5:54 PM Tuesday, August 15, 2023
Isolated to scattered strong to severe thunderstorms remain possible late Wednesday afternoon through late Wednesday evening across much of the Northland.
Primary severe weather threats on Wednesday include damaging wind gusts of 60 to 75 mph and large hail of 1″ to 1.50″ in diameter (quarter to ping pong ball size)
The tornado threat remains on the low side Wednesday in northeast and eastern Minnesota into far northwest Wisconsin, but still can’t completely rule out a tornado especially if storms remain somewhat discrete instead of them forming into a line.
Thunderstorms could develop over parts of northeast and north central Minnesota sometime late Wednesday afternoon around 4 PM to 7 PM. Storms that develop will likely move southeast or east-southeast through Wednesday evening, exiting northwest Wisconsin by late Wednesday evening.
Duluth area: Showers and thunderstorms are possible late Wednesday afternoon and evening from around 4 PM to 8 PM.
Note — Yellow area on the map below represents where the greatest potential for a few severe thunderstorms is for late Wednesday afternoon-evening.
One thing which may hinder thunderstorm development is the presence of these warm temperatures aloft or a cap with 700mb temperatures increasing to around +10 to +13C over much of northeast and east central Minnesota and northwest Wisconsin, but as stronger forcing tied with an approaching upper-trough and cold front along with a pocket of cooler temperatures aloft approaches from the northwest, we should see this cap weaken which will allow for thunderstorm development later Wednesday afternoon.
A strong low-level jet out of the southwest is forecast to be over the Northland on Wednesday with winds approaching 50 knots. This LLJ will help transport deeper moisture and increasing amounts of instability into our area Wednesday afternoon-evening.
As I mentioned above, we should see pretty strong moisture advection occurring over parts of the Northland Wednesday afternoon (yellow outlined area on map) with 850mb dew points climbing from around +10C around midday, to around +15C by late Wednesday afternoon.
***TIMING OF WEDNESDAY’S STORMS***
Here are two computer model radar forecasts for Wednesday valid from 1 PM to 11 PM.
Nam 3km model shows thunderstorms erupting around 5 PM to 7 PM Wednesday with storms farther south compared to the Hrrr model.
Hrrrv4 model holds onto stronger capping which limits how far south thunderstorms develop, with most of the storms focused over the Arrowhead and North Shore into far northern Wisconsin.
Northeast and eastern Minnesota and all of northwest Wisconsin have the greatest chances for picking up around 0.10″ to 0.75″ of rain late Wednesday afternoon/evening with higher rainfall totals of up to an inch possible.
Note — It does appear that will be going back into a pretty dry pattern after Wednesday.
Thanks for reading!
Tim