513  
FXUS63 KGRR 221150  
AFDGRR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND RAPIDS MI  
650 AM EST MON JAN 22 2018  
 
LATEST UPDATE...  
AVIATION  
   
SYNOPSIS
 
 
ISSUED AT 304 AM EST MON JAN 22 2018  
 
A STORM SYSTEM WILL TRACK THROUGH THE REGION TODAY AND INTO  
TONIGHT...BRINGING RAIN AND EVEN A FEW THUNDERSTORMS TO THE AREA.  
AS THE STORM PULLS AWAY ON TUESDAY...ANY REMAINING RAIN WILL  
CHANGE TO SNOW...ESPECIALLY IN THE AFTERNOON. AN AREA OF HIGH  
PRESSURE WILL MOVE IN FOR THE MIDDLE PART OF THE WEEK LEADING TO  
MOSTLY DRY WEATHER.  
 

 
   
UPDATE
 
 
ISSUED AT 539 AM EST MON JAN 22 2018  
 
THE DENSE FOG HAD DIMINISHED CONSIDERABLY AS THE HEAVIER SHOWERS  
MOVED IN. THE FORECAST HAS BEEN UPDATED TO REMOVE THE DENSE FOG  
ADVISORY.  
 

 
   
SHORT TERM
 
(TODAY THROUGH WEDNESDAY)  
ISSUED AT 304 AM EST MON JAN 22 2018  
 
MODELS ARE IN REASONABLE AGREEMENT IN SHOWING A DEEPENING AREA OF  
LOW PRESSURE TRACKING NORTHEASTWARD THROUGH THE GREAT LAKES REGION  
TODAY AND INTO TONIGHT. THIS SYSTEM WILL BE RATHER DYNAMIC WITH A  
FAVORABLE COUPLED UPPER LEVEL JET. THE COMBINATION OF STRONG LIFT  
AND A VERY MOIST AIRMASS WITH PWAT VALUES WELL OVER 200 PERCENT  
ABOVE NORMAL WILL SUPPORT WIDESPREAD RAIN...ESPECIALLY THIS  
MORNING. THERE COULD EVEN BE A FEW THUNDERSTORMS AS ELEVATED  
INSTABILITY WILL ADVECT IN FROM THE SOUTHWEST THIS MORNING AND IS  
THEN FORECASTED TO PERSIST FOR THE AFTERNOON. WILL MAINTAIN THE  
HIGH POPS AND SHOW A NORTHEASTWARD PROGRESSION OF THE THUNDERSTORM  
RISK TODAY. WILL KEEP THE DENSE FOG ADVISORY GOING TIL 7 AM...AND  
MAY NEED TO EXTEND IT DEPENDING ON HOW THE SHOWERS MOVING IN  
IMPACTS THE THICKER FOG.  
 
A MID LEVEL DRY SLOT MOVES IN FROM THE SOUTHWEST THIS AFTERNOON  
AND EVENING. WILL LOWER THE POPS INTO THE EVENING AS A RESULT.  
THERE IS STILL SOME UNCERTAINTY AS TO HOW QUICKLY WE TRANSITION  
OVER TO SNOW AND HOW MUCH PRECIPITATION WILL BE AROUND. THE LATEST  
TREND SUPPORTS A SLOWER TRANSITION. WILL TREND THE FORECAST THIS  
WAY. THERE IS STILL A RISK FOR SNOW RELATED IMPACTS ON  
TUESDAY...WITH THE HIGH RES EURO TRYING TO LOWER SURFACE  
TEMPERATURES BELOW FREEZING IN THE AFTERNOON.  
   
LONG TERM
 
(WEDNESDAY NIGHT THROUGH SUNDAY)  
ISSUED AT 304 AM EST MON JAN 22 2018  
 
THERE MAY BE A FEW SNOW SHOWERS ALONG THE LAKE SHORE AT THE START OF  
THE LONG TERM, BUT THEY WON'T LAST LONG. H8 TEMPS ARE MARGINAL AT  
BEST AND WILL BEGIN TO WARM WEDNESDAY NIGHT. A UPPER RIDGE WILL  
QUICKLY BUILD INTO THE GREAT LAKES AND WE'LL SEE A COUPLE OF DRY  
DAYS.  
 
