984
FXUS63 KGRB 151145
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
645 AM CDT SAT AUG 15 2026
UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE
KEY MESSAGES
- RAIN CHANCES CONTINUE TO TREND LOWER TODAY (15-30%). MANY AREAS WILL
STAY DRY. SCATTERED SHOWERS (30-70%) AND A FEW THUNDERSTORMS
(10-20%) TONIGHT AS COLD FRONT MOVES THROUGH.
- A BRIEF SHOWER OR STORM (20-30%) MAY OCCUR SUNDAY AFTERNOON
FROM DOOR COUNTY TO EAST-CENTRAL WI.
- NEXT CHANCE FOR SHOWERS AND SOME STORMS (60-80%) TUESDAY AND
TUESDAY NIGHT, TAPERING OFF WEDNESDAY MORNING. CONFIDENCE IN
STORM SEVERITY IS LOW, BUT LOCALLY HEAVY RAIN COULD OCCUR.
- TURNING COOLER MIDDLE TO END OF NEXT WEEK, WITH HIGHS IN THE
LOWER TO MIDDLE 70S.
DISCUSSION
ISSUED AT 300 AM CDT SAT AUG 15 2026
NEAR TERM THROUGH TONIGHT: DRY TREND FOR TODAY CONTINUES. FOR MOST
OF THE DAY, ORGANIZED SHOWERS AND STORMS WILL HAVE HARD TIME MAKING
IT EVEN INTO SOUTHERN WI AS GRADIENT OF INSTABILITY AND CONVERGENCE
FROM LOW-LEVEL JET REMAIN SOUTH. MOISTURE ADVECTION ON NORTH EDGE
COULD RESULT IN A FEW SHOWERS OVER FAR SOUTHERN AREAS, BUT MOST
LOCATIONS WILL STAY DRY THROUGH LATE AFTERNOON. EVEN SO, MID CLOUDS
WILL HOLD DOWN TEMPS IN THE UPPER 70S TO NEAR 80. A FEW MORE SHOWERS
AND MAYBE A STORM COULD DEVELOP OVER CENTRAL WI LATE THIS AFTERNOON
AS LIFT FROM SHORTWAVE MOVES IN FROM CENTRAL PLAINS AND INTERACTS
WITH CAPES UP TO 500J/KG ALONG A WARM FRONT. BETTER CHANCES FOR
SHOWERS AND ISOLATED STORMS OCCURS THIS EVENING INTO THE OVERNIGHT
AS TAIL OF SHORTWAVE OVER LAKE SUPERIOR AND COLD FRONT CROSS THE
STATE. RIGHT ENTRANCE REGION OF JET WILL ALSO HELP ORGANIZE
SHOWERS, ESPECIALLY OVER NORTHERN WI, WHERE SOME RAIN IS CERTAINLY
NEEDED. EVEN AS PWATS NEAR 1.8 INCHES (95+ PERCENTILE) WILL BE
INTERACTING WITH THE FORCING, RAINFALL AMOUNTS LOOK ON THE LIGHT
SIDE WITH MINIMAL INSTABILITY. IF A HEAVIER SWATH OF SHOWERS
DEVELOPS IT COULD PRODUCE OVER 0.5 INCH OF RAIN OVER NORTH-CENTRAL
WI, BUT THAT PROSPECT LOOKS QUITE LOCALIZED. SIGNAL IS THERE THAT
NOT MUCH RAIN AT ALL MAKES IT INTO NORTHEAST OR EAST-CENTRAL WI
WHERE HREF MEANS SHOWING A MIN IN QPF.
BRIEF SHOWER OR STORM CHANCE SUNDAY: DESPITE BEING BEHIND THE
FRONT ON SUNDAY, SHORTWAVE DRAGGING THROUGH DURING PEAK HEATING
MAY KICK OFF ISOLATED SHOWERS AND STORMS OVER FROM DOOR COUNTY TO
ALONG THE LAKESHORE IN THE EARLY AFTERNOON. NOT A LOT FOR POPS
(20-30%), BUT CAPES OVER 1000J/KG BOOSTED BY LINGERING HIGHER
DEWPOINTS AND EFFECTIVE SHEAR OVER 30 KTS COULD PRODUCE A STRONGER
STORM.
