Sunrise 5:36 AM   Sunset 8:00 PM Moonrise 3:34 AM   Moonset 2:32 PM

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LMZ541 Rock Island Passage To Sturgeon Bay Wi- 1213 Pm Cdt Fri May 3 2024
This afternoon - S wind 5 to 10 kts. Sunny. Waves 2 ft or less. Tonight - S wind 5 to 10 kts. Mostly clear. Waves 2 ft or less. Saturday - SE wind 5 to 10 kts. A chance of rain showers in the afternoon. Waves 2 ft or less. Saturday night - NW wind 5 to 10 kts. A chance of rain showers in the evening. Waves 2 ft or less.

LMZ500
No data

FXUS63 KGRB 031748 AFDGRB

Area Forecast Discussion National Weather Service Green Bay WI 1248 PM CDT Fri May 3 2024

Updated aviation portion for 18Z TAF issuance

KEY MESSAGES

- Scattered showers and isolated thunderstorms are possible Saturday into Saturday evening with more showers and thunderstorms Monday night through Wednesday.

- Slightly elevated fire weather conditions, mainly across northern WI, this afternoon and again Sunday and Monday afternoons due to RHs dropping into the 20-35 percent range.

- A few rivers will remain at or reach bankfull stage into the weekend.

DISCUSSION
Issued at 352 AM CDT Fri May 3 2024

Short Term
Today
Tonight...and Saturday

Main forecast issues will be dealing with lingering low clouds/fog early today, relative humidities in the 20/30s this afternoon and any fire weather issues, and shower/thunder chances Saturday afternoon.

Today...rain showers associated with a shortwave trough and weak low pressure/front will exit east of the area early this morning, with only some patchy fog/drizzle/sprinkles left around sunrise across mainly northern/eastern WI. As drier air advects in from the west, look for any light precip to end/exit, with the fog and low clouds mixing out through the morning hours. Plenty of sunshine is expected in the late morning and afternoon as high pressure builds across the western Great Lakes. Mixing to at least 4000-5000 ft will support warmer temperatures, with highs climbing into the upper 60s to middle 70s, and west winds gusting to 20 to 30 mph (strongest in northern WI) and low relative humidity (20-35 percent) in the sandy soil areas. If we can mix closer to 7000 ft, as the RAP suggests, wind gusts would be a little higher and RH's a little lower. The recent rainfall, along with the continued green-up, will limit the overall fire weather concern. However, locations across northern WI may see slightly elevated fire weather conditions as green-up has been the slowest, the deepest mixing is expected and winds will be the highest this afternoon.

Tonight...dry conditions continue as high pressure slides east of the region. Mostly clear skies are expected during the evening, with mid and high clouds spreading east across the area overnight.
Lows look to mainly be in the 40s with a light south/southeast wind.

Saturday...a dry start to the day is expected, but skies look to become cloudy through the morning. An area of rain showers will spread west to east across the area during the morning, as another shortwave trough and frontal boundary approach from the west.
This first area looks to be weakening as it traverses the area, but additional showers look to develop later in the morning and afternoon ahead of the front. Rain amounts look to remain under a quarter inch for most spots. As for thunder chances, assuming the front pushes through in the afternoon, should get at least 500 J/kg of CAPE across eastern WI by early-mid afternoon. This would be enough to support a few storms, but severe weather is not expected. Will carry a slight chance for thunder in the afternoon across parts of central and eastern WI. Light south/southeast winds will increase in the morning ahead of the front, then shift to the west/northwest behind the front in the afternoon. Winds could get a little gusty, up to around 35 mph ahead of the front, but will be difficult to break into the inversion to mix down the stronger winds. Will hold gusts closer to 20-25 mph for now. As CAA arrives behind the front, better mixing will promote gusts to ~25 mph.

Long Term...Saturday Night Through Thursday

Main focus of the extended period revolves around a well organized cyclone that is forecast to bring showers and thunderstorms to the region early to middle of next week.

Scattered showers and an isolated thunderstorm or two may linger Saturday night into early Sunday morning across far eastern WI as an upper-level trough and surface cold front depart from the region. A ridge of high pressure is forecast to build over area Sunday returning dry and calm conditions to the region through at least Monday afternoon. The ridge will also ushering in a drier air mass which may lower RHs to around 30 percent Sunday and Monday afternoons. These lower RHs and warmer temperatures in the low 60s to around 70 degrees may bring slightly elevated fire weather conditions to far northern WI, where vegetation has yet to green up, Sunday and Monday afternoons.

While there are still slight differences in timing and intensity, ensemble models are in decent agreement that a near vertically stacked low pressure system will eject out of the Great Basin toward the norther Plains late Monday into Tuesday. An initial wave of warm air advection out in front of the low along with diffluent flow aloft may bring a round scatter showers and storms Monday night into Tuesday. Perhaps the best chance for strong to potential severe storms comes Tuesday afternoon and evening as much of the CWA may reside in the warm sector allowing for an increase in instability, however, the question remains if there will be a forcing mechanism present for thunderstorm initiation.

Periods of rain and thunderstorms will remain possible through Wednesday and Thursday as the cyclone brings several pieces of jet energy across the region. With several area rivers and streams already at or near bankfull the active pattern for next week may create some minor flooding concerns particularly in low laying and flood prone areas.

AVIATION
for 18Z TAF Issuance Issued at 1235 PM CDT Fri May 3 2024

Expect VFR conditions to prevail through the TAF period, with patchy mid/high clouds expected into early Saturday, then thickening and lowering clouds in NC/C WI as showers arrive toward midday. Considered the possibility of patchy fog tonight, but the air mass has become well mixed this afternoon (warm temps and low dew points leading to large dew point depressions) and boundary layer winds will be increasing to 20 to 25 kts late tonight.
Models are hinting at some low clouds coming off Lake Michigan (near MTW) Saturday morning, but confidence is too low to mention a ceiling at this time.

Gusty west winds will drop off quickly late in the day, become light SE overnight, then moderate SE-S later Saturday morning.

GRB WATCHES/WARNINGS/ADVISORIES
None.

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