


Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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259 FXUS63 KILX 271609 AFDILX Area Forecast Discussion...Updated National Weather Service Lincoln IL 1109 AM CDT Fri Jun 27 2025 .KEY MESSAGES... - Scattered storms are expected this afternoon, primarily east of I-55 (40-50% chance). Additional storms are likely Sunday into Monday (50-80% chance). Isolated strong wind gusts could occur with any of the storms today through Monday. - Hot and humid conditions persist through Monday, with peak heat indices in the mid to upper 90s each day. Temperatures return to seasonable values by the middle of next week, with highs in the mid/upper 80s and lows in the 60s. && .UPDATE... Issued at 1100 AM CDT Fri Jun 27 2025 Continued the heat advisory until 7 pm from Danville to Charleston/Mattoon to Effingham southeast where heat indices peak at 98-104F, highest in Lawrence county where highs reach near 95F. This is the 7th consecutive day of the heat advisory that started this past Saturday. Lawrenceville heat index is currently at 101F and 100F at Mount Carmel airport. As outflow boundary moves into far southeast CWA late this afternoon, will see more convection chances and also some cooling from the convection. Updated forecast for isolated to scattered convection developing sooner se of the IL river and north of I-70 and more cloud cover. An outflow boundary was pushing se toward a Champaign to Shelbyville line at late morning with some convection developing near it. Also a few cells appearing in west central IL near western Morgan and Scott county border. Strongest cell was just north of Paxton over the southern Ford and Iroquois county border and tracking NE. Latest HRRR and HREF members showing scattered convection developing more along and south of I-72 through this afternoon and linger into the evening, with isolated convection north of I-72 and south of Peoria. SB CAPES are 3000-3500 j/kg in eastern IL while MLCape is 1500-2000 j/kg in eastern IL. PW values range from 1.5-1.9 inches and highest over heart of CWA just behind the outflow boundary. SPC day1 outlook has marginal risk of severe storms northeast of Vermilion county for damaging winds but a few cells in eastern IL could get strong into this afternoon with gusty winds and locally heavy rains in tropical airmass similar to past few days. 07 && .DISCUSSION... Issued at 314 AM CDT Fri Jun 27 2025 *** TODAY *** A sfc low was located across western WI early Fri AM (07z/2am), with a cold front extending SW across central IA. A decaying line of storms that pushed into west-central IL late Thurs eve produced an outflow boundary, which has transitioned to stable gravity waves nearing the I-55 corridor as of this writing (07z/2am). In the short term, renewed scattered storm development has occurred from far west central IL and back to the west. This activity should primarily stay west of the IL River into the morning. The outflow boundary and front will be of interest for later storm development this afternoon. Most CAMs seems to initiate storms SE of the front this afternoon, suggesting it is the remnant outflow that kicks off storms. Similar to previous days, the ambient environment will feature moderate-high instability (over 2500 J/kg of CAPE) but weak shear (less than 20 knots). While the threat of organized severe storms is low (less than 5%), it would not be a surprise if a few stronger updrafts produce isolated strong/severe wind gusts today. There is uncertainty as to where exactly the remnant outflow boundary is located this afternoon, with CAMs differing in their placement of the main corridor of scattered storms. 27.00z HREF depicts east of I-55/south of I-72 is the most likely location, with a 30-60% chance for precip across those areas, diminishing quickly to less than 10% further northwest. However, given the weak shear, could see outflow pushing in all directions, kicking off storms further NW than where the initial development occurs (especially if outflows interact with and enhance convergence along the front). Therefore, brought a mention of slgt chnc (15-20%) PoPs as far northwest as near the IL River Valley through late afternoon. Storm coverage should gradually wane into the late evening as diurnal heating is lost. Hot and humid conditions will persist today, with highs in the upper 80s/low 90s (highest east of I-57) and afternoon dewpoints in the mid 70s. A Heat Advisory remains in effect east of I-57 through Fri afternoon. *** THIS WEEKEND INTO NEXT WEEK *** The weak cold front will sag towards SE IL by Sat, and some lingering precip could develop on Sat (20-30%), otherwise mostly dry conditions will prevail. The passage of this `cold` front will offer only modest relief from the heat, primarily in the form of slightly lower dewpoints. High temps are still forecast in the low 90s Sat, but afternoon dewpoints should be in the upper 60s/near 70, resulting in peak heat indices `only` in the mid 90s. Winds appear very light on Saturday though, so despite the modestly lower humidity, it may feel just as bad as previous days that had a breeze. By Sun, the synoptic pattern is characterized by flattened ridging across the southern US and an active jet stream across the northern border. The next best chance of precip after today is late Sun into Mon, as a wave over the upper Midwest pushes a stronger front towards the area, resulting in a 50-60% chnc of precip Sun PM and a 60-80% Mon PM (east of I-55). Ahead of this front, southerly flow reestablishes during the day Sun, which leads to dewpoints bouncing back into the mid 70s and heat indices back in the upper 90s. In terms of severe storm potential with this wave, the setup appears similar to earlier setup: moderate/high instability and weak shear. Into Mon, upper level flow increases as the trough digs closer, but the stronger flow still lags behind the front/precip, which should continue to limit an organized severe threat. Perhaps of greater concern could be localized heavy rains, as ensemble mean PWAT push to 1.75-2" on Sun/Mon, which is above the 90th percentile for this time of year. Forecast soundings also depict a deep warm cloud layer (over 12kft, supportive of efficient rainfall rates). The lack of shear will impact storm longevity, though, and unless a more mature storm complex forms the shorter storm duration (and progress nature of the front) should keep rainfall totals in check. After the front pushes south of the area Mon night, we finally return to more seasonable conditions for the start of July (Tues- Wed), with highs in the mid/upper 80s and lows in the mid 60s. Afternoon dewpoints are also forecast to fall into the mid 60s, which will be a very welcome change after the last week. Mostly dry weather is expected on these days (less than 15% PoPs) owing to the presence of weak sfc high pressure. The dry weather will be relatively short-lived, however, as ens guidance hints at a disturbance over the central Plains/Midwest late in the week. Details are low at this range, but there is at least a chance for precip on 4th of July and into the holiday weekend (30-40%). Erwin && .AVIATION... (For the 12z TAFs through 12z Saturday Morning) Issued at 544 AM CDT Fri Jun 27 2025 VFR conditions are expected for much, if not all, of the period. The exception would be with any TSRA activity this afternoon, or perhaps with patchy fog near the very end of the period (09-12z). Latest models have shifted the TSRA placement a bit south, and the TSRA could stay south of all TAF sites. Maintained a PROB30 of TSRA at the I-72 terminals, but think the chances are lower than previous forecasts. Winds will turn to southwesterly early this morning and stay southwesterly through much of the day, then become light and variable into the night. Erwin && .ILX WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 7 PM CDT this evening for ILZ046-056-057-062- 063-066>068-071>073. && $$