Northern Minnesota storms

At the 2021 HWT, one team of forecasters was working in eastern North Dakota and northern Minnesota yesterday. After monitoring a string of very weak-looking storms, a few storms finally tapped into some better deep-layer shear and overcame a capped environment.

One forecaster noted that a storm in Cass County looked severe, and while it was just outside of their county warning area, they would have warned it for 1" hail and 60-mph winds. The storm showed a small hail spike at 21:30 UTC (Figure 1). 

Figure 1: A small storm in Cass County, MN, with a hail spike. 

The team of forecasters also noted how PSv3 seemed to handle the marginally severe nature of this storm and others in the area better than PSv2, with PSv3 exhibiting higher probabilities earlier and maintaining them better than PSv2. 

Figure 2: ProbSevere contour with hover-readout and time series window, and MRMS MergedRef for the storm in Cass County. 

At 21:46, PWv3 was 49% whereas PWv2 was 11%. The MRMS VIL (30.3 kg/m^2), 0-3 km lapse rate (8.1 C/km), GOES intense convection probability (ICP; 24%), and 1-3 km mean wind were the top four contributors to the higher probability of wind for this storm

Further northwest, another storm showed a wind threat. PSv2 and PSv3 were fairly similar for this warned storm, which later produced a 61-mph wind gust near Red Lake. 15 minutes before the wind report, PSv3 achieved 67%, with the VIL, 0-3 km lapse rate, ICP, and 1-3 km mean wind contributing the most to the probability. 

Figure 3: ProbSevere contours, MRMS MergedRef, and official NWS severe weather warnings. 

Forecasters have remarked how they would use the time series feature in the ProbSevere AWIPS plug-in, if available at their offices. They also desire new enhancements, such as meteograms of more predictors and the ability to "dock" the window within a CAVE pane or tab.