Marine Weather and Tide Forecast for Ephraim, WI

DISCUSSION
Issued at 217 AM CDT Thu Apr 16 2026

Short Term
Today
Tonight...and Friday

Today...

Widespread dense fog this morning will begin to dissipate after 8-9 AM with most of the fog cleared out by 10 AM. A few scattered showers may also develop across central and east-central WI early this morning along a stalled boundary that is snaked from Green Bay back toward southwest WI. There may be a few rumbles of thunder, but no stronger storms are expected. Will need to watch precipitation rates as these showers pass over the flood sensitive areas of central and east-central WI, but based on upstream treads don't expect this round of precipitation to exacerbate ongoing flooding.
Any lingering precipitation should clear out early this afternoon as a ridge builds in. This will leave dry conditions across the region for the remainder of the day.

Severe Thunderstorms and Heavy Rain Potential Friday...

Beneath a stout cap a highly unstable airmass will be building during the day Friday. Southerly winds will usher in a tough of 60+ dew points as far north as HWY 8 along with temperatures well into the 70s away from Lake Michigan. A plume of 7-8 C/km mid-level lapse rates associated with an EML will also be overspreading the region at this time. This will result in an increase of surface based instability to around 2000 J/kg late Friday afternoon. Forecast soundings from across central WI also show strong low and deep layer shear across the warm sector with 40-45 kts in the 0-6km layer and 25-30kts in the 0-1km layer. As the cap erodes late in the afternoon isolated discrete super cells may be able to initiate across central WI within an area of subtly convergent surface winds. Any storms that do develop within the warm sector will pose a large hail (1-2") and tornado risk. Stronger and more widespread forcing will then arrive between about 5-6 PM as a sharp cold front and upper level trough push in from the west. With the cloud layer shear oriented nearly parallel to the cold front storms mode will likely transition from discrete cells to a line of storms. As this occurs the severe wind threat will increase as will the QLCS tornado risk.
One area of uncertainty is how far east surface based storms will persist. Surface winds will be out of the southeast most of Friday which will keep a stable marine boundary layer across our far eastern counties.

Along with the severe threat thunderstorms will also bring a risk for heavy rain. PWATs in increase to near 1" Friday afternoon which in near the 99th percentile for this time of year. HRRR 90th percentile hourly precipitation values which should be a good proxy for hourly rainfall rates within the strongest storms are around 0.75-1" per hour. With fast flow through the cloud layer (40-45kts)
storms should not sit over one location too long, however, any areas that see multiple storms could see upwards of 1.5-2" of rain Friday evening into early Saturday morning. As has been the case the last few days the greatest risk for flooding will be where there is ongoing river flooding or across parts of central and east-central WI where soils will still be saturated. On the back side of this system much cooler air may result in a brief chance over to snow, mainly across northern WI Saturday morning. However, with the ground thawed don't expect any accumulations.

Long Term...Friday Night Through Wednesday

Saturday night through Wednesday

High pressure will build in across the western Great Lakes region Saturday night, then slowly track east through the central Great Lakes during the early part of next week. The high will provide a much needed reprieve from precipitation for the area. Another cold front is slated to track through the region Monday night or Tuesday as the parent low tracks through southern Canada. This system is expected to track through the region mostly dry as the best moisture and lift will be closer to the upper level support across southern Canada. Therefore, impacts from this upcoming system early next week are expected to be minimal. Mainly dry weather is expected to last through at least the middle part of next week.

AVIATION
for 06Z TAF Issuance Issued at 1135 PM CDT Wed Apr 15 2026

Light winds and recent rainfall will result in areas of fog/low stratus development through early Thursday morning, which has already commenced across central Wisconsin. Conditions are expected to tumble to LIFR/VLIFR in the dense fog. As drier air advects in from the northwest, conditions will improve to VFR from northwest to southeast Thursday morning. Once settled in, VFR conditions are expected to persist through Thursday evening.

HYDROLOGY
Issued at 217 AM CDT Thu Apr 16 2026

Multiple rivers, namely the Wolf, Menominee, and Wisconsin Rivers, continue to read in minor to moderate flood stage, with the Menominee River now in major flood stage due to the additional influence of snow melt from the Upper Peninsula. Home evacuations are ongoing along the Wolf River. High flows and rising water levels have also resulted in several dams being compromised or overtopped.
If you live near a river or stream, continue to monitor the latest hydro forecasts and Flood Warnings from the National Weather Service in Green Bay.

GRB WATCHES/WARNINGS/ADVISORIES
Dense Fog Advisory until 10 AM CDT this morning for WIZ005- 010>013-018>022-030-031-035>040-045-048>050-073-074.