465
FXUS63 KGRR 061721
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1221 PM EST THU NOV 6 2025
KEY MESSAGES
- CLIPPER SYSTEM TO BRING WIND AND RAIN TONIGHT INTO FRIDAY
- ACCUMULATING SNOW POSSIBLE ACROSS SOUTHERN LOWER THIS WEEKEND
- LAKE EFFECT SNOW SUNDAY INTO MONDAY
DISCUSSION
ISSUED AT 405 AM EST THU NOV 6 2025
- CLIPPER SYSTEM TO BRING WIND AND RAIN TONIGHT INTO FRIDAY
A POTENT CLIPPER SYSTEM WILL MOVE THROUGH THE GREAT LAKES TONIGHT
INTO FRIDAY. A BAND OF RAIN WILL SWEEP THROUGH THE AREA OVERNIGHT
INTO INTO FRIDAY MORNING. RAINFALL AMOUNTS OF 0.10 TO 0.25 INCHES
WILL BE COMMON WITH A FEW HEAVIER SWATHS TOWARDS 0.40 INCHES. WE
CANNOT RULE OUT A RUMBLE OF THUNDER TOWARDS THE LAKE AND IN THE
SOUTH WHERE BETTER MOISTURE WILL BE POOLED. 850MB DEW POINTS RISE
TO AROUND +8C, 850MB LIS DROP TO AROUND -1 AND PWATS INCREASE TO
AROUND AN INCH. ALL THAT IS TO SAY THAT THE SYSTEM WILL HAVE
DECENT MOISTURE WITH IT FOR THIS TIME OF YEAR SO AN ISOLATED
THUNDERSTORM IS CERTAINLY POSSIBLE ESPECIALLY GIVEN A DECENT
SHORTWAVE PLOWING IN ALOFT. 30-40 MPH WIND GUSTS LOOK POSSIBLE
TONIGHT INTO FRIDAY. HIGHER GUSTS ARE LIKELY ALONG THE LAKESHORE.
FEEL WE WILL STAY BELOW WIND ADVISORY CRITERIA ALONG THE SHORE,
BUT IT WILL BE SOMETHING WE HAVE TO WATCH AS 45 MPH WINDS BRIEFLY
APPEAR IN THE MIXED LAYER.
- ACCUMULATING SNOW POSSIBLE ACROSS SOUTHERN LOWER THIS WEEKEND
MODELS SEEM TO BE CONVERGING ON A SOLUTION OF SOME WET SNOW ACROSS
OUR SOUTHERN CWA (FROM THE I-96 CORRIDOR TO THE SOUTH) SATURDAY
NIGHT INTO SUNDAY MORNING. THERE IS A GOOD CLUSTERING OF LOW
POSITIONS IN BOTH THE GFS AND ECMWF ENSEMBLES AT 03Z-06Z SATURDAY
ACROSS THE STATE OF INDIANA. THE GFS LOW POSITIONS ARE A BIT
FURTHER NORTH IN THE STATE, GENERALLY NORTH OF IND, WHILE THE
ECMWF LOW POSITIONS HAVE A BIT MORE SPREAD IN ALL DIRECTIONS. ALL
OF THESE SOLUTIONS WILL PUT PRECIPITATION INTO SOUTHERN LOWER
MICHIGAN DURING THE AFOREMENTIONED TIME, THE QUESTION IS TYPE AND
HOW MUCH. THE AIR TEMPERATURES AT THE SURFACE WILL START OFF TOO
WARM FOR SNOW, SO A RAIN TO RAIN/SNOW MIX TO POSSIBLY ALL SNOW
WILL BE THE LIKELY TRANSITION. THE SURFACE TEMPS NEVER LOOK TO GO
BELOW 32F SO WE ARE LOOKING AT A WET SNOW IF IT OCCURS. AT THIS
POINT WE FEEL THE FORECAST IS TRENDING TOWARDS SOME ACCUMULATING
SNOWFALL AT THIS POINT PROBABLY CENTERED ALONG THE I-94 CORRIDOR.
SEVERAL INCHES OF WET SNOW LOOKS POSSIBLE. GIVEN THIS EVENT IS OUT
IN THE 6TH AND 7TH FORECAST PERIODS TOUGH TO NAIL DOWN ALL THE
DETAILS AT THIS POINT. THE MAIN TAKEAWAY IS THE FORECAST IS
TRENDING TOWARDS SOME ACCUMULATING SNOW IN OUR SOUTH THIS WEEKEND.
STAY TUNED FOR FINE TUNING OF THE DETAILS.
- LAKE EFFECT SNOW SUNDAY INTO MONDAY
LAKE EFFECT SNOW IS LIKELY SUNDAY INTO MONDAY IN THE WAKE OF THE
SECOND CLIPPER SYSTEM (SATURDAY NIGHT/SUNDAY MORNING). IN THE LAKE
EFFECT EQUATION (VERY SIMILAR TO SUMMER CONVECTION) OF MOISTURE,
INSTABILITY AND LIFT...ALL THREE VARIABLES ARE ACCOUNTED FOR.
