420
FXUS63 KGRB 081814
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
114 PM CDT MON SEP 8 2025
UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE
KEY MESSAGES
- PATCHY-AREAS OF FROST EARLY THIS MORNING. FROST ADVISORY
CONTINUES ALONG AND NORTH OF HIGHWAY 29 THROUGH 8AM.
- TEMPERATURES CLIMBING BACK TO OR SLIGHTLY ABOVE SEASONAL NORMS
THIS WEEK, WITH SOME HIGHS IN THE 80S IN SPOTS POSSIBLE LATE IN
THE WEEK AND/OR NEXT WEEKEND.
- CHANCES (30-70%) FOR RAIN SHOWERS AND A FEW STORMS RETURN
TONIGHT INTO TUESDAY NIGHT.
- CONDITIONS HAZARDOUS TO SMALL CRAFT, ALONG WITH DANGEROUS
SWIMMING CONDITIONS, EXPECTED ON THE BAY AND LAKE MICHIGAN LATE
THIS AFTERNOON INTO TUESDAY AFTERNOON/EVENING.
DISCUSSION
ISSUED AT 429 AM CDT MON SEP 8 2025
EARLY THIS MORNING: MID-CLOUDS HAVE HAMPERED TEMPS FROM FALLING
ACROSS PARTS OF CENTRAL AND NORTHERN WI DURING THE EARLY MORNING
HOURS. WHERE SKIES WERE CLEAR, TEMPS DROPPED INTO THE UPPER 30S
TO MID 40S. THE MID-CLOUDS CONTINUE TO SLOWLY SHIFT TO THE
NORTH/EAST WHICH SHOULD ALLOW SOME SPOTS IN THE FROST ADVISORY TO
SEE TEMPS DROP THROUGH SUNRISE INTO THE MID 30S. SO WHILE SOME
SPOTS WON'T SEE ANY FROST, SOME WILL; SO WILL LET THE ADVISORY
RUN ITS COURSE. COULD HAVE SOME PATCHY GROUND FOG AS WELL, BURNING
OFF AFTER SUNRISE.
TODAY INTO TUESDAY: A STRONG PUSH OF WAA WILL SPREAD ACROSS THE
STATE, AS 850MB TEMPS CLIMB FROM 3C TO 13C. THIS WILL PRODUCE SOME
MID-CLOUDS, ALONG WITH SOME POSSIBLE SPRINKLES. BEST CHANCE FOR A
SPRINKLE LOOKS TO BE ACROSS CENTRAL AND NORTH-CENTRAL WI, WHERE
SOME CAMS STILL HAVE A LITTLE SPRINKLEY ACTION (BUT HAVE BACKED
OFF A LITTLE IN RECENT RUNS). FORECAST SOUNDINGS SHOWING SOME DRY
AIR IN PLACE IN THE LOWER LEVELS, SO THINKING VIRGA WILL BE THE
MAIN RESULT, BUT CAN'T RULE OUT A FEW DROPS MAKING IT TO THE
GROUND (HREF PROB OF MEASURING IS 10%). PREFER TO JUST KEEP THE
DRY FORECAST INTACT. THEN, A FRONTAL BOUNDARY POSITIONED ACROSS
NORTHERN WI AND THE U.P., ALONG WITH AN APPROACHING SHORTWAVE,
WILL INTERACT WITH A 30-40 KT LLJ TO PRODUCE SHOWERS AND A FEW
STORMS ACROSS MN AND PARTS OF NORTHWEST/NORTHERN WI. WILL CONFINE
THE SHOWER/STORMS CHANCES (30-70%) MAINLY NORTH AND WEST OF THE
FOX VALLEY, HIGHEST IN FAR NORTH-CENTRAL WI, AND KEEP THE FOX
VALLEY AND LAKE SHORE DRY THROUGH TUESDAY. ELEVATED CAPE UP TO
~500 J/KG WILL SUPPORT THE THREAT FOR SOME THUNDER. SOME POCKETS
OF HEAVY RAIN (OVER 1") WILL BE POSSIBLE OVER FAR NORTH-CENTRAL
WI, WITH TALL, SKINNY CAPE PROFILES AND PWATS CLIMBING TO AROUND
1.3". HREF PROBABILITIES RUNNING AROUND 30-45% FOR 1"+ IN/AROUND
VILAS COUNTY. RECENT DRY WEATHER AND THE SANDIER SOILS SHOULD
LIMIT ANY WIDESPREAD FLOODING ISSUES.
