Today has been about the same as the past two days. A south breeze is reinforcing the warm humid air in eastern KELOLAND, and the dry heat in the central and west. Wildfire smoke has thinned quite a bit from recent days. Temperatures have reached the 80s and 90s, setting the stage for thunderstorms as cooler air sweeps in from the west.
The Storm Prediction Center has rated western and central South Dakota as a slight risk for severe weather. Thunderstorms are firing up this afternoon, and we expect them to form a line that will move through western South Dakota this afternoon and evening, moving into Pierre around sunset or a little after. Hail and wind will be the primary threats.
Overnight, thunderstorms will move toward the James River overnight, and they could be strong, and may produce some heavy rainfall. Overnight lows will be in the 60s to low 70s – but Rapid City, behind the cold front, will probably drop back into the 50s.
Tomorrow will be cloudy with widespread thunderstorms. Brisk south winds will only be able to warm central and eastern KELOLAND to the low to mid 80s (and only the low 70s in Rapid City.
As far as the severe threat goes, much of KELOLAND east of the James River (including Sioux Falls) will be in a slight risk for severe weather Friday afternoon and night. Large hail, damaging winds, and isolated thunderstorms will be possible. There will also be some beneficial, if not excessive, rainfall from this system. Forecast models are outputting a broad ½” to 1” through Saturday morning. Extreme rainfall (over 2”) is possible, with the bullseye of that in far NE South Dakota.
Timing of the next round of thunderstorms would keep Saturday dry and cool and breezy, with temperatures in the upper 70s to around 80 degrees.
Sunday brings the potential for scattered thunderstorms – late in the day – as slightly warmer air returns to the region, highs in the low to mid 80s. If you have outdoor plans for Sunday, don’t change them. The best chance of thunderstorms – with limited moisture – will be late in the day. The early part of the day will be sunny.
Given the every-other-day thunderstorm pattern that seems to be setting up, we’ll keep Monday in the mid 80s with mostly sunny skies. That would give us isolated thunderstorms on Tuesday with highs in the mid to upper 80s.
The rest of next week looks cool, as below normal temperatures look to take over the second half of next week through the final days of August.