511  
FXUS63 KGRR 292035  
AFDGRR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND RAPIDS MI  
435 PM EDT WED MAR 29 2017  
 
LATEST UPDATE...  
MARINE  
   
SYNOPSIS
 
 
ISSUED AT 328 PM EDT WED MAR 29 2017  
 
THE ACTIVE PATTERN WILL CONTINUE IN THE FORESEEABLE FUTURE. A  
MIXTURE OF WINTRY PRECIPITATION IS POSSIBLE OVER CENTRAL LOWER  
MICHIGAN BOTH THURSDAY MORNING AND AGAIN FOR A BRIEF PERIOD  
THURSDAY NIGHT. HEAVY RAINFALL IS POSSIBLE THROUGH MUCH OF THE  
AREA THROUGH THE DAY THURSDAY. A COUPLE OF THUNDERSTORMS CANNOT BE  
RULED OUT THURSDAY AFTERNOON AND EVENING. A MAINLY DRY WEEKEND IS  
EXPECTED AFTER THE SYSTEM MOVE EAST, BUT ANOTHER ROUND OF WET  
WEATHER IS POSSIBLE GOING INTO NEXT WEEK. TEMPERATURES ARE  
EXPECTED TO BE NEAR NORMAL.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH FRIDAY NIGHT)  
ISSUED AT 328 PM EDT WED MAR 29 2017  
 
THE UPCOMING SYSTEM CONTINUES TO INTRODUCE VARIOUS CHALLENGES TO THE  
FORECAST IN THE NEXT 24-36 HOURS. THIS INCLUDES CHANCES FOR WINTRY  
PRECIPITATION OVER INTERIOR SECTIONS OF CENTRAL LOWER MICHIGAN, IN  
ADDITION TO HEAVY RAINFALL THROUGH MUCH OF THE FORECAST AREA AND  
THUNDER POTENTIAL OVER SOUTHERN LOCATIONS.  
 
DESPITE THE SYSTEM OF CONCERN BEING WELL TO OUR SOUTHWEST, OVER THE  
CENTRAL PLAINS, ITS AFFECTS ARE FAR REACHING. AMPLE MOISTURE IS  
STREAMING NORTHWARD FROM THE GULF, RESULTING IN CLOUD COVER AND  
RAINFALL ACROSS A BROAD PORTION OF THE CENTRAL U.S. MEANWHILE,  
SURFACE HIGH PRESSURE OVER THE GREAT LAKES WILL BREAK DOWN, SLOWLY  
GIVING WAY TO INCREASING CLOUDS FROM THE WEST THIS AFTERNOON.  
 
MID-LEVEL FORCING AND INCREASING MOISTURE IS EXPECTED TO RESULT IN A  
BAND OF DEVELOPING PRECIPITATION THROUGH CENTRAL LOWER MICHIGAN LATE  
TONIGHT INTO EARLY THURSDAY. MUCH OF THIS LOOKS TO BE SITUATED FROM  
I-96 NORTH NEAR/AFTER MIDNIGHT. THE WRENCH IN THE FORECAST IS  
THANKS IN PART TO THE DRY, LOW LEVEL FLOW OUT OF THE EAST, WHICH  
CONTINUES TO RAISE QUESTIONS WITH PRECIPITATION TYPE.  
 
THE NORTHEASTERN CORNER OF THE FORECAST AREA WILL LIKELY BE COLD  
ENOUGH TO START AS ALL SNOW, PRIMARILY EAST OF BALDWIN, NORTHEAST OF  
BIG RAPIDS AND NEAR/NORTH OF MT. PLEASANT. JUST SOUTH/WEST OF THESE  
LOCATIONS, A MIX OF RAIN/SNOW/SLEET COULD FALL. THE DRY LAYER SHOULD  
ALLOW WET BULBING TO OCCUR WITH A BRIEF BOUT OF SNOW, GRADUALLY  
CHANGING TO A MIX TO RAIN THROUGH THE MORNING. A BRIEF PERIOD OF  
MODERATE SNOW CANNOT BE RULED OUT IN THE ONSET. HOWEVER, THE HIGH  
LIQUID CONTENT SHOULD KEEP TOTALS IN THE ONE TO TWO INCH RANGE WHERE  
MOSTLY SNOW DOES FALL.  
 
