Marine Forecasts

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7 Day Forecast for Marine Location Near Green Bay, WI

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Area Discussion for - Green Bay, WI

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FXUS63 KGRB 080359 AFDGRB

Area Forecast Discussion National Weather Service Green Bay WI 1059 PM CDT Fri Aug 7 2020

Updated aviation portion for 06Z TAF issuance

SHORT TERM. Tonight and Saturday Issued at 326 PM CDT Fri Aug 7 2020

Quiet summer day ongoing across the area as surface high pressure slides into the eastern Great Lakes and mid-upper level ridging moves overhead. Dewpoints and humidity levels were slowly on the uptick, but remained near the comfortable range. A few showers attempted to push in from the west late this morning and early afternoon, but they met their demise as they moved into the the drier, more stable environment. Focus in the short term will be timing the shower/storm threat tonight into Saturday and marine and beach hazard headlines (see marine section).

Tonight . can't rule out a brief shower or sprinkle across central and north central WI this evening from the mid-deck pushing into the area, as a weak warm front lifts through, along with weak WAA/moisture push, but most/all spots will be dry. Models still in general agreement showing a complex of storms continuing to develop across northern MN late this afternoon and evening, in association with a potent shortwave/MCV. The brunt of this will stay north of the area, but pretty good agreement with the CAMs showing the southern end of this activity pushing into our area sometime around midnight (Vilas County) then sweeping southeast across the area into early Saturday morning. Limited instability (under 1000 J/kg and fading through the night) to work with and limited bulk shear (up to around 20-25 kts) in our area, so not expecting any widespread severe weather, however would not be surprised some gusty winds and locally heavy rain (PWATs climbing to around 1.5"), especially across north central WI where the instability will be highest. As the surface high pressure continues to exit to our east, return flow will slowly ramp up across the western Great Lakes. So you might feel a little more in the way of humidity tonight, but dewpoints should only climb into the lower 60s. Lows will drop into the 60s for most spots.

Saturday . ongoing activity will be pushing across portions of the area during the morning hours. Expect this activity to wane through the early morning hours as it moves farther away from the shortwave forcing and instability continues to wave. Models not in as good agreement on just where/when this will occur, or how far east it will get, so used a more broad-brushed approach in the POPs. Heavy rain looks to be the main threat with this activity, with PWATs of 1.5-2.0". As we work toward late morning and afternoon, subsidence behind the departing shortwave and a capping inversion should hold things in check with a mainly dry afternoon expected. However, as instability builds through the day, any weak boundaries could touch off a shower or storm. Clouds could limit how warm we get, but think enough breaks will occur to climb into the upper 70s to middle 80s for most locations. Dewpoints will be climbing into the middle and upper 60s across the area, so you will start to feel the humidity, especially in the afternoon.

LONG TERM. Saturday Night Through Friday Issued at 326 PM CDT Fri Aug 7 2020

Focus will be on the severe weather threat on Sunday afternoon and Sunday night.

We should be in a general lull in convective activity Saturday night, with perhaps isolated thunderstorms occurring in association with a weak warm frontal boundary over the region. This lull should continue through Sunday morning.

Sunday will be a very warm and humid day, with temperatures climbing into the middle to upper 80s, and dew points getting into the upper 60s and lower 70s. This will lead to heat indices reaching at least the lower 90s in the typical warm spots of central, east central and northeast WI. The expected heat and humidity, combined with very steep mid-level lapse rates of 8-8.5 c/km, will lead to very unstable conditions, with CAPE around 3000 j/kg and LI's of -8 to -12. Deep layer shear of 25 to 35 kts and 0-3 km SRH around 200 should be sufficient for storm organization. PWATs of 1.5 to 2 inches will also support heavy rainfall. Models have been consistent showing a well-defined short-wave trough moving through the region during the late afternoon and evening, and this should combine with the lingering warm frontal boundary to trigger thunderstorm development in north central and central WI by mid to late afternoon. These strong to severe storms should track across the forecast area during the evening, with a threat of damaging winds, torrential rainfall, localized flooding, and large hail. Additional storms will occur ahead of a cold front overnight into Monday, though the severe threat is less certain.

Mainly dry conditions are anticipated through the remainder of the extended forecast period. High pressure will be situated over the forecast area into midweek, then shift into eastern Ontario/Quebec later in the week. Even though the center of the high shifts east, the southwest periphery will remain ridged over northeast WI until Thursday night or Friday. There may be a chance of storms over our western counties by Friday, as return flow attempts to redevelop. Summer-like temperatures should prevail through the period.

AVIATION. for 06Z TAF Issuance Issued at 1059 PM CDT Fri Aug 7 2020

Mid clouds will continue to thicken and lower ahead of an MCV approaching from Minnesota. CAMS models continue to predict that this system will track through the area later tonight into Saturday morning, although a bit later than previously predicted as the system has had issues getting going. Although there are still doubts on how far south the system will make it, the models seem fairly insistent on the system at least making it through central Wisconsin. Therefore will keep the previous TAFs but update the timing a bit to reflect the later arrival. Conditions are expected to fall to IFR/MVFR with this activity. Once this activity tracks east of the area the weather should remain quiet for the rest of the morning and into the afternoon hours on Saturday.

MARINE. Issued at 326 PM CDT Fri Aug 7 2020

Hazardous conditions for small craft and dangerous swimming conditions are expected to develop on Saturday as south winds increase to 15 to 25 kts in the late morning and afternoon. Waves will build to 4-7 feet on Lake MI and to 2-4 feet on the bay, peaking in the late afternoon and early evening. Small craft advisories and beach hazard statements have been issued.

GRB WATCHES/WARNINGS/ADVISORIES. Beach Hazards Statement from 10 AM CDT Saturday through late Saturday night for WIZ022-040-050.

SHORT TERM . Bersch LONG TERM . Kieckbusch AVIATION . Kurimski MARINE . Bersch

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Weather Reporting Stations

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Stations	Dist	Age	Wind	Air Temp	Water Temp	Waves	Pressure	DewPt
KWNW3 - 9087069- Kewaunee, WI	26 mi	49 min	SSW 7 G 8.9	69°F			1019 hPa
MN4 - 9087088 - Menominee, MI	45 mi	49 min	S 7 G 9.9	71°F	72°F		1018.5 hPa	57°F

Wind History for Kewaunee MET, WI

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Airport Reports

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Airport	Dist	Age	Wind kt	Visibility	Sky/Weather	Temp	DewPt	Humidity	Pressure
Green Bay, Austin Straubel International Airport, WI	8 mi	44 min	S 5	10.00 mi	A Few Clouds	66°F	57°F	75%	1018.8 hPa

Link to 5 minute data for KGRB

Wind History from GRB (wind in knots)

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Tide / Current Tables for

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Weather Map

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Wind Forecast for Green Bay, WI (1,6,7,8)

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Ground Weather Radar Station Green Bay, WI

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