A few showers, isolated thunderstorms tonight; Strong to Severe Thunderstorms possible in the Northland Thursday afternoon-evening

A couple rounds of showers and thunderstorms are expected in the Northland through Thursday night.

Tonight’s activity will be due to a strengthening low level jet and warm front lifting NE across the area while warm and humid air along with increasing amounts of elevated instability move ENE out of the Dakotas and into the Northland. This setup will likely lead to a few showers and isolated thunderstorms in northeast Minnesota and northwest Wisconsin tonight into Thursday morning, but severe weather is not expected with this round of storms.

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The main time frame for possible strong to severe thunderstorms in the Northland comes Thursday afternoon into Thursday evening, roughly from ~2 PM to 11 PM (earliest west-northwest areas, latest south-east areas)

Primary threats from severe thunderstorms on Thursday include Damaging Wind Gusts of 60 to 70 mph, and Large Hail of Quarter to Ping Pong ball size (1.00″ to 1.50″ in diameter).

The synoptic setup for Thursday continues to look pretty interesting for severe thunderstorms, but there are also a few things which could keep storms from becoming severe.

*Winds aloft and the amount of wind shear will be on the strong side, and will be favorable for severe storms, this hasn’t changed in model guidance the last few days.

*0-6 KM shear and Effective Bulk Shear will be in the 30 to ~50 knot range on Thursday which is more than enough for severe storms.

*CAPE increases to ~1000 to 1500 J/kg Thursday afternoon/evening.

*Dew points in the upper 50s to mid 60s.

*Mid level lapse rates >7.0 c/km.

Onto the issues which may hinder storm development/intensity

-Warm air aloft (700mb temps +8 to +11 C)

-A narrow corridor of greatest instability right near the front which could mean that storms weaken once they reach northwest Wisconsin due to lesser instability in that area.

-Timing…In that a later timing of the best forcing tied with the cold front occurs too late for severe weather, with just non-severe storms occurring Thursday evening/overnight.

Stay Weather Aware on Thursday!

Based on what I’m seeing in model data today, that area in yellow has the greatest chance at seeing an isolated supercell risk for a few hours late Thursday afternoon-early Thursday evening.

500mb winds out of the SW, with more of a S-SW wind from the surface to 850mb…that change in wind direction with height could lead to a few rotating supercells which would increase the risk for large hail and damaging wind gusts.

Warm front lifts NE through the area tonight, and then will watch a cold front move east out of northwest/western Minnesota Thursday afternoon-Thursday evening. There should be just enough forcing with that cold front to produce scattered storms across the Northland on Thursday, especially in the afternoon/evening.

Low level moisture fueling Thursday’s storm risk will build NE out of the eastern Dakotas over the next 24 hours, with dew points climbing into the low to mid 60s over much of the Northland by Thursday afternoon.

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18z NAM 3km model simulated radar forecast valid through 7 AM Friday.

Note: Timing for when we could see a few strong to severe storms in Duluth and Superior is greatest from around 7 PM to 10 PM Thursday.

Rainfall forecast through early Friday morning.

Generally looking at a quarter to half inch of rain in most of the Northland, with higher totals in thunderstorms. Least amount of rain with this system is forecast around the Brainerd Lakes, and toward the Ashland, Hurley areas.

Tim

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