Scattered strong to severe thunderstorms possible Wednesday

Published by

Timothy Burr

on

June 11, 2024

6:57 PM Tuesday, June 11, 2024

Several showers and thunderstorms are anticipated across the Northland for Wednesday, extending into the evening. The Northland is likely to see an initial round in the morning due to a northeast-moving warm front, with a subsequent round in the late afternoon to evening associated with an eastward-moving cold front. This latter round may lead to some severe weather across north-central, east-central, and northeast Minnesota, as well as northwest Wisconsin.

Northeast Minnesota and much of northwest Wisconsin are under a level 2/5, or slight risk, for severe thunderstorms on Wednesday. Conditions may include large hail, damaging winds, and the possibility of isolated tornadoes. The risk for tornadoes is more pronounced in north central and east central Minnesota, with lower probabilities in northeast Minnesota and northwest Wisconsin.

There is considerable uncertainty regarding the development of Wednesday’s weather system, however, as it seems we will be contending with two distinct waves passing through the region. Should morning storms occur, the skies must clear sufficiently to destabilize the atmosphere for a potential late afternoon bout of storms. Conversely, if the skies stay mostly cloudy for the majority of the day, or if intermittent storms continue, then the likelihood of severe thunderstorms may significantly decrease.

The computer models today are indicating favorable conditions for severe thunderstorms on Wednesday, with strong jet dynamics and wind shear present, as well as a significant amount of warm, humid, and unstable air. The Convective Available Potential Energy (CAPE) could exceed 2000 J/kg in some areas later on Wednesday. Therefore, if storms do form, there is a potential for them to become severe in the afternoon or evening.

Here’s the NAM 500mb forecast valid 7 AM Wednesday to 1 AM Thursday.

Note: Brighter colors on the loop indicate more significant lift in the atmosphere, which is necessary for the formation of showers and thunderstorms.

The 1 KM Energy Helicity Index, or EHI, is a parameter utilized in severe weather forecasting. EHI values exceeding 1-2 have been linked with the occurrence of tornadoes within supercells.

Late Wednesday afternoon, the NAM forecasts EHI values as high as 3-4 in parts of the Northland, indicating a combination of instability and storm relative helicity which may correlate to increased tornadic potential if storms remain discrete and not form into a line/s.

Tornado Outlook for Wednesday

The highest probability of a tornado is indicated by the brown shaded region on the map below.

Severe Hail Outlook for Wednesday

Large hail, ranging from a quarter to ping pong ball size (1″-1.5″ in diameter), is possible across much of the Northland on Wednesday. There is also a potential for hail larger than golf balls within the designated hatched area on the accompanying map.