Marine Weather and Tide Forecast for Cornucopia, WI

DISCUSSION
Issued at 410 AM CDT Mon Apr 28 2025

High pressure was located over the eastern Great Lakes early this morning with low pressure in central South Dakota.
Southeasterly return flow was in place across the western Great Lakes and Upper Midwest, bringing warmer temperatures and moisture to the region. A southerly low-level jet was also present and giving rise to some isolated showers and embedded thunderstorms across the Northland. A larger area of showers and thunderstorms was located across central and eastern South Dakota. This area is forecast to lift through the Northland this morning. These elevated storms may lead to some marginally severe hail, mainly in the Brainerd Lakes region as they arrive.

As this first round clears the region around midday, questions remain as to the evolution of the second round of activity for this afternoon and evening. One of the questions is how much clearing, if any, will occur in the wake of the first round of activity. If clouds linger, that would limit how much instability is able to develop. Should some breaks develop, daytime heating should lead to pockets of higher instability in spots across central Minnesota into eastern Minnesota. The second question is how far north the warm front can push into the region by this afternoon. Dewpoints will be in the 60s to the south of the warm front and that is expected to lift north through much of northwest Wisconsin and eastern Minnesota.
Easterly winds off Lake Superior may slow or stall this progress and help reinforce it with the cooler air off the lake.
Further, forecast soundings show the presence of a capping inversion, which may lead to more elevated storms. Some of the CAMs do not show this capping inversion and keep convection in the area through much of the afternoon, which may also limit the max severe potential.

With all that said, the environment south of the warm front is forecast to be fairly potent. CAPE will be around 1000-1500 J/kg, with effective shear in excess of 40 knots. This may lead to some isolated cells early on, but quick upscale growth is expected to a QLCS. Mid-level lapse rates will be around 8 C/km, which will help with the large hail threat. SRH will be in excess of 300 m2/s2, so any surface based storm will have the potential to be tornadic. Looping hodographs in the low levels support this threat as well. Any bowing segments in the QLCS as the afternoon evolves will see a higher tornado threat also. The best estimate for where the warm front will end up roughly along and south of US2. Areas to the north of US2 will still likely see storms, but heavy rain will be the primary threat in those areas with PWATs around 1.25". The second round of activity may develop as early as 1 to 3 PM in the Brainerd Lakes area, reaching the I-35 corridor around 4 to 6 PM and possibly clearing northwest Wisconsin by 9 to 11 PM.

As the low departs to the east tonight, showers will linger on the backside through the night before slowly ending from west to east by mid-morning Tuesday. With cooler air pushing in overnight, some areas of rain/snow mix will be possible across northeastern Minnesota, but little to no accumulations are expected. After a warm day today in the 50s and 60s, with a few 70s in far southern areas, Tuesday will be much cooler with highs in the 40s and 50s. Temperatures quickly rebound for Wednesday into the 60s for most with 50s in the Arrowhead. Rain chances return for Thursday into Friday and will keep temperatures cooler in the 50s and 60s. Early indications are for a dry and warm weekend with widespread 70s possible by Sunday.



AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
Issued at 102 AM CDT Mon Apr 28 2025

VFR conditions prevail across much of the region currently with some MVFR ceilings starting to work in to western areas. This lowering trend is expected to continue through the early morning hours with widespread MVFR to IFR conditions in place by sunrise. Showers and thunderstorms will lift through much of the region starting around 12z through the morning hours. Another round of showers and storms is expected to develop around midday in the Brainerd area and work eastward through the afternoon and into the early evening. Timing on this second round is still in question as well as severity. If some clearing can develop between rounds, this second round could be stronger, especially across southern areas. LArge hail, damaging winds and tornadoes will all be possible with the second round of storms. Low level wind shear will also affect parts of the region as a low level jet and warm front work through. Wind shear will last longest at HYR with magnitudes of 30 to 45 knots.

MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/
Issued at 410 AM CDT Mon Apr 28 2025

Southerly winds along the immediate South Shore are expected to gust to around 25 knots this afternoon and Small Craft Advisories are in effect for this threat. Periods of showers and thunderstorms are expected today with the strongest storms possible this afternoon and early evening. These storms may contain large hail, damaging winds in excess of 50 knots, and tornadoes/waterspouts, primarily along the South Shore. A cold front will move through after the storms with winds becoming northwesterly in its wake. Wind gusts to 25 to 30 knots will be possible along parts of the North Shore with a 20 percent chance for gales in this area during the early morning hours into mid- morning Tuesday. Small Craft Advisories will likely be needed for these winds. Winds then diminish Tuesday afternoon and become light and variable at 10 knots or less Tuesday night.

For the open water discussion, refer to the NWS Marquette Area Forecast Discussion at weather.gov/mqt.

DLH WATCHES/WARNINGS/ADVISORIES
MN...None.
WI...None.
MARINE...Small Craft Advisory from noon today to 10 PM CDT this evening for LSZ121-145>148-150.