Chase Day 3: Spearfish, South Dakota

We're in the booming metropolis of Spearfish, South Dakota this morning, where we woke up to a bright and sunny hotel room at 4:30 this morning!

This morning's discussion looks to be the most promising chase day we've seen so far this week. There's a low over SW Nebraska and into NE Colorado that we're watching as a driving force this afternoon. South Dakota and even northeast Wyoming and southeast Montana look to have enough clear skies today to gather some good day time heating.

The jetstreak at 300mb has 60 to 70 knot winds from the west southwest, bringing in some cooling air toward our hotter and relatively drier air. The driving force today that should break the cap and send the storms climbing into the midlevels is a shortwave trough digging in east of the Black Hills this afternoon.

The model sounding for 3 p.m. this afternoon shows good wind turning with height in the low levels, paired with a forecasted CAPE of 2000-2500 j/kg and speed shear of at least 50 knots. There's a strong cap right now that will inhibit any vertical development, but the shortwave should bust through that cap later this afternoon and leave plenty of height for towering cumulus to do their work. There is some helicity in the forecast for the afternoon, so that leaves us with a chance of tornadoes this afternoon and likely some hail.

The forecast models also show the shortwave disintegrating into several small cells this afternoon that look to then organize individually and fire along a NW-SE line right over our heads.

So our call is to stay in this area most of the day, and we plan to kill time this morning by heading to Mount Rushmore and studying the topography of the Black Hills and how they may affect our storm development in this area later this afternoon!


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