Isolated Storms, Cooler Temperatures: Activity picks up through Friday

Storm activity is expected to increase as we approach the middle portion of the week, but not too much

  • You’ll notice today will feel a little less humid and a little cooler from yesterday, where we had dew points reach 70° by 6 pm!
  • The ridge that was supporting our summer-like conditions is already breaking down, and an uptick in storm activity will be noted with its departure

  • Temperatures will be about 10 degrees below normal in Rapid city, with other areas experiencing the same ratio
  • Areas like Deadwood and Hill City will see very pleasant temperatures in the lowers 70s with low relative humidity

  • This is thanks to a cold front that is making its way through our area, it was responsible for a few showers this morning in Northeastern Wyoming
  • If you look at the dew point map, you can see the “dry” line between moisture rich air and relatively drier air. This is where I believe isolated thunderstorm initiation is likely this afternoon and evening

  • Forecast Guidance has a few afternoon storms possibly popping up in the Black hills, and near the Newcastle, WY area.
  • A few of those could be on the stronger side, but isolated at best.

  • Overnight I could see a few more stronger storms popping up, particularly south of I-90 and along the Nebraska/South Dakota Border
  • This will be mostly determined by our cold front and where it decides to unpack for the evening, possibly making camp for the evening right through Fall River County into Oglala Lakota and Bennett County

  • I’m more a believer in Wednesday and Thursday’s storm potential, given much higher levels of Convective Available Potential Energy (basically heat, thunderstorm gasoline)
  • The good news is the upper level dynamics will be weaker even with the extra fuel.

  • THIS is why the jet stream being present was such a big deal over the last couple of months, because normally we would be talking about a sheared environment, and a more widespread concern for strong to severe weather.
  • We could have a few stronger storms over the next couple of days, but my level of concern is much lower given our relatively stable upper level dynamics. (bye bye jet stream!)
  • We’ll have a pretty close brush on Thursday evening, however, so we’ll need to keep an eye out for that. Otherwise, a good rumbler or two is manageable given what we’ve been through this Summer

The gulf of Alaska has been playing havoc with our weather system this Spring and Summer. Warmer than normal sea surface temperatures can pump more moisture into the atmosphere and really throw a monkey wrench into normal patterns. When Alaska is cooler, we’re generally warmer and vice versa. Alaska has been baking in an oven virtually all summer and and is only now seeing some cooler than normal temperatures on Monday. We’ll see what dynamics are at play as we approach the Fall season. Want to know the forecast for Rapid city? Call your friend in Fairbanks. Be safe out there! – Brant

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