Area Forecast Discussion

KEY MESSAGES

- There is a marginal, level 1 out of 5, risk of isolated severe storms along and south of I-80 late this afternoon and evening.

- Rounds of nocturnal and diurnal convection through Monday night will bring a risk of locally heavy rainfall due to weak winds aloft. If storms stall, excessive rainfall is possible.

- Heat and humidity will increase around the middle of next week with temperatures in the 90s and heat indices pushing 100 or higher. The probability of heat headlines for part of next week is currently 30 to 40 percent.

SHORT TERM /THROUGH MONDAY NIGHT/

Issued at 212 PM CDT Sat Jun 6 2026

The diffuse frontal zone remains over the same axis as yesterday, with southeast NE to northeast IL the placement of the main front, but additional convective outflow boundaries found to the south, with the main one found in northern Missouri this afternoon. This diffuse wind field is keeping confidence low on the placement of afternoon storm development, but in general, we prefer this southern boundary to be most at risk for afternoon storms today, and that is currently outlined by SPC's marginal risk area. The one thing we have today in abundance is CAPE. The warm and humid air mass is currently shown to have 2000 to 3500 surface based CAPE on SPC mesoanalysis page, with mixed layer CAPE of 1-2K. This unstable air, combined with weak flow in the mid levels and poor lapse rates should allow for pulse typed convection this afternoon and evening, with initially isolated coverage, possibly upticking to higher end scattered/likely coverage before waning again by mid evening. Another increase is possible towards late evening and overnight as the LLJ begins to impinge into the area, again resulting in a loosely organized zone of showers and storms. While an isolated severe storm is possible, the main threat will be localized torrential rainfall, that could reach 2+" / in one hour at peak intensity. Many locations, like last night, will certainly remain dry tonight.

Sunday morning through Monday, this chaotic pattern will slowly begin to be influenced by a broad upper low lifting northward from the southern Plains. This will lead to an extended period of pops and rain/thunder potential, with a high PWAT air mass in play. While QPF placement is uncertain, as is timing of any period but this is a wet pattern in general, with frequent chances for rainfall that could be heavy at times. PWAT values 1.5 to over 2 inches remain forecast by most models through this period.

LONG TERM /TUESDAY THROUGH FRIDAY/

Issued at 212 PM CDT Sat Jun 6 2026

Tuesday through Thursday, south to south flow returns the area, with very warm air aloft, resulting in hot and humid, but rather windy at times weather. The edge of the heat dome will be where the organized storm complexes are found. Right now the signal for the organized storm complexes is in the northern Plains. However, the models have a growing signal for organized storm development across Iowa Wednesday afternoon that could move into eastern Iowa Wednesday night. This signal will need to be watched to see if it remains consistent into early next week. Pops have now increased to 40 to 70% for Wednesday night. This late week system will have much strong winds aloft, and organized severe weather is more possible in that regime. SPC has begun outlining that system with slight risks areas in Days 4-5 earlier today. Regarding heat, heat indices on Tuesday generally look to be 95 to 100. Heat indices exceeding 100 have a 50 percent probability of occurring Wednesday and Thursday. Currently there is a 30-40 percent probability of heat headlines being needed in the Wednesday/Thursday time frame.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1216 PM CDT Sat Jun 6 2026

Quiet VFR hours will begin the forecast period today, as light winds and partly cloudy skies with bases over 3kft will continue through the afternoon hours. A few isolated thunderstorms may fire in the heat of the afternoon, and if they form they will move slowly, and produce a period of torrential rainfall, gusty winds and small hail. This coverage is limited and unfocused, so I have not placed into any TAF except for a prob30 at Burlington. Otherwise late this evening and overnight, a band of showers ands storms could form over the entire area, and lift northeast by sunrise Sunday. This is not certain, and handled with Pro30 groups at all sites except for DBQ. Some MVFR cigs are expected overnight at times with storms and possibly more consistently at DBQ where a temporary conditions of BKN025 is included for stratocumulus formation late tonight.

Sunday morning through afternoon, additional showers and storms may be forming in the area, but these are not yet included in the TAF.

DVN WATCHES / WARNINGS / ADVISORIES

IA...None. IL...None. MO...None.