844
FXUS63 KGRR 040549
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
149 AM EDT THU SEP 4 2025
KEY MESSAGES
- SHOWERS AND STORMS TO SLIDE EAST THIS EVENING AND TONIGHT
- STRONG WINDS TO SWEEP THROUGH THE AREA THURS NIGHT/FRI MORNING
- COOL WEATHER INTO THE WEEKEND
DISCUSSION
ISSUED AT 343 PM EDT WED SEP 3 2025
- SHOWERS AND STORMS TO SLIDE EAST THIS EVENING AND TONIGHT
A COLD FRONT STRETCHES FROM NORTHERN ILLINOIS NORTHEASTWARD ACROSS
LAKE MICHIGAN TO NEAR MUSKEGON AND UP TOWARDS CADILLAC. SHOWERS
AND EMBEDDED THUNDERSTORMS CONTINUE AT 330PM ALTHOUGH THE
LIGHTNING IS QUITE LIMITED NOW. MUCAPE VALUES PER THE SPC MESO
PAGE STILL SHOWS 500-1000 J/KG THOUGH SO FORCING FROM THE FRONT
SHOULD CONTINUE TO RESULT IN ISOLATED THUNDERSTORMS. THROUGH 800PM
THE CONVECTION WILL CONTINUE, BUT EXPECT THE LOSS OF DAYTIME
HEATING AND A FRONTAL MOVEMENT AWAY FROM LAKE MICHIGAN (WHICH IS
PROVIDING A BOOST IN LOW LEVEL MOISTURE) WILL RESULT IN DIMINISHED
CONVECTIVE ACTIVITY. THE RAIN SHOULD TAPER OFF CONSIDERABLY LATE
TONIGHT AND LIKELY OUTRIGHT END.
SOMETHING TO WATCH THROUGH IS THE COLD AIR ADVECTION WHICH WILL
BOLSTER OVER LAKE INSTABILITY DUE TO LAKE EFFECT PROCESSES. DELTA
T'S OVER THE LAKE WILL REACH THE UPPER TEENS C. RAIN SHOWERS OFF
THE LAKE WILL BE POSSIBLE TOWARDS THE LAKESHORE THURSDAY MORNING,
THROUGH DIURNAL PROCESSES ISOLATED SHOWERS COULD SPREAD INLAND ON
THURSDAY. RIGHT NOW THOUGH WE ARE BANKING ON VERY SHALLOW MOISTURE
TO RESULT IN A DRY FORECAST. AS MENTIONED ABOVE THOUGH THERE IS
QUITE A BIT OF INSTABILITY AND WE WILL BE MONITORING TRENDS.
- STRONG WINDS TO SWEEP THROUGH THE AREA THURS NIGHT/FRI MORNING
A SECONDARY REINFORCING SHOT OF COLD AIR COMES ON THURSDAY NIGHT
ASSOCIATED WITH A SHORTWAVE ROTATING AROUND THE CANADIAN/NORTHERN
GREAT LAKES UPPER LOW. A DEEPENING LOW WILL SHIFT THROUGH THE
REGION AND RESULT IN A SURGE OF WIND ACROSS THE ENTIRE AREA. WE
ARE STILL LOOKING AT A POTENTIAL WIND ADVISORY FOR THURSDAY NIGHT
AND FRIDAY MORNING. THE MAIN TIME FRAME OF CONCERN IS 200AM
THROUGH 1100AM FRIDAY MORNING. FOR NOW HOLDING OFF ON THE HEADLINE
BUT IT WILL REEVALUATED EACH SHIFT GOING FORWARD. ANOTHER ROUND OF
SHOWERS IS EXPECTED WITH THE FRONT THAT MOVES THROUGH ON FRIDAY.
NOTHING HEAVY IN TERMS OF RAINFALL AMOUNTS AND THE STEADIEST RAIN
WILL LIKELY BE ACROSS CENTRAL LOWER MICHIGAN CLOSER TO THE TRACK
OF THE LOW.
