1:13 PM Thursday, July 27, 2023
The risk for severe thunderstorms late this afternoon into early this evening has increased quite a bit across portions of the Northland, with an Enhanced Risk for severe thunderstorms covering all of northwest Wisconsin, and adjacent areas of eastern Minnesota, north to Duluth and Two Harbors, while a slight and marginal risk for severe thunderstorms covers areas farther to the west and north across north central Minnesota into the Arrowhead of Minnesota.
Enhanced Risk is a level 3/5
Slight Risk is a level 2/5
Marginal Risk is a level 1/5
The primary severe weather threats through this evening include damaging winds and large hail, with a 30% hatched area (red on map) for significant wind gusts of >70 mph which covers all of northwest Wisconsin and parts of eastern Minnesota.
There is also a 15 to 30% hatched area for significant hail of >2 inches in diameter, or larger than golf ball and hen egg size which covers all of northwest Wisconsin and much of east central Minnesota into parts of northeast Minnesota.
The tornado risk later today is on the lower end, but there is still a chance for a tornado in the green area on the map below.
***TIMING***
The potential for strong to severe thunderstorms looks greatest from around 3 PM to 9 PM this afternoon/evening across east central Minnesota into northern Wisconsin.
Again, damaging winds and large hail look to be the primary severe weather threats later today, and torrential rainfall is also likely with these storms.
Nam 3km model radar forecast through 10 PM tonight.
Hrrrv4 model radar forecast through 10 PM tonight.
A very warm, humid and unstable air mass is already in place near and out ahead of a cold front which as of Noon today stretched from west central to northeast Minnesota. This front will be moving southeast through tonight and there should be enough lift near this boundary which will allow thunderstorms to develop through this evening.
A very humid air mass was in place across east central Minnesota and northern Wisconsin early this afternoon with dew points of 65 to 75 degrees.
CAPE has already increased to around 3000 J/kg or greater over southern portions of the Northland early this afternoon with lower amounts of instability (CAPE) north of the Iron Range. So, there is plenty of fuel for thunderstorms to tap into once they develop over the next few hours.
One negative to get thunderstorms to develop and organize are these very warm temperatures in the atmosphere with 700mb temps around +10 to +13C as of early this afternoon, so this cap will need to erode in order to get storms to develop and become strong to severe later today.
Strong directional and speed shear was in place across the area this afternoon as winds increase and veer with height so this does increase the potential that we could see a few supercells before these storms line out which increases the risk for damaging winds.
Note — If supercells do develop, they will have the chance to produce very large hail of 2 inches or greater in diameter due to the large amounts of CAPE along with steep mid level lapse rates of around 7.0-8.0 c/km.
Thanks for reading!
Tim
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