440
FXUS63 KGRR 141715
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
115 PM EDT TUE OCT 14 2025
KEY MESSAGES
- LIGHT RAIN POSSIBLE TONIGHT
- MORE SUBSTANTIAL SYSTEM TO AFFECT THE AREA INTO THE WEEKEND
- TEMPERATURES A BIT UP AND DOWN
DISCUSSION
ISSUED AT 402 AM EDT TUE OCT 14 2025
- LIGHT RAIN POSSIBLE TONIGHT
AFTER A QUIET WEATHER DAY TODAY OUTSIDE OF SOME AREAS OF MORNING
FOG, RAIN CHANCES INCREASE TONIGHT. THE CHANCES FOR RAIN ARE NOT
HIGH, GENERALLY IN THE 20-50 PCT RANGE. THE PRECIPITATION TONIGHT
IS ASSOCIATED WITH A PUSH OF MID LEVEL MOISTURE ESPECIALLY. BUFKIT
OVERVIEWS SHOW THE BEST JUXTAPOSITION OF MOISTURE/LIFT IN THE
10,000-20,000 FOOT RANGE. THERE IS NOT MUCH MOISTURE ADVECTION
GOING ON BENEATH THAT WITH LOWER RH NOTED AROUND 850MB. THE BEST
PLACES TO SEE LIFT OR IMPLIED LIFT IS ON THE 300K ISENTROPIC
SURFACE AND IN AN INCREASE IN PWAT VALUES TO AROUND 1 INCH. FEEL
THE BEST CHANCES FOR RAIN TONIGHT WILL BE UPSTREAM IN WISCONSIN
AND OVER LAKE MICHIGAN, BUT SOME OF THIS WILL SLIDE INTO WESTERN
LOWER MICHIGAN ESPECIALLY. 4HR MAX REFLECTIVITY FROM THE SPC HREF
SHOWS THIS NICELY. THE 6HR PROBABILITY MATCHED MEAN PRECIPITATION
ALSO SHOWS THAT WHAT PRECIPITATION DOES FALL WILL BE LIGHT,
GENERALLY TRACE AMOUNTS TO PERHAPS A TENTH OF AN INCH.
- MORE SUBSTANTIAL SYSTEM TO AFFECT THE AREA INTO THE WEEKEND
RIDGING ALOFT WILL DOMINATE THE REMAINDER OF THE WORK WEEK WITH
DRY WEATHER EXPECTED FROM WEDNESDAY MIDDAY THROUGH FRIDAY. FOCUS
VERY MUCH IS ON THE SYSTEM FOR FRIDAY NIGHT THROUGH SUNDAY AS
RIDGING IS REPLACED BY A DEEP LONGWAVE TROUGH WHICH WILL BE
OVERHEAD SATURDAY NIGHT INTO SUNDAY. SOUTHWEST UPPER FLOW DEVELOPS
AHEAD OF THE TROUGH FRIDAY NIGHT INTO SATURDAY. THE EVOLUTION OF
THE UPPER TROUGH HAS SOME MODEL DIFFERENCES BETWEEN THE
OPERATIONAL ECMWF AND GFS, BUT WE HAVE SOME THINGS WE CAN NAIL
DOWN AT THIS POINT. THOSE INCLUDE PRECIPITATION WILL MOVE INTO THE
AREA FRIDAY NIGHT AND BE MOST SUBSTANTIAL ON SATURDAY IT APPEARS
AS A COLD FRONT DRIVES THROUGH THE REGION. SHOWERY WEATHER WILL
LINGER INTO SUNDAY AS WE WILL BE BENEATH CORE OF THE UPPER TROUGH.
SOME LOCALLY HEAVY RAIN IS POSSIBLE DURING THIS TIME FRAME AS PWAT
VALUES CLIMB TO 1.5 INCHES. THUNDERSTORMS ARE CERTAINLY POSSIBLE
AHEAD OF THE COLD FRONT AS WELL WITH 850MB DEW POINTS CLIMBING TO
+10C AND MUCAPE VIA THE ECWMF REACHING 1000+ J/KG JUST UPSTREAM.
- TEMPERATURES A BIT UP AND DOWN
TEMPERATURES WILL BE WARMER THAN NORMAL TODAY WITH HIGHS INTO THE
LOWER 70S IN MANY AREAS. NORMAL HIGHS TODAY ARE 62 AT BOTH GRR
AND AZO. WE COOL A BIT FOR WEDNESDAY AND THURSDAY BACK INTO THE
60S BEFORE RISING AGAIN AHEAD OF THE WEEKEND SYSTEM. HIGHS FRIDAY
AND SATURDAY WILL PUSH BACK TO AROUND 70. MUCH COLDER AIR SETTLES
IN WITH THE TROUGH THIS WEEKEND WITH HIGHS FALLING TO BELOW NORMAL
VALUES INTO THE 50S. SUNDAY NIGHT 850MB TEMPERATURES ACTUALLY DIP
TO -1C OVERHEAD.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 115 PM EDT TUE OCT 14 2025
SCATTERED TO BROKEN CUMULUS CLOUD BASES AROUND 2,500 FEET WILL
AFFECT LAN, AZO, BTL, AND JXN FOR A FEW HOURS THIS AFTERNOON, THEN
THIS EVENING IS LIKELY TO BE VFR WITH HIGH CLOUDS STREAMING IN.
TONIGHT, CEILINGS WILL LOWER FROM 15,000 FEET TO 6,000 FEET BY
MORNING. AREAS OF LIGHT RAIN WILL BE PRODUCED FROM THESE CLOUDS,
BUT WILL BE PARTIALLY EVAPORATING INTO DRIER AIR ON THE WAY TO THE
GROUND. LIGHT RAIN MAY REACH THE GROUND ONCE IN A WHILE, AND
VISIBILITY IS NOT EXPECTED TO BE MUCH AFFECTED.
MARINE
ISSUED AT 115 PM EDT TUE OCT 14 2025
NORTH WINDS 15 TO 20 KNOTS ARE EXPECTED TO BUILD 2 TO 4 FT WAVES
FROM THE SABLE POINTS THIS AFTERNOON DOWN THE SHORE TOWARD SOUTH
HAVEN AND ST JOSEPH BY LATE THIS EVENING. WINDS WILL BECOME MORE
FROM THE NORTHEAST TONIGHT AND KEEP THE LARGER WAVES OVER THE OPEN
WATERS. WED AND THU ARE EXPECTED TO HAVE SOME 1 TO 2 FT WAVES.
SMALL CRAFT ADVISORY CONDITIONS ARE LIKELY STARTING EARLY FRIDAY
AND CONTINUING THROUGH THE WEEKEND.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...DUKE
AVIATION...CAS
MARINE...CAS
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