Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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283 FXUS63 KILX 031915 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 215 PM CDT Wed Jul 3 2024 .KEY MESSAGES... - Scattered showers and storms are possible (30-50 percent) mainly south of I-70 late this afternoon into the evening. A few storms could be strong to severe with damaging wind gusts the primary hazard. - A couple rounds of showers and storms are expected Thursday; one during the morning and a second during the late evening and overnight. There is increasing confidence in a relative lull in precip coverage during the late afternoon and evening. && .DISCUSSION... Issued at 209 PM CDT Wed Jul 3 2024 This afternoon, synoptic cold front is located roughly near the I-55 corridor, while effective front from earlier convection just barely clips the southeastern forecast area near Lawrenceville. Temps jump from the low 80s north of the effective boundary to around 90F south. Anticipate this to be the main focus of convection as we head into the mid to late afternoon hours. Latest RAP suggests around 1500J/kg or higher MLCAPE is in place on the warm side of the boundary, but deep layer shear is marginal/sub- marginal around 20-30kt. Storms should begin to increase in coverage in this vicinity by late afternoon or early evening, and a few could be strong to marginally severe. Latest HRRR keeps this activity a county or two south of the forecast area which lines up well with current location of the front. Overnight into Thursday morning, a pair of shortwave troughs will move across central Illinois resulting in an increase in showers and a few storms. Weakening surface front will likely stay stalled across portions of southern Illinois with weak/negligible instability in place north of the front across central Illinois which will keep the threat for severe storms out of the local area. After the shortwave exits central Illinois early Thursday afternoon, there is growing confidence in a relative lull in precip later Thursday afternoon and at least early evening before a stronger shortwave digs across the Upper Midwest later Thursday evening into Friday. Despite passage of the weaker shortwave midday Thursday, mid level height falls will persist across central Illinois through the day in advance of the next deeper wave, contributing to at least some spotty convection during the afternoon/early evening, but coverage should be fairly isolated at this point, and should allow many locales to kick off their Independence Day celebrations. By mid to late evening, moderate instability (MUCAPE 1000-1500 J/kg) begins to lift back north into portions of central Illinois coinciding with the arrival of the deeper wave / closed 500mb low into the Midwest. Storm coverage will increase in response. Unfavorable diurnal timing should keep the severe threat low Thursday night into Friday morning, but a few stronger storms are possible, especially west of I-55, with seasonably strong deep layer shear overspreading central Illinois. As upper wave begins to depart the region Friday, strong cold air advection will overspread central Illinois in its wake and scour out some of the low level moisture. There will be a brief respite from the precip chances once this occurs and will persist into Friday. Temps will be lower, too, with afternoon highs generally in the upper 70s to lower 80s Friday and Saturday. Surface ridge axis will shift across the area Saturday afternoon with return flow overspreading the area Sunday. Heat and humidity will begin to creep back up in response and broad upper troughing over the Great Plains will be in place with several shortwaves ejecting across the region Sunday through the first half of next week bringing additional chances for showers and storms. Deubelbeiss && .AVIATION... (For the 18z TAFs through 18z Thursday Afternoon) Issued at 1204 PM CDT Wed Jul 3 2024 A slow moving cold front will settle south of I-70 and serve as the main focus for showers and thunderstorms the rest of today. Some patchy lingering MVFR ceilings in place now will scatter back to VFR over the next hour or so and remain VFR through the rest of today and tonight. The front will lift back north slightly late tonight into Thursday morning as an upper level disturbance moves across the region. Showers and MVFR ceilings will spread back north as well, reaching the I-72 corridor mid to late Thursday morning. Deubelbeiss && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$