526
FXUS63 KGRB 040328
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1028 PM CDT WED SEP 3 2025
UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE
UPDATE
ISSUED AT 810 PM CDT WED SEP 3 2025
DEEP UPPER LOW IS CENTERED OVER THE WESTERN GREAT LAKES THIS
EVENING. WHILE PARTIAL CLEARING IS OCCURRING, STILL PLENTY OF
CLOUDS AROUND AND ALSO UPSTREAM AS WELL OVER THE ARROWHEAD OF
MINNESOTA AND LAKE SUPERIOR. WINDS REMAIN BLUSTERY WITH GUSTS OF
20 TO 25 KTS OVER CENTRAL AND EAST-CENTRAL WI. WINDS HAVE
DIMINISHED SOMEWHAT OVER NORTH-CENTRAL WI BUT REMAIN IN THE 5 TO
10 KT RANGE.
THE FROST ADVISORY REMAINS LOW CONFIDENCE DUE TO PRESENCE OF
WINDS AND CLOUDS. MARATHON REMAINS THE MOST QUESTIONABLE.
TEMPERATURES ARE COMPARATIVELY COLDER FURTHER NORTH, AND MOSTLY
IN THE MIDDLE 40S. DESPITE THE PRESENCE OF CLOUDS, TEMPERATURES
JUST DON'T HAVE FAR TO FALL BEFORE FROST BECOMES A CONSIDERATION.
WINDS ARE ALSO EXPECTED TO FALL INTO THE 3-4 KTS AFTER MIDNIGHT.
STATISTICAL AND NBM GUIDANCE ALL SUPPORT LOW TEMPERATURES FALLING
INTO THE MIDDLE 30S OVERNIGHT. PROBABILITY OF TEMPS FALLING BELOW
37 DEGREES IS 70-90% OVER VILAS, ONEIDA, AND FOREST COUNTIES.
AS A RESULT, WILL EXPAND THE FRONT ADVISORY TO THE AFOREMENTIONED
COUNTIES LISTED ABOVE.
ALSO EXTENDED THE SMALL CRAFT ADVISORY THROUGH 1 AM TONIGHT.
MARINE HEADLINES WILL ALSO BE NEEDED ON THURSDAY NIGHT BUT WILL
LET THE FIRST ROUND EXPIRE BEFORE ADDING MORE HEADLINES TO THE
MIX. THERE LOOKS TO BE A BRIEF WINDOW FOR GALES FROM 3 AM TO 9 AM
FRIDAY.
KEY MESSAGES
- TEMPERATURES WILL BE UNSEASONABLY COOL THROUGH THE WEEKEND.
FROST MAY FORM TONIGHT ACROSS CENTRAL INTO NORTHERN WISCONSIN
WHERE SKIES CLEAR, WITH 40 TO 70 PERCENT CHANCES FOR
TEMPERATURES BELOW 37F.
- MORE SHOWERS WILL IMPACT THE REGION THURSDAY NIGHT INTO EARLY
FRIDAY WITH A SMALL (20%) CHANCE FOR A THUNDERSTORM. WINDS MAY
GUST NEAR 40 MPH EARLY FRIDAY, ESPECIALLY ACROSS EAST-CENTRAL
WISCONSIN.
- TEMPERATURES WILL SLOWLY MODERATE INTO NEXT WEEK WITH LITTLE
SIGNAL FOR ADDITIONAL IMPACTFUL PRECIPITATION.
DISCUSSION
ISSUED AT 257 PM CDT WED SEP 3 2025
TONIGHT-FRIDAY: UNSEASONABLY COOL, MORE SHOWERS/GUSTY WINDS THURSDAY
NIGHT INTO FRIDAY
THE COLD FRONT HAS CLEARED THE AREA WITH NORTHWEST WINDS IN ITS WAKE
AND FAIRLY STRONG LOW-LEVEL COLD ADVECTION. DEEP NORTHWESTERLY FLOW
WILL CONTINUE TO BECOME ESTABLISHED OVERNIGHT AS A TROUGH DEEPENS
ACROSS THE GREAT LAKES. FOR TONIGHT, CLOUDS LIKELY WILL IMPACT
TEMPS, WITH THE MOST LIKELY AREA FOR MORE CLOUDS/SHOWERS TO PERSIST
ARE ACROSS FAR NORTHERN WISCONSIN DOWNSTREAM FROM LAKE SUPERIOR.
MEANWHILE, THE NBM SHOWS MEDIUM TO HIGH PROBABILITIES (40-80%) FOR
LOW TEMPS DOWN TO AT LEAST 35 DEGREES AND SMALLER (20-50%)
PROBABILITIES FOR NEAR FREEZING TEMPS ACROSS FAR NORTH-CENTRAL
WISCONSIN. IN ADDITION TO ANY CLOUDS, RAP SOUNDINGS SHOW ONLY A
WEAK INVERSION WITH STRONGER FLOW ALOFT, SO WINDS MAY STRUGGLE
TO DECOUPLE. DUE TO EARLY SEASON TIMEFRAME, THOUGH, COORDINATED
WITH SURROUNDING OFFICES FOR A FROST ADVISORY ACROSS CENTRAL
WISCONSIN WHERE CONFIDENCE IS HIGHEST FOR CLEARING SKIES ALONG
WITH THE COOLER TEMPS. THESE TRENDS WILL NEED TO BE MONITORED
THIS EVENING, THOUGH.
THE COOL AIR WILL REMAIN ANCHORED OVER THE AREA THROUGH THE
WEEKEND WITH NAEFS 850 MB TEMPS BELOW THE 1ST PERCENTILE, AND
EVEN NEAR MIN VALUES IN SPOTS, RELATIVE TO CLIMATOLOGY. RECORD
LOW MAX TEMPS ARE STILL ON THE TABLE FOR SOME LOCATIONS OVER THE
NEXT FEW DAYS.
