Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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260 FXUS63 KILX 041911 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 211 PM CDT Tue Jun 4 2024 .KEY MESSAGES... - Slight risk (15-39% chance) of excessive rainfall with any thunderstorms that develop along/west of I-57 this afternoon through tonight. - Below normal temperatures will prevail through most of the forecast period. Highs remain mostly in the 70s and overnight lows dip into the 50s Thursday through next Tuesday. && .SHORT TERM...(Tonight through Wednesday) Issued at 211 PM CDT Tue Jun 4 2024 An upper low evident on 1830z/130pm water vapor imagery over northeast Missouri will provide the lift for scattered thunderstorm development this afternoon and evening. Severe weather potential will remain quite low due to meager MLCAPEs presently analyzed at just 1000J/kg and weak 0-6km bulk shear of 25-30kt. Primary risk with any convection that fires will be heavy downpours and localized flash flooding. 12z KILX upper air sounding showed precipitable water of 1.41 and the NAM indicates this value will climb into the 1.75-2.00 range this afternoon, which is close to the 99th percentile for this time of year. Due to ample environmental moisture and the relatively slow storm movement, think pockets of heavy rainfall will occur through this evening. Latest satellite shows the most robust Cu along/southwest of a Peoria to Decatur line, which will be the main area to watch for storm development over the next several hours. Based on satellite/radar trends and latest RAP/HRRR forecast, have ramped PoPs up to likely along/west of I-55 late this afternoon and evening. Once the initial area of convection lifts into northern Illinois, a lull in precip chances will be observed from mid-evening until shortly after midnight when an approaching cold front pushes a broken line of showers/storms into the area overnight into Wednesday morning. Based on the forward speed of the front, have dropped PoPs to slights along/west of the Illinois River by early Wednesday morning...with all rain chances dropped along/west of I-57 by early afternoon. May see a few showers linger near the Indiana border through the afternoon, but the bulk of the rain will be much further east by then. Barnes .LONG TERM...(Thursday through Next Tuesday) Issued at 211 PM CDT Tue Jun 4 2024 A secondary cold front will drop southward into central Illinois Wednesday night, potentially triggering scattered showers. Some of the CAMs show the showers, while others are completely dry...so forecast confidence is low at this point. Have included slight chance PoPs for showers north of a Macomb to Minonk line during the evening, but opted to go dry overnight as daytime instability wanes. Once the front passes, a return to cooler/drier weather is anticipated by the end of the week. The extended forecast will be dominated by deep upper troughing over the Great Lakes and prevailing ridging over the Desert Southwest into the Southern Plains. Central Illinois will remain sandwiched between these two features...leading to deep-layer northwesterly flow and resulting below normal temperatures and precipitation. Will need to keep an eye on nocturnal MCS activity that will develop along the N/NE periphery of the upper ridge Friday night through Sunday night: however, all synoptic models suggest this activity will remain well S/SW of the KILX CWA. The upper trough will likely be re-enforced by additional short-wave energy diving southward out of Canada early next week. If this scenario unfolds as currently thought, may need to add scattered showers to the forecast next Monday afternoon as the trough sharpens. For now will go with a cool/dry forecast with highs mostly in the 70s and overnight lows in the 50s Thursday through next Tuesday. Barnes && .AVIATION... (For the 18z TAFs through 18z Wednesday Afternoon) Issued at 1257 PM CDT Tue Jun 4 2024 The primary aviation forecast challenge will be predicting the areal coverage and timing of convection later today. 1730z/1230pm visible satellite imagery is showing Cu blossoming along/southwest of a KGBG to KDEC line and this will be the area to watch for thunderstorm development over the next 2-4 hours. Most CAMs indicate the highest concentration of storms will be focused along/west of I-55, so have hit the thunder forecast hardest across this area. Based on satellite trends and the latest RAP/HRRR forecast, have mentioned thunder at all sites between 21z and 04z, but have opted to go TEMPO thunder at KPIA/KSPI/KBMI due to higher confidence in greater areal coverage there. Once the late afternoon and early evening convection lifts northward, a lull in precip chances will be observed before an approaching cold front brings a broken line of showers/storms well after midnight. Once the front passes, the showers will come to an end and winds will veer to W/NW by Wednesday morning. MVFR ceilings will be observed at KSPI/KPIA for the next couple of hours before cloud bases diurnally rise to low VFR by around 20z. After that, VFR will generally prevail until after FROPA when models suggest a band of MVFR ceilings will form. Barnes && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$