


Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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514 FXUS63 KILX 290745 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 245 AM CDT Sun Jun 29 2025 .KEY MESSAGES... - Hot and humid through Monday, with heat indices in the mid 90s. Conditions cool slightly for Tuesday and Wednesday, with highs in the mid 80s and heat indices below 90 degrees. - Isolated to scattered storms are forecast through Monday. Locally heavy rainfall is possible, and there is a marginal risk (level 1 of 5) of severe storms, mainly on Monday. The primary hazard with any severe storms will be strong winds. && .DISCUSSION... Issued at 241 AM CDT Sun Jun 29 2025 *** THROUGH MONDAY *** Early Sun AM, convection was ongoing near a cold front draped across parts of WI/MN. Elsewhere, convergence along the leading edge of the LLJ has led to showers/storms over cntrl MO. A moist airmass remains in place across the region, with sfc Td in the low 70s and PWAT values around 1.5" sampled by the 29.00z KILX sounding (with models suggesting that values approach 2" across southern IL). With highs near 90 today, afternoon heat indicies will once again climb to 95- 100 degF. Over the next 24-36 hours, confidence is low in the convective evolution as the environment remains weakly sheared and several areas of convection are already ongoing. In this type of regime, it`s difficult to put much stock in specific CAM runs. Overall, CAM storm coverage is fairly low, so tried to keep PoPs at 30% or lower through Sun night. Think the most likely time for scattered precip today will be in the afternoon as a weak impulse aloft shifts towards central IL in conjunction with peak diurnal heating. Forecast soundings show mean cloud layer winds of less than 10 kts, and given the high PWATs could see localized heavy rain this afternoon. Similar to previous days in this pattern, an isolated strong wind gust can`t be ruled out. A more focused opportunity for storms is still expected on Monday as the approaching cold front moves across the region, but even for this front, CAM precip coverage appears scattered at best. Felt the NBM PoPs (80-90%) were far too aggressive, and instead went with 60- 70% (and wouldn`t be surprised if these are reduced in later forecast updates). The main upper level trough will be displaced to the north, resulting in unimpressive mid-level lapse rates. There is modest mid-level flow, however, which results in marginal deep layer shear of around 30 kts, perhaps sufficient to offer some convective organization. Moderate instability is expected to develop ahead of the front, particularly into Mon afternoon (2000-3000 J/kg of SBCAPE). PWATs also remain very high, around 2" which is above the 90th percentile for this time of year. The main hazards will be damaging winds (particularly if a more organized convective line forms) and locally heavy rainfall. The front and any associated storms should shift completely SE of the ILX CWA by late Mon eve. *** TUESDAY - SATURDAY *** No significant changes to the forecast for the middle of the week, with a brief cooldown to seasonable temps on track as the post- frontal airmass and sfc high pressure settle into the region. Tues and Wed will feature highs in the mid 80s, lows in the mid 60s, and afternoon heat indices in the mid/upper 80s. Confidence is high that temps will trend warmer late week as an upper ridge builds/shifts to the Midwest. Daily high temps push back to the upper 80s/low 90s Thurs-Sun, with increasing humidity as well. The upper ridge strength doesn`t appear as strong as our heat wave last week, at least, but we`re still on track to see afternoon heat indices in the upper 90s each day. Precip chances have trended a bit lower for the 4th of July, now at 15-20%, rather than 20-30%. This reduction is due to the fact that the upper ridge axis is now progged to be directly over IL on the 4th, which would promote synoptic-scale subsidence and help limit storm chances/coverage. Guidance does have disturbances tracking along the northern periphery of the ridge on the 4th, resulting in better precip chances across the northern Plains/upper Midwest, so we will still need to monitor this pattern for shifts, as it would not take much to shift the precip chances into our area. Even without an obvious lifting mechanism, fcst soundings for the afternoon of the 4th show a well-mixed PBL with uncapped profiles nearing the convective temp, which could support isolated storms (hence the 15-20%). Precip chances increase slightly into the holiday weekend (30% Sat, 40% Sun). Erwin && .AVIATION... (For the 06z TAFs through 06z Sunday Night) Issued at 1155 PM CDT Sat Jun 28 2025 Patchy fog is expected to form late tonight, especially near the I-72 corridor. Introduced a TEMPO for MVFR visibilities at KSPI- KDEC-KCMI from 09-13z. Otherwise a quiet aviation forecast with scattered diurnal cu. Calm to light/variable winds tonight will become south by late morning under 10 kt. 25 && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$