673
FXUS63 KGRR 080817
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
317 AM EST SAT NOV 8 2025
KEY MESSAGES
- RAIN TRANSITIONS TO SNOW SATURDAY NIGHT
- LAKE EFFECT SNOW BEGINS SATURDAY NIGHT, CONTINUES SUNDAY
- LAKE EFFECT SNOW CONTINUES SUNDAY NIGHT AND MONDAY
DISCUSSION
ISSUED AT 317 AM EST SAT NOV 8 2025
- RAIN TRANSITIONS TO SNOW SATURDAY NIGHT
THE GENERAL TREND OVER THE PAST 24 HOURS IS FOR A MORE SOUTHERN
TRACK POSITION OF THE OH VALLEY LOW TONIGHT, DURING WHICH TIME WE
EXPECT A NORTH TO SOUTH CHANGEOVER TO SNOW AS SURFACE TEMPERATURES
FALL DIURNALLY AND MID-LEVEL FORCING WITH THE ASSOCIATED PV MAXIMUM
HELPS TO INDUCE DYNAMIC COOLING. MODEL SOLUTIONS HAVE BEEN CONVERGING
TOWARDS MAXIMUM SNOWFALL AMOUNTS OCCURRING SOUTHEAST OF A BATTLE
CREEK TO LANSING LINE, WITH SOME OF THE DETERMINISTIC RUNS SUGGESTING
4 INCH ACCUMULATIONS AROUND JACKSON POSSIBLE BY SUNDAY AFTERNOON.
TRAVEL IMPACTS WILL BE MITIGATED BECAUSE A COUPLE TENTHS OF AN
INCH OF RAIN ARE EXPECTED TO FALL PRIOR TO ONLY MARGINALLY
FREEZING TEMPERATURES BEING REALIZED; THIS IS NOT A CONDUCIVE
SETUP FOR ICING. HOWEVER, POWER INTERRUPTIONS WITH SNOW
ACCUMULATING ON LEAF-BEARING BRANCHES IS STILL NOT OUT OF THE
QUESTION.
- LAKE EFFECT SNOW BEGINS SATURDAY NIGHT, CONTINUES SUNDAY
WITH THE AFOREMENTIONED SOUTHERN TRACK SHIFT OF THE OH VALLEY LOW
TONIGHT ALSO COMES A CORRESPONDING SOUTHWARD SHIFT IN COLD AIR AND
PV FORCING OVER LAKE MI ASSOCIATED WITH A SHARP AND DEEP UPPER
TROUGH DROPPING SOUTH ACROSS THE WESTERN GREAT LAKES REGION.
FORECAST SOUNDINGS INDICATE LARGE LAKE MICHIGAN BOUNDARY LAYER
DEPTHS THANKS TO A COMBINATION OF UPPER PV ADVECTION AND STEEPENING
LOW LEVEL LAPSE RATES WITH COLD AIR ADVECTION OVER SEASONABLY WARM
WATER. THE THERMODYNAMIC SETUP IS VERY IMPRESSIVE WITH A MIXED LAYER
REACHING AT LEAST 10000 FEET AND SBCAPE EXTENDING TO ABOVE THE MINUS
20C ISOTHERM, MEANING THAT EVEN THUNDERSNOW MAY BE OBSERVED OVER THE
LAKE SUNDAY AFTERNOON. CAMS INDICATE A DOMINANT N-S LAND BREEZE
ASSISTED LAKE EFFECT SNOW (LES) BAND SETTING UP OVER LAKE MI AND
PERHAPS STAYING JUST OFFSHORE FROM THE SABLE POINTS. HOWEVER, THE
NEWER 08/06Z HRRR NOTES THAT THIS BAND MAY CURL CYCLONICALLY INLAND
FARTHER SOUTH TOWARDS VAN BUREN AND WESTERN ALLEGAN COUNTY BY SUNDAY
AFTERNOON. THIS COULD EASILY YIELD ADVISORY LEVEL SNOWFALL THANKS TO
LARGE SNOWFALL RATES EXPECTED WITH THE IMPRESSIVE THERMODYNAMICS.
GREATEST ACCUMULATIONS COULD BE DISPLACED A BIT INLAND HOWEVER GIVEN
THE CONTINUED OVERALL WARMTH OF LAKE MI AT THIS TIME.
- LAKE EFFECT SNOW CONTINUES SUNDAY NIGHT AND MONDAY
LES WILL INITIALLY STAY CONFINED CLOSE TO THE LAKESHORE DUE TO
NORTHERLY FLOW, ALLOWING VAN BUREN COUNTY AND THE SABLE POINTS TO
RACK UP ADDITIONAL ACCUMULATIONS. THERE IS SOME EVIDENCE THAT WINDS
WILL TURN NORTHWEST BY MONDAY AFTERNOON AND WHAT'S LEFT OF THE
DOMINANT LES BAND WILL BE PUSHED INLAND AND DISSIPATE. AS NOTED
PREVIOUSLY, TEMPERATURES IN THE 20S MONDAY MORNING WILL BE FAVORABLE
FOR SLIPPERY TRAVEL CONDITIONS, ESPECIALLY WHERE LES IS MOST ACTIVE.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 1201 AM EST SAT NOV 8 2025
VFR CONDITIONS WILL PREVAIL THROUGH SATURDAY EVENING, WITH THE
EXCEPTION OF PATCHY MVFR FROM GRR TO LAN THROUGH ABOUT 09Z.
NORTHWEST WINDS AOB 10 KNOTS OVERNIGHT GOING NORTHEAST ON SATURDAY
MORNING.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR
LMZ844>849.
DISCUSSION...TJT
AVIATION...OSTUNO
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