Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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400 FXUS63 KILX 211100 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 600 AM CDT Sat Sep 21 2024 .KEY MESSAGES... - Patchy dense fog east of I-55 early this morning will lift by mid morning. - One more hot day lies ahead for central and southeast IL with highs in the upper 80s and lower 90s, as more humid conditions return this afternoon as a warm front lifts back north. - Isolated showers and thunderstorms are possible this afternoon and evening. Greater rain chances materialize later tonight through Monday evening with showers and chance of thunderstorms. There is a 50-70% chance of 1-2 inches of rain across central Illinois during that time period, with 2-3 inches possible in southeast IL. && .DISCUSSION... Issued at 345 AM CDT Sat Sep 21 2024 Areas of fog had developed past few hours east of I-55 with patchy dense fog from Champaign to Decatur to Taylorville east where more moist air present with low to mid 60s dewpoints and very light to calm winds. Some cirrus clouds arriving from the west has been keeping the dense fog from getting too widespread while less high clouds further east over Indiana to allow more widespread dense fog formation and they have a dense fog advisory until 8 am cdt. Have increased fog wording in eastern IL until 9 am, and will continue to monitor dense fog coverage and dense fog advisory possibility early this morning. A special weather statement will be issued for the patchy dense fog in eastern IL early this morning with visibilities restricted to a quarter mile at times. A frontal boundary over southeast IL and into sw IL, will lift back northeast across central IL during this afternoon. Dewpoints to increase back up into the upper 60s and lower 70s while highs reach the upper 80s and lower 90s, with afternoon heat indices peaking back in the 90s. Limited forcing today, but MLCAPES rising to 2k j/kg over western/sw CWA by mid/late afternoon with wind shear values of 20-30 kts could support a few strong storms western and sw CWA from mid afternoon into early evening for hail and gusty winds. SPC day1 outlook officially keeps marginal risk nw of CWA over much of Iowa, nw MO and central/western WI closer to a cold front. This cold front progged by CAMs to track se into nw IL late tonight and moving into central IL during Sunday afternoon. This system has stronger forcing and will produce more widespread showers and a chance of thunderstorms arriving late tonight into Sunday. SPC day2 outlook has marginal risk of severe storms sw of St Louis over central/southern MO. Cooler highs Sunday in the mid to upper 70s central IL and around 80F in southeast IL. Frontal boundary will be near southeast IL Sunday night and Monday as another system moves along it and likely brings another round of showers and a few thunderstorms with the heavier rains focused in southeast IL during that time frame. SPC day3 has marginal risk of severe storms over far southern IL from Carbondale to Evansville south on Mon/Mon night. Precipitatable water values of 1.5-2 inches are expected Sunday into Monday so heavier rain showers are possible at times. Between 1-2 inches of rainfall expected over CWA Sunday through Monday night with 2-3 inches possible in southeast IL where rain likely linger into Tue morning. Even cooler Monday with highs in the lower 70s over much of central IL with mid to upper 70s in southeast IL. Models diverge with handling upper level pattern during mid/late week so stayed close to model blend with this forecast package. Generally dry conditions forecast for Tue night through Thu with below normal temperatures with highs in the low to mid 70s and lows in the low to mid 50s from Tue night through rest of the week. There is potential for tropical system to move northward over the Gulf of Mexico and into the central Gulf coast or southeast States late next week. Consensus of models keep its moisture south and southeast of central and southeast IL. Highs get closer to normal for late September in the upper 70s on Friday and next Saturday. 07 && .AVIATION... (For the 12z TAFs through 12z Sunday Morning) Issued at 600 AM CDT Sat Sep 21 2024 Patchy fog lingering at KDEC will see tempo IFR/LIFR conditions until around 13-14z. After that, scattered mid level clouds will dominate the area into this evening. Calm winds early this morning will increase from the southeast this morning, and south to southwest this afternoon up to 10 kt. A broken line of thunderstorms is forecast to develop over west central IL this afternoon, with these storms possibly impacting KPIA-KSPI before fading, so icluded a PROB30 group there. Late tonight a more widespread area of showers will move in from the west. Some thunder could accompany this but confidence impacting a terminal is too low to include in TAFs. 25 && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$