192 FXUS63 KILX 271729 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 1229 PM CDT Tue May 27 2025 .KEY MESSAGES... - Occasional showers remain possible through the work week, with the best chance of rain being late Tuesday night into early Wednesday morning (40-60% chance). - A gradual warming trend is expected through early next week. Highs will stay near 70 degrees the next few days, but climb into the 80s this weekend into early next week. && .DISCUSSION... Issued at 227 AM CDT Tue May 27 2025 Satellite imagery reveals expansive mid/high cloud cover across the Midwest early Tues AM. Current analyses (2am/07z) show a sfc frontal boundary was still draped across the far southern US, while a closed upper low had formed over the northern Plains. Closer to home, the regional radar mosaic shows some weak returns to the southwest of Lincoln, but cloud bases are around 10kft and have yet to see any sfc obs reporting rain. Dewpoint depressions remain around 15-20 degF at Jacksonville and Springfield. The local forecast remains light on weather impacts through this week, with the main challenge being the specifics of occasional rain chances. A gradually deepening sfc low is expected to lift from the lower MS Valley today towards the IN/OH border by Tues AM. In previous cycles, the ECMWF (and its associated ensemble) had been an outlier, showing a deeper sfc low tracking closer to the ILX CWA, ultimately resulting in greater precip coverage/amounts today. However, these models have trended towards the rest of the ensemble consensus (slightly weaker low/further SE track), and the latest HREF shows just isolated light rain (15-20%) today into the evening. Another rain chance arrives late tonight into Wed AM, as deterministic models consistently show a shortwave pivoting around the primary upper low, encroaching upon the ILX CWA towards/after midnight Wed AM. The resultant DPVA should be sufficient to kick off some showers/light rain. The activity could linger into the daytime hours on Wed, but should be lifting to the northeast in time. The best chance for precip into the day Wed is near/north of I-74 (40% chance). Will need to keep an eye on the potential for cold air funnels Wed. The latest guidance has the vort max lifting out of our area before peak heating occurs (which would limit funnel potential). Forecast soundings show steep low-level lapse rates, but lackluster mid-level lapse rates. Based on the timing of the vort max the chances of funnels seem fairly low, but then again ILX is the self-appointed 'funnel cloud capital of the world', so I wouldn't rule funnels out. Additional rain chances exist on Thurs, and as discussed in previous discussions the GFS/GEFS remain notable outliers with a higher QPF solution. An ensemble cluster analysis shows that the solution dominated by GEFS members is the only solution with median rainfall amounts over 0.25" on Thurs. All other solutions have median rainfall below 0.10". That wetter solution makes up about 25% of the Grand Ensemble. So there is a 1 in 4 chance that Thurs winds up fairly wet across central IL (with potential for over 0.50" of rain), and a 3 in 4 chance that any precip on Thurs ends up being similar to what is expected today: isolated to scattered coverage and light amounts. That is a challenging scenario to communicate through the gridded forecast. For now, the gridded forecast more closely resembles the drier scenario with just a 20-30% chance of rain during the day Thurs. Some additional low probability precip chances could linger Fri into the weekend, depending on how that upper low evolves, but confidence is low at this range. The expectation of gradually warming temps is unchanged from previous forecasts. The strongest signal for warm temps is by early next week, at which point the ensemble mean shows sfc high pressure to our southeast and sfc low pressure to our northwest, which would set the stage for southerly sfc flow and continued WAA. By that point, ensembles have a 40-70% chance for temps at least +5 degF above normal (normal temps for the first week of June include highs near 80F and lows near 60F). Despite the warmup, machine-learning tools still show little in the way of organized severe storm potential for the ILX CWA through at least early next week. Erwin && .AVIATION... (For the 18z TAFs through 18z Wednesday Afternoon) Issued at 1224 PM CDT Tue May 27 2025 Clouds will thicken and lower tonight ahead of an atmospheric disturbance. Ceilings and visibility will lower to MVFR sometime between 06z-12z as a band of rain pushes across the central IL terminals. Rain will gradually end from west to east on Wednesday, with MVFR ceilings beginning to break up by late in this TAF period. MJA && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$