7:03 PM Sunday, June 23, 2024
Significant uncertainty remains concerning the likelihood of severe thunderstorms developing late Monday afternoon into the evening.
The only aspect currently agreed upon is the timing of potential storms passing through parts of the Northland. This is expected to occur from late Monday afternoon into the evening, with the likelihood decreasing after midnight.
The degree to which significant instability and moisture will spread northward on Monday is still unclear. The positioning of the CAPE gradient may be a crucial indicator for identifying potential zones of scattered storms or the path of a bow echo on Monday evening. Presently, it seems likely that this setup may extend into central or southern Minnesota and eastward into the west-central regions of Wisconsin with lower chances for this to occur in northern Minnesota including the Arrowhead, North Shore, Twin Ports and far northern Wisconsin.
However, due to the considerable variation in computer models, a slight risk (indicated by the yellow area on the map) or level 2 out of 5 for severe thunderstorms persists for the entirety of northeast Minnesota and northwest Wisconsin from late Monday afternoon into the evening, but changes to this severe weather outlook will probably occur during the day Monday.
The potential for damaging winds is a major concern for severe weather threats on Monday evening, with wind gusts possibly reaching 70-75+ mph especially in the designated hatched area on the map.
There is a possibility of large hail late Monday afternoon or evening, with potential for hailstones to reach 2 inches in diameter or larger in the designated hatched area on the map.
Here are six convective model (CAMS) forecasts, all valid for 7 PM Monday, illustrating the range of possible outcomes.
Several models indicate minimal or no thunderstorm activity in northeast Minnesota and northwest Wisconsin on Monday evening.
At least two models indicate a line of storms, potentially a bow echo, with a threat of damaging winds moving south/east out of northern Minnesota on Monday evening.
Severe thunderstorms frequently follow the CAPE gradient, which is the boundary where high instability meets lower instability. This gradient may establish itself between I94 in central Minnesota and Highway 2 in northeast Minnesota. If this occurs, the highest risk for severe thunderstorms would likely be positioned south of northeast Minnesota and far northern Wisconsin on Monday evening.
The moisture gradient could influence the trajectory of severe storms on Monday evening. It is predicted that very humid air with dew points exceeding 70 will arrive in central Minnesota by Monday afternoon, while drier, yet still moderately humid air with dew points around 60 will prevail over northeast Minnesota and northwest Wisconsin.
On Monday, the setup will be bolstered by dynamic support, including a robust jet stream with speeds of 80-100 knots or more, surging eastward from the northern Rockies.
The 700mb temperatures, ranging from +12 to +16C in western/southern Minnesota on Monday afternoon, are quite warm. As this airmass moves further north/east into Monday evening, it may inhibit thunderstorm development, also known as ‘the cap’.
A persistent disturbance over Southern Ontario, Canada, coupled with colder upper-level temperatures and warmer surface air, created atmospheric instability in the Northland this afternoon. This resulted in sporadic showers and a few thunderstorms.
Goes-16 water vapor loop from Sunday, June 23, 2024, loop time ends 5:20 PM CT.
The forecast for the next ten days suggests an active pattern, with multiple systems moving across the upper Midwest region. This will likely result in periods of showers and the possibility of thunderstorms as we head into early July.
Between 2 to 3 inches, or possibly more, of rainfall is expected across all of northeast Minnesota and northwest Wisconsin through July 3rd.
Thanks for reading!
Tim
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