Marine Weather and Tide Forecast for Manitowoc, WI

DISCUSSION
Issued at 237 AM CDT Tue May 20 2025

Short Term
Today
Tonight...and Wednesday

The latest RAP analysis and satellite/radar imagery show surface low pressure centered over eastern Nebraska and Kansas ahead of a deep upper trough centered over the Great Plains. Broad moisture advection continues aloft in a corridor stretching from the mid- Mississippi Valley into northern Minnesota. This moisture advection is running into a dry airmass which is being funneled into northeast Wisconsin from a Hudson Bay high pressure system.
As a result, showers have mainly remained southwest of Wood County so far early this morning. Between the low over the Plains and the high to the north, a tightening pressure gradient exists over the southwest half of Wisconsin where persistent gusts have been observed from 20 to 30 mph. As low pressure lifts northeast today, precipitation trends, wind potential, and fire weather are the main forecast concerns.

Precipitation trends: Low pressure will travel northeast from eastern Nebraska/Kansas and across Iowa today, then northern Illinois tonight. Precipitation within moderately strong moisture advection will surge northeast ahead of the low track and into central and east- central Wisconsin from late morning through the afternoon. This rainfall will run into a wall of dry air (850-700mb RH < 10%), which will slow the northeast progress of the precip. Have therefore sided with the slower guidance for timing of the precip across the region. It's quite possible that areas near the U.P. border won't see a drop of rain due to the low humidities in that area, while areas south of Oshkosh to Wisconsin Rapids have greater than a 50% chance of seeing a half inch of rainfall by the end of the afternoon. As the previous forecaster noted, there will likely be a sharp cutoff to the precip today.

Due to more of an eastward motion of the low pressure system tonight, the rain will likely not make much progress northward.
But areas across central and east-central will see the showers continue tonight. The light precipitation will then gradually shift south on Wednesday as flow aloft backs more northerly.

Wind Potential: A tightening pressure gradient will bring gusty winds to the region tonight. The strongest winds are forecast to occur over central and east-central WI from about mid-morning through early afternoon before the steady rain arrives. Gusts of 30-40 mph appear possible from forecast soundings. Once the rain arrives, should see gusts subside somewhat. Consensus among surrounding offices was to refrain from any Wind Advisory headlines.

Fire Weather: Very dry air will continue to funnel into far northern WI from a Hudson Bay high pressure system. Stuck with minimum dewpoints near what was observed over the Upper Peninsula yesterday (near 20F). Min humidities with dewpoints this low are forecast to fall in to the middle 20s in this afternoon. Combined with wind gusts of 30 to 35 mph, near critical fire weather conditions will exist over far northern WI this afternoon with high temps in the middle 50s holding back from any Red Flag headlines. Per coordination with WFO DLH and fire weather partners, will continue to message with a SPS.

Long Term...Wednesday Night Through Monday

A relatively stable pattern will be shaping up across North America over the next week. This pattern will consist of an upper ridge over north-central Canada and troughing over the Gulf of Alaska and also the Great Lakes to New England. This trough will generally provide the region with northerly flow, clouds and showers at times, and below normal temperatures.

Rain chances: Low chances (<40%) of light rain will linger over central and east-central WI on Wednesday evening before northerly flow brings in drier air late on Wednesday night. Some clearing is likely thanks to this dry air into Thursday afternoon. Then an upper level low will drop southeast and spread clouds across the area on Thursday night into Friday. Some spotty showers or drizzle look possible at times, particularly near the Upper Peninsula border. A few other widely scattered showers also look possible with diurnal heating beneath persistent troughing on Saturday. In general, rain chances look low (<20%) from Thursday night through Saturday.

Temperatures: Northerly flow looks to be present for much of the period, which will lead to below normal temperatures. The coldest temps at 850mb appear to be on Thursday and Friday and would anticipate temps to trend colder on those days, particularly on Friday if cloud cover is widespread. While cloud cover will pose an issue, low temperatures in the middle 30s are forecast from Wednesday night through Saturday night when there is some frost potential.

AVIATION
for 06Z TAF Issuance Issued at 1109 PM CDT Mon May 19 2025

VFR CIGs are expected across the area through early Tuesday morning as high clouds stream in across the region. Rain will then lift north through the region Tuesday morning through Tuesday afternoon. Conditions should gradually deteriorate to MVFR across central and east-central Wisconsin late Tuesday afternoon into Tuesday evening, with VFR conditions continuing across the north.

Winds will be gusty through the period, with near surface gusts around 20 to 25 knots during the overnight hours and up to 20-30 knots by late tonight through early Tuesday morning.

MARINE
Issued at 237 AM CDT Tue May 20 2025

Poor boating weather is forecast through Wednesday evening thanks to persistent east to northeast winds. Winds will be peaking this afternoon around 25-30 kts before settling in the 20-25 kt range tonight and Wednesday. A Small Craft Advisory remains in effect for the Bay and Lake through Wednesday evening.

GRB WATCHES/WARNINGS/ADVISORIES
None.