360  
FXUS63 KGRR 252334  
AFDGRR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND RAPIDS MI  
634 PM EST TUE NOV 25 2014  
 
LATEST UPDATE...  
AVIATION  
   
SYNOPSIS
 
 
ISSUED AT 320 PM EST TUE NOV 25 2014  
 
WE WILL SEE A BREAK IN WINTER PRECIPITATION THROUGH WEDNESDAY. THE  
NEXT UPPER DISTURBANCE WILL BRING ANOTHER ROUND OF ACCUMULATING LAKE  
EFFECT SNOW MAINLY NEAR THE LAKESHORE FROM WEDNESDAY NIGHT THROUGH  
THANKSGIVING. THEN...A MIX OF RAIN...SNOW....AND SLEET IS EXPECTED  
FROM FRIDAY THROUGH THE WEEKEND. TEMPERATURES WILL GENERALLY BE NEAR  
NORMAL THROUGH THE PERIOD.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH THURSDAY NIGHT)  
ISSUED AT 320 PM EST TUE NOV 25 2014  
 
MAIN CONCERN IS LAKE EFFECT SNOW WEDNESDAY NIGHT THROUGH  
THANKSGIVING. ALTHOUGH WE ONLY ADVERTISE ABOUT 3 INCH TOTALS NEAR  
THE LAKESHORE DURING THIS PERIOD THERE IS SOME POTENTIAL FOR THIS  
EVENT TO OVER-PERFORM GIVEN AGREEMENT BETWEEN THE NAM/GFS FORECAST  
SOUNDINGS FOR THERE TO BE A DEEP SATURATED MIXED LAYER THROUGH THE  
DGZ UP TO AROUND 10000 FT. THERE ARE TWO OFFSETTING FACTORS  
HOWEVER. 1) FAIRLY WARM DAYTIME TEMPERATURES ON THANKSGIVING THAT  
MAY LIMIT ACCUMULATIONS. 2) DIRECTIONAL SHEAR IN THE FORECAST  
SOUNDINGS COMBINED WITH NON-LAMINAR FLOW DURING DAYTIME HEATING THAT  
WILL LIKELY PREVENT PERSISTENT SNOW BANDS FROM OCCURRING AND  
CONCENTRATING SNOWFALL.  
 
NONETHELESS...BRIEFLY INTENSE SNOWFALL RATES AND RESTRICTIONS TO  
VISIBILITY ARE NOT OUT OF THE QUESTION ESPECIALLY NEAR THE LAKESHORE  
AND COULD STILL IMPACT THANKSGIVING TRAVEL. SNOW SHOULD SHUT OFF  
RATHER QUICKLY THURSDAY NIGHT AS LOW LEVEL FLOW BECOMES ANTICYCLONIC  
WITH A SHARP SURFACE PRESSURE RIDGE MOVING INTO THE AREA.  
   
LONG TERM
 
(FRIDAY THROUGH TUESDAY)  
ISSUED AT 320 PM EST TUE NOV 25 2014  
 
WIDE TEMPERATURE VARIABILITY IS EXPECTED DURING THE LONG TERM. A  
GENERAL ZONAL UPPER FLOW PATTERN WILL DEVELOP LATER THIS WEEK AND  
PERSIST INTO NEXT WEEK. SEVERAL SYSTEMS WILL MOVE ACROSS MICHIGAN  
PRODUCING A MIX OF RAIN AND SNOW.  
 
FRIDAY WILL START OFF WITH TEMPS WELL BELOW NORMAL AND WE MAY SEE  
SOME LIGHT SNOW AS A WARM FRONT APPROACHES FROM THE SOUTHWEST.  
STRONG ISENTROPIC LIFT DEVELOP FRIDAY MORNING AND THEN MOVES NEWD.  
SNOW CHANCES WILL DIMINISH FRIDAY NIGHT AS WARMER AIR MOVES IN.  
SATURDAY LOOKS MAINLY DRY. A CLIPPER IS THEN PROGD TO MOVE ACROSS  
SOUTHERN CANADA DRAGGING A COLD FRONT THROUGH MICHIGAN SUNDAY. THIS  
MAY PRODUCE LIGHT RAIN OR MIXED LIGHT RAIN/SNOW BUT MUCH OF THE  
MOISTURE WILL REMAIN NORTH OF THE CWA NEAR THE LOW. COLDER TEMPS ARE  
THEN EXPECTED SUNDAY NIGHT AND MONDAY BEFORE WARMER AIR MOVES IN  
TUESDAY ON THE BACK SIDE OF THE HIGH. ANOTHER SHOT OF WARMER AIR  
TUESDAY MAY RESULT IN LIGHT RAIN WITH HIGHS AROUND 40.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)  
ISSUED AT 629 PM EST TUE NOV 25 2014  
 
THE STRATOCUMULUS ISN'T GOING ANYWHERE FOR THIS SET OF TAFS.  
LITTLE CHANGE IN CIGS IS EXPECTED. WINDS MAY GO CALM BETWEEN 06Z-  
12Z BEFORE A LIGHT SE WIND (OR JUST LIGHT AND VARIABLE) DEVELOPS.  
NO PRECIPITATION IS EXPECTED FOR THIS TAF PERIOD.  
 

 
   
MARINE
 
 
ISSUED AT 320 PM EST TUE NOV 25 2014  
 
LATEST LOCAL RUN OF THE GLERL WAVE MODEL SUPPORTS THE CURRENT  
FORECAST. TIMING THEREFORE STILL LOOKS GOOD FOR A LATE EVENING  
CANCELLATION/EXPIRATION OF THE SMALL CRAFT ADVISORY.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 255 PM EST TUE NOV 25 2014  
 
SEVERAL LOCATIONS ON AREA RIVERS REMAIN AT OR ABOVE ADVISORY  
CRITERIA. MANY LOCATION HAVE REACHED THEIR PEAK AND ARE BEGINNING  
THEIR DECLINE...WHILE A FEW OTHERS WILL SEE CRESTS OVER THE NEXT  
48 HOURS OR SO. THERE ARE A FEW CHANCES AT PRECIPITATION THROUGH  
THE WEEK BUT IT MOSTLY LOOKS TO BE IN THE FORM OF SNOW AND MAINLY  
IN THE LIGHTER VARIETY. PRECIPITATION IS ALSO SPREAD OUT OVER  
THE COURSE OF SEVERAL DAYS. THIS IS ANTICIPATED TO HAVE  
LITTLE...IF ANY...AFFECT ON AREA RIVERS. WE SHOULD SEE IMPROVING  
CONDITIONS AS WE GET LATER INTO THE WEEK.  
 

 
   
GRR WATCHES/WARNINGS/ADVISORIES
 
 
MI...NONE.  
LM...SMALL CRAFT ADVISORY UNTIL 11 PM EST THIS EVENING FOR LMZ844>849.  
 

 
 

 
 
SYNOPSIS...TJT  
SHORT TERM...TJT  
LONG TERM...93  
AVIATION...HOVING  
HYDROLOGY...JAM  
MARINE...TJT  
 
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