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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- 851 Am Cdt Sat Apr 20 2024
Today - W wind 10 to 20 kts. A chance of sprinkles in the afternoon. Waves 1 to 3 ft. Tonight - W wind 10 to 15 kts. Partly cloudy in the evening then clearing. Waves 2 ft or less. Sunday - W wind 10 to 20 kts veering nw 10 to 15 kts in the afternoon. Sunny in the morning then becoming partly cloudy. Waves 2 ft or less. Sunday night - NE wind 5 to 10 kts veering S after midnight. Mostly clear. Waves 2 ft or less.

LMZ500
No data

FXUS63 KGRB 201127 AFDGRB

Area Forecast Discussion National Weather Service Green Bay WI 627 AM CDT Sat Apr 20 2024

Updated aviation portion for 12Z TAF issuance

KEY MESSAGES

- Elevated fire weather conditions are possible on Sunday and Monday afternoons due to low relative humidities ranging from 20 to 30 percent and winds of 15 to 25 mph.

- The next chance for precipitation returns late Monday through late Tuesday. Rain will be the main precipitation type, but some snow may mix in across the far north on Tuesday. A few thunderstorms are also possible on Tuesday, but severe weather is not expected.

DISCUSSION
Issued at 415 AM CDT Sat Apr 20 2024

Short Term
Today
Tonight...and Sunday

A mid level PV anomaly, currently visible on water vapor imagery across northwest Wisconsin, will swing through northern Wisconsin early this morning. This shortwave will bring scattered light snow showers or flurries as it tracks through the area, with subsidence behind it possibly clearing skies for a bit across northeast and east-central Wisconsin with aid from some downsloping.

Recent mesoscale models have backed off a bit on the precipitation for the rest of today as moisture is not quite as deep as previous runs. Although a sprinkle can't be ruled out, especially across central and east-central Wisconsin, the weather should mainly be dry for today with continued breezy west to west-northwest winds.
Any clearing that occurs will cloud back over later this morning and into the afternoon as upstream IR satellite data indicates abundant cloud cover that will move in across the region. Highs today will be below normal, generally from 45 to 50 degrees.

Surface ridging will build across the southern Great Lakes region tonight, which should clear out the clouds across northeast Wisconsin this evening. Surface winds will continue to be gusty at 10 to 15 mph, which will limit how far temperatures fall tonight.
Lows tonight are generally expected to range from the upper 20s across north-central, to the lower 30s across east-central Wisconsin.

High pressure will continue to build south on Sunday, keeping the weather dry across the western Great Lakes. However, a deep mixed boundary layer up to 700 mb will cause breezy conditions Sunday afternoon along with very dry air and warmer temperatures. This could cause some fire weather concerns as fuels continue to dry out along with gusty winds and warmer afternoon temperatures.
Highs on Sunday are expected to be around normal; ranging from the lower to middle 50s across the north, with around 60 across the Fox Valley and portions of central and northeast Wisconsin.

Long Term...Sunday Night Through Friday

Precipitation...Dry conditions will prevail from Sunday night through much of Monday, ahead of an approaching shortwave/trough and associated surface low pressure system expected to bring the next chance for precip. Although some uncertainty remains with the exact timing and track of the shortwave and surface low, model guidance has come into better agreement regarding the overall evolution of this system. There is clear agreement with the precip occurring in two rounds, first from the surface cold front sliding west to east across the area Monday evening/night, and the second Tuesday afternoon/evening from the trailing shortwave/trough energy dropping southeast across the area.

The first round of precip will be supported by an impressive 40-50kt low-level jet, but a lack in instability and the timing of the frontal passage will lead to a little to no chance of thunderstorms.
For the second round, mid-level lapse rates around 7.5 C/km and MUCAPE around 300-700 J/kg will support the potential for a few thunderstorms as the precip moves across the area. Probabilities for snow to mix in on the back side of the system remains low (less than 20%). If snow were to occur, impacts would not be expected given the system will be exiting.

Dry conditions return for Wednesday and Thursday with high pressure and ridging overhead. The next chance for precip arrives Friday with a southern stream system.

Temperatures...Monday will be the warmest day next week, with high temps about 5 to 10 degrees above normal ranging from the low to mid 60s. Temperatures will then fluctuate around normal for the remainder of the week.

AVIATION
for 12Z TAF Issuance Issued at 626 AM CDT Sat Apr 20 2024

A few snow showers or flurries will linger this morning across north-central Wisconsin before ending. Ceilings should prevail in the 4000-6000 ft AGL range for much of the TAF period; however, MVFR ceilings may accompany any snow showers, and will prevail at times early this morning across north-central and portions of central Wisconsin. Gusty WNW winds will increase again late this morning, then diminish this evening. Clearing skies are anticipated by sunset.

FIRE WEATHER
Issued at 415 AM CDT Sat Apr 20 2024

Moderating temperatures and a dry airmass will lead to elevated fire weather days on Sunday and Monday. Winds will be a little stronger on Sunday compared to Monday with sustained values of 15-20 mph and gusts up to 25 mph (sustained winds 10-15 mph with gusts to 25 mph on Monday). In addition, minimum relative humidities will fall to 20 to 30 percent on Sunday, with 25 to 35 percent on Monday.
While elevated fire weather conditions will be present each day, concern is a little higher on Sunday due to slightly stronger winds and lower RH values.

Another period of elevated fire weather conditions is possible next Wednesday and Thursday, as a dry airmass moves into the region.
Ensembles indicate PWATs are forecast to be 20-40% of normal.
Winds will likely be below critical levels due to the proximity of the prevailing high pressure system.

GRB WATCHES/WARNINGS/ADVISORIES
None.

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