341
FXUS63 KGRR 030606
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
206 AM EDT WED SEP 3 2025
KEY MESSAGES
- WEDNESDAY COLD FRONT AND ASSOCIATED THUNDERSTORM CHANCES
- FRIDAY COLD FRONT AND WIND
- COOLER WEATHER AND FROST POTENTIAL
DISCUSSION
ISSUED AT 226 PM EDT TUE SEP 2 2025
- WEDNESDAY COLD FRONT AND ASSOCIATED THUNDERSTORM CHANCES
RAIN CHANCES WITH OUR NEXT SYSTEM BEGIN AS EARLY AS TONIGHT, BUT ARE
CENTERED ON WEDNESDAY AFTERNOON AND NIGHT. A STRONG COLD FRONT IS
POISED UPSTREAM OVER NORTHERN MINNESOTA, WHICH IS SET TO MOVE
THROUGH SOUTHWEST LOWER MICHIGAN WEDNESDAY AFTERNOON AND EVENING.
THE COLD FRONT IS SUPPORTED BY A STRONG UPPER LOW THAT IS PLOWING
SOUTH ACROSS MANITOBA AND SASKATCHEWAN THIS AFTERNOON. SURFACE DEW
POINT SURGE TO 60-65F BETWEEN 10AM AND 10PM ACROSS OUR FORECAST AREA
AND THAT IS WHEN WE EXPECT THE HIGHEST CHANCES FOR RAIN AND
THUNDERSTORMS. WE FEEL MUCAPE VALUES WILL SURGE TO 1,000 TO 1,500
J/KG DURING THE HEAT OF THE DAY. THE STRONGER SHEAR LAGS THE FRONT
SO NOT EXPECTING SIGNIFICANTLY ORGANIZED STORMS WHICH IS WHY WE
ARE ONLY IN A GENERAL THUNDER OUTLOOK FROM THE SPC. THAT SAID,
WITH LOWER FREEZING LEVELS, 10,500 FEET, PLENTY OF INSTABILITY AND
30 KNOTS OF WIND AT 850MB THERE IS POTENTIAL FOR SOME HAIL
(0.50" TO 0.75") AND SOME WIND GUSTS OF 40-50 MPH. THE STRENGTH
OF THE COLD FRONT SHOULD DRIVE SOME EMBEDDED FAIRLY VIGOROUS
CONVECTION, JUST LIKELY SUB SEVERE. RAIN MOVES INTO THE LUDINGTON
AREA TOWARDS DAYBREAK WITH THE BEST CHANCE AT SOME STRONGER CELLS
OCCURRING MID AFTERNOON FROM SOUTH HAVEN NORTHEAST THROUGH GRAND
RAPIDS TO MT. PLEASANT. CHANCES FOR RAIN TOMORROW WILL BE NORTH OF
70 PCT IN ALL AREAS. THE RAIN WILL LINGER INTO WEDNESDAY NIGHT
BEFORE DRYING OUT A BIT INTO THURSDAY
- FRIDAY COLD FRONT AND WIND
THURSDAY NIGHT ANOTHER COLD FRONT APPROACHES WITH RAIN CHANCES
INCREASING LATE AND ESPECIALLY INTO FRIDAY. THERE WILL LIKELY BE A
LAKE BOOST TO THE RAIN SHOWERS WITH THE SECOND FRONT GIVEN LAKE
WATER TEMPS PER OVERNIGHT SATELLITE PASSES OF 68F TO 72F DEGREES
OVER MUCH OF THE SOUTH HALF OF THE LAKE. USING A 21C AVERAGE
TEMP, WE WILL BE PUSHING DELTA T'S ON FRIDAY INTO THE UPPER TEENS
C. PLENTY OF INSTABILITY (500-800 J/KG), ALTHOUGH MOISTURE DEPTH
IS ON THE LOWER SIDE. A SOLID AREA OF RAIN SHOWERS, POSSIBLY
EMBEDDED WITH A RUMBLE OF THUNDER (MUCH LOWER CHANCE THAN WED)
WILL MOVE THROUGH THE AREA.