IT IS IMPORTANT TO NOTE THAT WHILE TEMPERATURE PROFILES WARM THROUGH  
THE DAY THURSDAY , SURFACE TEMPERATURES ARE EVER-SO-SLIGHTLY ABOVE  
FREEZING IN PLACES LIKE REED CITY AND HARRISON. FREEZING RAIN COULD  
BE ARGUED, BUT THE WARM NOSE COMING IN FROM THE SOUTH IS IMPRESSIVE  
AND SEEMS TO DO ENOUGH TO KEEP IT ALL RAIN UNTIL TOMORROW NIGHT.  
FREEZING RAIN MAY MIX BACK IN, BUT FOR ANY DECENT ICE ACCUMULATION,  
TEMPERATURES AROUND 31/32 DO NOT USUALLY LEAD TO HIGH IMPACT ICING.  
IN ADDITION, RECENT TEMPERATURES HAVE CONSISTENTLY BEEN IN THE 40S  
AND 50S KEEPING THE GROUND FAIRLY MILD. SLICK CONDITIONS ARE  
POSSIBLE, BUT NOT ALL THAT LIKELY TO LAST. AFTER COORDINATING WITH  
GAYLORD, WE LEANED AWAY FROM ISSUING HEADLINES AT THIS TIME.  
 
FOR THOSE ALONG I-96, LITTLE OR NO WINTER WEATHER IS EXPECTED WITH  
ALL RAIN EVEN FURTHER SOUTH. RAIN COULD BE HEAVY AT TIMES THURSDAY.  
THE MAIN SURFACE LOW FINALLY APPROACHES THE MI/IN BORDER LATE  
THURSDAY INTO FRIDAY. A SURFACE WARM FRONT, MARKED BY A DRAMATIC  
SPREAD IN SURFACE TEMPERATURES FROM NORTH TO SOUTH, WILL EXTEND EAST  
OF THE LOW THROUGH THURSDAY AFTERNOON. ELEVATED INSTABILITY MAY GIVE  
RISE TO THUNDER POTENTIAL THURSDAY AFTERNOON AND EVENING, ESPECIALLY  
FOR THOSE NEAR AND SOUTH OF I-94. RAINFALL TOTALS COULD PUSH ONE  
INCH FOR MANY LOCATIONS, LEADING TO RISING RIVERS (SEE HYDRO).  
 
THE UPPER WAVE BEGINS TO PUSH EAST OF THE AREA FRIDAY AFTERNOON.  
SCATTERED SHOWERS WILL CONTINUE, BUT WIDESPREAD HEAVIER RAINFALL IS  
EXPECTED TO MOVE EAST, AS WELL. THE SILVER LINING IN THE CLOUDS IS  
THAT ALL RAIN SHOULD MOVE EAST BY LATE FRIDAY INTO SATURDAY.  
   
LONG TERM
 
(SATURDAY THROUGH WEDNESDAY)  
ISSUED AT 328 PM EDT WED MAR 29 2017  
 
THE OVERALL WEATHER PATTERN SHOWS LITTLE SIGN OF SIGNIFICANT CHANGE  
FOR A LONG TIME TO COME (MORE THAN TWO WEEKS). EXPECT TO GET A  
SIGNIFICANT RAIN EVENT ABOUT EVERY 3 TO 4 DAYS. THIS PATTERN WILL  
CONTINUE THROUGH NEXT WEEK AND FOR THAT MATTER MUCH LONGER THAN  
THAT.  
 
THE NEXT MAJOR SYSTEM WILL BE IN THE MONDAY TIME FRAME. THEN  
AFTER THAT IN THE THURSDAY TIME FRAME. THE ONLY REAL QUESTION WITH  
THESE STORMS IS JUST HOW FAR NORTH THEY TRACK. THE LATEST RUNS OF  
MOST OF THE MODELS (ECMFW, GFS, CANADIAN AND THE ENSEMBLE MEAN OF  
THE GFS AND ECMWF) FOR THE MOST PART AGREE WITH EACH OTHER.  
AGREEMENT IS SUCH THAT THE MONDAY SYSTEM'S SURFACE LOW WILL TRACK  
SOUTH OF HERE. EVEN SO, THERE WILL BE ENOUGH MOISTURE BROUGHT  
NORTH SO AS TO BRING AT LEAST SOME LIGHT RAIN TO THE AREA. THE GFS  
IS SIGNIFICANTLY WETTER WITH THAT SYSTEM THAN THE ECMWF THOUGH  
WITH OVER A HALF INCH OF RAIN. THE THURSDAY SYSTEM SEEMS TO TRACK  
FARTHER NORTH SO THE ENTIRE AREA WOULD GET SIGNIFICANTLY MORE  
RAIN. THERE COULD BE A THUNDERSTORM THREAT WITH THE THURSDAY  
SYSTEM, TOO.  
 
