433  
FXUS63 KGRR 111144  
AFDGRR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND RAPIDS MI  
644 AM EST MON DEC 11 2017  
 
LATEST UPDATE...  
AVIATION  
   
SYNOPSIS
 
 
ISSUED AT 328 AM EST MON DEC 11 2017  
 
A LOW PRESSURE SYSTEM WILL TRACK SOUTH SOUTHEAST FROM NORTHWEST  
MINNESOTA EARLY THIS MORNING TO NEAR CHICAGO BY LATE THIS  
AFTERNOON. THAT WILL BRING SNOW TO THE AREA TODAY INTO THIS  
EVENING. TONIGHT AND ARCTIC FRONT COMES THROUGH BRINGING IN THE  
COLDEST AIR OF THE SEASON WITH VERY STRONG WINDS. HEAVY LAKE  
EFFECT SNOW SQUALLS ARE EXPECTED NEAR THE LAKE MICHIGAN SHORE  
TONIGHT INTO WEDNESDAY MORNING. TRAVEL IN THAT AREA WILL BE  
CHALLENGING TUESDAY. OUTSIDE OF THAT EXPECT SNOW SHOWERS AND HIGHS  
ONLY IN THE LOWER 20S. WE GET A BREAK BETWEEN SYSTEMS WEDNESDAY  
BUT BY LATE WEDNESDAY THE NEXT SYSTEM WILL BRING MORE SNOW TO THE  
AREA INTO THURSDAY.  
 

 
   
SHORT TERM
 
(TODAY THROUGH TUESDAY NIGHT)  
ISSUED AT 328 AM EST MON DEC 11 2017  
 
I HAVE DECIDED (IN COORDINATION WITH OUR GAYLORD AND NORTH WEBSTER  
OFFICES) TO ISSUE A WINTER STORM WARNING FOR ALL OF OUR LAKE SHORE  
COUNTIES FOR TONIGHT THROUGH TUESDAY INTO WEDNESDAY MORNING. THIS  
IS A DANGEROUS SITUATION AS THERE WILL BE HEAVY SNOW SQUALLS FROM  
WITH WINDS WILL BE GUSTING TO OVER 40 MPH RESULTING IN NEAR ZERO  
VISIBILITIES IN THE HEAVIER SNOW BANDS.  
 
WE HAVE A CLIPPER TYPE LOW TRACKING SOUTH SOUTHEAST TOWARD  
CHICAGO FOR LATE THIS AFTERNOON. THAT WILL KEEP ALL OF OUR CWA IN  
THE SNOW FROM THE WARM ADVECTION / ISENTROPIC LIFT PART OF THE  
EVENT. THIS WILL BRING TWO PERIODS OF SNOW. THE FIRST ONE IS THE  
WARM ADVECTION PART OF THE EVENT, WHICH WILL LAST ONLY ABOUT 3  
HOURS IN ANY ONE PLACE. IT WILL FOR THE MOST PART OCCUR FROM  
AROUND 8 AM NEAR MUSKEGON END BY JACKSON BY 1 PM. THAT SHOULD BE A  
1 TO 2 INCH SNOWFALL EVENT. THE SECOND PART OF THIS IS THE  
DEFORMATION ZONE SNOW BAND THAT FROM MOST OF THE HIGH RESOLUTION  
MODELS (FOR SEVERAL RUNS IN A ROW) TO OCCUR NEAR I-94 FROM AROUND  
4-5 PM TILL AROUND 9 PM. THIS WILL HAVE HEAVIER SNOW WITH IT, MORE  
LIKE 2 TO 3 INCHES. I CONSIDERED AN ADVISORY FOR THIS EVENT BUT  
THE EVENT TONIGHT INTO WEDNESDAY MORNING SEEMS TO THIS FORECAST TO  
BE A MUCH MORE SIGNIFICANT EVENT SO TO KEEP THE HEADLINES SIMPLE  
I ONLY HAVE HEADLINES FOR THE LAKE EFFECT EVENT TONIGHT INTO  
WEDNESDAY MORNING.  
 
WITH THE COLDEST AIR OF THE SEASON CROSSING WATER THAT IS STILL  
OVER 40 DEGREES, AND 850 TEMPERATURE NEAR ZERO, THAT IS BY FAR AND  
AWAY A VERY UNSTABLE SETUP. BUFKIT TIME SECTIONS SHOW STRONG LIFT  
IN THE DGZ FROM AROUND MIDNIGHT TONIGHT TILL AROUND EARLY  
WEDNESDAY MORNING. THE INVERSION HEIGHTS ARE NEAR 10000 FT. GIVEN  
THERE IS 40 KNOTS IN THE MIXED LAYER FOR WIND GUSTS, THIS SEEMS  
LIKE AN EVENT THAT WOULD NEED A WARNING.  
 
I PUT AN ADVISORY FOR THE COUNTIES NEXT TO THE WARNING AREA AS  
THERE WILL BE SOME SNOW SQUALLS THAT GET INTO THOSE COUNTIES. THE  
INLAND COUNTIES NEAR ROUTE 10 WILL HAVE A LAKE SUPERIOR CONNECTION  
AND SOME UPSLOPE TO HELP THE CAUSE.  
 
INLAND OF ALL THAT IT WILL JUST BE WINDY AND COLD TUESDAY INTO  
TUESDAY NIGHT.  
   
