474
FXUS63 KGRB 200329
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1029 PM CDT SUN JUL 19 2026
UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE
KEY MESSAGES
- LEVEL 3 OF 5 RISK OF SEVERE STORMS MONDAY, INCLUDING RISK FOR DAMAGING
WINDS, LARGE HAIL, AND A FEW TORNADOES. HIGHEST RISK IS LATE
AFTERNOON AND EARLY EVENING.
- SMOKE VISIBILITY AND AIR QUALITY IMPACTS CONTINUE INTO MONDAY.
- DRIER AND COOLER FOR MID-WEEK.
DISCUSSION
ISSUED AT 225 PM CDT SUN JUL 19 2026
SEVERE STORM POTENTIAL MONDAY:
ANOMALOUSLY STRONG DEEP WIND FIELDS FOR LATE JULY COMBINED WITH
AMPLE INSTABILITY AND ASCENT FROM AN APPROACHING SHORTWAVE TROUGH
AND COLD FRONT WILL PROVIDE A VERY CONDUCIVE ENVIRONMENT FOR SEVERE
STORMS ON MONDAY.
EARLY DAY WARM ADVECTION DRIVEN SHOWERS/STORMS MAY IMPACT THE AREA,
HOWEVER THESE WILL BE AHEAD OF THE GREATER INSTABILITY, SO THE
OVERALL SEVERE WEATHER RISK APPEARS LOW DURING THIS TIME.
THE HIGHER RISK FOR SEVERE WEATHER WILL BE LATE IN THE AFTERNOON
INTO THE EVENING AS FORCING FROM THE APPROACHING TROUGH AND COLD
FRONT INCREASE AND ERODE A STOUT CAPPING INVERSION. OVERALL,
19.12Z CONVECTION ALLOWING MODELS SUGGEST GENERALLY SCATTERED
STORM DEVELOPMENT AFTER 3 OR 4 PM WITH STORMS MOVING
SOUTHEASTWARD. GIVEN THE ELONGATED HODOGRAPHS, SUPERCELL MODE OR
BOWING SEGMENTS MAY BE FAVORED WITH A RISK OF ALL HAZARDS,
INCLUDING HAIL OF AT LEAST 2 INCHES AND SIGNIFICANT WINDS. LOW-
LEVEL WINDS REMAIN SOUTHWESTERLY, BUT ENOUGH SPEED SHEAR IS
FORECAST TO INCREASE LOW-LEVEL SHEAR. TORNADIC POTENTIAL MAY BE
INCREASED WITH ANY RIGHT-MOVING SUPERCELLS. SOME GUIDANCE
SUGGESTS PREFERRED CORRIDORS FOR MORE ORGANIZED STORM
DEVELOPMENT WITHIN A BROADER AREA FROM NORTHERN IOWA NORTHWARD
THROUGH WISCONSIN AND THE UP. THESE TRENDS WILL BE EVALUATED
LEADING UP TO THE EVENT.
ALTHOUGH HIGH RAIN RATES WILL ACCOMPANY STORMS, THE SCATTERED NATURE
OF THE STORMS AND PROGRESSIVE MOVEMENT LIKELY WILL LIMIT
WIDESPREAD HIGHER RAIN AMOUNTS, BUT LOCALIZED 2 INCH AMOUNTS
COULD OCCUR. URBAN AREAS OR POOR DRAINAGE AREAS WILL BE
SUSCEPTIBLE TO HIGHER RAIN RATES AND LOCALIZED FLOODING.
SMOKE:
SMOKE FROM WILDFIRES TO THE NORTH CONTINUES TO IMPACT THE AREA TODAY
WITHIN THE RIDGE OF HIGH PRESSURE WITH CONTINUED VISIBILITY/AIR
QUALITY IMPACTS. SOME GRADUAL IMPROVEMENT IN VISIBILITY HAS
BEEN OCCURRING TODAY WITH DIURNAL MIXING, WITH MORE SUBSTANTIAL
IMPROVEMENT SUGGESTED BY THE RRFS/HRRR THROUGH THE DAY ON MONDAY
AS WINDS INCREASE OUT OF THE SOUTH AHEAD OF THE COLD FRONT.
REST OF THE WEEK:
HIGH PRESSURE BUILDS SOUTH BEHIND THE COLD FRONT PROVIDING COOLER
AND DRIER WEATHER FOR MID-WEEK. BY LATE WEEK INTO NEXT WEEKEND, MID-
LEVEL RIDGING IS FORECAST TO BUILD EASTWARD FROM THE ROCKIES WITH
GRADUALLY WARMING TEMPS. NO STRONG SIGNAL FOR PRECIPITATION IS
APPARENT LATE WEEK WITH LOW PREDICTABILITY IN PLACEMENT OF ANY
SMALLER SCALE SHORTWAVE TROUGHS.
