734  
FXUS63 KGRR 151907  
AFDGRR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND RAPIDS MI  
307 PM EDT WED OCT 15 2025  
   
KEY MESSAGES
 
 
- PLEASANT FALL DAY TOMORROW  
 
- WET PATTERN SETS UP FRIDAY THROUGH THE WEEKEND  
 

 
   
DISCUSSION
 
 
ISSUED AT 307 PM EDT WED OCT 15 2025  
 
- PLEASANT FALL DAY TOMORROW  
 
HIGH PRESSURE CONTINUES TO BUILD INTO THE AREA TONIGHT INTO  
THURSDAY. WINDS WILL BE LIGHT AND VARIABLE WITH TEMPERATURES  
DROPPING TONIGHT INTO THE 30S TO AROUND 40 ALONG THE LAKESHORE.  
SOME PATCHY FROST IS POSSIBLE ALONG THE US-127 CORRIDOR AND IS  
EXPECTED TO BE MORE WIDESPREAD NORTH OF M-20. MOSTLY SUNNY SKIES  
THURSDAY AND AFTERNOON TEMPERATURES IN THE MID TO UPPER 60S WILL  
RESULT IN A PLEASANT FALL DAY FOR ANY OUTDOOR ACTIVITIES.  
 
- WET PATTERN SETS UP FRIDAY THROUGH THE WEEKEND  
 
AN APPROACHING UPPER LEVEL TROUGH WILL BRING ROUNDS OF RAIN FRIDAY  
THROUGH SUNDAY WITH THE BEST CHANCES SATURDAY INTO SUNDAY.  
SOUTHWEST FLOW ANS WARM AIR ADVECTION WITH PRECIPITABLE WATER  
VALUES AROUND 1.5 INCHES WILL SPARK OFF SOME SHOWERS LATE THURSDAY  
NIGHT WITH 20 PERCENT POPS LINGERING INTO FRIDAY, BEST CHANCE FOR  
SHOWERS WILL BE DURING THE MORNING HOURS WITH THE AFTERNOON  
LARGELY STAYING DRY. FRIDAY NIGHT INTO SATURDAY POSITIVE  
VORTICITY ADVECTION, WARM AIR ADVECTION, THE LOW LEVEL JET, AND  
SOME UPPER LEVEL JET DIVERGENCE MOVE IN BRINGING ANOTHER ROUND OF  
RAIN WITH EMBEDDED THUNDERSTORMS. AT THIS TIME THERE AREN'T ANY  
CLEAR DRY BREAKS WITH RAIN LIKELY THROUGH THE DAY (60-80 PERCENT).  
 
SUNDAY AS THE TROUGH AXIS MOVES THROUGH THERE IS A CONSISTENT  
SIGNAL FOR A SURFACE LOW TO DEVELOP RAPIDLY OVERHEAD. ADDITIONAL  
RAINFALL THROUGH SUNDAY ALONG WITH GUSTY NORTHWEST WINDS ARE  
EXPECTED. NBM PROBABILITIES OF AN INCH OR MORE OF RAIN FRIDAY  
THROUGH SUNDAY ARE IN THE 40 TO 70 PERCENT RANGE ACROSS MUCH OF  
THE AREA WITH THE LOWEST PROBABILITIES OF 20 TO 30 PERCENT IN THE  
JACKSON, CALHOUN, INGHAM COUNTY AREA.  
 

 
   
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
 
 
ISSUED AT 1253 PM EDT WED OCT 15 2025  
 
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. A CLOUD DECK  
IN THE 4-6KFT RANGE WILL LIFT AND SCATTER THROUGH THE AFTERNOON  
AND EVENING WITH CLEAR SKIES TONIGHT AND TOMORROW. A FEW CLOUDS  
AROUND 1KFT ARE PRESENT BUT SHOULD NOT LEAD TO PREVAILING  
CEILINGS AND SHOULD QUICKLY DIMINISH. LIGHT NORTHERLY WINDS TODAY  
WILL BECOME SOUTHEASTERLY BY THURSDAY MORNING.  
 

 
   
MARINE
 
 
ISSUED AT 307 PM EDT WED OCT 15 2025  
 
AT PRESENT, MARINE CONDITIONS ARE RELATIVELY BENIGN AS HIGH PRESSURE  
DOMINATES THE FORECAST. WINDS OF 15 KNOTS OR LESS AND WAVES NEAR OR  
BELOW A FOOT ARE EXPECTED THROUGH TOMORROW. ONGOING NORTHEAST FLOW  
WILL BECOME SOUTHEASTERLY FOR THURSDAY.  
 
THE AFOREMENTIONED HIGH PRESSURE SYSTEM SLIDES EAST THURSDAY NIGHT,  
RESULTING IN AN INCREASING PRESSURE GRADIENT AS A LOW DEEPENS ACROSS  
THE NORTHERN PLAINS AND CENTRAL CANADA. INCREASING SOUTH TO  
SOUTHWEST FLOW DEVELOPS LATE THURSDAY NIGHT, PEAKING FRIDAY NIGHT,  
AND CONTINUING INTO SATURDAY. 20-25 KNOT SUSTAINED WINDS WITH THIS  
SYSTEM WILL DRIVE WAVES OF 4-8 FEET, HIGHEST NEAR AND NORTH OF  
HOLLAND. GUSTS TO 30 KNOTS ARE LIKELY, WITH A LOW (AROUND 10  
PERCENT) POTENTIAL FOR GALES ACROSS THE WATERS. ISOLATED  
THUNDERSTORMS ARE ALSO POSSIBLE SATURDAY.  
 
A SIGNAL IS EMERGING FOR A POTENTIALLY STRONGER WIND/WAVE EVENT  
SUNDAY. MODEL GUIDANCE IS BEGINNING TO ALIGN ON THE IDEA THAT A  
SECOND LOW PRESSURE SYSTEM DEVELOPS AND DEEPENS ACROSS THE CENTRAL  
GREAT LAKES. WHERE THIS SYSTEM DEVELOPS AND HOW DEEP IT GETS REMAIN  
IN QUESTION WHICH MEANS UNCERTAINTY IN THE WIND FORECAST IS STILL  
PRESENT. EVEN WITH THIS UNCERTAINTY, THE POTENTIAL FOR GALES IS  
INCREASING ACROSS LAKE MICHIGAN. WAVES TO 10 FEET MAY ALSO OCCUR.  
REFINEMENT OF THE FORECAST AND GALE POTENTIAL WILL OCCUR OVER THE  
NEXT FEW DAYS AS GUIDANCE COMES MORE INTO ALIGNMENT.  
 

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

 
 

 
 
DISCUSSION...RAH  
AVIATION...THOMAS  
MARINE...THOMAS  
 
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