Sunrise 5:45 AM   Sunset 7:53 PM Moonrise 12:00 AM   Moonset 7:28 AM

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LMZ542 Sturgeon Bay To Two Rivers Wi-two Rivers To Sheboygan Wi- 122 Pm Cdt Sat Apr 27 2024
.small craft advisory in effect through Sunday evening - .
This afternoon - SW wind 15 to 25 kts with gusts to around 30 kts. A chance of rain showers and a slight chance of Thunderstorms. Waves 4 to 7 ft. Tonight - W wind 10 to 15 kts veering ne after midnight. Gusts to around 25 kts. A chance of Thunderstorms in the evening. A chance of rain showers. Waves 4 to 7 ft subsiding to 1 to 3 ft. Sunday - NE wind 10 to 20 kts with gusts to around 30 kts. Rain. Waves 2 to 4 ft building to 3 to 5 ft in the late morning and afternoon. Sunday night - NE wind 10 to 20 kts veering E after midnight. Rain in the evening. A chance of Thunderstorms. Rain showers after midnight. Waves 2 to 4 ft subsiding to 1 to 3 ft late in the evening, then building to 2 to 4 ft after midnight.

LMZ500
No data

FXUS63 KGRB 271731 AFDGRB

Area Forecast Discussion National Weather Service Green Bay WI 1231 PM CDT Sat Apr 27 2024

Updated aviation portion for 18Z TAF issuance

KEY MESSAGES

- Southwest winds could gust to 45 mph or more in the Fox Valley and Manitowoc and Kewaunee counties this afternoon.

- It remains possible that conditions will support a few strong to severe storms this afternoon into this evening across northeast Wisconsin, with the greatest risk of severe storms from 3 pm to 9 pm south of highway 29 from the Fox valley to the lakeshore.
There is still a lot of uncertainty in the coverage of strong or severe storms.

- Several systems will bring periods of showers and thunderstorms tonight through mid-week. Periods of moderate to heavy rain Sunday into Sunday night could result in isolated flash flooding in urban and low lying areas. Rivers will be on the rise through the middle of next week, with a few of them reaching bankfull stage.

- Conditions hazardous to small craft are expected this weekend on the Bay and Lake. A few gale force gusts are possible this afternoon, especially on the southern end of the bay.

DISCUSSION
Issued at 414 AM CDT Sat Apr 27 2024

Short Term
Today
Tonight...and Sunday

Wind and convection trends today are primary concerns.

Deep sfc low around 995mb is lifting into southwest MN with sfc warm front as close as northern IA and far southwest WI. Warm air advection aloft and very limited elevated instability resulted in bands of showers lifting across the area since last evening. More recent activity has carried isolated thunder as well as the instability aloft is building in from the southwest. Clusters of convection lifting across the bay and Lake Michigan and over central WI will lift north next few hours leaving rest of the morning mainly dry as sfc warm front mixes northeast battling cool, moist SE flow off northern Lake Michigan and the bay.

Eventually by early afternoon as sfc low tracks over Lake Superior effectively the warm sector will be over most if not all of the area. Soundings continue to show well mixed sfc-H85 layer leading to SW gusts 45-50 mph for at least a few hours over east-central WI, maximized across the Fox Valley to the southern shore of Green Bay. Gusts of 40-45 mph will likely make it into portions of Marinette and Oconto counties this afternoon, but left the going wind advisory in place where confidence was highest winds will shift to SW and mixing will be strongest. Though there is still some concern about S flow holding down temps near the immediate lakeshore and downwind of the bay, continued to favor continuity and model/MOS consensus in running high temps well into the 70s for all but far north-central WI.

