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LMZ543 Expires:202312092100;;167156 Fzus53 Kgrb 091228 Nshgrb
nearshore marine forecast national weather service green bay wi 628 am cst Sat dec 9 2023
for waters within five nautical miles of the shore on lake michigan
lmz542-543-092100- sturgeon bay to two rivers wi-two rivers to sheboygan wi- 628 am cst Sat dec 9 2023
.small craft advisory in effect from 10 am cst this morning through Sunday morning...
Today..SW wind 10 to 20 kts with gusts to around 25 kts. Rain in the morning, then a slight chance of light rain in the afternoon. Waves 1 to 3 ft building to 3 to 5 ft in the late morning and afternoon.
Tonight..SW wind 10 to 20 kts veering nw after midnight. Gusts to around 25 kts. A chance of light snow and a slight chance of light rain. Waves 2 to 4 ft subsiding to 1 to 3 ft in the late evening and overnight.
Sunday..NW wind 10 to 20 kts with gusts to around 25 kts. Mostly cloudy. Waves 1 to 3 ft.
Sunday night..NW wind 5 to 10 kts. Mostly clear. Waves 2 ft or less.

LMZ500
No data

FXUS63 KGRB 091110 AFDGRB

Area Forecast Discussion National Weather Service Green Bay WI 510 AM CST Sat Dec 9 2023

Updated aviation portion for 12Z TAF issuance

KEY MESSAGES
- Rain will be widespread over northeast Wisconsin this morning.
The rain will be mixing with and perhaps changing over to snow across north-central to far northeast Wisconsin by mid to late morning. The mild temperatures will result in little to no snow accumulations.

- Slippery stretches on area roads will likely develop tonight into Sunday morning due to periods of light snow. Snow accumulations will range from a dusting to 2 inches for most locations. Locally higher totals are possible across the snow belt of north-central Wisconsin.

- Temperatures will remain at or above normal over the next week.
Probabilities of significant snow accumulations remains low.

DISCUSSION
Issued at 310 AM CST Sat Dec 9 2023

SHORT TERM
Today
Tonight...and Sunday

The latest RAP analysis and satellite/radar imagery show a large trough headed east across the northern Plains. A rather potent shortwave impulse is lifting northeast on the forward flank of the upper trough and across the mid-Mississippi Valley. Rain is spreading rapidly northeast ahead of this shortwave and associated surface wave and sliding into central and east-central Wisconsin.
Temperatures early this morning have been gradually cooling, and generally falling below short term guidance (middle 30s) across north-central Wisconsin. Meanwhile, readings remain into the low 40s across parts of east-central and far northeast WI. Forecast concerns remain on precip trends and snowfall accumulations.

Today...Forecast remains complex today as the previously mentioned potent shortwave and strengthening surface low track from southeast Wisconsin to northern Lake Michigan this morning. With the developing cyclone, higher resolutions models produce a precip pattern resembling a barolclinic leaf structure as precip is thrown west after the initial surge early this morning. This will create widespread precip for most of the region this morning before the comma head departs far northeast Wisconsin early this afternoon.

Strong forcing and reduced stability will accompany the shortwave trough. Thought about adding thunder to the forecast, but trajectories of ongoing thunderstorm would place higher chances over southern Lake Michigan. Precip amounts will range from around a tenth of an inch across far western portions of the area to around a half inch along the lakeshore.

The complicated part of the forecast resides with the thermal profiles and precip types. Temps and dewpoints remain very mild for this time of the year early this morning and short term guidance generally shows temps remaining steady. Concern is highest for accumulating snow over Vilas, eastern Oneida, Forest and Florence counties this morning as the precip gets thrown west.
The column will be cooling through the morning with critical thickness values aloft sliding east of the concerned area by mid to late morning. Therefore think that snow will begin to mix in with rain by the mid-morning timeframe, but with a warm boundary layer and fast forward speed of the cyclone, that leaves very little time for significant accumulations to take place. Don't think precip rates will be high enough to overcome the warm boundary layer. As result, think snow accumulations will be little to none over the far north with the cyclone this morning as temps hold in the mid 30s.

After a lull in the precip, trailing northern stream shortwave will be spreading light precip from west to east across the region this afternoon. With temps in the mid 30s to low 40s, precip will likely consist of a wintry mix region wide, perhaps with more snow over central and north-central WI but with little to no accumulations.

Tonight and Sunday...The upper trough moves overhead tonight with nocturnal cooling setting the stage for falling temps. Therefore should see a rain/snow mix change over to snow over the eastern half of the forecast area. With help from low level convergence along a surface trough and a lake effect component off Lake Superior, much of the area will see some accumulations by early Sunday morning, but the highest will reside in the north-central WI snow belt where 1-3 inches of snow will be possible. The rest of the area will see an inch or less. The snow (with help of wet roads after this morning rain) will likely create slippery or icy roads tonight into Sunday morning.

Light snow will be exiting eastern WI Sunday morning, and should be ending over north-central WI in the afternoon. Although there will be increasing sunshine in the afternoon, temps will be much colder and range from the middle 20s to middle 30s Sunday afternoon. These temps will be close to normal.

LONG TERM...Sunday Night Through Friday

The main story for this period will be for the continuation of above normal temperatures. High temperatures will be mainly in the 30s with some 40 degree readings next Thursday and Friday ahead of a cold front.

For Monday night, gusty southwest winds are expected with gusts approaching gale force on the northern bay and northern Lake Michigan ahead of a clipper system. Per coordination with WFO Marquette, added a small chance of rain/snow late Monday night across far northeast Wisconsin with the passage of the clipper system passing to the north. Confidence is low that we would see measurable precipitation, but the models could shift the system further to the south and west in the coming days. The next chance for a precipitation event would be next Friday and Friday night with the passage of a cold front. With precipitation expected to below normal over the next week, some concern that drought conditions will again worsen in the coming weeks. At this point, the ECMWF is not depicting a lot of precipitation out through 240 hours. The above normal temperatures are typical of an El Nino winter. At some point, there will be an arctic blast that will bring the arrival of below zero temperatures. According to our official records, every winter has recorded at least 4 days of subzero temperatures at Green Bay.

AVIATION
for 12Z TAF Issuance Issued at 510 AM CST Sat Dec 9 2023

Low pressure will track northeast from northern Illinois to northern Lake Michigan this morning. The system will bring widespread precipitation, mainly in the form of rain, across northeast Wisconsin. The rain will mix with and possibly change over to snow over far north-central to northeast Wisconsin (near the U.P. border) from mid to late morning.

The system will bring poor flight conditions (IFR/LIFR) to much of northeast Wisconsin this morning. The back edge of the precip will roughly stretch from Wausau to Rhinelander, and it's possible that AUW/RHI misses out on the poor flying conditions.

After this system departs by early afternoon, a second system will spread light snow across the region from late this afternoon through late tonight. Visibilities will likely fall to IFR in the snow at times this evening into overnight. Most locations will see a trace to 2 inches of accumulations. Locally higher amounts will be found in the snow belt of Vilas county.

GRB WATCHES/WARNINGS/ADVISORIES
None.

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