Ingredients are coming together for the potential for some severe weather over parts of the Northland late Friday night. Strong instability with CAPE 2000-4500 J/kg along with dew points of 65 to 75 degrees will be in place across southern Minnesota by late Friday afternoon. A strengthening southerly low level jet will help advect this deep moisture and instability northward into our area Friday night. Meanwhile severe thunderstorms are expected to develop over the Dakotas late Friday afternoon or Friday evening, these storms are then expected to race east or east-southeast late Friday night into Saturday morning. Note: A swath of wind damage and possibly some hail may accompany these storms as they move through parts of the Northland late Friday night or Saturday morning.
Note: Additional updates on Friday will help pinpoint timing and what parts of the Northland will be most at risk for severe weather Friday night.
Another round of severe weather is possible for Saturday afternoon or Saturday night, but this is more uncertain as a lot will depend on where the storms track Friday night, and also on where the boundary/s, instability/moisture gradients will be later Saturday, and also on the strength of a CAP (warm layer of air aloft) and whether or not this cap will break or hold strong. With that said, the setup for Saturday looks pretty potent with high amounts of instability and moisture once again along with strong winds aloft and wind shear. At the moment it looks like an area from southwest to east-central Minnesota into north-central Wisconsin is most at risk for severe weather late Saturday afternoon/night, but this area could shift a bit more north or further south depending on how things setup on Saturday. Stay tuned!
Here’s a look at two computer model radar simulations on how things could play out for Friday night – Both forecasts are from 7 PM Friday to 1 AM Saturday.
As you can see from the two model forecasts below, there is quite a bit of uncertainty on where storms develop and how they track Friday night.
18z HRRR model
18z NAM 3km model
Looks pretty tropical across the Northland on Saturday with potential for dew points to be in the upper 60s to middle 70s! But relief won’t be too far away as a much drier air mass heads this way out of northwest Minnesota for Sunday.
Source: 12z European model 7.16.2020; https://weathermodels.com/
An Excessive Heat Watch has been issued for parts of southern and east-central Minnesota from Saturday morning thru Saturday evening (dark red area on map)
Heat Index temperatures of up to 108 degrees are possible in the watch area Saturday afternoon.
Drought conditions continue to cover much of northeast Minnesota, south into parts of central and southwest Minnesota.
Latest Drought monitor map for Minnesota as of July 14, 2020.
4% of Minnesota is in D2 or Severe Drought (dark orange area on map)
20% of Minnesota is in D1 or Moderate Drought (light orange area on map)
38% of Minnesota is Abnormally Dry (yellow area on map)
Drought conditions continue to cover far northwest Wisconsin.
Latest Drought Monitor map as of July 14, 2020.
<1% of Wisconsin is in D2 or Severe Drought (dark orange area on map)
~1% of Wisconsin is in D1 or Moderate Drought (light orange area on map)
4% of Wisconsin is Abnormally Dry (yellow area on map)
A pretty cool radar image from late Thursday afternoon, July 16, 2020 showing three strong thunderstorms north of Duluth. A stronger west-northwest flow at 500mb helped to push the anvil/cirrus clouds to the east-southeast while southwest winds at 850mb pull in warm, humid and unstable air. The storms north of Duluth late Thursday afternoon certainly showed supercell structures per radar imagery.
Here’s the 60 minute GrEarth Rotation tracks on three different storms which moved across parts of the Northland late this afternoon.
Basically the darker red colors on the images below mean stronger rotation was showing up on radar imagery, but surprisingly only 1 of the storms were severe warned, the one up near Whyte, Minnesota.
Local Storm Reports for Thursday, July 16, 2020
6:58 PM: 0.50″ HAIL. Little Marais, MN (Lake County)
6:50 PM: 0.25″ HAIL. 2 SW Two Harbors, MN (Lake County)
6:48 PM: 0.50″ HAIL. 1 SSE Two Harbors, MN (Lake County) Quarter to half inch size hail.
6:35 PM: 0.88″ HAIL. 4 W Finalyson, MN (Pine County)
6:29 PM: Heavy Rain 3.00″. 7 W Finlayson, MN (Pine County)
6:29 PM: 0.50″ HAIL. 7 W Finlayson, MN (Pine County)
6:25 PM: 1.00″ HAIL (Quarter sized) 1 SSW Fredenberg, MN (St. Louis County) Mainly dime to nickel size hail with a few quarter size.
6:08 PM: 0.25″ HAIL. 1 WSW Twig, MN (St. Louis County)
5:36 PM: 0.70″ HAIL. 1 NW Chisholm, MN (St. Louis County)
5:09 PM: 0.25″ HAIL. McGregor, MN (Aitkin County)
7:40 AM: 0.25″ HAIL. 6 S Whipholt, MN (Cass County)
Here’s a look at one hour Maximum Estimated Hail Size per radar imagery ending ~6:30 PM Thursday. The tracks of the storms late this afternoon show up nicely on this image.
Rainfall Reports from Thursday, July 16, 2020
International Falls, MN: 0.86″
Eveleth-Virginia Airport: 0.74″
Two Harbors, MN: 0.65″
Bigfork, MN: 0.60″
Grand Marais, MN: 0.42″
Cook, MN: 0.31″
McGregor, MN: 0.25″
Longville, MN: 0.25″
Isabella, MN: 0.20″
Silver Bay, MN: 0.11″
Hill City, MN: 0.10″
Saginaw, MN: 0.09″
Brainerd, MN: 0.09″
Duluth Airport: 0.03″
Cass Lake, MN: 0.03″
Pockets of heavier rainfall across north-central and northeast Minnesota with today’s storms.
Goes-16 Sandwich Satellite loop showing the scattered storms across the region today, Thursday, July 16, 2020.
Loop time 2:11 PM to 6:51 PM CDT.
Thanks for reading!