ANOTHER ELEMENT TO THE VERY FALLISH WEATHER THAT WE WILL NEED TO
KEEP AN EYE ON IS THE WIND ON FRIDAY. A SUB 1000MB LOW WILL PUSH
NORTHEAST THROUGH THE GREAT LAKES ON FRIDAY WITH WHEN COMBINED WITH
A 1018MB HIGH IN THE PLAINS WE WILL SEE A WINDY DAY ON FRIDAY. SOME
MODELS HAVE US TAPPING INTO WIND THAT IS 40+ MPH. WE WILL BE
MONITORING FOR POTENTIAL WIND HEADLINES. AT THIS POINT A WIND
ADVISORY LOOKS MARGINAL, BUT ITS CLOSE. THE SURGE IN WIND REALLY
LOOKS TO COME IN EARLY MAYBE EVEN BEFORE DAYBREAK LASTING INTO THE
DAY.
- COOLER WEATHER AND FROST POTENTIAL
OVERALL, THIS IS A FAIRLY SIGNIFICANT CHANGE IN THE WEATHER. HIGH
TEMPERATURES TODAY WILL BE AROUND 80F WITH TEMPS TUMBLING THROUGH
THE WEEK. HIGHS THURSDAY THROUGH SUNDAY WILL BE IN THE 60S IN MANY
AREAS WITH 50S EVEN ACROSS INTERIOR CENTRAL LOWER MICHIGAN. WE HAVE
LOWS IN OUR FORECAST SATURDAY NIGHT AND SUNDAY NIGHT DIPPING INTO
THE 30S IN SPOTS UP ALONG U.S. 10 IN CENTRAL LOWER. SO, THERE WILL
LIKELY BE SOME FROST UP THERE ON THOSE NIGHTS, ESPECIALLY FOR
TRADITIONALLY COLD PLACES LIKE LEOTA IN CLARE COUNTY. TALKING DELTA
T'S, POTENTIAL WIND ADVISORIES AND PLENTY OF LAKE EFFECT
CLOUDS AND RAIN SHOWERS...FALL IS HERE!
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 206 AM EDT WED SEP 3 2025
MULTIPLE RAIN SHOWERS AND CHANCE OF THUNDERSTORMS WILL MOVE
THROUGH LATE MORNING INTO EVENING. THE LIKELIHOOD FOR MVFR
CEILINGS SHOULD REACH MKG AFTER 17 Z, THEN MOVE EAST AND
SOUTHEAST, REACHING JXN AFTER 00 Z. VISIBILITY MAY TEMPORARILY GO
IFR UNDER HEAVIER RAIN SHOWERS OR THUNDERSTORMS.
MARINE
ISSUED AT 125 PM EDT TUE SEP 2 2025
WINDS WILL INCREASE AHEAD OF A STRONG COLD FRONT WEDNESDAY. WAVES
WILL INCREASE TO AT LEAST 3 FEET AROUND SUNRISE; WE'VE ISSUED A
SMALL CRAFT ADVISORY AND BEACH HAZARDS STATEMENT FROM 6AM
WEDNESDAY THROUGH 8 AM SATURDAY. WIND AND WAVES WILL BE HAZARDOUS
TO SMALL CRAFT AND BEACH GOERS. ADDITIONALLY, SCATTERED THUNDERSTORMS
WEDNESDAY WILL ALSO POSE A THREAT.
GRR WATCHES/WARNINGS/ADVISORIES
MI...BEACH HAZARDS STATEMENT FROM 6 AM EDT THIS MORNING THROUGH
SATURDAY MORNING FOR MIZ037-043-050-056-064-071.
MARINE...SMALL CRAFT ADVISORY FROM 6 AM THIS MORNING TO 8 AM EDT SATURDAY
FOR LMZ844>849.
DISCUSSION...DUKE
AVIATION...CAS
MARINE...04
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