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LMZ521 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- 401 Pm Cdt Tue May 7 2024
Rest of this afternoon - E wind 5 to 10 kts. Patchy fog. Rain showers and a slight chance of Thunderstorms. Waves 2 ft or less.Tonight - NE wind 5 to 10 kts with a few gusts to around 25 kts backing W after midnight. Patchy fog. A chance of showers and Thunderstorms. Waves 2 ft or less. A small craft advisory may be needed. Wednesday - NW wind 5 to 10 kts veering ne 10 to 15 kts in the afternoon. Patchy fog in the morning. Waves 2 ft or less. Wednesday night - NE wind 10 to 20 kts. A chance of rain showers. Waves 1 to 3 ft. Thursday - NE wind 10 to 20 kts. Mostly cloudy. Waves 1 to 3 ft.

LMZ500
No data

FXUS63 KGRB 071954 AFDGRB

Area Forecast Discussion National Weather Service Green Bay WI 254 PM CDT Tue May 7 2024

Forecast discussion for routine afternoon forecast issuance

KEY MESSAGES

- A few strong storms are possible through early this evening, mainly south of a line from Marshfield to Waupaca to Oshkosh.
The primary hazards will be small hail and gusty winds.

- Areas of dense marine fog are expected through late this evening along Lake Michigan to the south of Algoma.

- Areas of frost are expected to develop over parts of central and north-central Wisconsin on Thursday night.

- Active pattern to continue into early next week.

DISCUSSION
Issued at 253 PM CDT Tue May 7 2024

Short Term...Tonight and Wednesday

Arc of steady rain that swept through earlier driven by mid-level fgen has given way to scattered showers and a few thunderstorms into central WI. Thus far the strongest thunderstorms by far are over southern WI closer to warm front and on edge of MLCAPES up to 1000J/kg. An isolated strong storm remains possible 3-7p as warm front and instability attempt to shift northward. Easterly flow off Lake Michigan will slow the progress somewhat. SW/S areas generally south of a Marshfield to Waupaca to Oshkosh line will see greatest risk for small hail and gusty winds. Then, will have to see if another cluster of showers and storms currently developing ahead of occluded front over western WI can make it into western area later this evening. Likely these will outrun greater instability while working eastward, so they should be in a weakening state. Chances of showers and storms drop off after late evening. Fog will be an issue right along the Lake Michigan shore this evening then more areas could see patchy fog overnight with today's rain and nighttime low-level inversion setting up.

Wednesday begins mainly dry though a few spot showers or sprinkles could still occur along the Upper Michigan border closer to departing H85 low and cyclonic flow to the west of it. Expect a mix of sun and clouds otherwise into early afternoon. Possible that a few showers develop mid to late afternoon either from pop-up showers or storms due to buildup of at least weak instability farther inland or due to weak H85 trough dropping in from the north during the afternoon as the Canadian has been showing for the last couple days. GFS on board now too, so there may be something to it. Soundings and instability progs would only support thunder over central WI though. Decent range in temps on Wednesday from highs only around 60 in the north, to readings well into the 70s over the southwest forecast area.

Long Term...Wednesday Night Through Tuesday

An active weather pattern to continue over northeast WI into early next week as a series of systems traverse the region. The first system to be a weakening upper low into an upper trough with precipitation chances Wednesday night into Thursday. Mean flow turns northwest into WI by late week with the passage of two shortwave troughs (Friday night and Sunday afternoon/night)
bringing additional precipitation chances. Temperatures to generally be at or below normal through the weekend, then slightly above normal early next week.

Wednesday night and Thursday...
An elongated shortwave trough stretching from eastern Canada to the Midwest will swing through northeast WI Wednesday evening into Thursday morning. Instability looks minimal at best over the northern half of the state and stronger forcing to be focused to our south, thus have kept thunder out of the forecast. Anticipate shower chances to range from slight from Hwy 8 northward, to likely from Hwy 21 southward. Rainfall amounts over parts of central and east-central WI will range from one-tenth to one-third of an inch. Min temperatures Wednesday night to range from 35-40 degrees far north, middle to upper 40s south. High pressure is forecast to begin building south into the western Great Lakes by Thursday morning which should start to dry things out. Max temperatures Thursday to be in the middle 50s to lower 60s.

Thursday night and Friday...
This high pressure will move across the forecast area Thursday night, allowing for skies to clear as well as bring a cooler air mass to the region. Min temperatures across north-central WI could drop to around 30 degrees with lower to middle 30s for central and far northeast WI. This may bring frost headlines into play if winds can decouple which is looking more likely. Anyone with sensitive plants may want to take the appropriate precautions. By Friday, clouds will be on the increase as a sharp upper trough digs southeast across the Upper MS Valley. By the afternoon, enough lift from the left exit region of the upper jet, in concert with increasing Q-G/FGEN mid-level forcing, could bring a chance of showers into central WI. Max temperatures on Friday to mainly be in the lower to middle 60s.

Friday night and Saturday...
This upper trough sweeps southeast across the western Great Lakes Friday night with a chance of showers and a slight chance of thunderstorms. Even as this trough departs on Saturday, lingering cyclonic flow may keep shower chances in the forecast through at least the morning hours. Limited sunshine and north wind will keep max temperatures Saturday in the upper 50s to middle 60s.

Saturday night and Sunday...
After a brief lull in the precipitation Saturday night as a weak surface ridge slides across WI, a weaker upper trough is progged to move into the western Great Lakes Sunday afternoon. This trough will be accompanied by a cold front, thus another chance for showers across northeast WI. A minor uptick to temperatures aloft will bring max temperatures on Sunday into the lower 60s near Lake MI, lower to middle 60s north and middle 60s to around 70 degrees south.

Sunday night and Monday...
The chance for showers will linger into Sunday evening until the cold front clears the area. The rest of Sunday night should be dry under partly to mostly cloudy skies. A cool air mass is left behind over northeast WI on Monday with 8H temperatures of 0 to +4C. This cooler air and the passage of a mid-level shortwave could kick off a few showers Monday. If the showers stay away, max temperatures on Monday could reach the middle 60s lakeside, upper 60s to lower 70s inland.

Monday night and Tuesday...
Models diverge after Monday with the GFS bringing a push of warmer air toward WI with more rain chances versus the ECMWF which sends high pressure into WI. Have followed the blended guidance which does bring a chance of showers to all of northeast WI by Tuesday.
Max temperatures on Tuesday to be in the middle 60s near Lake MI, upper 60s to middle 70s inland.

AVIATION
for 18Z TAF Issuance Issued at 113 PM CDT Tue May 7 2024

Widespread rain impacting north-central WI to far northeast WI.
Scattered showers are developing in wake of swath of rain and these will impact all the TAF sites the remainder of the afternoon through 22-24z. Expect isolated thunder to develop later this afternoon (after 20z) but coverage was too uncertain to include anything more than VCTS at this point. Another period of isolated showers and possible thunder will occur after 00z before showers end after midnight from west to east. Flight conditions will mainly prevail at IFR/MVFR this afternoon. MVFR conditions will occur this evening but then will improve to VFR from west to east as a front slides past the area.

GRB WATCHES/WARNINGS/ADVISORIES
None.

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