723  
FXUS63 KGRR 181108  
AFDGRR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND RAPIDS MI  
708 AM EDT WED SEP 18 2019  
 
LATEST UPDATE...  
AVIATION  
   
SYNOPSIS
 
 
ISSUED AT 308 AM EDT WED SEP 18 2019  
 
- WARM AND DRY THROUGH FRIDAY  
 
- RAIN CHANCES START ON SATURDAY AND WILL BE LIKELY ON SUNDAY  
 
- COOLER WEATHER EXPECTED EARLY NEXT WEEK  
 

 
   
DISCUSSION
 
(TODAY THROUGH NEXT TUESDAY)  
ISSUED AT 308 AM EDT WED SEP 18 2019  
 
FOG AND STRATUS HAS NOT BEEN NEARLY THE ISSUE TONIGHT AS IT WAS LAST  
NIGHT FOR MOST OF THE AREA. SOME FOG/STRATUS IS AFFECTING THE FAR  
EASTERN PORTION OF THE AREA, LIKELY DUE TO LESS WIND ALOFT AND ALSO  
WITH A FLOW OFF OF LAKE HURON/SAGINAW BAY FOR OUR NE COUNTIES. THE  
LESS EXTENSIVE STRATUS SHOULD ALLOW SKIES TO BECOME SUNNY EARLIER  
THAN YESTERDAY MORNING.  
 
OTHER THAN THE FOG/STRATUS THIS MORNING, NOTHING MUCH TO DEAL WITH  
THROUGH FRIDAY. WE WILL SEE TEMPERATURES WARM A COUPLE OF DEGREES  
EACH DAY AS WARMER AIR SLOWLY ADVECTS IN AND UPPER HEIGHTS BUILD.  
SOME RAIN WILL TRY TO APPROACH ON THURSDAY FROM THE NW, AND THEN THE  
GFS KEEPS TRYING TO BRING SOME ISOLATED LIGHT RAIN SHOWERS FRIDAY  
AFTERNOON. A FRONT TRIES TO LEAN IN ON THURSDAY, BUT ALL OF THE  
SUPPORT (LOW LEVEL JET AND UPPER WAVE) STAY FAR ENOUGH NW TO LIKELY  
KEEP US DRY. THE FRIDAY CHANCES FROM THE GFS IS LIKELY THE MODEL  
DEALING WITH SOME DIURNAL INSTABILITY. WE BELIEVE FRIDAY WILL BE OUR  
LAST FULLY DRY DAY WITH LITTLE TO NO DEEP MOISTURE RETURN OCCURRING  
AT THAT POINT YET.  
 
RAIN CHANCES WILL START TO APPEAR ON SATURDAY, BUT WE ARE NOT  
EXPECTING A WASHOUT BY ANY MEANS. THE UPPER RIDGE AND ASSOCIATED  
SUBSIDENCE WILL MOVE EAST BY SAT MORNING. A LEAD SHORT WAVE WILL  
MOVE IN, AND MOISTURE RETURN WILL BE A BIT BETTER THAN FRIDAY. WE  
CAN NOT RULE OUT THUNDER ON SATURDAY AS SOME INSTABILITY DOES  
DEVELOP. RAIN CHANCES WILL BECOME BETTER SAT NIGHT AND SUN AS THE  
LOW LEVEL JET MOVES IN, AND MOISTURE RETURN IS MUCH BETTER AT THAT  
TIME.  
 
SEVERE WEATHER THREAT IS NOT LOOKING VERY HIGH RIGHT NOW, BUT  
WE ARE MONITORING THE SITUATION. RIGHT NOW, IF SHOWERS AND STORMS  
ARE MOVING THROUGH SAT NIGHT AND SUN MORNING, INSTABILITY WILL NOT  
HAVE A GOOD CHANCE TO BUILD. IF FOR SOME REASON SHOWERS AND STORMS  
ARE LIMITED EARLY SUN, AND INSTABILITY CAN BUILD SUN, THINGS MAYBE A  
LITTLE MORE CONCERNING. RIGHT NOW IT LOOKS LIKE THE CHANCES OF THAT  
ARE LOWER.  
 
THE FRONT WILL SLIP SOUTH OF THE AREA SUN NIGHT, BUT RAIN CHANCES  
WILL REMAIN POSSIBLE INTO MONDAY. THIS IS BECAUSE IT TAKES UNTIL MON  
AFTERNOON FOR A TRAILING WAVE TO PUSH THROUGH THE AREA, AND CLEAR  
THE MOISTURE AND FORCING OUT. CHANCES ARE BETTER THAT TUE WILL BE A  
QUIET AND COOLER DAY WITH HIGH PRESSURE BUILDING IN BEHIND THE  
WEEKEND SYSTEM.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)  
ISSUED AT 702 AM EDT WED SEP 18 2019  
 
THERE WERE ONLY A FEW PATCHES OF FOG IN THE REGION SO MUCH LESS  
IN THE WAY OF IMPACTS ARE EXPECTED AT THE TAF SITES TODAY. A  
RELATIVELY DRY AIRMASS PREVAILS THROUGH FORECAST PERIOD. WE WILL  
THEREFORE KEEP THE CLOUD COVER TO A MINIMUM. THE FOG POTENTIAL FOR  
TONIGHT LOOKS SIMILAR OR LESS TO WHAT WE HAVE TODAY.  
 

 
   
MARINE
 
 
ISSUED AT 308 AM EDT WED SEP 18 2019  
 
WE SHOULD REMAIN HEADLINE FREE FOR THE NEARSHORE WATERS UNTIL WE  
COME UP TO THE WEEKEND. WINDS WILL START TO SLOWLY INCREASE A  
LITTLE, BUT SHOULD REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA. THIS  
WIND SHOULD HELP KEEP FOG POTENTIAL MORE LIMITED THAN YESTERDAY.  
 
WE SEE THE POTENTIAL NEED FOR HEADLINES BEGINNING LIKELY FOR THE  
SATURDAY PERIOD AND THROUGH MUCH OF SUNDAY AS THE FRONTAL SYSTEM  
MOVES THROUGH THE AREA, AND WINDS AND WAVES SHOULD INCREASE ENOUGH.  
 

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

 
 

 
 
SYNOPSIS...NJJ  
DISCUSSION...NJJ  
AVIATION...MJS  
MARINE...NJJ  
 
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