CHICAGO, ILLINOIS — Today marks the last day of below-normal temperatures across the Midwest for a long time, as a powerful upper-level ridge overtakes the region Sunday before becoming parked directly overhead by Monday and persisting through all of next week. Atmospheric heights reaching an exceptional 594 decameters will allow air temperatures to surge dramatically across Illinois, Indiana, and the broader Great Lakes region.
Low-level moisture trapped under the ridge from soil and corn crop evapotranspiration will send dewpoints soaring into the 70s and locally near 80 degrees next week, levels comparable to a rainforest or the Persian Gulf. Above-average soil moisture from a wet spring will make this heat dome significantly worse than typical summer heat events.
594 DM Ridge Parks Overhead Monday Bringing Extreme Heat
The upper-level ridge building into the Midwest is exceptionally strong, with atmospheric heights of 594 decameters forecast to sit directly overhead by Monday. This level of ridge strength is capable of producing and sustaining dangerous heat for an extended period, suppressing any storm development and locking in oppressive conditions through the entire work week.
Dewpoints Near 80 Degrees Create Rainforest Level Humidity
The combination of a wet spring leaving soils saturated and active corn crop evapotranspiration will trap extraordinary moisture under the ridge next week. Dewpoints climbing into the 70s and locally near 80 degrees will make heat index values far exceed actual air temperatures, creating conditions that feel dangerously oppressive even in the shade.
Hot Ridge Suppresses Severe Weather Through the Week
One temporary silver lining of this intense heat dome is that the strong ridge typically prevents fronts and triggers from penetrating the area, meaning severe weather chances will be relatively low through most of next week. Storm chances are not expected to return until later next week when the ridge weakens slightly.
Return of Storms Late Next Week Could Be Explosive
When the ridge finally begins to weaken later next week, thunderstorms returning to the region will have access to the extraordinary moisture that has built up underneath the dome. This combination of extreme instability and deep moisture could make any storm complex that develops late next week particularly intense.
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