Marine Weather and Tide Forecast for Beloit, WI

UPDATE
Issued 957 PM CDT Fri Apr 18 2025

A few showers will linger into early tonight, with the main thunder threat over at this point. Cooler temperatures will continue to settle into southern Wisconsin tonight behind a cold front, with lows in the 40s most places tonight. Overall, the forecast looks on track through the rest of the night.

DDV

SHORT TERM
Issued 317 PM CDT Fri Apr 18 2025

Tonight through Saturday night:

A mid level shortwave is approaching from the northern plains this afternoon. Showers/storms are already starting to fire ahead of the cold front and ahead of this mid level shortwave across far southern Wisconsin. The effective front is likely across portions of southern Wisconsin where temperatures are in the 70s and dewpoints are in the 60s. This will be the area to watch convection as it starts to bubble up this afternoon.
Effective shear has been great across the state today with values around 60 or greater. CAPE is still on the lower end, but mid level lapse rates are great at 9c/km. Any low/mid level capping will keep storms in check for a while. Once we break through the capping the game is on for any stronger to severe storms.

The cold front is likely to provide that forcing necessary to have storms break the cap. South central and southeastern Wisconsin are like to have the best potential for stronger to severe storms given the set up. Strong wind and large hail will be the main concerns. Mid level lapse rates are great for hail support. For anything that does become surface based can't rule out the potential for a brief tornado, but the play for that looks limited to roughly, Rock, Dane and Walworth where the effect front has pulled far enough north to put them in a "warm" sector. This window could close quickly as rain moves over this area.

As the cold front moves through winds will shift to northwesterly behind the front and dry air will begin to work in on the backside. The last of the rain/storms are expected to move out of southeastern Wisconsin by roughly 10 to 11 PM. High pressure will begin to move in behind the this system tonight into Saturday from the central Plains. This will keep conditions dry throughout the day Saturday and into Saturday night.
Slightly cooler temperatures expected Saturday under the northwest winds and weak caa. Highs will be in the lower to upper 50s.

Patterson

LONG TERM
Issued 317 PM CDT Fri Apr 18 2025

Sunday through Friday:

The next chance for rain/storms will be Sunday into Monday. Good model consensus remains for a low pressure system to advect northeast out of the Central Plains and move through southern Wisconsin Sunday night into Monday. Warm air advection will be good ahead of this system bringing temperatures into the upper 50s to low 60s prior to the start of the rain. WAA and theta e advection will kick off the start of the rain/shower Sunday afternoon. Then rain/storms will continue as the low moves in with increased lift and instability give us a chance for chances for thunderstorms. Once the rain moves in cooler air will prevail.

Rain will linger through Monday morning as the shortwave and low pressure system pull out to our east. Skies are expected to remain cloudy behind the exiting low. Temperatures are still a bit uncertain Monday due to the timing of the wind shift behind the low and the CAA. Temperatures in the 40s to 50s are likely but that 10 degree swing between could make for either a pleasant or chilly day.

High pressure will slide into the area Monday night and quickly exit to the east Tuesday morning as another weak short wave approaches the region. As the shortwave, approaches the state there will be a small chance (20-40%) for some showers and storms.

Mostly dry conditions are expected Wednesday and Thursday, but the pattern is open to shortwaves moving through during this period, so low end precip chances will continue through mid- week. Near to above normal temps are likely to continue for Wed and Thu.

Patterson

AVIATION
Issued 957 PM CDT Fri Apr 18 2025

Showers and occasionally reduced visibilities will wind down late this evening into early tonight, with dry weather then expected the rest of the night through Saturday as high pressure begins to build in from the west. Seeing a few observations in the southeast that have popped up to VFR with their ceilings this evening, but expecting MVFR to IFR ceilings to settle in behind the departing cold front over the next couple hours.
Widespread ceilings of 5-15 hft should linger much of the night, with VFR conditions likely to gradually return west to east Sat morning into the afternoon as the high builds in.

Northwest winds behind the cold front tonight will persist into Saturday, aside from winds turning onshore near the lake in the afternoon.

DDV

MARINE
Issued 317 PM CDT Fri Apr 18 2025

Breezy southerly winds persist as low pressure continues northeastward from IA into WI and then crossing central portions of the Lake this afternoon. Expect to see small craft conditions across southern WI nearshore zones through this afternoon/evening. A cold front will extend southwest from the low crossing the southern half of lake later this afternoon and evening. Modest south winds will veer northwest through this evening (beginning with the northern lake, then the southern half as the front passes). There are chances for thunderstorms along with some hail and strong winds across southern half of the Lake later today into tonight with the cold front. Modest northwest winds continue behind the cold front overnight followed by lighter north winds Saturday, as high pressure builds into the Great Lakes region.

Patterson

MKX WATCHES/WARNINGS/ADVISORIES
WI...None.
LM...None.