122 FXUS63 KDVN 282314 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 614 PM CDT Sun Jun 28 2026 .KEY MESSAGES... - A prolonged period of hot and very humid conditions will expand area-wide Monday, highlighted by day-to-day peak heat index values of 100 to 110 and nighttime low temperatures no cooler than the mid 70s. Increasing potential to extend the Extreme Heat Warning through midweek. - Thunderstorm chances will be limited tonight through midweek, with increasing chances Wednesday night onward (including the July 4th weekend), with the resultant cloud cover potentially having an impact on how high of temperatures but at least will remain very humid. && .SHORT TERM /THROUGH WEDNESDAY NIGHT/... Issued at 240 PM CDT Sun Jun 28 2026 After thunderstorms depart the area by sunset, we will settle into a true midsummer hot and very humid pattern. This is characterized by an expansive and slightly retrograding 500 mb high pressure ridge just to our southeast (591+ dm center), and channeled low-level thermal ridge directly over the area (850 mb temps of 21-24C). Confidence is high in convective cloud cover being limited over the area, though there is some model signature for some cirrus Monday afternoon. The setup is also not supportive of storms in the CWA through Wednesday morning, and if they were to occur they would likely only be in the northwest portion of the CWA (near/north and west of Cedar Rapids) and during nighttime hours. In addition, confidence is high in very warm nighttime lows, with NBM membership probabilities over 70 percent of 75+ degree lows for most of the CWA through Wednesday night. So their seems little that would work against the going Extreme Heat Warning, issued especially for persistence, and an increasing likelihood that some or all of the CWA will see it extended through Wednesday. The warm nighttime lows start tonight, thanks to 70-75 degree dew points and a more southerly wind direction. That theme looks to be consistent during the upcoming nights. For dew point adjustments, have capped some of the NBM upper 70s to 80 dew points to more mid 70s, which are more consistent with upstream trusted observations. Also in line with that is the fact we are still a little ahead of the peak evapotranspiration season (mid July into early August). On the note of the winds, these will be breezy again on Monday, with gusts of 20-25 mph, maybe slightly higher at times. While that can nudge heat effects a bit down when near thresholds, we are comfortably into the multi-day extreme heat values (heat index of 105+). So that should only offer a slight reprieve. For Wednesday and even Wednesday night, the chances for thunderstorms continue to ease, with the convective breeding ground likely being the western Corn Belt region to Minnesota, and steering vectors still favoring more of a northeast movement. && .LONG TERM /THURSDAY THROUGH SUNDAY/... Issued at 240 PM CDT Sun Jun 28 2026 For this time period, confidence is high in continued very humid air especially through Saturday. However, convective effects may influence temperatures as the upper pattern flattens a bit over the Upper Midwest and Corn Belt. Using ensemble means and deterministic guidance, the current best convective potential looks to be over the weekend as a short wave trough approaches. That said, predictability at this distance is low, and some noteworthy shifting such as MCS effects prior or a change in trough passage timing certainly can occur. Otherwise, synoptically the pattern of 850 mb temperatures of 20-22C support high temperatures at least in the lower 90s, which would mean heat index values into the 100+ range, and potentially 105-110. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 611 PM CDT Sun Jun 28 2026 Thunderstorms have departed to the east of the region, though in the wake of northern storms, strong southeast winds continue early this evening, along with some MVFR cigs. This period of MVFR cigs and strong winds will lift north of the area by 02-04Z this evening, leaving south winds and mainly VFR conditions into Monday. Through 02Z, expect some gusts to 30-35 kt. While gusts abate after sunset, sustained winds should hold around 10 kt, maybe higher at times. The setup also favors a 35-40 kt low-level jet AOA 1.5 kft, and that is borderline for true LLWS development given those sustained surface winds. If it occurs atop area airports, 03Z-09Z is the most favored time. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...Extreme Heat Warning from noon Monday to 9 PM CDT Tuesday for IAZ040>042-051>054-066. Extreme Heat Warning until 9 PM CDT Tuesday for IAZ063>065-067- 068-076>078-087>089-098-099. IL...Extreme Heat Warning from noon Monday to 9 PM CDT Tuesday for ILZ001-002-007-009-016>018. Extreme Heat Warning until 9 PM CDT Tuesday for ILZ015-024>026- 034-035. MO...Extreme Heat Warning until 9 PM CDT Tuesday for MOZ009-010. && $$ SHORT TERM...Friedlein LONG TERM...Friedlein AVIATION...Ervin