KILX 130804 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 304 AM CDT Tue Aug 13 2024 .KEY MESSAGES... - Severe thunderstorms are possible Thursday evening as a cold front pushes into the area. - Mild and dry conditions will return to central Illinois by the weekend into early next week. && .SHORT TERM...(Today through Wednesday) Issued at 304 AM CDT Tue Aug 13 2024 High pressure anchored from the Upper Midwest E/SE into the Appalachians will continue to be the dominant weather feature across central Illinois today. The end result will be a partly sunny and mild day with highs in the upper 70s/lower 80s. As the high shifts further eastward, the prevailing baroclinic zone currently extending from the lee of the Rockies into the Southern Plains will begin to lift northward tonight. 00z Aug 13 models agree that convection associated with the nocturnal low-level jet will develop across Kansas into Missouri and will remain W/SW of the KILX CWA through dawn Wednesday. This activity will gradually shift eastward Wednesday morning: however, as the jet weakens and the precip enters a drier/more subsident environment east of the Mississippi River, it will dissipate in intensity and areal coverage. Have added low chance PoPs (20-30%) along/southwest of a Galesburg...to Taylorville...to Flora line Wednesday morning as the showers approach. The slowly advancing warm front will likely extend from southwest Iowa into the Ozarks by Wednesday evening. Given the nearing front and increasing boundary layer moisture, have spread low chance PoPs as far east as I-55 Wednesday afternoon: however, think most locations will remain dry. As the front moves further eastward and the nocturnal low-level jet strengthens, convection will blossom across Iowa/Missouri/western Illinois by late evening...then will spill into much of central Illinois overnight. Based on model consensus, have added likely to categorical PoPs along/northwest of a Shelbyville to Danville line after midnight. Any storms that occur will be elevated in nature and will pose minimal severe weather risk. Gusty winds, small hail, and locally heavy downpours will be possible with the strongest cells. Barnes .LONG TERM...(Thursday through Monday) Issued at 304 AM CDT Tue Aug 13 2024 Showers/storms will be ongoing along/north of I-70 Thursday morning...with the activity quickly shifting into Indiana and dissipating toward midday. A lull in precip chances will then occur for much of the afternoon until an approaching cold front activates toward sunset. As boundary layer flow veers from SE to S/SW, higher dewpoint air will return...leading to a highly unstable environment with SBCAPEs exceeding 3000J/kg. At the same time, a modest increase in deep-layer shear will set the stage for strong to potentially severe thunderstorms along the cold front by evening. 00z Aug 13 GEFS shows a 10-20% chance of SBCAPEs exceeding 500J/kg and bulk shear increasing to greater than 40kt. At this time, think the primary risks from the storms will be pockets of damaging wind gusts around 60mph and hail larger than quarters between 5pm and midnight. 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 mostly 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 06z TAFs through 06z Tuesday Night) Issued at 1143 PM CDT Mon Aug 12 2024 Rain showers have shifted east of all our terminal sites, leaving variable cloud cover across central IL. Clearing has developed north of I-74 from PIA to BMI to CMI. HRRR/HREF output continue to advertise a return of clouds from the west along I-74, but light fog will become increasingly possible the longer that clearing remains across that area. Some MVFR and IFR ceilings are not far off to the west and I would not be surprised to see PIA and/or SPI have an MVFR ceiling develop later tonight. Actually seeing IFR cig and vis forecast by several CAMs in SPI later tonight. Since fog potential continues for the other terminals, we continued with MVFR vis later tonight for all but SPI, where IFR vis was forecast. Clearing is expected during the morning tomorrow, but did not jump on that just yet with the expansive cloud cover upstream. Winds will remain light and variable under the weak pressure gradient. Shimon && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$