710
FXUS63 KGRB 202330
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
630 PM CDT MON JUL 20 2026
UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE
KEY MESSAGES
- LEVEL 3 OF 5 RISK OF SEVERE STORMS TODAY. DAMAGING WINDS, LARGE
HAIL, AND A FEW TORNADOES ALL POSSIBLE. HIGHEST RISK IS MID
AFTERNOON TO EARLY EVENING (3 TO 8 PM).
- DRIER AND COOLER FOR MID-WEEK.
DISCUSSION
ISSUED AT 255 PM CDT MON JUL 20 2026
MLCAPE OF 2500-3000 J/KG IS BUILDING INTO NORTH CENTRAL WI AT
THIS TIME ON SWLY FLOW AHEAD OF A WEAK SFC TROUGH. MEANWHILE 0-8KM
SHEAR HAS INCREASED TO 50-60 KT ACROSS THE AREA. 994 MB LOW
PRESSURE OVER NORTH CENTRAL ONTARIO WILL DEEPEN SLIGHTLY 991 MB
AS IT MOVES NEAR THE SRN TIP OF JAMES BAY BY 12Z TUE. THE PRE-
FRONTAL SFC TROUGH OVER NW WI WILL MOVE ACROSS THE NRN HALF OF
WI LATE THIS AFTERNOON AND EARLY EVENING. SFC CONVERGENCE ALONG
THIS FEATURE WILL BE MODEST, BUT AIDED BY THE MAIN UPPER WAVE
OVER SW ONTARIO MOVING OVER NRN LAKE SUPERIOR FOR LATE
AFTERNOON, AND THEN DEEPEN SLIGHTLY AS IT MOVES ACROSS ERN LAKE
SUPERIOR THIS EVENING. OVERALL 12HR 500 MB HT. FALLS OF 60-80
METERS ARE EXPECTED ACROSS THE NRN HALF OF WI. WITHOUT STRONG
FORCING, BELIEVE THE CAMS ARE CORRECT WITH DISCRETE SUPERCELLS
AFTER MAINLY 21Z INTO THE EARLY EVENING. CANNOT RULE OUT SOME
CONSOLIDATION OF CELLS FARTHER TO THE EAST TOWARD LAKE MI AND
WILL FORECAST 50-70 PERCENT CHANCES FOR SHOWERS AND STORMS.
EFFECTIVE SRH OF 200 M2/S2 IS FORECAST WITH 0-1KM SRH OF 100-150
M2/S2. LCLS AND LFCS WILL BE SUFFICIENTLY FAVORABLE FOR
TORNADOES ALONG WITH THE AFOREMENTIONED LOW LEVEL WIND SHEAR.
DCAPE OF 1200-1600 J/KG WILL BE A LIMITING FACTOR FOR TORNADOES,
AND A STRONGER FACTOR FOR DAMAGING WINDS. OVERALL THOUGH, ALL
HAZARDS, POSSIBLY SIGNIFICANT SEVERE, ARE FORECAST.
THE ACTUAL COLD FRONT WILL THEN PASS LATE TNT ON INCREASING NWLY
WINDS. BREEZY NWLY WINDS AND COLD ADVECTION WILL PREVAIL INTO
TUE NT. BROKEN STRATOCUMULUS, RELATIVELY COLD AIR ALOFT AND LAKE
EFFECT RAIN SHOWERS FROM LAKE SUPERIOR MAY LEAD TO A FEW
SHOWERS OVER FAR NORTH CENTRAL WI LATE TNT-TUE. RELATIVELY COOL
TEMPS ARE FORECAST TUE-WED BUT WITH LESS CLOUDS FOR WED WHEN
HIGH PRESSURE APPROACHES FROM THE WEST.
NWLY FLOW ALOFT WILL THEN PREVAIL INTO THE WEEKEND. HIGH
PRESSURE OVER MN AND IA ON WED WILL TRACK ACROSS THE OHIO VALLEY
AND INTO NEW ENGLAND FOR THU-FRI. TEMPERATURES WILL CLIMB BACK
TO NORMAL FOR THU-FRI THEN ABOVE NORMAL FOR THE WEEKEND AS SWLY
WINDS RETURN. CHANCES FOR SHOWERS AND STORMS RETURN TO THE
FORECAST FOR SAT NT-MON AS A WEAK CANADIAN COLD FRONT WILL PASS
OR STALL OVER THE REGION.
AVIATION
FOR 00Z TAF ISSUANCE
ISSUED AT 614 PM CDT MON JUL 20 2026
KOSH - SCATTERED THUNDERSTORMS WILL MOVE INTO EASTERN WI THIS
EVENING. THE HIGHEST CHANCES OF STORMS WILL BE FROM 01-03Z.
THE STORMS WILL BE CAPABLE OF PRODUCING GUSTY WINDS, HAIL,
AND BRIEF HEAVY RAIN. SINCE THE STORMS ARE SCATTERED, WILL WAIT
CLOSER TO ARRIVAL TO BETTER PINPOINT WIND GUSTS IF THEY SHOULD
MOVE ACROSS THE AIRPORT. SYNOPTIC WINDS WILL GUST TO 20 TO 25 KTS
THROUGH 03Z, THEN WIND GUSTS DIMINISH TO AROUND 18 KNOTS INTO
EARLY TUESDAY MORNING. GUSTY NORTHWEST WINDS ARE EXPECTED ON
TUESDAY, GENERALLY AROUND 25 KNOTS FROM MID MORNING THROUGH MUCH
OF THE AFTERNOON.
FOR THE REST OF THE AREA, SCATTERED THUNDERSTORMS WILL END FROM
WEST TO EAST LATER THIS EVENING. SOME OF THE STRONGEST STORMS
COULD PRODUCE STRONG WINDS, HAIL AND BRIEF HEAVY RAIN.
MARINE
ISSUED AT 255 PM CDT MON JUL 20 2026
BREEZY SLY WINDS THIS EVENING WILL BECOME BREEZY NW WINDS TUE-
TNT AS DEEP LOW PRESSURE MOVES ACROSS SRN CANADA. A SMALL CRAFT
ADVISORY IS IN EFFECT INTO TNT BUT WILL LIKELY NEED TO BE
EXTENDED FOR TUE-TUE NT. A BEACH HAZARDS STATEMENT WILL CONTINUE
THROUGH TNT FOR THE LAKE MI BEACHES.
GRB WATCHES/WARNINGS/ADVISORIES
BEACH HAZARDS STATEMENT THROUGH TUESDAY MORNING FOR WIZ022-040-
050.
DISCUSSION.....MG
AVIATION.......ECKBERG
MARINE.........MG
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