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LMZ543 Expires:202404262000;;402439 Fzus53 Kgrb 261151 Nshgrb
nearshore marine forecast national weather service green bay wi 650 am cdt Fri apr 26 2024
for waters within five nautical miles of the shore on lake michigan
lmz542-543-262000- sturgeon bay to two rivers wi-two rivers to sheboygan wi- 650 am cdt Fri apr 26 2024
.small craft advisory in effect from this evening through late Saturday night - .
Today - SE wind 10 to 20 kts with a few gusts to around 25 kts. A chance of rain showers in the afternoon. Waves 2 to 4 ft. Tonight - SE wind 15 to 25 kts with gusts to around 30 kts. Rain showers likely in the evening. A chance of Thunderstorms. A chance of rain showers after midnight. Waves 2 to 4 ft building to 4 to 7 ft. Saturday - S wind 15 to 25 kts. A chance of light showers and Thunderstorms. Waves 4 to 7 ft. Saturday night - SW wind 10 to 20 kts with gusts to around 25 kts veering N 10 to 15 kts after midnight. Rain showers likely and a chance of Thunderstorms. Waves 4 to 7 ft subsiding to 2 to 4 ft after midnight.

LMZ500
No data

FXUS63 KGRB 261142 AFDGRB

Area Forecast Discussion National Weather Service Green Bay WI 642 AM CDT Fri Apr 26 2024

Updated aviation portion for 12Z TAF issuance

KEY MESSAGES

- Elevated fire weather conditions are expected today over northern Wisconsin as relative humidity values fall to around 25 percent and southeast winds increase to 15 to 20 mph with gusts to 30 mph. Rain arriving this evening will bring some relief to the fire concerns.

- Two systems will result in several chances for showers and thunderstorms tonight through Monday. The main hazard with the storms tonight into early Saturday will be small hail and gusty winds. There is a potential for strong to severe storms with large hail and damaging winds Saturday afternoon into Saturday evening, though coverage of storms is still uncertain.

- Storms on Sunday into Sunday night could produce periods of moderate to heavy rain, resulting in chances for isolated flash flooding.

- Conditions hazardous to small craft will be possible at times tonight through the weekend on the Bay and Lake.

DISCUSSION
Issued at 411 AM CDT Fri Apr 26 2024

Short Term
Today
Tonight...and Saturday

One more day of fire weather concerns, then convection potential is main story tonight and Saturday.

SE flow is steady early this morning on western edge of high pressure now centered over southern Ontario up the St. Lawrence Valley. Dry low-levels tied to the high will hold off most of showers today ahead of vigorous shortwave trough, deep sfc low over the central Plains. Given the slower arrival of showers, elevated fire weather concerns will linger for one more day from northwest of the Fox Valley on into northern Wisconsin.

Showers will not arrive until very late this afternoon, so a slower trend continues. Currently, showers and storms are on the edge of sharp H85 moisture gradient. This will mainly lift across our region tonight as warm front aloft arrives from the south ahead of negative tilted mid-level low moving into eastern SD/southwest MN. Expect a period of showers and storms to lift south to north across WI, with coverage tailing off after midnight over southern CWA Generally, elevated CAPEs and effective shear have diminished (MUCAPE around 300J/kg and shear less than 30 kts), so think this takes us out of much risk of large hail. Even so, could see smaller hail (pea to nickel sized) in the isolated strong storms as mid-level lapse rates are aoa 7c/km. Gusty winds not out of question as well with stronger winds aloft of decent low-level inversion. All of these expectations should be covered with the age-old adage in meteorology to never trust a warm front.
Thus, would not be shocked if an isolated severe storm occurs as the warm front moves through. Temps will rise late as the warm front approaches which then brings us to Saturday.