A PRONOUNCED EMBEDDED SHORTWAVE WILL SLIDE SOUTHEAST THROUGH THE
BASE OF THE TROUGH THURSDAY NIGHT, WHICH SHOULD BRING WIDESPREAD
SHOWERS TO THE AREA. INSTABILITY LOOKS QUITE WEAK, BUT ISOLATED
THUNDER COULD NOT BE RULED OUT. THIS SYSTEM SHOULD BE A QUICK HITTER
WITH A FEW LINGERING SHOWERS ON FRIDAY. HOWEVER, STRONG COLD
ADVECTION AND A TIGHTENING PRESSURE GRADIENT SHOULD LEAD TO GUSTY
WINDS ON FRIDAY. THE EPS SHOWS A ROBUST SIGNAL FOR GUSTS NEAR/ABOVE
40 MPH, ESPECIALLY ACROSS EAST-CENTRAL WISCONSIN, WHILE THE 90TH
PERCENTILE NBM VALUES ALSO EXCEED 40 MPH IN SOME AREAS, ESPECIALLY
NEAR THE LAKE MICHIGAN SHORELINE.
SATURDAY-WEDNESDAY: GRADUALLY WARMING UP, MAINLY DRY
THE DEEP MID-LEVEL TROUGH CENTERED ACROSS THE GREAT LAKES WILL
SLOWLY PASS EASTWARD AS MID-LEVEL RIDGING BUILDS EASTWARD INTO THE
MIDDLE OF NEXT WEEK. THIS WILL RESULT IN A SLOW MODERATING TREND IN
TEMPS AS DRY CANADIAN SURFACE HIGH PRESSURE SLOWLY WORKS ACROSS THE
MIDWEST, WITH RETURN SOUTHERLY FLOW EVENTUALLY SETTING UP BY EARLY
TO MID WEEK.
WITH THE DRY AIRMASS AND SURFACE HIGH OVER THE AREA, PATCHY FROST
WILL BE POSSIBLE DURING THE EARLY MORNING HOURS THROUGH MONDAY
BEFORE WARMER AIR RETURNS.
RAIN CHANCES OVERALL LOOK LOOK DURING THIS TIME, WITH LOW END (20-
30%) CHANCES SATURDAY WITHIN THE CYCLONIC MID-LEVEL FLOW AS A
SHORTWAVE TROUGH ROTATES THROUGH THE BROADER TROUGH. ADDITIONAL
SMALL RAIN CHANCES EXIST EARLY NEXT WEEK WITH ANY WEAK WAVES AS THE
PATTERN TRANSITIONS TO LARGER SCALE RIDGING.
AVIATION
FOR 06Z TAF ISSUANCE
ISSUED AT 1028 PM CDT WED SEP 3 2025
BENEATH AN UPPER LOW, CEILINGS REMAIN PRIMARILY VFR LATE THIS
EVENING. SHOWER ACTIVITY HAS MOSTLY FIZZLED AND PARTIAL CLEARING
HAS OCCURRED. A SUBTLE BACKING OF WIND TRAJECTORIES SHOULD
SUPPORT RISING CEILINGS AND SLOW CLEARING OVERNIGHT.
SHALLOW FAIR WEATHER CLOUDS, AROUND 4-5 KFT, ARE LIKELY TO
REDEVELOP WITH THE HEAT OF THE DAY AROUND 15-16Z AND PERSIST
THROUGH THE AFTERNOON.
WINDS WILL SUBSIDE THIS EVENING, WITH SOME DIURNAL INCREASE ON
THURSDAY AS MIXING COMMENCES IN THE 15-16Z TIMEFRAME.
A STRONG LOW PRESSURE SYSTEM WILL BRING RAIN TO THE REGION AFTER
00Z FRI. LOOK FOR STEADY RAIN TO MOVE INTO NORTH-CENTRAL WI
BETWEEN 00-03Z AND INTO NORTHEAST WI BETWEEN 03-06Z FRI.
DETERIORATING FLIGHT CONDITIONS CAN BE EXPECTED WITH BOTH CEILINGS
AND VISIBILITIES FALLING TO MVFR.
MARINE
ISSUED AT 257 PM CDT WED SEP 3 2025
GUSTY POST-FRONTAL WINDS WILL PERSIST THIS AFTERNOON WITH WINDS
DECREASING OVERNIGHT. A REINFORCING COLD FRONT WILL MOVE THROUGH
THURSDAY NIGHT INTO FRIDAY WITH SOME POTENTIAL FOR GALES FOR THE
NEARSHORE WATERS OF NORTHERN LAKE MICHIGAN LATE THURSDAY NIGHT
INTO FRIDAY MORNING. THE NBM SHOWS HIGHER END (90TH PERCENTILE)
WIND GUST VALUES NEARING 40 KTS FOR A RELATIVELY SHORT TIME, SO
A PERIOD OF GALE FORCE GUSTS ARE POSSIBLE. WATERSPOUTS COULD NOT
BE RULED OUT WITH DEEPER EQUILIBRIUM LEVELS AND SOME INSTABILITY
AS THE COLD AIR MOVES OVER WARM WATERS.
GRB WATCHES/WARNINGS/ADVISORIES
FROST ADVISORY FROM 2 AM TO 8 AM CDT THURSDAY FOR WIZ005-010-011-
018-019-030.
UPDATE.........MPC
DISCUSSION.....JM
AVIATION.......MPC
MARINE.........JM
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