Sunrise 5:38 AM   Sunset 7:59 PM Moonrise 3:10 AM   Moonset 1:12 PM

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LMZ541 Rock Island Passage To Sturgeon Bay Wi- 359 Am Cdt Thu May 2 2024
Early in the morning - N wind around 5 kts. Partly cloudy. Waves 2 ft or less. Today - NE wind 10 to 15 kts. A chance of rain showers. Waves 1 to 3 ft. Tonight - E wind 10 to 20 kts veering S 10 to 15 kts after midnight. Patchy fog. A chance of rain showers in the evening. A chance of Thunderstorms. Light rain showers likely after midnight. Waves 1 to 3 ft. Friday - SW wind 5 to 10 kts. Mostly cloudy in the morning then clearing. Waves 1 to 3 ft. Friday night - S wind 5 to 10 kts backing E after midnight. Mostly clear. Waves 2 ft or less.

LMZ500
No data

FXUS63 KGRB 020911 AFDGRB

Area Forecast Discussion National Weather Service Green Bay WI 411 AM CDT Thu May 2 2024

Forecast discussion for routine morning forecast issuance

KEY MESSAGES

- Round of showers and a few storms are forecast today and tonight. Best chance for thunderstorms will be this afternoon and evening with brief heavy rain, small hail and gusty winds expected to be the main impacts with any storms that do develop.

- Due to recent and upcoming rainfall, some rivers and streams will be on the rise late this week. Some rivers are forecast to remain at or reach bankfull stage.

- Additional showers are possible Saturday into Saturday night with more showers and thunderstorms Monday night through Wednesday.

DISCUSSION
Issued at 410 AM CDT Thu May 2 2024

Short Term
Today
Tonight...and Friday

Timing the precip, assessing thunder/heavy rain potential, along with gusty wind and fog (land/lake) chances highlight the main forecast concerns in short term, as a low pressure and upper trough/shortwave push across the western Great Lakes.

Rain/Thunder Trends: Initial push of FGEN/WAA will spread thicker/lower clouds across the area this morning, along with a few light showers and sprinkles over the south/west. Some of the radar returns are virga early this morning as there is plenty of dry air to overcome, but the stronger echoes are reaching the ground. As the boundary layer moistens and stronger forcing arrives later this morning and afternoon, a large area of showers and embedded storms (currently over IA) will overspread most locations. Activity looks to become more scattered later in the day into tonight as strongest WAA push and LLJ exits/weakens.
Could get a little more organized activity overnight, especially over eastern WI, as the front/shortwave swings east across the state. Models consistent with bringing the surface instability as far north as the Hwy 10 corridor this afternoon/evening, near the surface warm front, with elevated CAPE up to 400-700 J/kg spreading across much of the area this evening. Severe weather is not expected as instability will be limited and lapse rates are not steep, but a strong storm with brief gusty winds and possibly small hail can't be ruled out near/south of the front as deep layer shear looks to be 35-50 kts. Friday is looking dry as shortwave lifts to the north and the front pushes to our east.

Heavy Rain & Flooding Threat / Rivers: Overall trend the last few days has been to back off on QPF totals with the system today, with chances of an inch or more now between 10-25 percent in central WI, ender 10 percent elsewhere. This will help limit/reduce the flood threat across the region. Plus, we have had recovery time in between each round of rain the past week. That said, models continue to advertise a possibly band of heavier rain (over an inch), but the location is not pinned down. With PWATs climbing to between 1.0-1.2 inches, some locally heavy downpours will be possible, possibly creating some minor low-land flooding. While we already have a handful of rivers at bankfull, not expecting any significant flooding over the next couple of days...with mainly slow rises in many of the rivers into/near bankfull (except the Yellow where a faster rise is expected), with a few sites in central/northeast WI possibly approaching flood stage depending on if/where any of the heavier rainfall falls into the basins that are already at/near bankfull.

