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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- 126 Pm Cdt Thu Apr 18 2024
.small craft advisory in effect from Friday morning through Friday evening - .
This afternoon - SW wind 5 to 10 kts. A chance of rain showers. Waves 2 ft or less. Tonight - W wind 10 to 15 kts. A chance of rain showers in the evening. Waves 2 ft or less. Friday - W wind 10 to 20 kts with gusts to around 30 kts. Partly cloudy. Waves 1 to 3 ft building to 2 to 4 ft in the afternoon. Friday night - W wind 10 to 20 kts with gusts to around 25 kts. Partly cloudy. Waves 2 to 4 ft subsiding to 1 to 3 ft in the late evening and overnight.

LMZ500
No data

FXUS63 KGRB 181926 AFDGRB

Area Forecast Discussion National Weather Service Green Bay WI 226 PM CDT Thu Apr 18 2024

Forecast discussion for routine afternoon forecast issuance

KEY MESSAGES

- Light rain will exit the region late this evening or early overnight.

- Gusty west winds of 30 to 40 mph over central to northeast Wisconsin will create conditions hazardous to small craft and may blow loose objects around on Friday.

- Elevated fire weather conditions are possible on Sunday and Monday afternoon due to low relative humidities ranging from 20 to 30 percent and sustained winds of 10 to 20 mph.

DISCUSSION
Issued at 224 PM CDT Thu Apr 18 2024

Short Term...Tonight and Friday

Breezy on Friday

Light rain that has been over central WI much of the day has struggled to make much eastward progress. Main forcing remains well to the south closer to sfc low pressure wave across the western Ohio Valley and there was quite a bit of dry air on the 12z GRB sounding. Even so, axis of deeper moisture to the north of the trough (along a weak cold front/moisture gradient) will move through 22z-02z so this will represent the best chance for seeing some spotty *light* rain from the Fox Valley to the lakeshore. Beyond this, drying and clearing skies takes over the rest of the night. Low temperatures are expected to range from around 30 across the north, to the middle 30s across east-central Wisconsin.

A vigorous mid level shortwave will track through northern Wisconsin during the day on Friday on the southern edge broader mid-level low over northwest Ontario. This wave along with steepening low-level lapse rates will result in chance pops (20-30 percent) for light snow showers over north-central Wisconsin late Friday morning through the afternoon. Any snowfall will likely just be in the air instead of accumulating on the ground due to higher sun angle as we work into later April.

As we have highlighted a while, Friday will be a breezy day for all areas. A tight pressure gradient and deep boundary layer to 700-750 mb will result in breezy west winds gusting to 30-35 mph with a few higher gusts around 40 mph possible from central to east-central WI where there will be more breaks in the clouds. Highs on Friday are expected to range from the lower 40s across the north (though these readings could drop back to the mid-upper 30s once any precip begins), to the lower 50s across east-central Wisconsin.

Long Term...Friday Night Through Thursday

Fire Weather...As a deep upper trough lifts to the northeast and the upper flow backs around to the west, temperatures will be moderating and the airmass will remain quite dry on Sunday and Monday. Minimum humidities will be falling into the 20 to 30 percent range each afternoon. Winds will be a little stronger on Sunday compared to Monday with sustained values of 10-20 mph and gusts up to 25 mph (sustained winds 10-15 mph with gusts to 20 mph on Monday). While elevated fire weather conditions will be present each day, concern is a little higher on Sunday due to stronger winds expected. Will therefore add the concern to the HWO.

Precipitation...A compact, yet dynamic shortwave trough is then expected to impact the region during the Monday evening through Tuesday afternoon period. Spread is higher for timing of the system, but there is also considerable model differences for the strength of the shortwave and associated surface low. Regardless, the ensemble means generally support a further south track like the ecmwf that brings the highest precip chances to the southern half of the forecast area.

Ensemble means point towards precipitation of a 0.25 to 0.50 inches will be possible. Given the dynamics, mid-level lapse projected to reach up to 7 C/km, and a potent low level jet up to 40 kts, it's not unreasonable to think that some embedded storms will be possible and will pass concerns to the next shift.

Very cold air for this time of the year will be present over northern Ontario and Lake Superior by Tuesday. Some of this cold air will get pushed into northern WI as the precip is ending on Tuesday morning. Guidance is showing up to around a 20% chance of light snow mixing in on Tuesday morning across far northern WI.
But given the time of day and year, no accumulations are expected if snowfall occurs. A small craft advisory may also be possible as the colder air arrives behind the system on Tuesday.

Temperatures: Will be on a roller coaster ride over the next week, but no anomalous cold or heat is expected.

AVIATION
for 18Z TAF Issuance Issued at 121 PM CDT Thu Apr 18 2024

VFR conditions will gradually give way to MVFR conditions this afternoon as a weak low pressure system brings scattered light rain showers across central and eastern WI. Conditions should then improve back to VFR this evening as the rain exits the area to the east and drier air advects into the region. Clouds and a few snow showers will build into northern WI on Friday. Conditions should remain VFR. Otherwise, expect just scattered mid clouds across the area.

W/WSW winds are expected this afternoon with gusts up to 20 knots.
Winds will ease below 10 knots this evening, before becoming 10-15 knots overnight. On Friday, west winds will increase to 15-20 kts with gusts to around 30 knots. The strongest wind gusts will impact the central to east-central WI terminals.

GRB WATCHES/WARNINGS/ADVISORIES
None.

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