756  
FXUS63 KGRR 212000  
AFDGRR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND RAPIDS MI  
300 PM EST TUE NOV 21 2017  
 
LATEST UPDATE...  
SYNOPSIS/SHORT TERM/LONG TERM/MARINE  
   
SYNOPSIS
 
 
ISSUED AT 300 PM EST TUE NOV 21 2017  
 
LIGHT LAKE EFFECT SNOW SHOWERS AND FLURRIES WILL DEVELOP TONIGHT  
BUT WITH VERY LITTLE TO NO SNOW ACCUMULATION. A WEAKENING CLIPPER  
SYSTEM MAY ALSO BRING A FEW LIGHT SNOW SHOWERS AND FLURRIES MAINLY  
NORTH OF MUSKEGON DURING THE EARLY MORNING HOURS OF THANKSGIVING  
DAY.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH THURSDAY NIGHT)  
ISSUED AT 300 PM EST TUE NOV 21 2017  
 
A RELATIVELY TRANQUIL WX PATTERN WILL CONTINUE THROUGH THE SHORT  
TERM FCST PERIOD. A FEW LIGHT NORTHWEST FLOW LAKE EFFECT SNOW  
SHOWERS AND FLURRIES WILL DEVELOP TONIGHT AS H8 TEMPS FALL TO -11  
TO -13 C YIELDING DELTA T/S IN THE UPPER TEENS.  
 
HOWEVER LAKE EFFECT SNOW SHOWER POTENTIAL IS MITIGATED BY SEVERAL  
FACTORS INCLUDING LACK OF DEEPER MOISTURE AND LOW INVERSION HEIGHTS  
OF ONLY AROUND 4-5 KFT AGL. AREAS MAINLY NEAR TO WEST OF US-131 WILL  
HAVE VERY LIGHT SNOW ACCUMULATIONS OF UNDER AN INCH. VERY LITTLE TO  
NO SNOW ACCUMULATION IS FCST OVER OUR EASTERN FCST AREA.  
 
FLURRIES OR VERY LIGHT SNOW SHOWERS WILL LINGER NEAR TO WEST OF US-  
131 INTO EARLY WEDNESDAY MORNING BEFORE ENDING. DRY WX IS FORECAST  
WEDNESDAY AFTERNOON THROUGH WEDNESDAY EVENING.  
 
A WEAKENING CLIPPER SYSTEM WILL BRING A FEW LIGHT SNOW SHOWERS  
AND FLURRIES TO OUR NORTHWEST FCST AREA (MAINLY NORTH OF KMKG)  
MAINLY BETWEEN 06Z AND 12Z THURSDAY WITH ONLY A FEW TENTHS OF AN  
INCH OF SNOW ACCUMULATION UP THERE. OTHER THAN THAT TRANQUIL AND  
DRY WX IS FORECAST FOR THE THANKSGIVING HOLIDAY AND FOR THURSDAY  
NIGHT.  
   
LONG TERM
 
(FRIDAY THROUGH TUESDAY)  
ISSUED AT 300 PM EST TUE NOV 21 2017  
 
NO MAJOR SYSTEMS ARE EXPECTED IN THE LONG TERM BUT THE PATTERN OF A  
COLD FRONT EVERY FEW DAYS WILL CONTINUE. NO SIGNIFICANT COLD AIR  
OUTBREAKS WILL OCCUR SINCE THE POLAR JET STAYS NORTH MOST OF THE  
TIME WHICH ALSO MEANS MINIMAL LAKE EFFECT PRECIPITATION.  
 
OUT NEXT COLD FRONT IS PROGGED TO COME THROUGH ON FRIDAY NIGHT AND  
OUT AHEAD OF IT GUIDANCE BRINGS IN H8 TEMPS AROUND 10C ON FRIDAY.  
THAT SHOULD LEAD TO HIGH TEMPS AT OR ABOVE 50 ALTHOUGH BREEZY  
CONDITIONS WILL MAKE IT FEEL COLDER.  
 
