Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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817 FXUS63 KILX 241714 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 1214 PM CDT Mon Jun 24 2024 .KEY MESSAGES... - Hot weather will briefly return on Tuesday when afternoon heat index readings exceed 100 degrees. - Thunderstorm chances come back into the picture on Tuesday as well...with the latest guidance suggesting a Slight Risk (15-30% chance) for severe weather along and north of the I-72 corridor. - Cooler conditions are on tap Wednesday through Sunday as temperatures return to more seasonable values in the 80s. && .UPDATE... Issued at 1021 AM CDT Mon Jun 24 2024 Surface high pressure centered over eastern IL/western IN will get shunted further east today as an upper wave sends a cold front through the Midwest states early this week. Temperatures are on track to return back into the upper 80s to low 90s today as dewpoints steadily climb. Heat indices will be similar to air temperature readings this afternoon, but will jump back into the low to mid 100s by Tuesday as highs approach the middle 90s with dewpoints in the low 70s. A couple rounds of showers and storms will be seen at times through midweek with the highest probabilities being on Tuesday as the front nears. There is some uncertainty on how convection may pan out Tuesday morning with a leftover MCS possibly working through the area. Precipitation chances become more likely by later Tuesday afternoon/night when the LLJ interacts with a remnant outflow boundary. 12Z guidance is starting to trickle in and should provide some clarity on evolution of convective activity, especially on Tuesday morning. NMA && .SHORT TERM...(Today through Tuesday) Issued at 350 AM CDT Mon Jun 24 2024 A warm front currently extending from the western Dakotas to the Ozarks is serving as the focus for scattered convection across western Iowa/northwestern Missouri early this morning. This activity is gradually shifting to the S/SE, but will dissipate after sunrise as the nocturnal LLJ weakens. While CAMs show the precip remaining west of the KILX CWA, will need to keep an eye on the far western counties later this morning as an isolated shower is not completely out of the question. The warm front will lift N/NE through the area today...allowing winds to gradually veer from southeasterly to southerly as the day progresses. This will help gradually bring slightly warmer/more humid air back into central Illinois. Resulting afternoon high temperatures will climb into the upper 80s to around 90 degrees. A vigorous short-wave trough evident on 08z/3am water vapor imagery over Saskatchewan/Montana will track eastward today, interacting with the advancing warm front to trigger several clusters of thunderstorms across Minnesota/northern Iowa later this afternoon. These storms will track E/SE across Wisconsin and Michigan overnight into Tuesday morning. While a few models show storms potentially spreading/developing as far south as the far NE CWA late tonight, the bulk of the significant convection will remain well to the north. Have included low chance PoPs (20-30%) along/north of the I-74 corridor well after midnight, but think most of the area will remain dry. Once the Wisconsin/Michigan storm cluster passes to the N/NE, an accompanying outflow boundary will sink southward into Illinois Tuesday morning. Exactly how far south the boundary drops before becoming stationary is still in question: however, it is becoming increasingly likely that this boundary will serve as the focus for scattered thunderstorm development. Based on initial thoughts on boundary location, have included high chance PoPs (40-50%) along/north of a Macomb to Bloomington line on Tuesday. The environment to the south of the outflow boundary will become strongly unstable with HREF ensemble mean SBCAPEs of 2500-3500J/kg, but weakly sheared with 0-6km bulk shear of only around 20kt. Any storms that develop will have plenty of fuel to tap into, but not much shear for organization this far south. Think the main risk with storms along/south of the outflow during the day Tuesday will be scattered large hail/damaging wind gusts due to vigorous updrafts and sufficient dry air below cloud level. A cold front will drop southward into central Illinois Tuesday night, bringing another round of thunderstorms. The exact areal coverage and severe potential is still somewhat uncertain and will be highly dependent upon convective evolution earlier in the day. Stay tuned for later forecasts for more details. Barnes .LONG TERM...(Wednesday through Sunday) Issued at 350 AM CDT Mon Jun 24 2024 The cold front will settle southward into the Ohio River Valley on Wednesday, allowing a cooler/drier airmass to filter into central Illinois. With zonal to weakly NW flow expected through the remainder of the extended, high temperatures will remain in the 80s Wednesday through Sunday. In addition, a second cold front will bring another chance of much-needed rainfall Friday night into Saturday. Barnes && .AVIATION... (For the 18z TAFs through 18z Tuesday Afternoon) Issued at 1213 PM CDT Mon Jun 24 2024 Low pressure will track east across the Upper Midwest and Great Lakes through tomorrow with a trailing cold front sagging towards central Illinois Tuesday morning. Ahead of the low, south winds and VFR conditions are expected to prevail across central Illinois the rest of today and tonight. There remains uncertainty on placement and timing of showers and storms associated with the cold front Tuesday morning, but several models bring precip as far south as the central Illinois terminals and have included a prob30 in the forecast to account for this possibility of storms. Southwest winds will begin gusting to around 20 kt starting mid to late Tuesday morning. Additional storms are likely later in the day Tuesday beyond the current forecast period. Deubelbeiss && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$