Lingering elevated convection should be on the slow exit northward in the morning over northern and far northeast WI across the Door Peninsula. These storms too could carry a small hail threat. By early afternoon, initial mid-level trough will be over western Lake Superior while next shortwave trough will be well upstream over CO/KS. That leaves much of WI within weak shortwave ridging and sure enough, forecast soundings show capping H8-H7 even over central to east-central WI ahead of approaching cold front and into what will be a moderately unstable warm sector (temps mid- upper 70s and dewpoints into the lower 60s). If convection initiation can occur, MLCAPES at least 1000J/kg and effective shear at least 40 kts will support organized convection. From this perspective it appears larger scale forcing and capping may limit storm coverage but any storms that do form will be strong to severe, so a conditional setup. SPC Day2 outlook maintains the slight risk for severe for large hail and damaging winds and we continue to message the severe potential at this time. Being farther away from forcing ahead of the cold front and not as much into the unstable airmass, north-central WI will see less of a chance of any showers and storms by Saturday afternoon.

Long Term...Saturday Night Through Thursday

The first of two systems will move across the area Saturday night. A cold front will move across northeast Wisconsin Saturday evening, bringing the chances of showers and thunderstorms to the area. The biggest concern tonight is the bufkit soundings are showing a warm layer between 700-800mb that could inhibit or reduce the cover of storms as the cold front moves across the area. Except for the NAM, models are not impressive with QPF totals which would suggest isolated to scattered coverage of storms if it can break the warm layer. The NAM was considerably more bullish with activity along the cold front.
If storms do get going, CAPE values of 1,000 to 2,000 J/KG and 0-6km shear values of 35 to 45 kts will support strong to severe storms.
The best chance for the strong or severe storms will be across northeast Wisconsin, especially along the Interstate/Highway 41 corridor east to the lake.

The front is expected to sag southward Saturday night, likely being aided by outflow boundaries from any convection and a more dense air mass as winds turn northeast off the colder waters of the bay and Lake Michigan. Latest MET/MAV guidance indicating northeast winds sustained at 12 to 16 kts at Green Bay by 12z Sunday. With this in mind, the boundary should be well south of the area Sunday morning, which may impact the northward extent of the thunderstorm activity. For the morning hours, only have a slight chance of storms south of Highway 29. With easterly flow, thick cloud cover and rain expected through much of the day, lowered high temperatures by 4 to 7 degrees. The warm front will try to approach our southern counties by late in the day, which will result in the chances of storms pushing northward.

The better chances for stronger storms will be Sunday night as the warm front lifts northward across the area. The cold front then is expected to move across the area on Monday which will bring continued chances of showers and storms. If this feature slows down any, will need to consider the possibility of stronger storms across eastern Wisconsin due to the heating of the day and better CAPE values, especially if there is some partial clearing. Dry conditions are expected Monday night before the next system brings another chance of showers and storms on Tuesday afternoon and evening. For Wednesday into Thursday, there are some model difference on when a system moves across the area. Did not make any significant changes in this time frame until there is better resolution in the timing of this system.

AVIATION
for 12Z TAF Issuance Issued at 641 AM CDT Fri Apr 26 2024

Dry conditions will prevail until mid-afternoon, with increasing mid to high clouds. Showers are expected to overspread the region from SW to NE mid-late afternoon through early evening, with numerous showers and scattered thunderstorms impacting the region tonight. Conditions should remain VFR until the steadier showers arrive this evening, then deteriorate to MVFR and localized IFR conditions thereafter.

Southeast winds will increase and become quite gusty by late this morning. LLWS is expected regionwide tonight as robust low- level jet shifts arrives atop of strong low-level inversion.

FIRE WEATHER
Issued at 411 AM CDT Fri Apr 26 2024

Elevated fire weather conditions are expected today as the rain showers are further delayed across the region. North-central and northeast Wisconsin will continue to see elevated fire weather conditions as relative humidity values fall to as low as 25 percent during the afternoon while southeast winds of 15 to 20 mph with gusts to 30 mph occur along with temperatures near 60.
A special weather statement has been issued to highlight the elevated fire weather conditions. Rain showers finally arriving during the evening will bring some relief to fire concerns.

GRB WATCHES/WARNINGS/ADVISORIES
None.

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