Marine Weather and Tide Forecast for Ephraim, WI

DISCUSSION
Issued at 339 AM CDT Thu Jul 17 2025

Short Term
Today
Tonight...and Friday

Showers will wind down this morning as a low pressure system continues to move east as a high pressure system settles in across the western Great Lakes region. The high will bring much cooler temperatures to the area today, as highs only range from around 70 across the north to the lower 70s across the rest of the region.

The high will drift east over the central Great Lakes tonight, but still maintain its influence across the area. Light winds and mostly clear skies will allow temperatures to fall into the upper 40s across the north tonight, with lows in the lower 50s across central and east-central Wisconsin and upper 50s along the lakeshore.

The high will continue to drift east on Friday, which will allow surface winds to turn to a southerly direction and daytime highs to inch upward a few degrees. A shortwave tracking across the northern Great Lakes will bring a small chance (20-30 percent) for showers across portions of north-central Wisconsin Friday afternoon. Highs on Friday are expected to range from around 70 across the north to the middle 70s across central and east-central Wisconsin.

Long Term...Friday Night Through Wednesday

Rain and thunderstorm chances return Friday evening and Saturday as a system approaches from the west. However, exact timing and location details remains challenging to pin down as models vary on the strength and location of associated features. With a surface warm front to the south, some LL warm advection, and a weak LL jet pointing towards the area late Friday, this could aid in developing a rain/storm complex Friday night into Saturday morning somewhere in the vicinity; however, not all models are in agreement on this. Additional rain chances occur throughout the rest of Saturday with broad lift from the RRQ of an upper jet, a weak mid- level shortwave to the north, and a ill-defined surface low moving across the state. PoPs are generally in the 40-70% range from Friday evening through Saturday afternoon, but do not expect all hours to be rainy. Severe weather potential is also tough to determine for the same reasons, but other than the often overdone NAM, CAPE maxes out around 1000 J/kg Saturday afternoon.
Shear is higher across northern WI, but this is offset from the better CAPE, and lapse rates are modest. Therefore, while an isolated severe threat cannot be ruled out, the potential for any widespread severe storms appears low. NBM and LREF probabilities only show a 10% chance for 1.0" or more of rain throughout this time period, but if a more substantial complex develops late Friday some localized heavy rain could be possible, mainly across the southern forecast area where pwats up to ~1.7" are noted and where precip is more likely in general due to proximity to the warm front.

After Saturday, there is agreement that high pressure will result in dry conditions on Sunday.

An active weather pattern sets up next week as slow moving and waffling frontal boundaries stall out over or around the area, along with various shortwaves and an active LL jet. This will lead to on/off chances for rain and thunderstorms, with the potential for heavy rains and/or stronger storms in the mix. But determining the specifics will be difficult other than 1-2 days out due to the dynamic nature of the setup and each day will impact the next.

Temperatures will be at or just below normal Saturday and Sunday, and then trend warmer through the rest of the week.

AVIATION
for 12Z TAF Issuance Issued at 542 AM CDT Thu Jul 17 2025

IFR/MVFR ceilings and isolated showers and sprinkles will dissipate this morning as high pressure brings drier air across the region. Flying conditions are expected to improve to VFR everywhere later this morning and remain there for the rest of the TAF period. Some afternoon cumulus clouds are expected later this morning and afternoon with the heating of the day, with mostly clear skies expected tonight. Gusty northerly winds to 15 to 20 knots will ease later this afternoon below 10 knots and continue through tonight.

GRB WATCHES/WARNINGS/ADVISORIES
None.