A COLD FRONT WILL MOVE ACROSS THE STATE FRIDAY NIGHT. DYNAMICS WITH  
THIS FRONT ARE FAIRLY WEAK AS THE SUPPORTING SFC LOW IS WELL NORTH  
IN ONTARIO AND THE TRAILING UPPER TROUGH IF MOSTLY DIFFUSE. MOISTURE  
POOLING ALONG THE FRONT MAY LEAD TO SOME RAIN SHOWERS FRIDAY NIGHT  
AND SATURDAY AND A FEW RAIN SHOWERS ASSOCIATED WITH THE UPPER TROUGH  
SATURDAY NIGHT INTO SUNDAY WILL MIX WITH AND THEN TURN TO LIGHT SNOW  
SHOWERS AS COLDER AIR FLOWS IN BEHIND THE DEPARTING COLD FRONT. THIS  
SYSTEM DOESN'T LOOK LIKE A BIG PCPN PRODUCER.  
 
FRIDAY AND SATURDAY WILL BE THE WARMEST DAYS WHEN TEMPERATURES CLIMB  
INTO THE 40S. OTHERWISE, HIGHS WILL BE IN THE MID 30S.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)  
ISSUED AT 644 AM EST MON JAN 22 2018  
 
A POWERFUL STORM IS FORECASTED TO PUSH THROUGH THE TAF SITES  
TODAY WITH IMPACTS EXPECTED. WIDESPREAD IFR AND LOWER CONDITIONS  
AROUND THE REGION TO START THE PERIOD. THERE WERE EVEN A FEW  
THUNDERSTORMS TO THE SOUTHWEST OF KMKG MOVING NORTHEAST. THESE LOW  
CONDITIONS ARE EXPECTED TO PERSIST FOR MUCH OF THE MORNING ALONG  
WITH A RISK FOR THUNDERSTORMS...BUT AS WE GO THROUGH THE  
AFTERNOON...THE CLOUDS MAY START TO BREAK UP FROM THE  
SOUTHWEST...ESPECIALLY FROM MID AFTERNOON ON. HOWEVER...THE  
ATMOSPHERE REMAINS UNSTABLE...THUS TOWARD EVENING...STORMS MY  
START TO DEVELOP UPSTREAM AND OVERHEAD. AVIATORS WILL NEED TO  
MONITOR TRENDS THROUGH THE DAY.  
 
MOISTURE WRAPPING AROUND THE DEPARTING STORM LATER TONIGHT COULD  
SUPPORT A RETURN OF THE LOW CONDITIONS.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 214 PM EST SUN JAN 21 2018  
 
A COMPLETE MELTING OF THE NATURAL SNOWPACK IS EXPECTED BY MONDAY  
IN THE GRAND, KALAMAZOO, AND MUSKEGON RIVER BASINS. THIS WILL  
RELEASE A QUARTER TO PERHAPS HALF INCH OF WATER. RAIN TOTALS ON  
MONDAY WILL MOSTLY RANGE BETWEEN 0.6 AND 1.2 INCHES (ECMWF AND  
ENSEMBLE HAVE BEEN CONSISTENTLY LOWER THAN GFS AND ENSEMBLE).  
DEPTH OF FROZEN SOIL VARIES BUT OVERALL EXPECT THE GROUND TO  
REMAIN FROZEN ENOUGH TO ALLOW EFFICIENT RUNOFF.  
 
A NUMBER OF RIVER FORECAST POINTS WILL LIKELY RISE ABOVE BANKFULL  
IN THE UPCOMING WEEK. THERE IS A CHANCE OF MINOR FLOOD STAGE BEING  
REACHED AT A FEW SITES (OF EARLIEST CONCERN ARE HOLT AND EAGLE),  
PARTICULARLY IF HIGHER RAINFALL TOTALS VERIFY. A BREAKUP OF RIVER  
ICE IS EXPECTED, AND ANY ICE JAMS THAT FORM CAN CAUSE  
UNPREDICTABLE FLUCTUATIONS IN WATER LEVELS. ROAD CLOSURES ARE  
POSSIBLE IN LOW SPOTS NEAR RIVER BANKS. WATER COULD ALSO APPROACH  
BUILDINGS IN FLOOD PRONE AREAS.  
 

 
   
GRR WATCHES/WARNINGS/ADVISORIES
 
 
MI...NONE.  
LM...NONE.  

 
 

 
 
UPDATE...MJS  
SYNOPSIS...MJS  
SHORT TERM...MJS  
LONG TERM...04  
AVIATION...MJS  
HYDROLOGY...CAS  
 
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