/Issued 6:18 PM CDT, Wednesday, July 11, 2018/
Tonight’s severe weather outlook — All modes of severe weather possible tonight including a risk for a few tornadoes especially in portions of north central Minnesota from around International Falls to Bigfork and Grand Rapids to Cass Lake, Walker and Brainerd.
Increased risk of flash flooding tonight in parts of the Northland with a moderate risk and slight risk for excessive rainfall and flash flooding — Technical Discussion from the Weather Prediction Center at this link http://www.wpc.ncep.noaa.gov/qpf/ero.php?opt=curr&day=1
Thursday’s severe weather outlook — Isolated to scattered strong to severe thunderstorms are possible mainly over parts of northwest Wisconsin and east central Minnesota.
Feeling like the amazon over a large part of Minnesota this afternoon with widespread 70 to 75 degree dew points, even a few locations into the upper 70s and lower 80s! Lower dew points due to the cooler temps around Lake Superior today, but dew points jump to around 70 or so on Thursday even near Lake Superior!
Potential is there for a rough night across the Northland — The setup late this afternoon features a cold front over the eastern Dakotas and a warm front over central Minnesota. The warm front lifts NE tonight while the cold front heads E. Very moist and unstable airmass covered the upper Midwest this afternoon with dew points in the 70s and PWATS of 1.80 to 2.10 inches (Record or near record moisture levels for this time of the year!) As for the instability, that too is quite impressive with meso-analysis showing anywhere from 1000 to 5000 J/kg of Convective Available Potential Energy (CAPE) with the highest values in west central Minnesota. SW Low level jet is ramping up late this afternoon, at 6 PM its in the 30 to 40 knot range, and this continues to advect deeper moisture and instability into the Northland.
The cap or warmer air aloft is keeping a lid on convective development thus far with 700mb temps of +12C over the western half of Minnesota with MLCIN of 25 to 100 J/kg over the Northland with little or no CIN remaining farther west where temperatures are considerably warmer, thus the cap has been weakening late this afternoon.
We should see showers and thunderstorms develop and expand in coverage over north central Minnesota this evening, these storms will then track south/east overnight into Thursday morning. Locations that get hit multiple times tonight will have a greater chance for flash flooding.
Note: Some model runs throughout the day have looked scary with potential rainfall amounts of 4 to 10″+ in portions of the Northland, however, each new model run has shifted the axis of heaviest rainfall so there is still uncertainty in regards to what part of our area gets hit the hardest later tonight.
As for severe weather: Some of the storms could contain damaging winds and or large hail tonight. Wind gusts of 60 to 75 mph are possible with hail of 1 to 2 inches in diameter (Quarter sized to slightly larger than Golf Ball sized) The risk is greatest in parts of north central into east central Minnesota but certainly can’t be ruled out anywhere in the Northland.
There is also a chance for a few tornadoes tonight over north central Minnesota with 30 to 45 knots of shear along with veering winds with height coupled with 25-35 knots of 1km Shear, and Storm Relative Helicity values of 300 to 400 m2/s2 — Favorable parameters in place for a few rotating supercells and tornado genesis tonight from the Brainerd Lakes north toward Grand Rapids and International Falls.
Thursday: Looks warm and muggy but may not be all that sunny thanks to the cold front which will continue to move slowly south/east out of north central Minnesota. Scattered showers and thunderstorms are possible Thursday mainly in east central Minnesota into northwest Wisconsin with a few strong to severe storms and heavy rainfall possible. Highs Thursday mainly in the 80s with dew points in the mid 60s to mid 70s, but lowering dews/drier air pushes south out of northern Minnesota later in the day or Thursday evening behind the cold frontal boundary.