MODEL CONSENSUS IS FOR HIGH POPS FOR LIGHT RAIN SHOWERS WITH FROPA  
ON FRIDAY NIGHT, THEN A CHANCE OF MIXED RAIN AND SNOW SHOWERS IN THE  
COLDER AIR BEHIND THE FRONT SATURDAY. LITTLE OR SNOW ACCUMULATIONS.  
 
SUNDAY AND MONDAY LOOK DRY WITH MODERATING TEMPERATURES AS SFC HIGH  
PRESSURE MOVES FROM THE PLAINS TO THE MID ATLANTIC. ANOTHER COLD  
FRONT APPROACHES ON TUESDAY ALTHOUGH TIMING IS LOW CONFIDENCE AT  
THIS TIME. ECMWF SUGGESTS HIGHS IN THE 50S IN THE WARM ADVECTION  
AHEAD OF THIS NEXT FRONT.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)  
ISSUED AT 100 PM EST TUE NOV 21 2017  
 
BAND OF RAIN WILL PRODUCE AREAS OF MVFR CIGS/VSBYS THIS  
AFTERNOON, MAINLY SOUTH AND EAST OF GRR. MODERATE ICING IN THE  
CLOUDS IS LIKELY WITHIN THIS SOUTHEASTWARD MOVING BAND OF RAIN,  
WITH CURRENT FREEZING LEVELS AROUND 2000 FT FALLING THROUGH THE  
AFTERNOON.  
 
THE RAIN WILL BE OUT OF THE AREA BY 00Z WITH VFR FOLLOWING IN  
IT'S WAKE TONIGHT AND WEDNESDAY. HOWEVER THERE WILL BE LAKE EFFECT  
SNOW SHOWERS THIS EVENING THAT COULD OCCASIONALLY/BRIEFLY IMPACT  
MKG AND AZO WITH MVFR OR LOWER CONDITIONS. WEST WINDS GUSTING TO  
25 KTS WILL BECOMING NORTHWEST AND SUBSIDE TO AROUND 10 KNOTS THIS  
EVENING.  
 

 
   
MARINE
 
 
ISSUED AT 300 PM EST TUE NOV 21 2017  
 
A SMALL CRAFT ADVISORY REMAINS IN EFFECT THROUGH TONIGHT INTO  
EARLY WEDNESDAY MORNING. WAVE MODELS CONTINUE TO SUGGEST WAVE HEIGHTS  
WILL FINALLY SUBSIDE TO BELOW SCA CRITERIA AFTER 13Z WED. HOWEVER  
WAVE HEIGHTS WILL RAMP BACK UP ON THANKSGIVING DAY WHEN ANOTHER  
SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 100 PM EST TUE NOV 21 2017  
 
SEVERAL RIVERS REMAIN AT ADVISORY/ACTION STAGE LEVEL AS RUNOFF  
CONTINUES FROM RAIN THAT FELL OVER THE WEEKEND. WATER LEVELS IN  
THESE AND OTHER RIVERS WILL REMAIN FAIRLY STEADY OR SLOWLY FALL  
THROUGH THE END OF THE WEEK. RAIN AND SNOW SHOWERS TODAY AND TONIGHT  
WILL ONLY PROVIDE LIGHT AMOUNTS OF PRECIPITATION, AND WILL NOT HAVE  
AN IMPACT ON WATER LEVELS IN RIVERS, CREEKS AND STREAMS. ADDITIONAL  
FLOODING IS NOT EXPECTED.  
 
A FEW MORE ROUNDS OF LIGHT RAIN/SNOW ARE EXPECTED THROUGH THE END OF  
THE WEEK, BUT SHOULD NOT HAVE A SIGNIFICANT IMPACTS ON RIVER LEVELS.  
 

 
   
GRR WATCHES/WARNINGS/ADVISORIES
 
 
MI...NONE.  
LM...SMALL CRAFT ADVISORY UNTIL 7 AM EST WEDNESDAY FOR LMZ844>849.  
 

 
 

 
 
SYNOPSIS...LAURENS  
SHORT TERM...LAURENS  
LONG TERM...MEADE  
AVIATION...MEADE  
HYDROLOGY...HLO  
MARINE...LAURENS  
 
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