ProbSevere V3 and Splitting Cells over Montana on 10 Jun 2021

Posted in ProbSevere on by Kevin Thiel.

Our team was assigned to the Glasgow, MT WFO on this day.  The area was primed for explosive convective development, with the “triple point” over the CWA.  The dryline, cold front, and warm front were all apparent in radar imagery prior to convective initiation.

Radar reflectivity from KGGW from 1833-1920 UTC 10 Jun 2021. Note how the boundaries are readily apparent with the radar still in Clear-Air mode.

Although the main “action” fired east of the dryline, in NE Montana and eventually NW North Dakota (see SPC Storm Reports), a few robust storms also developed in the highly-sheared environment over the SE corner of the Great Falls, MT CWA. 

1200 UTC sounding from Great Falls, MT (KTFX). Note the steep lapse rates aloft and particularly the 67 knots of Surface-6 km shear.

A splitting cell was noted in radar imagery from KBLX (Billings, MT).  There was an mPing report of one-inch hail with this cluster of storms.

Radar reflectivity loop from KBLX from 2105-2133 UTC 10 Jun 2021. The split can clearly be seen by 2115 UTC.
MRMS Reflectivity At Lowest Altitude and ProbSevere3 time-series for the left-splitting (left) and right-splitting (right) storms. Within a couple of minutes of the split, ProbSevere3 correctly predicted that the right storm would become dominant and generally maintain its intensity. Meanwhile, the left-splitter would quickly weaken.

Suppose you were thrown into radar duties without time for a full-on environmental analysis.  In an environment conducive to splitting cells, ProbSevere3 can quickly provide guidance allowing the warning forecaster to anticipate which cell will become dominant.

– Professor Frink

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