Isolated strong to severe thunderstorms possible in parts of the Northland late Monday afternoon/evening

A large portion of the Northland is in a Marginal Risk (green shaded area on map) for severe thunderstorms on Monday. It’s a 1/5 risk (lowest risk on the 5 point scale) but still stay weather aware especially in the afternoon and evening when we could see a few thunderstorms develop or move through some parts of the Northland.

Main threats with the storms on Monday will be from lightning and brief downpours, with hail and gusty winds possible in the strongest storms. Time frame for when we could see a few stronger storms in parts of the Northland is from about 4 PM to 10 PM Monday.

It’s going to take most of the day Monday for deeper low level moisture to work its way north into our area, but eventually we should see higher dew points (more moisture) advect into the Northland by late Monday afternoon-evening with dew points climbing into the 40s and possibly even into the low 50s. This isn’t a ton of moisture, but it should be enough when combined with some forcing associated with a northeastward lifting warm front, and southeastward moving cold front to produce isolated to scattered showers and thunderstorms. Note: There is a chance that these storms will be high-based (not much rain) especially if moisture return ends up delayed prior to when convection develops.

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Setup for Monday afternoon/evening includes low pressure approaching from the west while a warm front and cold front move through the Northland later in the day on Monday and Monday night.

  • Computer models are showing upwards of a 1000 j/kg of mostly elevated CAPE advecting into at least southern/eastern portions of the Northland by late Monday afternoon. These values could end up lower if dew points end up lower than model guidance shows.
  • Mid Level Lapse Rates look pretty steep on Monday with values of around 7.0-8.0 c/km, this could increase the chances for some hail, especially when coupled with -20C 500mb temps which are forecast to be over the Northland per model guidance.
  • Southerly low level jet of around 20-30 knots is forecast to be in place with stronger mid/upper level winds over the area which should be favorable for an isolated severe thunderstorm threat late Monday afternoon/evening.

Here’s a look at the 18z European computer model CAPE forecast for Monday. Notice how the higher CAPE (instability) builds N-NE into southern/eastern portions of the Northland which is represented by the blue colors on the animation below.

Here’s a look at two model radar simulation forecasts for Monday, both are valid from 7 AM Monday to Midnight Tuesday.

Both models show mainly dry conditions for most of the day Monday, and then the development of a few showers and thunderstorms occurring later Monday afternoon or Monday evening.

18z NAM 3km model.

18z HRRR model.

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…70s were widespread in the Northland today, Sunday, April 4, 2021…

  • Brainerd, MN: 77 F (record high 81 F set in 1929)
  • Moose Lake, MN: 77 F
  • Siren, WI: 77 F
  • Ashland, WI: 75 F (record high 77 F set in 1910)
  • Hayward, WI: 75 F
  • Hinckley, MN: 75 F
  • McGregor, MN: 73 F
  • Pine River, MN: 72 F
  • Cloquet, MN: 72 F
  • Eveleth, MN: 71 F
  • Hibbing, MN: 70 F (new record high for the date, previous record high was 67 F set in 1991)
  • Ely, MN: 70 F
  • Orr, MN: 70 F
  • Cook, MN: 70 F
  • Longville, MN: 70 F

…Record Highs for April 5th…

  • Brainerd, MN: 82 F set in 1991
  • Ashland, WI: 81 F set in 1991
  • Duluth, MN: 79 F set in 1991
  • Hibbing, MN: 76 F set in 1991
  • International Falls, MN: 75 F set in 1991

Probably won’t be tying or breaking any record highs in the Northland on Monday, but it’s going to be another warm day away from Lake Superior, with highs a good 20 to nearly 30 degrees warmer than normal.

Tim

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