NEXT CHANCE FOR RAIN IS TUESDAY INTO WEDNESDAY: SHARPENING NORTHWEST
FLOW PUSHES STRONGER SHORTWAVE AND COLD FRONT ACROSS THE WESTERN
GREAT LAKES REGION. THOUGH FORECAST INSTABILITY AND VARIOUS
MACHINE LEARNING OUTPUT SUGGEST HIGHEST SIGNAL STAYS SOUTHWEST
FROM SOUTHERN MN INTO IA, IT WILL NOT TAKE MUCH INCREASE IN CAPE
TO LEAD TO SOME SEVERE THREAT ACROSS WI AS THE FORCING ARRIVES
DURING PEAK HEATING ON TUESDAY AFTERNOON. UNCERTAINTY ON HOW FAST
THIS SYSTEM EXITS AND MODELS ARE NOT SURPRISINGLY SHOWING SOME
VARIABILITY WITH THAT. OVERALL, OTHER THAN TONIGHT'S SHOWER
CHANCES, THIS SYSTEM LOOKS LIKE THE GREATEST OPPORTUNITY FOR
RAIN NEXT WEEK. COOLER AIR PUSH BEHIND THIS SYSTEM REMAINS ON TRACK,
WITH HIGHS SETTLING INTO THE LOWER TO MIDDLE 70S WEDNESDAY THROUGH
FRIDAY.
AVIATION
FOR 12Z TAF ISSUANCE
ISSUED AT 645 AM CDT SAT AUG 15 2026
VFR CIGS WITH A SPOTTY SHOWER ARE EXPECTED THROUGH THIS AFTERNOON.
FRONT MOVES THROUGH TONIGHT, WITH INCREASING CHANCES (30-70%) OF
SHOWERS. GREATEST POTENTIAL FOR SHOWERS WILL BE AT RHI INTO THE
EARLY OVERNIGHT HOURS, WHERE PUT IN A PREVAILING FM GROUP. OTHERWISE,
COVERED THE SHOWER POTENTIAL OVER CENTRAL AND NORTH- CENTRAL WI
WITH PROB30 GROUPS AND ONLY USED A VCSH FARTHER EAST AS THE
SHOWERS WILL BE DIMINISHING LATER AT NIGHT. INSTABILITY WANING BY
THIS EVENING, SO DID NOT INCLUDE ANY MENTION OF THUNDER. CONDITIONS
WILL DETERIORATE TO IFR/MVFR OVERNIGHT TONIGHT, MAINLY FROM LOWER
CIGS.
LIGHT NE-E WINDS INCREASE TO 5-10 KTS FROM THE SE TODAY, THEN TURN
SW TONIGHT AS A WARM FRONT BRIEFLY PASSES THROUGH. COLD FRONT
ARRIVES LATE TONIGHT INTO SUNDAY MORNING, SWITCHING THE WINDS TO
W-NW.
MARINE
ISSUED AT 300 AM CDT SAT AUG 15 2026
SOUTHEAST WINDS WILL INCREASE TODAY ACROSS THE LAKE MICHIGAN
NEARSHORE WATERS AS A COLD FRONT APPROACHES THE AREA. THIS WILL
BRING SMALL CRAFT ADVISORY CONDITIONS, WITH GUSTS OVER 20 KTS AND
WAVES UP TO 4 FEET, HIGHEST SOUTH OF TWO RIVERS.
GRB WATCHES/WARNINGS/ADVISORIES
BEACH HAZARDS STATEMENT THROUGH THIS EVENING FOR WIZ050.
DISCUSSION.....JLA
AVIATION.......JLA
MARINE.........JLA
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