4 PM Saturday – A Severe Thunderstorm Watch has been issued for northern Minnesota and far northeast North Dakota effective this Saturday afternoon and evening from 3:55 PM until 11 PM.
Primary threats include
Large hail to 2 inches in diameter possible
Damaging wind gusts to 65 mph possible
A tornado or two possible
Counties in the Northland included in this severe thunderstorm watch are: Koochiching, Itasca, Cass, Crow Wing and Aitkin including the cities of International Falls, Bigfork, Grand Rapids, Cass Lake, Walker, Longville, Nisswa, Brainerd, Hill City, Aitkin and McGregor.
Remember a severe thunderstorm watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes.
Here’s the setup for late this afternoon and this evening
A trough will be moving in from the NW while some instability develops out ahead of this system. Late afternoon CAPE was generally in the 500-1000 J/kg range across north-central Minnesota and these values probably won’t increase by a whole lot through the evening. Temperatures aloft were on the chilly side with 500mb temperatures of -15 to -17C across northern Minnesota. The combination of cold air aloft, surface heating, instability and the approaching trough sets the stage for the development of widely scattered to scattered thunderstorms through this evening over north-central Minnesota.
There is a lot less moisture for storms to work with today compared to what we had on Friday as dew points this afternoon were mostly in the 50s to around 60 degrees while Precipitable water was in the 0.80-0.90″ range, but the amount of wind shear is quite strong with 0-6 KM and Effective Bulk Shear in the 30-40 knot range late this afternoon, and we also have a change of wind direction with height as S-SW winds near the surface veer more SW at 850mb and WNW at 500mb, so this is favorable for potential supercell thunderstorms and perhaps even some splitting supercells where one storm tracks east while another storm drops south.
Large hail is the main severe weather threat through this evening across north-central Minnesota, but damaging wind gusts are also possible.
Stay Weather Aware!
Note: The greatest potential for severe weather this evening should remain west and northwest of Duluth. Forecast models show the storms weakening possibly to nothing at all by the time they reach the Arrowhead, North Shore, Twin Ports and far northwest Wisconsin later this evening, but like I always say with this weather stuff, you just never know for sure what will happen so keep an eye on things through the evening!
Goes-16 water vapor loop shows the upper level trough digging SE out of Manitoba, note the darkening colors moving into the Red River Valley area of northwest Minnesota late this afternoon.
Loop time: 11 AM to 4:10 PM Saturday, August 15, 2020
Thanks for reading!