/Issued 11:45 AM CDT, Sunday, August 26, 2018/
11:46 AM — Mesoscale Discussion issued for parts of west-central/central Minnesota and southeast North Dakota, link to the technical discussion https://www.spc.noaa.gov/products/md/md1360.html
12z HRRR model
Note: Timing could be off by a little bit, but the majority of the convection-allowing-models (CAMS) have been showing scattered thunderstorms developing, probably a few different waves of storms which should impact some parts of the Northland through tonight, the trend in model guidance is to lift most of the storms farther north into northern Minnesota later tonight, will see what happens.
With the amount of shear and other ingredients that are in place today, an isolated threat for tornadoes does exist anywhere in the green, brown and yellow areas on the map — But the greater chance for a tornado appears to be setting up over southeast North Dakota, northeast South Dakota into west-central Minnesota.
…Strong to severe thunderstorms and heavy rainfall possible in parts of northeast Minnesota and northwest Wisconsin this afternoon into tonight…
Late Sunday morning analysis has an area of low pressure over central Montana and another low across central South Dakota. A cold front/stationary front stretched from northern Minnesota to northern South Dakota with a warm front in far southern Minnesota.
We had two rounds of scattered thunderstorms Saturday evening into early this morning, the first one impacted extreme northern Minnesota, the other one developed over southeastern North Dakota and moved generally southeast through central/eastern Minnesota early this morning. Large hail was reported with the southern storms early this morning.
We’re seeing another area of showers and thunderstorms move E-NE out of western Minnesota as of 11 AM and these storms have been strong to severe at times. These storms are likely somewhat elevated though with Surface-Based CIN values of 100 J/kg per 11 AM meso-analysis.
The atmosphere is already becoming unstable across most of the Northland late this morning with CAPE of 1000-2000 J/kg and mid level lapse rates from 7.0 to 8.0 c/km. There is also 40-50 knots of mid level winds and up to 80 knots of upper level wind over the Northland late this morning — This is leading to increasing amounts of wind shear which ranged from 40 to around 50 knots.
The overall setup favors the development of scattered showers and thunderstorms in northeast Minnesota and northwest Wisconsin through tonight with some risk for strong to severe thunderstorms as well due to the increased instability and wind shear. Heavy rainfall rates are also possible which could lead to flash flooding, although there is a chance that storms will remain progressive enough and not move over the same location for very long which would lessen the flood threat.