Marine Weather and Tide Forecast for Manitowoc, WI

DISCUSSION
Issued at 218 PM CDT Fri May 15 2026

Near term through Saturday...Clear skies along with warm and breezy conditions this afternoon. 12z MPX sounding showed high dewpoint depressions in low-levels and expect sfc dewpoints to mix out this afternoon. This is already happening north-central WI.
Weak front, more of a wind shift, approaches late today but the dry air and low dewpoints leads to less instability/MUCAPEs than what was projected earlier. Thus, like the CAMs that are more muted with convection late today into early this evening. Most showers and a few storms likely will not occur until after 8p.
Given effective shear of 40kts, stronger storm could occur, but less likely given lower MUCAPE mainly below 500J/kg through the evening. Decaying showers and storms shift into eastern WI overnight. All areas should be clear of rain by 7a on Saturday.
Rest of Saturday will be warm, breezy and mostly sunny.

Chances for showers and storms Sunday through Monday night...Warm front lifts across the area late Sunday through Sunday night.
WI being on the northern edge of building instability from plains, increasing low-level jet and hint of wave aloft generated out of convection to the southwest Saturday night will bring showers and some stronger storms late Sunday morning through Sunday afternoon. Small risk of marginally severe hail, but greater chances will be farther south/southwest into higher instability. Sunday night will bring another round of elevated storms and with greater elevated instability a better potential for severe storms.

Monday in terms of dynamics and instability is the most favorable day for severe weather as western Great Lakes region is ahead of deeper trough and sfc pre-frontal trough and sharper cold front.
Sfc MUCAPEs increase to 1500-3000 J/kg as temperatures reach the lower 80s and dewpoints make it into the 60s area-wide. As this occurs, effective shear peaks at 40-60 kts late Monday afternoon into Monday evening. Despite this, models are not completely on board with high-end severe signal yet. Some models keep conditions mainly dry until later Monday evening when initial trough arrives.
ML projections show mixed signals too. Thankfully, there is time to further hone in on these details. Currently SPC has highlighted much of our area in a Day 4 30% which would typically equate to at least an enhanced risk once we get closer to the event. Given the CAPE and shear, there is a potential for all hazards.

There is also a potential for locally heavy rainfall this weekend through Monday night due to increasingly moist airmass (PWATs of 1.2 to 1.6 inches). LREF shows a 60-80% chance of seeing over 1 inch of rain Saturday night through Monday night, but less than a 20% chance of over 2 inches. Greatest probabilities are over central to north- central WI.

Cooler and not as active rest of next week...Cold front moves through late Monday night into Tuesday, followed by a decreasing threat of showers and storms. Once the front clears the area, drier weather and a return to near normal temperatures is expected through the rest of next week.

AVIATION
for 00Z TAF Issuance Issued at 703 PM CDT Fri May 15 2026

Main concern to watch over the TAF period is developing thunderstorms. At 00Z storms were located across southeast MN and north-central IA. Some recent trends show these storms following an instability gradient northeast into central WI and the Fox Valley during the mid to late evening, and potentially impacting KGRB and KATW a little earlier than previously anticipated.
Adjusted PROB30 groups in TAFs to account for this, but confidence in timing is medium to low given the more recent shift and the amount of dry air to overcome as this precip shifts east.
Overall, scattered showers and thunderstorms are expected from mid to late evening through late tonight (~02Z to 10Z) area wide. The potential for isolated strong to marginally severe storms remains highest in central WI, but more likely south and west of there.

South to southwest winds remain gusty through late evening, with gusts up to 25 kts. Additionally, LLWS develops this evening and then tapers off late tonight. Winds veer to the west Saturday morning, and then increase with gusts to 25 kts again from late morning through the afternoon.

FIRE WEATHER
Issued at 218 PM CDT Fri May 15 2026

Pine fuels have reached their peak volatility and fine fuels have still not greened up over northern WI, so periods of dry and windy weather will bring near-critical fire weather conditions through Saturday.

A Red Flag Warning continues through 9 pm this evening over Vilas County. Weather conditions should reach critical levels, with highs into the 80s, RHs around 20% and southwest winds around 15 mph gusting to 25-35 mph.

Have to watch tonight as coverage and intensity of developing showers and storms will have impact on whether Saturday is another fire weather day. As it stands now, there is a chance for scattered showers and storms over northern WI which could impact dryness of fuels if coverage is high enough. If this doesn't occur though, dry air remains across northern WI on Saturday, with RHs dropping to 17-22% along with west winds around 15 mph with gusts to 20 to 25 mph. At this point an SPS will be issued for much of the Northwoods region Saturday afternoon.

GRB WATCHES/WARNINGS/ADVISORIES
Red Flag Warning until 9 PM CDT this evening for WIZ005.