Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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066 FXUS63 KILX 251748 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 1248 PM CDT Tue Jun 25 2024 .KEY MESSAGES... - A Heat Advisory remains in effect south of I-70 today as afternoon heat index readings peak at 100-105 degrees. - Severe thunderstorms are possible across all of central and southeast Illinois today. The primary time frame will be afternoon and evening north of I-70...and evening into the overnight hours to the south. && .SHORT TERM...(Today through Wednesday) Issued at 355 AM CDT Tue Jun 25 2024 08z/3am regional radar mosaic shows a severe MCS tracking E/SE across central Wisconsin into western Michigan. Based on radar trends and consistent solutions from the HRRR/WRF-ARW, this system will remain well N/NE of the KILX CWA early this morning. Further south, a couple clusters of thunderstorms formed along and old outflow boundary across northeast Illinois late last evening. One cell has dropped S/SE into Iroquois County and will likely push into northern Vermilion County over the next hour. Gusty winds and large hail will be possible with this storm before it tracks into Indiana and dissipates before sunrise. Most CAMs suggest scattered convection will develop along the trailing outflow boundary left behind by the Wisconsin MCS later this morning. This should generally occur along/north of I-80...with the storms gradually sinking southward into the northern KILX CWA by mid-morning. As the atmosphere destabilizes, some of these cells may pose a severe risk toward midday into the early afternoon north of the I-72 corridor: however, am not expecting widespread severe. A more significant risk for strong to severe storms will materialize late this afternoon into this evening as a cold front dropping southward from the Northern Plains interacts with a moderately unstable, but weakly sheared environment. 00z HREF ensemble mean SBCAPEs are not quite as impressive as in previous runs, with values of 1500-2500J/kg across central Illinois. Meanwhile deep-layer wind shear remains paltry as evidenced by NAM 0-6km bulk shear of only around 20kt. Stronger instability/shear appear to be focused further W/NW across central/southern Iowa into far northern Missouri, where a greater potential for vigorous updrafts and storm organization warrants a risk for large hail and even a few tornadoes. Further east into central Illinois, the weaker shear will likely mean loosely organized thunderstorm cells primarily capable of scattered damaging wind gusts and localized downpours. May see some large hail as well, but with lower SBCAPE values and the freezing level near 15,000ft, think the potential for hail larger than golf balls is slim. Based on model consensus, have kept PoPs in the chance category through the day, then have ramped up to likely to categorical (70-80%) this evening as areal coverage increases in advance of the cold front. The storms will drop southward overnight into Wednesday morning...with rain chances coming to an end from north to south during the day Wednesday. Storm total rainfall will be highly variable across the area, but will generally range from 0.50 to 1.00. Some spots will exceed 1 inch, particularly along/west of I-55 where storms may be most concentrated tonight. Barnes .LONG TERM...(Thursday through Monday) Issued at 355 AM CDT Tue Jun 25 2024 Once the front passes, high pressure will build into the Great Lakes and bring central Illinois a period of comfortable weather. Low temperatures Wednesday night will drop into the lower to middle 60s while highs on Thursday remain in the lower to middle 80s. Another cold front will approach from the northwest late in the week, bringing rain chances back into the picture...particularly Friday afternoon through Saturday morning. Temperatures will briefly climb back into the upper 80s/lower 90s ahead of the front on Saturday, but will once again drop back into the lower to middle 80s after FROPA Sunday/Monday. Barnes && .AVIATION... (For the 18z TAFs through 18z Wednesday Afternoon) Issued at 1248 PM CDT Tue Jun 25 2024 Thunderstorms are ongoing over a large portion of central Illinois early this afternoon, bringing occasional drops in visbys/ceilings and sporadic wind gusts to SPI, DEC, and CMI. Another round of storms is possible later this evening, though confidence remains low on exact placement, timing, and duration. A cold front will drop south through the area on Wednesday, shifting winds from the west- southwest to north-northwest. MVFR ceilings are possible (40-60% chance) between 09-12Z, sticking around through most of Wednesday morning. NMA && .ILX WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 8 PM CDT this evening for ILZ066>068-071>073. && $$