Sunrise 5:34 AM   Sunset 8:03 PM Moonrise 4:17 AM   Moonset 5:16 PM

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LMZ522 Expires:202405052000;;666599 Fzus53 Kgrb 051337 Nshgrb
nearshore marine forecast national weather service green bay wi 837 am cdt Sun may 5 2024
for waters within five nautical miles of the shore on lake michigan
lmz521-522-052000- 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- 837 am cdt Sun may 5 2024
Today - NW wind 5 to 10 kts backing S in the afternoon. Mostly Sunny. Waves 2 ft or less. Tonight - SE wind 5 to 10 kts. Mostly clear. Waves 2 ft or less.Monday - SE wind 5 to 10 kts. Sunny. Waves 2 ft or less. Monday night - E wind 5 to 10 kts veering se 10 to 20 kts after midnight. Mostly clear. Waves 2 ft or less.

LMZ500
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FXUS63 KGRB 051136 AFDGRB

Area Forecast Discussion National Weather Service Green Bay WI 636 AM CDT Sun May 5 2024

Updated aviation portion for 12Z TAF issuance

KEY MESSAGES

- Patchy dense fog this morning, mainly across central and northern WI. Otherwise, quiet conditions expected today into Monday.

- Relative humidity dropping into the upper 20s and 30s this afternoon and Monday afternoon. Recent rain, lack of gusty winds and continued green-up will limit fire weather concerns.

- Next round of showers and storms arrives Tuesday morning. Best chance for non-severe thunderstorms will be Tuesday afternoon and evening.

DISCUSSION
Issued at 345 AM CDT Sun May 5 2024

Short Term
Today
Tonight...and Monday

Quiet early May weather on tap for the region today into Monday.
Only weather concerns will be fog/frost potential and low RH's each afternoon.

Precip / Clouds / Fog:

High pressure will build across the Great Lakes today, slowly sliding to our east on Monday, bringing dry conditions. Fog, locally dense, will continue across parts of central and northern WI early this morning. May need a SPS if the fog can become a little more dense/widespread. So far satellite and webcams are showing more patchy ground fog. The low clouds and fog will lift/burn off after sunrise, leaving sunny skies. Then look for fair weather cumulus to develop later this morning into the afternoon as we hit our daytime convective temps. These will fade in the mid-late afternoon, with clear skies expected tonight. Fog potential tonight looking very low as the lower levels dry out even more and winds just off the surface remain between 10-20 kts.
Plenty of sunshine is expected on Monday with only a few fair weather cumulus expected in the late morning and afternoon. As flow turns back to the south/southeast on Lake Michigan late tonight into Monday, a few lake clouds or even a little fog will be possible.

Winds / Relative Humidity:

Northwest winds will shift to the west and gust up to around 15 mph today. As return flow sets up on Monday, southeast winds could gust up to 20 mph. Afternoon relative humidities are forecast to drop into the upper 20s and 30s this afternoon and Monday afternoon, lowest in the sandy soil regions. Recent rain and lack of gusty winds will limit any fire weather concerns today.
Slightly elevated fire weather conditions are possible on Monday as soils dry out and slightly warmer temps are expected, especially over northern WI where the green-up has been the slowest.

Temps / Frost Potential:

925/850mb temps support highs in the 60s to around 70 today. A lake breeze will keep afternoon temps cooler near Lake Michigan.
Lows tonight are forecast to drop into the 30s across much of the Northwoods. Some of the colder spots in central WI could also drop into the upper 30s. Frost is looking likely over northern WI, but frost/freeze headlines have not begun yet. Further south, some patchy frost will be possible in the cold spots of central WI.
925/850mb temps increase slightly on Monday, so most spots should be a a couple/few degrees warmer than today.

Long Term...Monday Night Through Saturday

Monday night through Tuesday...Focus of the extended forecast remains on a well organized system shifting over the northern Plains Tuesday. A warm air advection regime and deep layer moisture (PWAT values 1-1.3") out in front of this system will likely bring an initial round of rain to the region Tuesday morning spreading from southwest to northeast. There will be some dry air to overcome in front of this system, so areas in east- central and northeast WI may not see rain arrive until Tuesday afternoon. Best chance for thunderstorms comes Tuesday afternoon and evening as models show a thin band of instability (MUCAPE 200- 500 J/kg) building over center and east- central WI. Additionally mid-level lapse rates approach 7-7.5 C/km during this period.
Forcing comes in the form of a left exit region and 500mb PV anomaly. The strength of these features will be key in determining if severe storms develop. Currently, confidence in any storms becoming severe is low with the better chance for severe storms remaining south toward the WI/IL boarder. In terms of rainfall amounts the long term grand ensemble (GEFS, ENS, and GEPS) shows a 50-70% chance for over 0.5" of QPF Monday to Tuesday night.
Probabilities drop to about 10-30% when looking at the chance for greater than 1".

Wednesday through Thursday...Ensemble models have come into decent agreement with a period of dry weather Wednesday morning as dry air behind an occluding front filters over the region. Dry conditions may not last long as the weakening cyclone moving east out of the norther Plains merges with a developing southern stream system returning rainfall to the region late Wednesday into Thursday. The GFS in particular shows the potential for a band of heavier rainfall Thursday over central to southern WI as these systems merge. The potential for any convective activity is low during this period as the region resides of the non-favorable northwest side of the low.

Rest of the extended...The details beyond Thursday become difficult to pin down as as the GFS and Euro show a trough digging down from Ontario keeping scattered shower and storms possible, while the Canadian has a ridge developing over the region. One note to make is depending on if skies clear out early Friday morning temperatures across northern WI may drop to or near freezing. With Frost/Freeze headlines starting for northern WI May 7th this will be a period to monitor, particularly for those who may have gotten an early start to the growing season.

AVIATION
for 12Z TAF Issuance Issued at 636 AM CDT Sun May 5 2024

Patchy ground fog will lift/burn off across central and northern WI early this morning. Otherwise, VFR conditions are expected through the TAF period. Look for fair weather cumulus to develop later this morning, then dissipate late this afternoon and evening. Very low chance of a little ground fog early Monday morning, especially over north-central WI.

Northwest to west winds will generally stay under 10 kts, but a few gusts up to 15 kts are possible later this morning and afternoon. A lake breeze will turn winds south/southeast across eastern WI this afternoon. Light and variable winds are expected tonight.

GRB WATCHES/WARNINGS/ADVISORIES
None.

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