These temps along with dewpoints to around 60 by mid to late afternoon will result in building MLCAPES upward of 1000-1500J/kg, but the greatest instability still looks to be locked up southeast of a line from Wood County into Brown/Kewaunee counties and even more so into the far southern fringe of our cwa. As has shown up last two days, even with the forecast instability, convective initiation is uncertain given H8-H7 capping still forecast in shortwave ridging and mid-level drying between negative tilted shortwave trough lifting the sfc low to our northwest and north and next shortwave trough well upstream over the high plains. This even as there will be a cold front crossing the area late this afternoon (north-central) to early evening (east-central). Models are very underwhelmed in additional convection this afternoon especially northwest of the Fox Valley into northern WI. Still some isolated convection showing up in various model runs over far south portion of cwa late today, after 21z. Real tough situation because as was mentioned in previous discussion, if convection can form, it would certainly have the potential to become severe with more than sufficient instability and strong effective shear over 40 kts. All modes of severe weather could occur. But the main question is will there be any storms in our area at all or will they develop just to the south? We will continue to message the conditional threat as our area is still within Day1 marginal and slight risks from SPC. But, considering parts of our area (north-central) now have limited if any pops, it is becoming more of a challenge.

Late tonight, next round of leftover showers and some storms will approach from the southwest. These showers will gradually develop into more widespread area of moderate rain on Sunday spreading from southwest to northeast. Rain totals on Sunday will be from a half inch to an inch. The rain will be supplemented by a cool, moist northeast wind flowing in off Lake Michigan and the bay as the wave of low pressure will remain to the southwest. Temps were lowered as a result and it seems like some areas over north- central WI and closer to the bay and lake may spend most of the day with readings below 50.

Long Term...Sunday Night Through Friday

500mb ridging across the mid-Atlantic states and a closed low across the northern plains will result in a moist southwest flow pattern Sunday night into Monday. At 00z Monday, the surface warm front will be located along the Wisconsin/Illinois border. A low level jet is expected to increase to 40 to 50 knots Sunday evening, resulting in showers and increasing chances for thunderstorms as the better elevated instability lifts northward into the area. With precipitable water values of 1 to 1.5 inches, locally heavy rainfall is a distinct possibility. Localized flash flooding, especially in urban areas will be highlighted. The steadier rain should taper off to scattered showers and storms after 06z Monday. A few strong or severe storms are possible in the late evening and overnight hours as reflected in the Storm Prediction Center Day 2 Outlook that has a Marginal Risk across portions of central Wisconsin east into Winnebago County.

The chances of thunderstorms continue on Monday until the cold front moves east of the area. Current thinking is the cold front should move east of the lakeshore counties around 20z. May need to watch to see if there would be some stronger storms across far eastern Wisconsin with the better chance to warm up. Dry conditions are expected Monday night and for most of the day on Tuesday. The next system will bring chances of showers and storms Tuesday night into early Wednesday morning. The forecast becomes muddled Wednesday afternoon into Thursday due to timing differences of the next feature, which the timing has been inconsistent the last few night. Mainly dry conditions are anticipated for Friday.

AVIATION
for 18Z TAF Issuance Issued at 1230 PM CDT Sat Apr 27 2024

Windy conditions will continue at the TAF sites this afternoon with southwest winds gusting to 30 to 40 knots at times. Winds will slowly ease this evening below 20 knots then increase again late tonight into Sunday morning as they turn to the northeast and gust to around 20 knots.

Isolated showers and storms may redevelop after 22z, mainly south and southeast of GRB and ATW as a cold front moves through the area. After these showers and storms end this evening, most of the night should stay mainly dry.

Ceilings will be IFR near the Lake Michigan shore, although satellite imagery shows the low stratus is dissipating from south to north. MVFR ceilings are expected across north-central Wisconsin with VFR across most of central and east-central Wisconsin. Other than RHI, most sites will be VFR this evening then trend towards MVFR late tonight into Sunday morning. Another low pressure system will bring steady rain to the area late tonight into Sunday morning and last through Sunday night.

GRB WATCHES/WARNINGS/ADVISORIES
Wind Advisory until 4 PM CDT this afternoon for WIZ030-031- 035>040-045-048>050.

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