635  
FXUS63 KGRR 262300  
AFDGRR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND RAPIDS MI  
700 PM EDT FRI MAY 26 2017  
 
LATEST UPDATE...  
AVIATION  
   
SYNOPSIS
 
 
ISSUED AT 330 PM EDT FRI MAY 26 2017  
 
SHOWERS AND ISOLATED THUNDER WILL MOVE ACROSS AREAS MAINLY ALONG AND  
SOUTH OF I-96 TONIGHT. SOME AREAS SOUTH OF I-94 COULD PICK UP AS  
MUCH AS A HALF INCH OF RAIN. THEN AS WE OPEN UP THE HOLIDAY WEEKEND,  
SATURDAY WILL BE DRY AND COMFORTABLE, WITH HIGHS IN THE 70S. HOWEVER  
A MORE WIDESPREAD AREA OF SHOWERS AND STORMS WILL ARRIVE LATE  
SATURDAY NIGHT, THAT WILL LINGER INTO SUNDAY EVENING. ALL AREAS  
SHOULD SEE A QUARTER TO A HALF INCH OF RAIN IN THIS PERIOD.  
 
MORE WIDELY SCATTERED SHOWERS AND STORMS WILL BE POSSIBLE MEMORIAL  
DAY INTO TUESDAY, BEFORE WE DRY FOR MUCH OF THE REST OF THE WEEK. WE  
WILL STAY AT OR SLIGHTLY BELOW NORMAL NEXT WEEK, WITH MOST DAYTIME  
HIGHS IN THE UPPER 60S TO MID 70S.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH SUNDAY NIGHT)  
ISSUED AT 330 PM EDT FRI MAY 26 2017  
 
AN MCS WILL SLIDE EAST ACROSS SOUTHERN LOWER MI TONIGHT. THEN A  
BREAK FROM THE RAIN WILL OCCUR SATURDAY, FOR THE BEST DAY OF THE  
HOLIDAY WEEKEND. THEN ANOTHER PERIOD OF SHOWERS AND STORMS MOVES IN  
BY LATE SATURDAY NIGHT AND CONTINUES ON AND OFF SUNDAY AND SUNDAY  
EVENING.  
 
MCS WAS LOCATED OVER NORTH CENTRAL IL AS OF 19Z AND IS EXPECTED TO  
TRACK EAST, THEN EAST SOUTHEAST TONIGHT. THE JET DYNAMICS AND BEST  
INSTABILITY REMAINS TO OUR SOUTH. SO ONLY EXPECT SHOWERS ON THE  
NORTH END OF THE MCS, WITH EMBEDDED THUNDER. MUCH OF THE RAIN WILL  
STAY ALONG AND SOUTH OF I-96, WITH ONLY HIT AND MISS PCPN NORTH. A  
PERIOD OF MODERATE TO HEAVY WILL BE POSSIBLE ALONG THE I-94 CORRIDOR  
WHERE SOME AREAS MAY SEE UP TO A HALF INCH OF RAIN. HOWEVER ANY  
SEVERE RISK WILL STAY WELL TO OUR SOUTH. I REMOVED LOWERED POPS  
TOWARD DAYBREAK AS MOST OF THE PCPN SHOULD BE EAST AFTER 09Z.  
 
WEAK SURFACE HIGH PRESSURE AND UPPER RIDGING BUILDS BACK INTO THE  
REGION FOR SATURDAY. WILL KEEP THE FORECAST DRY, HOWEVER THEIR  
APPEARS TO BE A FAIR AMOUNT OF LINGERING LOW LEVEL MOISTURE,  
ESPECIALLY SOUTH. FOR THAT REASON I HAVE GONE WITH MORE CLOUDS ON  
SATURDAY, BUT STILL MOST AREAS SHOULD SEE PARTLY SUNNY CONDITIONS  
INTO THE AFTERNOON. TRIMMED MAX TEMPS TO HOLD IN THE 70S, AND  
STAYING IN THE LOWER 70S FOR THE CLOUDIER SE CWA.  
 