LONG TERM
 
(WEDNESDAY THROUGH SUNDAY)  
ISSUED AT 328 AM EST MON DEC 11 2017  
 
MORE COLD AIR AND INTERVALS OF SNOW SHOWERS WILL CONTINUE THROUGH  
THE END OF THE WORK WEEK. WE WILL THEN SEE A DECENT SHOT AT A PERIOD  
OF MILDER WEATHER FOR NEXT WEEKEND, WITH A MIX OF PCPN TYPES  
POSSIBLE.  
 
SNOW SHOWERS WILL BE TRENDING DOWN A BIT BY WED AFTER THE DECENT  
LAKE EFFECT EVENT EXPECTED FOR MON NIGHT INTO TUE NIGHT. THE CHANCE  
OF SNOW WILL REMAIN ON WED HOWEVER, ESPECIALLY FOR WESTERN AND  
SOUTHERN AREAS. THIS IS THE RESULT OF THE NEXT SHORT WAVE ROUNDING  
THE LONG WAVE TROUGH. THIS WAVE IS EXPECTED TO DIVE MOSTLY SOUTH OF  
THE AREA. IT COULD CLIP THE WESTERN AND SOUTHERN PORTION OF THE AREA  
WITH SOME LIGHT SNOW. THE TRACK OF THE LOW WILL PRODUCE AN OFFSHORE  
FLOW, SO THE LAKE SHOULD NOT BE MUCH OF A FACTOR.  
 
LAKE EFFECT WILL RAMP UP A BIT ON THU IN THE WAKE OF THE WED SYSTEM.  
COLDER AIR ON THE ORDER OF AROUND -14- TO -16C WILL POUR IN OVER THE  
RELATIVELY WARMER WATERS OF LAKE MICHIGAN. THE FLOW WILL BE W/SW AS  
ANOTHER SYSTEM WILL BE APPROACHING THE AREA WITH THE LOW NORTH OF  
THE CWFA. A SLIGHT MODERATION IN TEMPS WILL OCCUR ON FRI WITH THE  
LOW LEVEL SW FLOW.  
 
A BETTER MODERATION IN TEMPS IS STILL EXPECTED NEXT WEEKEND WITH  
CHCS OF RAIN/SNOW. THE LONG WAVE TROUGH THAT HAS BEEN SITTING OVER  
THE REGION OVER THE LAST WEEK WILL GET PUSHED OUT WITH THE STRONG  
WRN RIDGE GETTING BEAT DOWN SOME BY A STRONG PACIFIC JET. THE  
TRANSITION WILL BRING MORE CHCS OF PCPN. THESE WILL GRADUALLY SHIFT  
NORTH AS THE JET FLATTENS OUT A BIT, AND THE SYSTEMS ARE A BIT  
FURTHER NORTH.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)  
ISSUED AT 644 AM EST MON DEC 11 2017  
 
CURRENTLY MOST OF THE GRR TAF SITES ARE MVFR. HOWEVER THERE IS A  
STORM TRACKING TOWARD NORTHERN INDIANA WHICH HAS A LARGE AREA OF  
LIGHT SNOW IN FRONT OF IT. THIS WILL MOVE THROUGH ALL OF THE GRR  
TAF SITES BETWEEN NOW 16Z OR SO. WE THEN GET A BRIEF PERIOD EARLY  
TO MID AFTERNOON WHEN THE SNOW WILL STOP.  
 
THE SYSTEM SNOW WILL MOVE OUT OF THE AREA BY 9 PM OR SO. THEN THE  
LAKE EFFECT KICKS IN THAT WILL BRING GUSTY WINDS AND SNOW SQUALLS  
TO MKG, SBN LIKELY BECOME SOLID IFR WHILE THE OTHER TAF SITS  
SHOULD BECOME VFR.  
 

 
   
MARINE
 
 
ISSUED AT 328 AM EST MON DEC 11 2017  
 
WITH 45 KNOTS IN THE MIXED LAYER IT MADE SENSE TO JUST GO AHEAD  
WITH THE GALE WARNING FOR TONIGHT INTO TUESDAY NIGHT.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 1000 AM EST SUN DEC 10 2017  
 
RIVERS ARE RUNNING NEAR NORMAL LEVELS TO A LITTLE ABOVE NORMAL. NO  
FLOODING OR SIGNIFICANT RISES IN RIVER LEVELS ARE EXPECTED. SNOW IS  
FORECAST PERIODICALLY THROUGH THE WEEK.  
 
TEMPERATURES HAVE BEEN NEAR TO BELOW FREEZING SINCE LAST TUESDAY  
NIGHT AND SIMILAR TEMPERATURES ARE EXPECTED TO PERSIST THROUGH THE  
END OF THIS WEEK. THIS SHOULD ALLOW ICE TO BEGIN FORMING ON AREA  
RIVERS, ESPECIALLY ON THE MUSKEGON RIVER IN CENTRAL LOWER  
MICHIGAN.  
 

 
   
GRR WATCHES/WARNINGS/ADVISORIES
 
 
MI...WINTER STORM WARNING FROM 10 PM THIS EVENING TO 7 AM EST  
WEDNESDAY FOR MIZ037-043-050-056-064-071.  
 
WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 7 AM EST  
WEDNESDAY FOR MIZ038-039-044-057-065-072.  
 
LM...GALE WARNING FROM 7 PM THIS EVENING TO 7 PM EST TUESDAY FOR  
LMZ844>849.  
 

 
 

 
 
SYNOPSIS...WDM  
SHORT TERM...WDM  
LONG TERM...NJJ  
AVIATION...WDM  
HYDROLOGY...63  
MARINE...WDM  
 
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