OUR EXTENDED EAST ASIAN JET FEATURE IS FORECAST BY ALL OF THE MODELS  
TO CONTINUE FOR AT LEAST ANOTHER TWO WEEKS. THAT WOULD KEEP THE  
SPLIT FLOW AND ALSO CONTINUE THE PROGRESSIVE UPPER WAVE PATTERN. SO  
ONCE AGAIN EXPECT TEMPERATURES (OVER ALL) TO AVERAGE CLOSE TO NORMAL  
AND PRECIPITATION TO BE ABOVE NORMAL FOR THE NEXT WEEK PLUS.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)  
ISSUED AT 135 PM EDT WED MAR 29 2017  
 
LITTLE QUESTION IT WILL BE SOLID VFR AT ALL TAF SITES THROUGH  
AROUND 06Z. ALSO THERE IS LITTLE QUESTION OF SOLID IFR IN RAIN  
THURSDAY AFTER ABOUT 15Z OR SO. BETWEEN 06Z AND 12Z IS WHEN THERE  
ARE SOME FORECAST ISSUES.  
 
THE PRECIPITATION SHIELD AROUND THE STORM, CURRENTLY CENTERED IN  
SOUTHERN KANSAS, WILL BEGIN TO MOVE INTO OUR TAF SITES IN THE 06Z  
TIME FRAMES. IT IS POSSIBLE THAT MKG AND GRR COULD START WITH A  
MIX OF RAIN AND SNOW AS THERE IS ENOUGH DRY AIR TO ALLOW WET BULB  
COOLING AT THE LEADING EDGE FOR THOSE LOCATIONS. I PUT MIXED RAIN  
AND SNOW AT MKG BUT NOT GRR THROUGH SINCE THE RISK SEEMED HIGHER  
AT MKG THAN GRR. ALL TAF SITES WILL WE SOLID IFR IN RAIN WITH A  
GUSTY EAST WIND (15-25 KNOTS). THE RAIN WILL BE MODERATE TO HEAVY  
AT TIMES AFTER ABOUT 16Z TOMORROW SO THERE MORE THAN LIKELY WILL  
BE VISIBILITIES UNDER 2 MILES THURSDAY AFTERNOON AT ALL TAF SITES.  
 

 
   
MARINE
 
 
ISSUED AT 435 PM EDT WED MAR 29 2017  
 
EASTERLY FLOW WILL KEEP HIGHER WAVES OFFSHORE THROUGH THURSDAY.  
HOWEVER, WINDS WILL GUST TO AROUND 30 KNOTS, WHICH HAS WARRANTED A  
SMALL CRAFT ADVISORY THROUGH THURSDAY. WINDS WILL BACK OUT OF THE  
NORTH FRIDAY AND COULD RESULT IN ADDITIONAL HAZARDOUS WINDS AND  
WAVES THROUGH FRIDAY AFTERNOON, ESPECIALLY IN NORTHERN ZONES.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 1158 AM EDT WED MAR 29 2017  
 
WIDESPREAD PRECIPITATION IS EXPECTED ACROSS WEST MICHIGAN FROM  
LATE TONIGHT THROUGH FRIDAY. BASIN AVERAGE AMOUNTS OF THREE  
QUARTERS OF AN INCH TO AN INCH CAN BE EXPECTED. AREA RIVERS LEVELS  
ARE CURRENTLY ELEVATED FROM THE PREVIOUS RAINFALL EVENT...WITH  
ADVISORIES IN PLACE FOR IONIA, HASTINGS, AND HOLT. WHILE MOST LOCAL  
RIVERS SHOULD EXPERIENCE FALLING STAGES THROUGH TONIGHT...THE  
PRECIPITATION OVER THE NEXT 36 HOURS WILL CREATE A NEW ROUND OF  
RISES TO DEVELOP. CURRENT ADVISORY PRODUCTS ATTEMPT TO ILLUSTRATE  
THIS SCENARIO.  
 
SOME OF THE 12Z MODEL OUTPUT SUGGESTS HEAVIER PRECIPITATION THAN  
CURRENTLY INCLUDED AS INPUT TO THE RIVER MODELS. THESE HIGHER  
AMOUNTS...IF THEY MATERIALIZE... COULD PRODUCE ABOVE BANKFULL  
RISES ON MANY MORE RIVERS AND STREAMS ACROSS WEST MICHIGAN. THOSE  
WITH INTERESTS ON AREA RIVERS SHOULD CLOSELY MONITOR THE  
SITUATION.  
 

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

 
 

 
 
SYNOPSIS...JAM  
SHORT TERM...JAM  
LONG TERM...WDM  
AVIATION...WDM  
HYDROLOGY...MWS  
MARINE...JAM  
 
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