MORE SHOWERS AND STORMS ARRIVE LATE SATURDAY NIGHT AS THE UPPER  
RIDGE MOVES EAST AND A SHORT WAVE MOVES INTO THE UPPER MIDWEST. THIS  
WAVE EVENTUALLY BECOMES AN UPPER LOW INTO SUNDAY NIGHT. A SURFACE  
FRONT AND LOW PRESSURE ARRIVES AROUND MID DAY, SO THIS SHOULD SPREAD  
A FAIRLY WIDESPREAD AREA OF PCPN ACROSS THE AREA. MAINTAINING THE  
LIKELY POPS.  
   
LONG TERM
 
(MONDAY THROUGH FRIDAY)  
ISSUED AT 330 PM EDT FRI MAY 26 2017  
 
A COOLER AND UNSETTLED WX PATTERN WILL DEVELOP EARLY NEXT WEEK AS  
THE UPPER LEVEL TROUGH DIGS AND AMPLIFIES OVER THE GREAT LAKES  
REGION.  
 
HIGH TEMPERATURES MONDAY AND TUESDAY WILL REACH THE 60'S WITH FAIRLY  
EXTENSIVE DIURNAL CLOUD COVER AND SCATTERED INSTABILITY RAIN  
SHOWERS. SHOWERS WILL BE ENHANCED FROM TIME TO TIME BY SEVERAL  
SHORTWAVES THAT WILL ROTATE AROUND THE BASE OF THE UPPER TROUGH.  
 
TEMPERATURES SHOULD MODERATE A BIT TOWARD LATE NEXT WEEK AS THE  
UPPER TROUGH AXIS MOVES EAST OF OUR REGION AND H8 TEMPS MODERATE.  
HIGH TEMPERATURES SHOULD REACH THE LOWER TO PERHAPS MIDDLE 70'S BY  
THURSDAY. A HIGH PRESSURE RIDGE WILL BUILD IN AND BRING FAIR WX LATE  
IN THE WEEK.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)  
ISSUED AT 658 PM EDT FRI MAY 26 2017  
 
REGIONAL RADAR SHOWS AN AREA OF SHOWERS WITH EMBEDDED STORMS  
MOVING ACROSS NORTHERN IL AND LAKE MICHIGAN AND WILL SOON CROSS  
OVER SOUTHWEST MICHIGAN. THIS PCPN WILL AFFECT THE TAF SITES  
THROUGH MIDNIGHT OR SO AND THEN DRY WX SHOULD PREVAIL FOR THE REST  
OF THE PERIOD. VFR CIGS/VSYBYS EXPECTED THROUGH THE PERIOD.  
 

 
   
MARINE
 
 
ISSUED AT 330 PM EDT FRI MAY 26 2017  
 
WAVES WILL BE HELD TO TWO FEET OR LESS THROUGH SUNDAY NIGHT. THIS  
LEAVE THE THREAT OF THUNDER AS THE MAIN CONCERN FOR BOATERS THIS  
HOLIDAY WEEKEND. HIGHEST THUNDER CHANCE WILL COME LATE SATURDAY  
NIGHT THROUGH SUNDAY AFTERNOON.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 217 PM EDT FRI MAY 26 2017  
 
RIVER LEVELS IN THE UPPER GRAND AND THE KALAMAZOO BASINS ARE  
RUNNING ABOVE NORMAL FOR LATE MAY WHILE ELSEWHERE THE LEVELS ARE  
CLOSER TO NORMAL. RAIN TOTALS GENERALLY UNDER A HALF INCH IN  
SOUTHERN MICHIGAN FRIDAY NIGHT, THEN ACROSS MUCH OF THE AREA ON  
SUNDAY, WILL LIKELY NOT BE ENOUGH TO PRODUCE FLOODING.  
 

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

 
 

 
 
SYNOPSIS...JK  
SHORT TERM...JK  
LONG TERM...OSTUNO  
AVIATION...04  
HYDROLOGY...CAS  
MARINE...JK  
 
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