REST OF THE WEEK: LIGHT PRECIP CHANCES WILL LINGER INTO TUESDAY
NIGHT AND WEDNESDAY AS ANOTHER SHORTWAVE TROUGH SWINGS ACROSS THE
GREAT LAKES. ANY PRECIP LOOKS TO BE LIGHT AND WILL ONLY HAVE
20-35% CHANCES TUESDAY NIGHT AND KEEP ~10% POPS ON WEDNESDAY FOR
NOW. SURFACE AND UPPER LEVEL RIDGING IS THEN FORECAST TO BUILD
OVER THE WESTERN GREAT LAKES THURSDAY INTO FRIDAY MORNING,
BRINGING DRY CONDITIONS. CHANCES FOR SHOWERS AND STORMS LOOK TO
RETURN LATE FRIDAY INTO THE WEEKEND AS LOW PRESSURE, A WARM FRONT,
AND WAA ARRIVE FROM THE WEST. TEMPS WILL CONTINUE TO CLIMB BACK
TO NEAR SEASONAL NORMS THROUGH MID-WEEK, THEN POSSIBLY TO SLIGHTLY
ABOVE NORMAL READINGS LATE IN THE WEEK AND NEXT WEEKEND. HOWEVER,
NBM 25TH-75TH PERCENTILE TEMP SPREADS ARE QUITE LARGE (UP TO
10-15 DEGREES WITH THE GFS/GEFS ON THE WARM SIDE AND THE
ECMWF/EPS ON THE COOL SIDE), SIGNALING DIFFERENCES ON HOW THE
PATTERN WILL PLAY OUT.
AVIATION
FOR 18Z TAF ISSUANCE
ISSUED AT 114 PM CDT MON SEP 8 2025
WINDS WILL BE GUSTY ACROSS THE REGION THROUGH THE AFTERNOON, WITH
PERIODIC GUSTS UP TO 20 KNOTS AT TIMES THROUGH THE EVENING. AS
WINDS DROP OFF A BIT OVERNIGHT, SOME LLWS WILL DEVELOP ACROSS MUCH
OF CENTRAL TO EAST-CENTRAL WISCONSIN BEFORE DEEPER MIXING RETURNS
ON TUESDAY. SHOWERS ARE LIKELY TO SPREAD INTO NORTHERN WISCONSIN
DURING THE OVERNIGHT PERIOD AS WELL, BUT WILL PRIMARILY BE LIMITED
TO IMPACTING RHI DURING THIS TAF PERIOD. THE RAIN COVERAGE WILL
EXPAND SOUTH AND EASTWARDS INTO THE PORTIONS OF CENTRAL WISCONSIN
TUESDAY AFTERNOON AS WELL, BEYOND THE CURRENT TAF. THUNDER
POTENTIAL BEFORE THIS AFTERNOON PERIOD SEEMS LIMITED, SO EXCLUDED
A MENTION FOR NOW.
MARINE
ISSUED AT 429 AM CDT MON SEP 8 2025
WINDS WILL SHIFT TO THE SOUTHWEST/SOUTH AND INCREASE THIS
AFTERNOON AND EVENING. GUSTS TO AROUND 25 KTS ARE EXPECTED, BUT
WILL BE LIMITED DUE TO THE UNFAVORABLE WARM AIR OVER THE WARMER
WATERS, LIMITING MIXING. WAVE MODEL BROUGHT 4'+ WAVES IN A LITTLE
FASTER, SO HAVE BUMPED UP THE START TIME OF THE SMALL CRAFT
ADVISORY TO 4PM/21Z ON LAKE MICHIGAN. NO OTHER CHANGES WERE MADE
TO THE SMALL CRAFT ADVISORY, WITH THE BAY ENDING TUESDAY MORNING
AS WINDS DECREASE AND LAKE MICHIGAN ENDING TUESDAY
AFTERNOON/EVENING TO ALLOW FOR THE WAVE ACTION TO SUBSIDE. THE
LARGE WAVES WILL RESULT IN DANGEROUS SWIMMING CONDITIONS AT LAKE
MICHIGAN BEACHES. BUMPED UP THE START TIME OF THE BEACH HAZARDS
STATEMENT AS WELL.
GRB WATCHES/WARNINGS/ADVISORIES
BEACH HAZARDS STATEMENT THROUGH TUESDAY EVENING FOR WIZ022.
BEACH HAZARDS STATEMENT THROUGH TUESDAY EVENING FOR WIZ040-050.
DISCUSSION.....BERSCH
AVIATION.......UHLMANN
MARINE.........BERSCH
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