FXUS63 KILX 210655 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 155 AM CDT Sun Jun 21 2026 .KEY MESSAGES... - Widespread rain will occur across central and southeast Illinois today. Amounts of 1 to 2 inches will be common. Isolated higher amounts over 3 inches could result in flash flooding. - There is a Slight Risk (level 2 of 5) for severe weather along and south of a Jacksonville to Danville line from 2 PM to 10 PM today. && .DISCUSSION... Issued at 155 AM CDT Sun Jun 21 2026 The 00z high-resolution guidance indicates dual-threats today consisting of heavy rainfall and a severe weather risk this afternoon and evening. The primary forecast uncertainty revolves around the degree of destabilization following this mornings initial convective activity, and the location of the resulting outflow boundary/effective warm front. High- resolution models show a clear signal that the northern portion of the forecast area will remain overturned and stable. However, near and south of the I-72 corridor, guidance supports stronger destabilization. ...SEVERE RISK TODAY... The RAP and HRRR project MLCAPE values surging over 1000 J/kg late afternoon south of the warm front. This higher-instability reservoir will couple with favorable kinematics, as an upper- level jet streak provides 35 to 45 knots of effective bulk shear. Updraft helicity (UH) swaths show a distinct clustering across the southern half of the forecast area after 19z. This environment favors multi-cell clusters and transient supercells capable of producing damaging downburst winds and large hail. Low-level hodographs curve sufficiently near the surface boundary to support a localized tornado threat, reflected in SPC's 5% tornado risk. The primary forecast solution favors a targeted severe threat area focused along and south of a line from Jacksonville to Lincoln to Danville, peaking between 19z and 03z, before the instability axis is shunted east into Indiana. ...HEAVY RAIN TODAY... Anomalous atmospheric moisture is surging northward into central Illinois early this morning ahead of an approaching shortwave. High-resolution guidance shows precipitable water values climbing into the 2-2.25-inch range, which approaches climatological maximums for late June. This deep tropical moisture will interact with a 40-50 kt low-level jet streak, with its convergent nose aimed at central IL this afternoon. As a result, thunderstorms will become highly efficient rainfall producers. The 00z HREF probability-matched mean (PMM) indicates a widespread swath of 1-3 inches of rain across central and southeast Illinois, with localized totals exceeding 4 inches where storms train over the same areas. Given antecedent saturated soils, this rain will rapidly convert to runoff. The Weather Prediction Center (WPC) maintains a Moderate Risk (level 3 of 4) in the Excessive Rainfall Outlook (ERO) for today. Flash flooding is a primary threat, particularly in urban and low-lying areas. ...NEXT WEEK... Lingering rain showers remain possible over eastern IL into Monday morning as the upper- level trough crosses the region. Cooler, drier air filters in on Monday afternoon on northwest winds, with highs only in the mid-70s. Surface high pressure builds over the Midwest on Tuesday, bringing dry conditions and seasonably mild temperatures with highs in the upper 70s to lower 80s. For the mid-to-late week period, the official forecast relies closely on NBM guidance, though confidence drops due to notable model disagreements. The main forecast periods of precip are associated a frontal passage late Wednesday, and a stronger shortwave projected over the Midwest late Friday into Saturday. Ensemble guidance show a general trend toward rising geopotential heights next weekend, suggesting warming temperatures. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1233 AM CDT Sun Jun 21 2026 A storm system will spread increasingly heavy rain and embedded thunderstorms into the area starting around 13Z and continuing until 23Z-03Z before showers begin to taper off. Conditions should be VFR until 16Z-18Z before cigs and vsbys deteriorate to MVFR. Further decreases in cigs look to take place, with widespread IFR cigs expected by 23Z-02Z. Thunderstorms could be accompanied by IFR conditions as early as 16Z-18Z, as well as gusty and erratic winds. General winds light and variable until around 12Z, then ESE winds increasing to 12-16 kts with gusts 20-25 kts. && .ILX WATCHES/WARNINGS/ADVISORIES... Flood Watch from 7 AM CDT this morning through late tonight for ILZ027>031-036>038-040>057-061>063-066>068-071>073. && $$ KEY MESSAGES...25 DISCUSSION...25 AVIATION...37