Sunrise 5:32 AM   Sunset 8:02 PM Moonrise 4:33 AM   Moonset 6:32 PM

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LMZ366 Expires:202405061515;;710195 Fzus63 Kmkx 060755 Glflm
open lake forecast for lake michigan national weather service milwaukee/sullivan wi 255 am cdt Mon may 6 2024
for waters beyond five nautical miles of shore on lake michigan.
waves are provided as a range of significant wave heights, which is the average of the highest 1/3 of the wave, along with the average height of the highest 10% of the waves which will occasionally be encountered.
Synopsis -
currently light and variable surface flow will begin to increase out of the east today, ultimately shifting out of the southeast from tonight through Tuesday morning as a 29.0 inch low pressure center develops over the northern great plains. An area of showers and embedded Thunderstorms will approach from the west Tuesday morning, ultimately crossing the open waters during the afternoon hours. Said activity is not currently anticipated to be strong/severe. Additional shower and storm activity can't be ruled out on Tuesday evening, though coverage will be more scattered compared to the afternoon round of rainfall. Any storms developing Tuesday evening would be capable of gusty winds and hail. Winds will turn out of the southwest Tuesday night as a 29.5 inch low pressure center moves from the open waters toward lake huron, prior to turning out of the northeast on Wednesday afternoon as a second area of 29.5 inch low pressure approaches from the central great plains. Additional showers and Thunderstorms are possible as the second area of low pressure approaches. Winds will turn out of the north through the end of the week as high pressure builds into the great plains.
lmz261-362-364-366-563-565-567-868-061515- lake michigan from seul choix point to rock island passage 5 nm offshore to mid lake- lake michigan south of a line from seul choix point to the mackinac bridge and north of a line from charlevoix mi to south fox island 5 nm offshore- lake michigan from charlevoix to point betsie mi 5 nm offshore to mid lake- lake michigan from point betsie to manistee mi 5 nm offshore to mid lake- lake michigan from rock island passage to sturgeon bay wi- lake michigan from sturgeon bay to two rivers wi 5 nm offshore to mid lake- lake michigan from two rivers to sheboygan wi 5 nm offshore to mid lake- lake michigan from pentwater to manistee mi 5 nm offshore to mid lake- 255 am cdt Mon may 6 2024
sheboygan wi to pentwater mi north - .
Today - East winds 5 to 10 kt becoming northeast. Waves 1 ft or less. Tonight - Northeast winds 10 to 15 kt becoming southeast 10 to 20 kt. Waves 2 to 4 ft. Tuesday - Southeast winds 15 to 25 kt increasing to 30 kt. Rain showers likely in the afternoon. Waves 3 to 5 ft. Tuesday night - Southeast winds 15 to 25 kt veering to southwest 10 to 15 kt overnight. Chance of rain showers. Waves 3 to 5 ft subsiding to 1 to 3 ft. Wednesday - West winds 10 to 15 kt veering to northeast. Waves 1 to 2 ft. Wednesday night - Northeast winds 15 to 25 kt increasing to 30 kt. Chance of rain showers. Waves 1 to 3 ft building to 3 to 5 ft. Thursday - Northeast winds to 30 kt becoming north. Chance of rain showers. Waves 4 to 6 ft occasionally to 8 ft. Friday - North winds 10 to 20 kt becoming northwest. Waves 2 to 4 ft.

LMZ300
No data

FXUS63 KGRB 061159 AFDGRB

Area Forecast Discussion National Weather Service Green Bay WI 659 AM CDT Mon May 6 2024

Updated aviation portion for 12Z TAF issuance

KEY MESSAGES

- Relative humidity values are expected to drop into the middle 20s and 30s this afternoon. Recent rain, lack of gusty winds and continued green-up will limit fire weather concerns.

- Next round of showers and storms arrives Tuesday morning. Best chance for thunderstorms will be Tuesday afternoon and evening.
There is a marginal risk for severe storms south and west of an Antigo to Kewaunee line.

- Showers will again be possible Wednesday afternoon through Thursday with a few storms possible Wednesday afternoon and evening, mainly in central WI.

DISCUSSION
Issued at 419 AM CDT Mon May 6 2024

Short Term
Today
Tonight...and Tuesday

Quiet early May weather continues today, then active weather arrives on Tuesday. Main forecast concerns will be low relative humidities today and rain amounts / severe weather risk on Tuesday.

Rain Amounts / Thunder / Severe Threat / Clouds:

Any patchy ground fog over north/northeast WI early this morning will burn off quickly after sunrise, with sunny skies prevailing to start the day as high pressure slides into the eastern Great Lakes. Forecast soundings showing less moisture in the boundary layer today, but could just be enough to get some fair weather cumulus clouds to develop, especially north/west of the Fox Valley. High clouds will increase from the west in the afternoon and evening.

Attention turns to the deep low pressure that will sit and spin across western SD/ND today into Tuesday. Large band of rain will spread northeast across the area on Tuesday, arriving after 12z in central WI, as an occluded front approaches, and strong FGEN and PWATs of 1.0-1.25" sweep across the state. The band will be moving pretty quickly, with most spots only seeing the rain for 3-5 hours before it shuts off. This band will be encountering drier air as it works in, so some weakening is expected as well. Models vary from 0.10" to over an inch of rain with this first wave, with HRRR mean between 0.30-0.70" which seems reasonable, but leaning toward the lower amounts for most locations. Locally higher amounts would be associated with any storms in the afternoon.

