Sunrise 5:16 AM   Sunset 8:17 PM Moonrise 5:33 PM   Moonset 3:38 AM

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LMZ366 Expires:202405201515;;527509 Fzus63 Kmkx 200750 Glflm
open lake forecast for lake michigan national weather service milwaukee/sullivan wi 250 am cdt Mon may 20 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 -
southeast winds this morning will become more southerly by this afternoon as a weak area of low pressure around 29.7 inches tracks over wi and lake michigan. Expect to see more west to southwesterly component of the winds briefly overnight tonight. Winds will turn more south to southeasterly again Tuesday. Breezy southerly winds are expected as a deepening low pressure around 29.4 inches approaches the upper great lakes region and tracks northeast into Wednesday. There looks to be periods of Thunderstorms over the lake, especially southern portions Monday through Wednesday morning.
lmz261-362-364-366-563-565-567-868-201515- 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- 250 am cdt Mon may 20 2024
sheboygan wi to pentwater mi north - .
Today - Southeast winds 10 to 15 kt becoming south 10 to 20 kt. Chance of showers and slight chance of Thunderstorms this morning, then chance of showers and Thunderstorms this afternoon. Waves 1 to 3 ft. Tonight - Southwest winds 10 to 20 kt diminishing to 10 to 15 kt late in the evening, then veering to northwest after midnight diminishing to 5 to 10 kt late. Chance of showers and Thunderstorms in the evening, then slight chance of showers and Thunderstorms overnight. Waves 1 to 3 ft. Tuesday - North winds 5 to 10 kt becoming northeast late in the morning, then becoming east 10 to 15 kt early in the afternoon increasing to 10 to 20 kt late. Waves 1 to 2 ft. Tuesday night - Southeast winds to 30 kt becoming south. Showers with a chance of Thunderstorms. Waves 3 to 5 ft building to 6 to 9 ft occasionally to 12 ft. Wednesday - Southwest winds to 30 kt. Waves 6 to 9 ft occasionally to 12 ft. Wednesday night - West winds to 30 kt. Waves 4 to 6 ft occasionally to 8 ft subsiding to 3 to 5 ft. Thursday - West winds to 30 kt becoming southwest 15 to 25 kt. Waves 2 to 4 ft. Friday - Northeast winds 10 to 15 kt becoming southeast 10 to 20 kt. Waves 1 to 3 ft.

LMZ300
No data

FXUS63 KGRB 200353 AFDGRB

Area Forecast Discussion National Weather Service Green Bay WI 1053 PM CDT Sun May 19 2024

Updated aviation portion for 06Z TAF issuance

KEY MESSAGES

- Thunderstorms are possible Monday. An isolated severe thunderstorm could occur during the afternoon south of Highway 29. The main threats will be damaging winds and large hail.

- There is increasing confidence in the potential of a significant severe weather outbreak late Tuesday afternoon into Tuesday evening. Damaging winds, large hail and a few tornadoes are possible. Heavy rainfall and localized flooding is also possible.

DISCUSSION
Issued at 246 PM CDT Sun May 19 2024

Short Term...Tonight and Monday

High pressure ridge that is bringing dry weather this afternoon will give way to low pressure system and approaching warm front late tonight. Wave of low pressure eventually makes it to western Wisconsin on Monday while warm front attempts to lift south to north across Wisconsin.

As low-level jet and elevated instability shifts into western Wisconsin late tonight, swath of showers and some elevated thunder will shift into central Wisconsin late tonight, even more so toward daybreak on Monday. Coverage of these showers will be enhanced by divergence aloft from upper jet across Lake Superior.
On Monday, showers and some thunder will shift west to east through midday riding along the nose of low-level jet. Don't expect any of these storms to be severe, but with 1.25+ inch PWATs moving in there could be heavy downpours. Most areas will see less than 0.50 inch of rain through early afternoon.