- COOL WEATHER INTO THE WEEKEND
THE COOL FALL WEATHER TAKES HOLD TONIGHT AND REALLY REMAINS IN
PLACE THROUGH THE REST OF THE WEEK AND THE WEEKEND. ITS NOT
UNTIL MID NEXT WEEK WHERE SOME WARMER AIR TRIES TO SPREAD IN.
HIGHS WILL MAINLY BE IN THE 60S WITH SOME 50S POSSIBLE AS WELL
ACROSS CENTRAL LOWER MICHIGAN. LOWS WILL BE IN THE 40S MAINLY, BUT
30S ARE POSSIBLE SATURDAY NIGHT AND SUNDAY NIGHT ACROSS CENTRAL
LOWER.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 149 AM EDT THU SEP 4 2025
PATCHES OF CEILINGS BELOW 2,000 FEET WILL LINGER EARLY THIS
MORNING AROUND LAN AND JXN. OTHERWISE, MOST AREAS WILL HAVE
SCATTERED TO BROKEN 3,000 TO 5,000 FT CLOUDS DURING PORTIONS OF
THE MORNING TO MID-AFTERNOON. A PERIOD OF VFR IS HIGHLY LIKELY
DURING LATE AFTERNOON INTO THE EVENING.
MARINE
ISSUED AT 343 PM EDT WED SEP 3 2025
WE MADE SOME CHANGES TO THE MARINE HEADLINES TODAY GIVEN WE ARE
LOOKING AT A PERIOD OF GALE CONDITIONS THURSDAY NIGHT INTO FRIDAY
MORNING. SO, WE NOW HAVE A SMALL CRAFT ADVISORY RUNNING INTO
THURSDAY NIGHT. A GALE WATCH IS NOW IN EFFECT FROM THURSDAY NIGHT
INTO EARLY FRIDAY AFTERNOON. THE BEACH HAZARD STATEMENT REMAINS
UNCHANGED AND IS IN EFFECT THROUGH SATURDAY MORNING.
WE HAVE TWO PERIODS OF WIND AND WAVES, THE FIRST IS OCCURRING NOW
WITH WHAT WAS A STRONGER SOUTHWEST WIND THAT IS VEERING NORTHWEST
WITH A FRONTAL PASSAGE. THE SECOND PERIOD OF CONCERN IS THURSDAY
NIGHT AND FRIDAY MORNING WHEN A COMPACT LOW MOVES THROUGH THE
AREA. WINDS WILL SURGE TO GALE FORCE WITH THAT EVENING FROM AFTER
MIDNIGHT THURSDAY NIGHT THROUGH MIDDAY ON FRIDAY. THE LOW IS
DEEPENING WITH TIME ON FRIDAY TO 990-995MB BY 18Z. WE LOOK TO
REACH GALES TO 40 KNOTS IN ALL AREAS. PEAK GUSTS WILL LIKELY BE
JUST SHY OF STORM FORCE TOPPING OUT AROUND 45 KNOTS.
WAVES OF 4 TO 7 FEET ARE OCCURRING NOW AND WILL CONTINUE INTO
TONIGHT. THERE WILL BE A LULL IN THE WINDS AND WAVES ON THURSDAY
BEFORE THE SURGE IN WIND OVERNIGHT. WAVES WILL LIKELY TOP OUT IN
THE 6 TO 12 FOOT RANGE NEAR AND JUST AFTER DAYBREAK ON FRIDAY.
PEAK WAVES WILL BE AROUND 12 FEET FROM GRAND HAVEN TO PENTWATER
AROUND 8-9AM FRIDAY.
GRR WATCHES/WARNINGS/ADVISORIES
MI...BEACH HAZARDS STATEMENT THROUGH SATURDAY MORNING FOR MIZ037-043-
050-056-064-071.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT FRIDAY FOR LMZ844>849.
GALE WATCH FROM LATE TONIGHT THROUGH FRIDAY AFTERNOON FOR
LMZ844>849.
DISCUSSION...DUKE
AVIATION...CAS
MARINE...DUKE
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