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Showers and thunderstorms are possible this evening into the overnight. Severe weather is possible over central South Dakota with the primary risk 65 mph wind gusts. Storms are expected to weaken as they move east.

Heat indices climb to 95 to 105 today, mainly south of I-90. Locally higher heat indices are possible along and south of the Highway 20 corridor. A Heat Advisory remains in effect until 8 pm for areas south of I-90 into portions of southern Minnesota.

Showers and thunderstorms are possible again both Wednesday and Thursday afternoon and evening. An isolated storm could be severe.

Discussion

Hot and humid conditions improve behind a cold front that passed through the region this morning. Winds behind the front are out of the north and a bit breezy with gusts to around 20 mph. Dewpoints are falling rapidly to the low 60s. However, highs are still expected to climb into the 90s and low 100s, and so Heat Index values will be 100 to 104 degrees F. A Heat Advisory remains in effect for areas along and south of I-90 until 8 pm CDT.

In addition to heat there is a Marginal risk (level 1 of 5) for strong to severe thunderstorms. A shallow wave will pass through the region, triggering storms over western South Dakota late this afternoon into the early evening. These will travel east and begin to impact areas of central South Dakota some time after 9 pm CDT. As storms approach they will be encountering an increasingly stable environment. While severe weather cannot be ruled out, the area most likely to see any stronger storms will be west of the James River. The main risk with storms will be damaging wind gusts of 65 mph. Storm intensity will weaken as they continue east becoming scattered rain showers and weak thunderstorms. Rain accumulation will be light, a trace to a hundredth for most of the forecast area. West of the James River may see up to a tenth of an inch. Showers may linger into the morning commute Tuesday, but impacts should be minimal.

Tuesday surface high pressure settles over central South Dakota turning winds to the southeast. Highs will be cooler, in the 80s east of Highway 81, and in the low 90s to the west. Dew points will climb into the mid 60s to low 70s and will result in muggy conditions once again. However, Heat Index values will remain below critical. Still, it's important to maintain proper hydration and to take breaks out of the heat. Wednesday will be another quiet day with highs in the 90s.

Wednesday night a short wave will work through the upper ridge bringing chances for showers and thunderstorms. There is a very large difference in mid-range guidance on convective parameters, therefore the severity of the storms is uncertain. Thursday isolated to scattered light showers will continue periodically through the day. Thursday afternoon a stronger upper wave moves into the region. This will result in another round of showers and thunderstorms. Mid-range guidance continues to have a wide range of solutions, and severity of storms is once again in question. Over the coming days the trends will be monitored and updates issued as details become clear.

An upper level ridge will push into the region behind the wave for the weekend. Partly cloudy skies and highs in the 80s to low 90s with dry conditions are expected.

One final note: Smoke from wildfires in the western US and Canada is expected to begin to flow into the region today. This will result in milky looking skies and a decrease in air quality. You may even be able to smell smoke at times depending on how deeply we mix each day. With our current upper level pattern smoke is expected to remain in the forecast through at least the middle of the week. People who are sensitive to air pollutants should use precautions. For the latest on Air Quality please visit AirNow.gov.