Sticky front

29 May 2014

Today’s setup was a substantial change from the previous pattern over the southern states. As the cut-off upper low that had dominated the severe weather for nearly 6 days was pushing off to the far south east, moisture was returning to the northern states including Montana and the Dakotas. We invested a full day making the 1000 mile drive up to South Dakota, leaving us in good position for the next 3 or 4 days of weather. We don't mind the long drives but they do take a toll on the car and the insect population...

Road kill insects

Today would see a cold front slowly moving through this new batch of moisture, being pulled through by a low in southern Canada. Storms were therefore likely to get going, however a ridge over the north east was pushing the jet stream north. This meant the upper air flow would be parallel to the cold front, which in turn meant unidirectional shear. This would make supercells very unlikely, but multicell, pulse mode thunderstorms were on the cards.

We started the day in Rapid City and decided that we’d position a little further to our northwest and headed for Sturgis, where we waited for around an hour as a cumulus field developed around us.  Around 1pm a few cumulus towers started to go up leaving us torn between a few areas that all looked interesting. We started by heading north for what looked to be the most vigorous convection, however it wasn’t long before they started to weaken and the best storms in the area were back near where we’d started. All the initiation was happening along the cold front which was essentially stationary, and with each storm cell being very short lived, the areas of storm activity were somewhat static. In the end we came back around on the storms from the east and moved in reasonably close to the precipitation to get some views of such structure as they had. They had some good striations embedded in the cloud, a decent hail core and lightning, although sadly they struggled to intimidate us!

Multiple cells on the cold front

Unfortunately by the time we came around to deciding to call it a day on the storms had dropped over 3 inches of rain on the shortest route back, so with a bit of a detour to play it safe we made our way back to Rapid City which would be our base for the next day.

Key points:

-          Weak unidirectional shear parallel to the front yielded pulse mode storms, pinned to the cold front.

-          Road network to north east of Rapid City fairly sparse but good visibility.

-          Farm roads were gravel and fairly quick.

SPC Day 1 Weather Outlook as at 06:00UTC (01:00 Central Time the night before)

SPC 01:00UTC day 1 forecast for Thu May 2014

SPC Day 1 Weather Reports for the day.

SPC storm reports for Thu May 2014

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