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LMZ541 Rock Island Passage To Sturgeon Bay Wi- 844 Pm Cst Sat Dec 2 2023
Rest of the night..E wind 10 to 20 kts. A slight chance of light rain and light snow after midnight. Waves 1 to 3 ft.
Sunday..NE wind 10 to 20 kts. Light snow and light rain. Waves 1 to 3 ft building to 3 to 5 ft in the late morning and afternoon. A small craft advisory may be needed.
Sunday night..N wind 10 to 15 kts. Cloudy. Waves 2 to 4 ft subsiding to 1 to 3 ft in the late evening and overnight.
Monday..NW wind 5 to 10 kts backing W in the afternoon. Partly cloudy. Waves 2 ft or less.

LMZ500
No data

FXUS63 KGRB 030317 AFDGRB

Area Forecast Discussion National Weather Service Green Bay WI 917 PM CST Sat Dec 2 2023

New Information added to update section

UPDATE
Issued at 901 PM CST Sat Dec 2 2023

Have increased snowfall amounts across much of east central and far northeast WI. Models show steady snow developing late tonight and continuing through much of the day on Sunday, as a short-wave and associated low pressure system lift northeast from the Central Plains. Most of the accumulation should occur between 3 am and noon, with totals of 2-3 inches (and locally higher amounts) in the Fox Valley/bayshore/lakeshore areas, and lesser amounts farther west and north. Nearly every model showed at least 2-4 inches over the southeast half of GRB CWA, and the current forecast matches well with the SPC HRRR mean snowfall and current WPC forecasts. Guidance is showing surface temperatures getting warm enough to limit accumulations, but feel they are too warm, and have lowered them accordingly. Areas near Lake Michigan have the greatest uncertainty, as NE winds will offer potential for lake-enhancement (with Lake-H8 delta-t's around 12 C), but may also boost temperatures enough for a rain/snow mix right along the shoreline. Aside from lakeshore locations, 925-850 mb temperatures, low-level wet-bulb temperatures, and 1000-850 mb thicknesses are widely supportive of all snow.

SHORT TERM
Tonight and Sunday Issued at 256 PM CST Sat Dec 2 2023

Key messages:

- Light snow is likely late tonight and Sunday with the highest totals across eastern counties.

Skies were mostly cloudy this afternoon as temperatures warmed into the 30s to around 40. For tonight, low pressure will move into southern Wisconsin as an upper trough moves into the western Great Lakes. Light snow will break out ahead of the system. The latest model trends is to slow the arrival of the snow which will now be after midnight across central and east-central Wisconsin and probably won't make into northern Wisconsin until after 12z.
Low pressure will continue to move east into lower Michigan on Sunday. Light snow is expected to continue across much of the area during the morning, then taper off and end across much of the area during the afternoon.

Confidence is growing that most locations will see 1 to 3 inches of snow, except over the far north where totals will be less than an inch. The previous run on the ECMWF had nearly fourth tenths of an inch of liquid precipitation. The 12z run has backed off on those totals. The Dynamic Ensemble-based Scenario output indicated the highest chances of 3 inches of snow was over Calumet County which was only around 40%. One other area to watch is from eastern Marinette and eastern Oconto counties into Door County where the models try to wrap the precipitation across the counties longer on Sunday. Low level eastern winds and delta T's over the lake are around 13C and over the bay of 10C could add some enhancement to snowfall totals. However, low levels winds are only 10 to 15 knots and air temperatures will be a few degrees above freezing that may limit snowfall totals in this region.

The light snow will taper off and end across much of the area Sunday afternoon. High temperatures in the lower to middle 30s are expected.

LONG TERM
Sunday Night Through Saturday Issued at 256 PM CST Sat Dec 2 2023

Key Messages:

- A mild weather weather pattern is expected next week, with a few chances for precipitation.

The upper wind pattern is forecast to be relatively low amplitude with high heights and split flow for most of next week. There is a Clipper system that will largely pass by to our soutwest Monday night and early Tuesday, but could bring a little snow to the southwest half of the forecast area.

There is some chance of a significant synoptic scale storm a week from tomorrow, as strong jet energy moves through the southern stream and weaker jet energy moves along the northern jet along the United States Canadian border. The models show varying degrees of phasing, and tracks for the storm, so it's too early to make any forecasts of precipitation types and amounts.

Temperatures will be five to ten degrees above normal on most days next week.

AVIATION
for 00Z TAF Issuance Issued at 534 PM CST Sat Dec 2 2023

Much of the forecast area was covered by stratocumulus with bases of 2500-3500 ft AGL at TAF issuance. The ceilings are expected to gradually lower this evening and into the early overnight hours.
Steady light snow is expected to overspread much of the area from south to north late tonight, and continue through at least midday before gradually tapering off from west to east Sunday afternoon.
Flight conditions will deteriorate to IFR/LIFR once the steady snow begins, and won't improve much until the snow tapers off. An inch or less of accumulation is expected across far northern Wisconsin, with 1 to 3 elsewhere, so plowing operations will be needed at many area airports.

GRB WATCHES/WARNINGS/ADVISORIES
None.

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