There is then loose agreement of a lull behind this initial wave of showers and thunder from the subsidence before additional showers and storms develop as sfc warm front and building instability arrive from the southwest as highs most areas rise into at least the lower 70s and dewpoints push toward the 60 mark.
Appears greatest coverage of the additional convection will stretch from central Wisconsin to east-central Wisconsin. Though MLCAPEs could rise above 1000J/kg, effective shear is weaker mainly 20 kts or less, suggesting pulse type mode to any storms. However, the lack of forecast shear may be offset by convective modulated shortwave that moves through as well mid to late aftn. If that wave is stronger (models differ on the strength), then at least isolated severe storms would be possible over southern portion of the forecast area where SPC currently has a marginal risk. Any storms will have the potential to produce heavy downpours as the PWATs stay in the 1.30 to 1.50 inch range.

Long Term...Monday Night Through Sunday

Thunderstorms trends, including severe and heavy rainfall potential Monday evening and Tuesday afternoon and evening, will be the main forecast concerns.

Depending on the timing of an MCV, there may still be a chance of thunderstorms and a marginal severe threat over the southeast part of the forecast area early Monday evening. This would occur as the SE CWA briefly resides in the warm sector of a weak low pressure system tracking through the area. If the MCV moves through quicker, the severe threat would be confined to the afternoon. Regardless, there does appear to be a lull in the precipitation chances from 03z-12z/Tuesday, along with potential for patchy fog. Lows should be in the upper 40s and 50s.

Confidence is increasing for a potentially significant severe weather event Tuesday late afternoon and evening. A potent low pressure system (990 mb low) is expected to track just west of the forecast area late Tuesday afternoon and evening. Timing of this will be critical, as an earlier arrival would help to maximize instability in the warm sector over the southern part of the forecast area area. Even if the system arrives in the evening, advection of warm/moist air (dew points in the 60s) and steep mid-level lapse rates (7-8 C/km) should support at least a narrow tongue of modest instability into the SW part of the CWA The strength of the dynamics (negatively-tilted short wave trough and low-level convergence with a 50-60 kt LLJ) and shear (0-6 km shear of 50-60 kts, and 0-3 km helicities of 400-800) should help overcome limited instability and bring a round of impactful severe weather to the region. Supercells with damaging winds, large hail and a few tornadoes will be possible. Given the dynamics and anomalously moist air mass, heavy rainfall and localized flooding will also be a concern, especially in any areas that received heavy rainfall with earlier rounds of convection.

Wrap-around showers to persist over the northwest part of the forecast area on Wednesday, followed by mainly dry conditions Wednesday night through Thursday night. A cold frontal passage will bring the next significant chance of rain later Friday into Saturday, but timing issues are evident.

AVIATION
for 06Z TAF Issuance Issued at 1053 PM CDT Sun May 19 2024

VFR conditions will continue late this evening and most of tonight with mainly mid and high clouds spreading across the area.
A few sprinkles or light showers are are possible, but will have no impacts to flying conditions.

An area of showers will arrive from southwest to northeast after 08z ahead of an approaching low pressure system and frontal boundary, continuing at times into Monday morning. Weak instability could allow for a few embedded thunderstorms. A break is expected for much of the late morning and afternoon, with additional showers and storms developing later in the day as the warm front lifts across the area, especially across eastern WI, with more spotty activity further west. Still some uncertainty just how long the break will be and where the second round of activity will be focused. VFR conditions look to last through at least 11z then MVFR and possibly some IFR conditions are expected at times on Monday, associated with the heavier showers and stronger storms. The strongest storms could produce gusty/erratic winds, hail and heavy rain. Tried to limit the thunder/ceilings/ visibilities conditions as best as possible to 2-3 hour windows where the threat looks to be greatest, but those may need to be shifted/changed as models hone in on exact timing of each round of showers/storms. Another round of showers and storms looks to arrive late Monday night (after 06z).

Fog may develop on Lake Michigan Monday into Monday night as dewpoints climb ahead of the low, but should stay mainly over the lake, so will not include at MTW. In addition, some fog will be possible across most land areas Monday night as winds die off and recent rain will provide moist low levels, but winds just off the surface and cloud cover may limit this threat.

GRB WATCHES/WARNINGS/ADVISORIES
None.

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