Temps / Winds: It will be cooler for most spots today as eastern flow prevails. NBM actually came in warmer over the south and cooler over the north, likely due to the cooler start north and warmer start south. Will trend in this direction, which brings highs in the 50s and low 60s. The east flow will keep temps cooler near Lake Michigan. Lows in the 40s to low 50s are expected tonight. Despite being behind the front on Friday, we lose the flow over the lake and get more sunshine, so it looks to be 10-15 degrees warmer. Highs look to range from the mid 60s to low 70s, with cooler readings near the immediate shores of Lake Michigan.

It will be less windy today as winds do a full 180, with light and variable winds becoming east this morning. As winds aloft pick up to 30-40 kts at 2000 ft, some of this will mix down later this morning and afternoon. But with limited mixing and inversion in place, surface gusts should hold between 20-30 mph, highest across central WI where a few higher gusts are possible as winds aloft are the highest. Winds will drop off for a period this evening as the low moves overhead, then winds will shift and increase out of the west behind the surface low/front, with west winds gusting up to 25 mph overnight into early Friday. CAA not overly impressive, so gusts may be reduced. Winds aloft not impressive (up to 25 kts) on Friday, so even with some weak CAA (early in the day) and mixing up to 2000 ft, surface winds should remain under 25 mph for most locations.

Fog Potential: Some patchy fog developed during the early morning hours across far northern WI where winds were the lightest and clear skies prevailed for part of the night, but was limited due to the increase in clouds during the early morning hours. Any fog this morning will quickly burn off/lift after sunrise. Some models are hinting at some lake fog tonight into early Friday as dewpoints climb into the 40s and winds shift to the east/southeast then south. Lake Michigan water temps sitting in the low to mid 40s, so would need at least mid 40 dewpoints and ideally upper 40s dewpoints to get fog to develop on the lake. Forecast dewpoints upstream in MI look to be in the upper 40s to mid 50s, so fog will definitely be possible, possibly pushing into the bay and adjacent land. Any fog that does develop will get pushed away from the shore Friday morning as the flow turns west/northwest.

Long Term...Friday Night Through Wednesday

The active spring pattern will continue this weekend and into next week with a few rounds of showers and storms possible. Rising water levels on area rivers and streams will remain a minor concern through the extend period, particularly in northeast WI and along the Wisconsin River where several locations are already at or near bankfull.

Dry start to the weekend as a weak high pressure system and dry air mass move across the region behind a departing cold front Friday night. There is a chance for scattered showers late Saturday morning through Saturday evening as a digging upper- level trough and PV anomaly are forecast to move across the Minnesota Arrowhead. Not expecting any thunderstorms during this period as instability is expected to be nearly zero. Deep layer moisture is also lacking compared to the Thursday/Thursday night system with PWAT values expected to be around 0.5-1". In terms of QPF the GEFS ensemble is the most aggressive with a 20-40% chance for over 0.1" while the EPS and GEPS are more convective with around a 5-25% for greater than 0.1" of QPF by Saturday night.

A ridge of high pressure is progged to take control of the region Sunday and most of Monday returning dry and mostly sunny conditions to the region. Ensemble guidance has consistently been showing the next weather maker pushing out of the Rockies toward the Northern Plains late Monday into Tuesday. Warm advection rain looks possible late Monday as mean southerly flow brings deeper Gulf moisture to the region. With the low center currently forecast to reside over the Dakotas Tuesday that would place central and northeast WI in the warm sector and thus allowing for increasing low-level moisture and instability. Forecast soundings are also showing 20-40kt of surface to 6km bulk shear Tuesday afternoon. While there is still plenty of time for the forecast to change with those convective elements in play, Tuesday afternoon and evening will be a time period to monitor for a few potentially strong thunderstorms.

AVIATION
for 06Z TAF Issuance Issued at 1051 PM CDT Wed May 1 2024

VFR conditions will continue overnight. Low pressure will move from Kansas to northern Lake Michigan and bring showers and thunderstorms and IFR/MVFR conditions as they arrive during the late morning and early afternoon hours Thursday. Poor flying conditions are likely Thursday night as showers and scattered thunderstorms continue.

Flying weather should improve quickly Friday as a surface high pressure system moves in from the Plains states.

GRB WATCHES/WARNINGS/ADVISORIES
None.

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