Marine Weather and Tide Forecast for Cedar Grove, WI

SHORT TERM
Issued 318 PM CDT Sun Apr 20 2025

Tonight and Monday:

Rainfall continues across southern Wisconsin as a low pressure system starts to advect north northeast out of MO. A wing of 850mb warm air advection is the driving force for our showers and few rumbles of thunder this afternoon. With some drier air and weaker ascent behind the leading edge of the WAA has led to some scattered showers across southwestern and south central Wisconsin. Scattered showers/convection is expected to continue through the evening until the Low pressure system lifts into Wisconsin. Due to the scattered nature of the showers its likely for a few lulls in activity, especially across southeastern Wisconsin. Once the Low behinds to lift through the region it will bring an additional "round" of rain to the state.

With the large scale ascent and the cold front dragging across the region as well there will be a greater chance for a few rumbles of thunder (roughly 60% chance). The greater the warm air advection at the surface prior to the passage of the cold front this evening the better the chances for thunder.

Meanwhile areas along and west of I-39 continue to have the best potential for rainfall near an inch. Guidance and ensembles continue to show support for longer duration and more steady rainfall for locations west of I-39. Areas to the east are expected to continue to see the showery activity with lower rainfall rates which will result in 0.25 to 0.5 inches of rain for areas to the east. Outside of any thunderstorms rainfall rates are expected to remain light to moderate with rates around 0.1 inches or less. Can't rule out some heavier but brief rainfall with any thunderstorms along the cold front.

Not anticipating any stronger or severe storms today. Heating at the surface is very limited today under the rain and continued cloud cover to even make southern Wisconsin unstable. While there is mid level WAA there is little in the way of large scale lift until the Low and cold front move through, but the environment they are moving into is fairly stable. Lapse rates are low and MUCAPE is tiny with values around 200 J/kg or less.
Essentially enough upward instability and momentum in the mid levels to get some thunder, maybe some small hail, but otherwise not much to write home about.

A few wrap around showers will be possible early Monday as this low pressure system departs the state, otherwise dry conditions are expected to return by late Monday morning into Monday afternoon. Showers will end from southwest to northeast. Cooler temperatures similar to today are expected Monday. Those along the lakeshore may feel the greatest impact here as there will not be breezy winds coming off the cool lake.

Patterson

LONG TERM
Issued 318 PM CDT Sun Apr 20 2025

Monday night through Sunday:

The surface low that brought rain will continue to move northeast into Ontario and Quebec Monday night into Tuesday. On its heels will be a surface high pressure and an upper level ridge. These two features will move though the Great Lakes quickly with the dry weather and light winds ending by Tuesday evening into Wednesday. A shortwave trough will slide through the state late Tuesday into Wednesday bringing with it a 40-60% chance for rain. The shortwave will provide some upper level lift while WAA and a LLJ in the mid to low levels increase lift and moisture. There remains some uncertainty on the track of this shortwave and location of the LLJ. Little shifts could lead to some more moisture or more instability leading to a great potential for thunderstorms and more widespread rain.

Strong to severe storms are pretty conditional here similar to systems earlier in the weak. Being a bit on the pessimistic side, the presence and location of the LLJ will be fairly crucial. Not only will this provide ascent and moisture, but it could further destabilize the mid levels. Models do try to bring in CAPE around 1000 J/kg, but we might not be able to actualize if there is a cap. Lots of things to consider, but based on current models if anything does become stronger its likely to be more a hail and wind concern. Will have to keep an eye on it moving forward.

Zonal flow aloft is expected Wednesday through Friday across the Great Lakes Region. During this time weak high pressure will keep the state largely dry through this period. Any small shortwave moving through the larger flow could briefly add low chance POPs of roughly 20%. There is much more uncertainty here on if these shortwaves will actually be there or if there track is correct. Thus models are all over the place here. Friday night into Saturday looks to be the best potential for our next chance for rain as the zonal flow begins to break down.

Patterson

AVIATION
Issued 318 PM CDT Sun Apr 20 2025

VFR conditions are expected to continue across southern Wisconsin through this afternoon. Rain is moving in from the southwest this morning and will overspread the entire area over the next couple hours. As a low pressure system advances from MO, lower MVFR to IFR ceilings will move from the southwest.
These lower ceilings are expected to overspread southern Wisconsin this evening into tonight. More specifically,areas west of I-39 (MSN and JVL) will see more persistent rainfall and lower flight conditions while areas further east are likely to see more off and on type of showers this afternoon and tonight. Can not rule out a few thunderstorms this evening and tonight.

Breezy easterly winds this morning are expected to continue into tonight before becoming southerly. Southerly winds overnight will become westerly behind the exiting low pressure system Monday. Westerly winds are expected through Monday night.

Patterson

MARINE
Issued 318 PM CDT Sun Apr 20 2025

High pressure around 30.5 inches continue to pull northeast toward the New England states. On its heels is a low pressure system around 29.6 inches in Missouri that will advect northeast into Wisconsin tonight. This low pressure system will continue northeast into Ontario then Quebec by Tuesday. East to south winds will become gusty between this incoming low and exiting high. Gusts to around 30 knots will be possible through tonight until winds become southwest to westerly. A Small Craft Advisory is in effect for the nearshore waters this evening and tonight.
Winds will increase as the low pressure moves over the lake leading to gale force gusts across the southern 2/3rds of the lake.

High pressure will briefly build back into the Great Lakes Region Tuesday leading to some lighter northwest becoming light and variable. Additional chances for rain and thunderstorms midweek.

Patterson

MKX WATCHES/WARNINGS/ADVISORIES
WI...None.
LM
Small Craft Advisory
LMZ643-LMZ644-LMZ645-LMZ646...7 PM Sunday to 7 AM Monday.

Gale Warning...LMZ080-LMZ567-LMZ643-LMZ644-LMZ645-LMZ646- LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-LMZ868-LMZ870- LMZ872-LMZ874-LMZ876-LMZ878...7 AM Monday to 7 PM Monday.