105 FXUS63 KILX 131702 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 1202 PM CDT Mon Sep 13 2021 .SYNOPSIS... Issued at 311 AM CDT Mon Sep 13 2021 Temperatures remain above average to start the week, with highs in the upper 80s today and Tuesday. A cold front moves into the area Tuesday evening bringing a chance for scattered thunderstorms, some of which could be strong to severe. && .UPDATE... Issued at 1201 PM CDT Mon Sep 13 2021 Going forecast is on track with no significant changes made this morning. Expect winds to continue to increase this afternoon with gusts of 15 to 20 mph most of the afternoon. && .SHORT TERM...(Today and tonight) ISSUED AT 311 AM CDT Mon Sep 13 2021 A stationary front remains draped across northern IL and southern IA as of early Monday morning. Temperatures were in the mid 60s across the area at 3am/08z...a few degrees cooler than last night but still above average. The above average temperatures are set to continue into the work week as central Illinois remains firmly to the south of the stationary boundary in a southwesterly surface flow regime. Overall, a similar conditions to Sunday are expected today, with the primary difference being that the wind speeds/gusts will be lower today than Sunday. The wildfire smoke that dulled sunshine over the weekend should begin to lift north out of the area today. Highs today will once again be in the upper 80s. Tonight, a shortwave lifts across the upper Midwest. The track of this wave is such that as it passes by to the northwest, it will induce weak ascent across the northwest portion of the CWA. However, the expectation is for these areas to remain dry due to dry air in the mid-levels beneath cloud base. By Tuesday morning, the surface low associated with this shortwave will be located in the upper Great Lakes. .LONG TERM...(Tuesday through Sunday) ISSUED AT 311 AM CDT Mon Sep 13 2021 A cold front will extend from the aforementioned surface low into Wisconsin and Iowa on Tuesday morning. In response to the pressure falls, the pressure gradient tightens across the Midwest resulting in breezy southwest winds gusting to 25 mph ahead of the cold front. This front will push into the ILX CWA Tuesday evening, with scattered thunderstorms expected along the front. Moisture advection and pooling along/ahead of the front will result in PWAT values near 2" and dewpoints around 70 degrees. This, in conjunction with fairly steep mid-level lapse rates of about 7 degC/km, will lead to the development of robust instability Tuesday afternoon, with forecast soundings indicating upwards of 3000 J/kg of MLCAPE. The latest high-res guidance suggests there could be a subtle wind shift/convergent zone out ahead of the actual cold front, which could act to initiate thunderstorms in central IL by around 00z Wednesday. That would allow storms to tap into the more robust instability than if they did not develop until the overnight hours. There is still uncertainty as to the timing of these features, and some guidance maintains that the front/storms will not move into the area until well after sundown, but the trend has been towards earlier arrival times. 30-40 knots of deep layer shear is expected to develop, but the better flow may lag behind the front which would limit the severe potential somewhat. Nonetheless, the potential exists for severe storms Tuesday evening with damaging winds as the primary hazard, and large hail also possible. On Wednesday, the front lingers in the southeastern half of the CWA, keeping precip chances in the forecast. The post-frontal air mass will provide a short-lived return to seasonable temperatures with highs near 80 on Wednesday. Temperatures rebound quickly as ridging builds over the eastern half of the CONUS late in the week. Southerly flow will reestablish across the local area and boost high temperatures back above average, into the upper 80s by Friday and remaining there into the weekend. There doesn't appear to be much in the way of widespread precip chances after the mid- week cold front, but the evolution of Tropical Storm Nicholas bears monitoring. If moisture from the system streams northward late in the week it could result in isolated showers/light rain for the eastern portions of the CWA on Friday/Saturday. && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 549 AM CDT Mon Sep 13 2021 VFR conditions and southwesterly winds prevail through the period. Occasional southwesterly wind gusts of 18-20 knots are possible in the afternoon, then again after about 05z Wednesday. Scattered high clouds are filtering through the northern terminals this morning, with additional high clouds expected to move in from the west during the day. A few diurnal cumulus are possible in the afternoon, with the NAM CU rule suggesting CU development will only extend as far north as KSPI/KDEC. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Deubelbeiss SYNOPSIS...Erwin SHORT TERM...Erwin LONG TERM...Erwin AVIATION...Erwin