AVIATION
FOR 06Z TAF ISSUANCE
ISSUED AT 1028 PM CDT SUN JUL 19 2026
SMOKE TRENDS MAIN ISSUE THROUGH LATE TONIGHT. GIVEN STEADY SW
WINDS AND SMOKE NOT AS THICK AS SATURDAY, EXPECT VSBY 2-5 SM,
LOWEST OVER CENTRAL WI. FIRST CHANCE OF SHOWERS AND STORMS ARRIVES
OVER CENTRAL/NORTH-CENTRAL WI ON MONDAY MORNING. EXPECT THESE
STORMS TO BE ON WEAKENING TREND, BUT BRIEF IFR VSBY COULD OCCUR.
REMNANTS OF THESE STORMS COULD REACH EASTERN WI TAF SITES LATE
MORNING, BUT WITH EXPECTED WEAKENING, CONTINUE TO ONLY MENTION
SHOWERS, WITH NO TS. MODELS STILL PRETTY LOCKED ON TO MORNING
CONVECTIVE EVOLUTION, THOUGH LESS THAN IDEAL HANDLING OF UPSTREAM
SHOWERS AND STORMS THIS EVENING DOESN'T MEAN THESE TRENDS ARE A
LOCK. OTHERWISE, MVFR VSBY FROM SMOKE WILL SLOWLY IMPROVE BY
MIDDAY OVER CENTRAL WI, THEN OVER EASTERN WI MID TO LATE AFTERNOON.
LOWEST VSBY WILL BE 3-4SM.
LATE AFTERNOON AFTER 22Z, EXPECT SHOWERS AND STORMS TO BLOSSOM
OVER CENTRAL/NORTH-CENTRAL WI, BEFORE SPREADING TO EASTERN WI
THROUGH 03Z-05Z. IN THIS ITERATION OF THE TAFS HAVE TRIED TO FRAME
OUT 3-4 HR TIME FRAME OF WHEN TS ARE THE MOST FAVORED AT EACH TAF
SITE. DETAILS FOR THE TIMING AND SPECIFICS FOR IMPACT WITH TS CAN
BE ADDED IN LATER UPDATES.
KOSH
DRY REST OF TONIGHT WITH SMOKE TRENDS MAIN CONCERN. ENOUGH WIND
TONIGHT AND LESS CONCENTRATED SMOKE TO PROHIBIT VSBY LOWER THAN 3
SM MOST OF THE NIGHT.
ON MONDAY, THE FIRST CLUSTER OF SHOWERS AND THUNDERSTORMS WILL
APPROACH OSH BETWEEN 15Z-18Z MONDAY. STILL NO TS MENTIONED AS
STORMS WILL BE ON THE WEAKENING TREND AND OUTRUNNING BETTER
INSTABILITY TO THE WEST. YET, EVEN THOUGH WEAKENING, THE SHOWERS
COULD STILL PRODUCE BRIEF GUSTY OUTFLOW WINDS FROM THE NW. DECENT
AGREEMENT THAT PRIMARY WINDOW FOR SHOWERS AND STORMS AT OSHKOSH
HAS SHIFTED LATER NOW, NOT UNTIL AFTER 00Z. RAN WITH A PREVAILING
FOR TS STARTING AT 21/01Z. SIMILAR TO OTHER EASTERN WI TAF
SITES, DID NOT INCLUDE SPECIFICS YET WITH THE TS MENTION IN TERMS
OF HEAVY RAIN, GUSTY WINDS, HAIL, AS THESE DETAILS CAN BE ADDED
IN LATER UPDATES. A DIRECT HIT FROM TS WOULD RESULT IN IFR
CONDITIONS, BUT NOT ENOUGH CONFIDENCE TO INCLUDE ANY NOTABLE
REDUCTION TO VSBY YET.
MARINE
ISSUED AT 225 PM CDT SUN JUL 19 2026
SOUTH TO SOUTHWEST WINDS WILL INCREASE TONIGHT INTO MONDAY, WITH
GUSTS TO 30 KTS LIKELY MONDAY AFTERNOON. WAVES ON LAKE MICHIGAN
WILL BUILD TO 4-7 FT ON MONDAY, AND TO 2-4 FT ON THE BAY. A SMALL
CRAFT ADVISORY HAS BEEN ISSUED. A BEACH HAZARDS STATEMENT HAS
ALSO BEEN ISSUED.
WILDFIRE SMOKE WILL ALSO CONTINUE TO IMPACT GREEN BAY AND LAKE
MICHIGAN THROUGH LEAST MONDAY MORNING, DROPPING VISIBILITIES TO
AROUND 1NM AT TIMES. THE DENSE MARINE SMOKE ADVISORY CONTINUES
INTO TONIGHT.
GRB WATCHES/WARNINGS/ADVISORIES
BEACH HAZARDS STATEMENT FROM 10 AM CDT MONDAY THROUGH TUESDAY
MORNING FOR WIZ022-040-050.
DISCUSSION.....JM
AVIATION.......JLA
MARINE.........JM
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