A few strong to severe thunderstorms are possible in parts of the Northland through Friday with the greatest chance across northern Minnesota (north of Duluth) where a Marginal Risk of severe thunderstorms exists through Friday morning. Hail and gusty winds will be the main threats from the strongest storms along with downpours and lightning.
A frontal boundary will be nearly stationary over north-central Minnesota into far northern Wisconsin the next few days. This front will act as a source of lift while a warm and humid air mass helps to make the atmosphere a bit unstable with CAPE of around 1000-2000 J/kg either surface-based or elevated. Winds aloft don’t look particularly strong so the amount of wind shear will be rather low, and mid level lapse rates aren’t looking overly impressive either through Friday as values remain <7.0 C/km, so the risk for widespread severe weather is very low through Friday, but isolated strong to severe storms are still possible from time to time, mainly across northern Minnesota and over the tip of the Arrowhead.
Rainfall forecast through late Friday afternoon.
A strong temperature gradient (baroclinic zone) is in place today with temperatures of around 100 degrees in parts of the Dakotas while temperatures are in the 60s north of Lake Superior today. A sign that the seasons are beginning to change are these big time temperature contrasts!
Source: RTMA model; https://lab.weathermodels.com/
Starting to feel a little more humid today with dew points in the upper 50s to middle 60s in northeast Minnesota and northwest Wisconsin, but it’s downright tropical over the Red River Valley with dew points of around 70 degrees this afternoon.
Note: Dew points look to remain on the muggy side through early next week ranging from around 60 to 70 degrees across the Northland.
Source: RTMA model
Thursday will probably start out kind of warm and humid in the Twin Ports, but a stronger NE wind is forecast to develop resulting in cooling temperatures during the afternoon/early evening. Might be one of those days where temperatures near Lake Superior fall from around 80 to 60 in a matter of an hour.
A lake wind is forecast to carry over into Friday as well with temperatures in the 60s and 70s near Lake Superior, warmer inland.
Source: 18z NAM 3km model temperature forecast for Thursday, August 20, 2020; https://weathermodels.com/
Rainfall Reports from Wednesday, August 19, 2020
Note: Totals below are thru 4 PM Wednesday.
Cass Lake, MN: 0.60″
Grand Portage, MN: 0.17″
Walker, MN: 0.15″
Longville, MN: 0.09″
International Falls, MN: 0.02″
Brainerd, MN: 0.01″
Moose Lake, MN: 0.01″
Grand Marais Airport: 0.01″
Thanks for reading!