5:05 PM Monday, June 24, 2024
The likelihood of severe thunderstorms occurring in the Northland tonight remains highly dependent on whether or not the cap erodes, and the timing of when it might erode.
A mass of warm air aloft, with 700mb temperatures ranging from +12 to +16C, continues to move north/eastward from western and central Minnesota this afternoon.
Another indicator of a robust cap is the Mixed Layer CIN (Convective Inhibition) parameter, which ranges from 200-400 J/kg this afternoon. This zone of convective inhibition needs to be surpassed for storm initiation to take place.
The CAP can erode through warm air and moisture advection, coupled with adequate forcing from frontal boundaries, or a sufficiently strong low-level jet. Whether or not we get any of those three things to occur tonight is very uncertain this afternoon.
Thick cloud cover has enveloped northeast Minnesota and northwest Wisconsin this afternoon, greatly limiting the entry of warm, humid, and unstable air into our area. It’s improbable that the clouds will dissipate in time to allow a significant accumulation of warm, humid, and unstable air before sunset.
Goes-16 visible satellite loop from Monday, June 24, 2024, loop time ends 3:26 PM CT.
Once again, the cloud cover across the Northland has significantly restricted the amount of CAPE moving north/east into our region. However, in areas where there has been sufficient sunshine today, CAPE values have surpassed 4000-5000 J/kg, indicating an extremely unstable air mass.
Note: The primary hazards if severe thunderstorms develop in the Northland tonight include damaging winds to 60 mph and large hail of 1 to 2 inches in diameter.
The NAM 3km model aggressively predicts the development of supercell thunderstorms over western Minnesota by early evening, which are expected to merge into a line of storms. This system is forecasted to move east-southeast across central and eastern Minnesota, reaching into a large portion of Wisconsin later tonight.
NAM 3km model simulated radar forecast through 7 AM Tuesday.
The delay in the erosion of the cap increases the probability of thunderstorms developing mainly in parts of Wisconsin and southeast Minnesota tonight, while the chances diminish in northeast Minnesota. This scenario is well depicted in this afternoon’s HRRR model simulations.
HRRR model simulated radar forecast through 7 AM Tuesday.
Late this afternoon, surface analysis indicated a low-pressure area near Watertown, South Dakota, with a warm front extending over southwest Minnesota into western Iowa and a cold front trailing southwest from the low across southern South Dakota. The system is expected to move east-northeast tonight.
Another cold front was over central North Dakota this afternoon, and it is expected to move eastward tonight.
Should thunderstorms develop tonight, there is potential for torrential downpours, with rainfall totals of 1 to 2 inches or more in localized areas of eastern Minnesota and northwest Wisconsin, and a lesser chance of such totals in northeast Minnesota. The storms are expected to move through quickly, which may limit the potential for widespread flooding; however, localized flash flooding could occur in some areas of the Northland.
Tonight, northeast Minnesota, including Duluth, may receive around a quarter to half an inch of rain. Higher amounts ranging from 0.50 to 1 inch, or more are forecasted for eastern Minnesota and much of northwest Wisconsin, as per the NWS Blend of Models forecast.
Looking ahead through early next week, there appear to be at least two more systems that could impact the Northland, bringing additional chances of rain.
The amount of rainfall and the timing of these systems may vary slightly in the coming days. However, the current forecast suggests that there may be some rain on Friday and the following Monday.
Here is the second system that might impact our area next Monday, as it moves northeast from the northern Rockies.
Accumulating the various systems through the beginning of next week, we anticipate a widespread 2 to 3 inches of rainfall across northeast Minnesota and northwest Wisconsin, according to the NWS Blend of Models forecast.
Duluth has experienced only one day at or above 80 degrees this month. Typically, the average number of days reaching or exceeding 80 degrees in June is five.
- In Duluth, several years recorded no days with temperatures in the 80s. These years include 1998, 1981, 1916, 1915, 1904, and 1877.
- Out of the six years mentioned, three experienced a nearly average number of days with temperatures at or above 80 degrees for the remainder of the season (the annual average is 27 such days), while the other three years fell significantly below the average.
- In 2011, Duluth experienced only one day in June with temperatures hitting 80 degrees. By the end of that year, there were 35 days with temperatures of 80 degrees or higher, surpassing the average of 27 days.
- Last June, Duluth recorded ten days with temperatures reaching 80 degrees. Furthermore, the year 2023 saw a total of forty days with temperatures at or above 80 degrees.
Temperatures are expected to reach 80 degrees in Duluth on Tuesday, which may be the final opportunity to experience such warmth for the remainder of the month.
Thanks for reading!
Tim