008  
FXUS63 KGRR 160102  
AFDGRR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND RAPIDS MI  
802 PM EST SUN DEC 15 2024  
   
KEY MESSAGES  
 
- FOG TONIGHT, RAIN MONDAY  
 
- COLDER WITH SNOW CHANCES WEDNESDAY THROUGH SATURDAY  
 
 
   
DISCUSSION  
 
ISSUED AT 323 PM EST SUN DEC 15 2024  
 
- FOG TONIGHT, RAIN MONDAY  
 
PATCHY DENSE FOG WILL CONTINUE THROUGH TONIGHT WITH LIGHT WINDS  
AND SATURATED LOW LEVELS. THERE WILL BE SLOW IMPROVEMENT MONDAY  
MORNING AS LIGHT RAIN HELPS TO SLOWLY DISPERSE THE FOG. WEST  
WINDS PICK UP IN THE AFTERNOON AND EVENING WHICH WILL DISPERSE ANY  
REMAINING FOG. LOW LEVEL MOISTURE REMAINS ALTHOUGH RH PROFILES  
SHOW A PARTIALLY UNSATURATED DGZ, RESULTING IN ONLY LIGHT SHOWERS  
AND DRIZZLE PERHAPS MIXING WITH SNOW FLAKES BEFORE ENDING MONDAY  
NIGHT.  
 
- COLDER WITH SNOW CHANCES WEDNESDAY THROUGH SATURDAY  
 
COOLER AIR ADVECTS IN ON TUESDAY AND THIS COULD SET THE STAGE FOR  
SOME SNOW LATE TUESDAY NIGHT INTO WEDNESDAY MORNING IN AN AREA OF  
MID LEVEL FRONTOGENESIS TO THE NORTH OF A SFC LOW TRACKING EAST  
NORTHEAST ACROSS THE OHIO VALLEY. THIS IS FOLLOWED BY A THERMAL  
TROUGH AND CYCLONIC FLOW RESULTING IN LIGHT LAKE EFFECT SNOW  
SHOWERS INTO WEDNESDAY EVENING.  
 
THERE HAS BEEN A SIGNAL IN THE MODEL GUIDANCE FOR A CLIPPER TO  
MOVES ACROSS THE GREAT LAKES WITH SNOW BY LATE IN THE WEEK. THE  
UNCERTAINTY IN TIMING AND TRACK IS DECREASING AS TODAY THERE  
APPEARS TO BE A CONVERGENCE OF MODEL TIMING ON THURSDAY NIGHT TO  
FRIDAY FOR SOME SYNOPTIC SNOW FOLLOWED BY A VERY COLD SHOT OF AIR  
AND LAKE EFFECT SNOWS FOR THE WEEKEND.  
 
 
   
AVIATION /00Z TAFS THROUGH 00Z TUESDAY/  
 
ISSUED AT 800 PM EST SUN DEC 15 2024  
 
LIFR AND LOWER CIGS DUE TO DENSE FOG WILL CONTINUE FOR MOST OF THE  
TAF SITES FOR MOST OF THE FORECAST PERIOD. THERE IS SOME DRIER  
AIR THROUGH THE SOUTH BUT THAT SHOULD DROP BACK DOWN OVERNIGHT.  
RAIN SHOWERS WILL MOVE IN EARLY MONDAY ALLOWING FOR IFR AND LOWER  
CIGS AND VSBYS TO CONTINUE THROUGH MOST OF MONDAY. IFR TO LIFR  
VSBYS WILL IMPROVE BETWEEN 15Z TO 18Z WITH CIGS FINALLY IMPROVING  
TO NEAR MVFR LATE MONDAY AFTERNOON.  
 
WITH THE SYSTEM MOVING IN HAVE PUT A PERIOD OF LLWS BETWEEN 14Z  
AND 18Z.  
 
 
   
GRR WATCHES/WARNINGS/ADVISORIES  
 
MI...NONE.  
MARINE...NONE.  
 
 
 
 
 
DISCUSSION...OSTUNO  
AVIATION...CERU  
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