Speaking of the storm threat, a few embedded non-severe storms will be possible with the first band of rain, but MUCAPEs look to lag the best forcing. Chances for thunder look to be under 15% in the morning so will not include. The threat for strong to possibly severe storms is increasing later in the day, especially across central and east-central WI. Still some questions regarding just how much clearing/heating will occur, which will determine how unstable we can get. But models continue to show MLCAPE increasing to 500-1000 J/kg, possibly as much as 1500 J/kg with shear up to 30-35 kts (at least early in the afternoon, then decreases late in the day). In addition, mid-level lapse rates approach 7.5-8.5 C/km and a shortwave will all combine to produce another round of showers and storms. If the instability is realized, low-topped supercells would be expected, aided by 0-3km CAPE climbing to 300 J/kg. Damaging winds, hail (aided by wet- bulb zero heights under 8000 ft) and an isolated tornado would be possible. SPC has introduced a marginal risk of severe weather from Antigo to Kewaunee southward, which seems reasonable with expected ingredients but still some uncertainty. If it becomes clearer that the better instability will be realized and work far enough north into our area, the severe threat will increase.

Temps / Relative Humidity / Winds:

925/850mb temps support highs in the upper 60s to low 70s across most of the area today, with cooler readings near Lake Michigan as an onshore flow will prevail. Southeast winds will increase later this morning and afternoon with gusts of 15 to 20 mph expected at most spots. Relative humidities this afternoon will drop into 20s to mid 30s across most locations away from Lake Michigan, lowest in the sandy soil areas. Recent rain and lack of gusty winds will limit the overall fire weather concern today. However, slightly elevated fire weather conditions are possible this afternoon as soils dry out, especially over northern WI where the green-up has been the slowest.

Lows tonight will stay in the 40s to around 50 for most of the area. Winds aloft will really ramp up overnight (to nearly 40 kts at 2000 ft), but an inversion should limit gusts at the surface.

Highs on Tuesday will be tricky with the wave of rain/clouds holding temps down over the north, but some brief clearing behind the band and south/southwest winds allowing for a push of warmer air in the afternoon. Still some question just how far north this push will be and how warm it will get. Looking like most spots will likely stay in the 60s, but some 70s will be possible over the south. As mixing increases Tuesday morning, southeast winds will get gusty, up to ~35 mph.

Long Term...Tuesday Night Through Sunday

There is a chance for showers and a few storms nearly everyday during the extended period. However, the potential for any severe weather or a washout is low at this time.

Tuesday night through Thursday...Showers and a few storms may linger through Tuesday night into Wednesday morning, mainly across northern WI where the deeper moister remains thanks in part to northerly winds off Lake Superior. Expect much of the region to turn dry Wednesday morning as drier air filters over the area behind an occluded front. The dry conditions may not last long as the next round of showers and storms is progged to arrive Wednesday afternoon as a weakening cyclone slowly moving east out of the northern Plains merges with a surface low pushing northeast out of the central Plains. As these systems merge models are picking up on a band of heavier rainfall setting up across central and southern WI. Best chance for stronger storms would be across central WI where a swath of 100-200 J/kg MUCAPE is expected to develop and mid-level lapse rates approach 7- 7.5 C/km. The exact location of the strongest storms will be tied to how far north clouds clear out Wednesday morning. Chance for storms developing over east-central WI looks rather low at this time given easterly winds off Lake Michigan creating a more stable boundary layer. Showers may linger across central and east- central WI through Thursday, however, winds turning northeasterly brings cooler drier air to the region greatly limiting any convective potential. Additionally, with the winds shifting around to the northeast Thursday it will be noticeable cooler with highs in the mid 50s to near 60 degrees compared to the low 60s to mid 70s expected Wednesday.

Rest of the extended....Ensembles are trending toward a mostly dry Friday as a brief ridge of high pressure develops over the region. Depending on how much rain falls Thursday and how quickly clouds clear out Thursday night there is the potential for fog or frost to develop across northern WI with temperatures forecast to fall to or near freezing Friday morning. Temperatures should recover back into the 60s by Friday afternoon. Models have come into a broad consensus with a quick moving short-wave passing over the region next Saturday that may bring another round of showers and a thunderstorms.

AVIATION
for 12Z TAF Issuance Issued at 659 AM CDT Mon May 6 2024

VFR conditions will prevail through the TAF period with mainly high clouds drifting across the region. A few daytime cumulus clouds are possible late this morning and afternoon. Conditions will deteriorate from southwest to northeast after 12z Tuesday morning.

Light winds early this morning will become southeast and gust to around 15 kts late this morning and afternoon. LLWS is expected to develop as winds between 1500-2000 feet increase to 30-40 knots. An inversion will limit the higher winds making it to the surface through sunrise on Tuesday.

MARINE
Issued at 419 AM CDT Mon May 6 2024

Southeast winds will increase Tuesday morning, with some gusts to 25 kts possible. Cooler waters will create more stable conditions compared to land, so still some question just how much of the wind aloft will mix down. The persist southeast winds will produce building waves, especially south of Algoma on Lake Michigan, where waves will climb to around 4 feet Tuesday morning. Have held off on a Small Craft Advisory due to the uncertainty and better chances staying just to our south. As dewpoints increase Tuesday afternoon, dense fog will be possible, which could linger into at least Tuesday evening.

Gusty and persistent northeast winds will bring a period of hazardous conditions for small craft Wednesday night into Thursday.

GRB WATCHES/WARNINGS/ADVISORIES
None.

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