1000-700MB MOISTURE IS IN PLACE RIGHT THROUGH THE PERIOD.
INSTABILITY WILL BE STRONG GIVEN 850MB TEMPERATURES AROUND -8C
TO -10C WHICH WILL COMBINE WITH LAKE WIDE AVERAGE WATER
TEMPERATURES OF +13C TO YIELD DELTA TS NEAR AND IN EXCESS OF 20C.
FINALLY, STRONG LIFT IS NOTED IN BUFKIT OVERVIEWS THROUGH THE
LOWEST 10,000 FEET AT SOUTH HAVEN FOR EXAMPLE WITH A SATURATED DGZ
BETWEEN 5,000 AND 8,000 FEET. WE WILL LIKELY SEE ACCUMULATING LAKE
EFFECT SNOWS ALONG THE LAKESHORE FROM SUNDAY INTO MONDAY AS AIR
TEMPERATURES WILL BE COLDER THAN SATURDAY NIGHT. THE MAIN QUESTION
WILL BE WIND DIRECTION AND WHETHER IT STAYS NORTHWEST OR TRENDS
MORE NORTHERLY. RIGHT NOW THE BULK OF THE EVENT LOOKS NORTHWEST SO
WE WILL SEE LAKE SNOWS IN OUR WESTERN CWA. THE CAVEAT IS THAT IT
IS EARLY SEASON, THE GROUND IS WARM AND THE LAKE IS WARM. SO,
THERE IS THE ELEMENT OF MELTING FROM BELOW AND HAVING RAIN RIGHT
AT THE LAKESHORE GIVEN WATER TEMPERATURES ARE IN THE 50S F.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 1221 PM EST THU NOV 6 2025
CLOUD COVERAGE WILL INCREASE THROUGH THE DAY WITH BASES LOWERING
AS A DISTURBANCE APPROACHES THE AREA. A PERIOD OF LLWS WILL
DEVELOP THIS EVENING AS STRONG WINDS, AS HIGH AS 50 KTS AT 2KFT. A
COLD FRONT CROSSING THE AREA OVERNIGHT WILL BRING MVFR CONDITIONS
AS CIGS FALL BELOW 2KFT. A SURGE OF LOW-LEVEL MOISTURE WILL LIKELY
ALSO SUPPORT MVFR VISBYS AS SHOWERS CROSS THE TERMINALS. LOW
(10%) CHANCE OF IFR CEILINGS AT THE TERMINALS OVERNIGHT. ENOUGH
ELEVATED INSTABILITY NEAR AZO, BTL, AND JXN TONIGHT THAT A
THUNDERSTORM CANNOT BE RULED OUT THOUGH CONFIDENCE IS TOO LOW FOR
TAF INCLUSION. WINDS INCREASE TONIGHT TO 12-20 KNOTS GUSTING TO 30
KNOTS FROM THE SOUTH BECOMING WESTERLY BEHIND THE FRONT.
MARINE
ISSUED AT 405 AM EST THU NOV 6 2025
WE WILL CARRY THE SMALL CRAFT ADVISORY THROUGH 800AM. THE END
TIMING ON THAT HEADLINE LOOKS GREAT. WAVES ARE ON THE DECLINE,
BUT AT LAST CHECK ARE STILL IN THE 4-5 FOOT RANGE. BY 800AM THE
WAVES SHOULD SUBSIDE TO BELOW 4 FEET. RIDGING WILL MOVE THROUGH
THE SOUTHERN GREAT LAKES TODAY BRINGING US A BRIEF RESPITE FROM
THE TYPICAL ACTIVE FALL WIND/WAVES ON THE BIG LAKE.
THAT RESPITE WILL BE SHORT LIVE HOWEVER AS A STRONG CLIPPER SYSTEM
WILL MOVE THROUGH THE GREAT LAKES TONIGHT AND ON FRIDAY. WINDS
WILL RAMP UP QUICKLY THIS EVENING TO GALE FORCE BY MIDNIGHT. WE
HAVE OPTED TO ISSUE A GALE WARNING FROM THIS EVENING INTO FRIDAY
MORNING. LOOKING AT BUFKIT PROFILES FOR ALL OF THE LAKESHORE SITES
AND THE MID LAKE BUOY SITE IT APPEARS GALE CONDITIONS MAY DEVELOP
AS EARLY AS AROUND 1000PM THIS EVENING. GALES SHOULD CONTINUE
THROUGH THE NIGHT AND PERSIST INTO THE MORNING HOURS OF FRIDAY. WE
ARE STILL SEEING GALE FORCE WINDS ALOFT AT THE MID LAKE BUOY SITE
MID MORNING ON FRIDAY, SO WE CONTINUED THE WARNING THROUGH 1000AM.
A SMALL CRAFT ADVISORY WILL BE NEEDED ON THE BACK END OF THE GALE
WARNING, BUT WE WILL NOT ISSUE THAT UNTIL THE GALE IS ENDING.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...GALE WARNING FROM 10 PM THIS EVENING TO 10 AM EST FRIDAY FOR
LMZ844>849.
DISCUSSION...DUKE
AVIATION...THOMAS
MARINE...DUKE
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