Sunrise 5:17 AM   Sunset 8:19 PM Moonrise 4:33 PM   Moonset 3:27 AM

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LMZ522 Expires:202405200800;;505493 Fzus53 Kgrb 192300 Nshgrb
nearshore marine forecast national weather service green bay wi 600 pm cdt Sun may 19 2024
for waters within five nautical miles of the shore on lake michigan
lmz521-522-200800- green bay south of line from cedar river to rock island passage and north of a line from oconto wi to little sturgeon bay wi- green bay south of line from oconto wi to little sturgeon bay wi- 600 pm cdt Sun may 19 2024
Tonight - SE wind 5 to 10 kts. A slight chance of rain showers after midnight. Waves 2 ft or less. Monday - S wind 5 to 10 kts. Rain showers likely in the morning. A chance of Thunderstorms. A chance of rain showers in the afternoon. Waves 2 ft or less. Monday night - SW wind 5 to 10 kts veering W after midnight. A chance of Thunderstorms in the evening. A chance of rain showers. Waves 2 ft or less. Tuesday - E wind 5 to 10 kts. Patchy fog in the morning. A chance of rain showers. Waves 2 ft or less.

LMZ500
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FXUS63 KGRB 191946 AFDGRB

Area Forecast Discussion National Weather Service Green Bay WI 246 PM CDT Sun May 19 2024

Forecast discussion for routine afternoon forecast 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 instabilty 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 18Z TAF Issuance Issued at 1243 PM CDT Sun May 19 2024

A surface high moving across Wisconsin this afternoon will bring mostly clear skies, light winds and excellent visibility.

Middle and high clouds will increase tonight as low pressure and a warm front approach from the Central Plains. Showers and some thunderstorms will arrive late tonight after 09z across central and north-central Wisconsin. Conditions will remain VFR.

On Monday, ongoing showers and thunderstorms will shift from west to east through midday. Additional showers and thunderstorms will develop in the afternoon as the warm front lifts across the area.
IFR to MVFR conditions expected, lowest across central and north- central Wisconsin. Conditions may slowly improve late in the day especially across central and east-central Wisconsin.

GRB WATCHES/WARNINGS/ADVISORIES
None.

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