337
FXUS63 KGRR 261743
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
143 PM EDT SAT APR 26 2025
KEY MESSAGES
- FROST POTENTIAL TONIGHT
- THUNDERSTORM POTENTIAL MONDAY NIGHT AND TUESDAY
UPDATE
ISSUED AT 1125 AM EDT SAT APR 26 2025
SOME CLEARING IS BEGINNING TO OCCUR BUT THE H8 THERMAL TROUGH IS
STILL OVERHEAD SO GETTING TO FULL SUNSHINE MAY BE A SLOW PROCESS
THIS AFTERNOON. EASTERN SECTIONS SHOULD BE THE LAST TO FULLY CLEAR
WHERE THE COLD AIR ALOFT AND CYCLONIC FLOW LINGERS LONGEST.
DESPITE THE EMERGING SUNSHINE HIGHS WILL BE STUCK IN THE 50S THIS
AFTERNOON WITH EVEN SOME 40S PERSISTING ALONG THE COAST DUE TO
BRISK NORTHERLY WINDS OFF THE CHILLY LK MI WATERS.
DISCUSSION
ISSUED AT 351 AM EDT SAT APR 26 2025
- FROST POTENTIAL TONIGHT
WINDS GRADUALLY BECOME LIGHTER TODAY WITH LIGHT AND VARIABLE WINDS
TONIGHT. WITH 925 MB TEMPERATURES AROUND 4C AND AN INVERSION WE'LL
SEE TEMPERATURES DROP INTO THE 30S ACROSS MUCH OF THE AREA. THE
BEST CHANCE FOR FROST WITH PROBABILITIES OF TEMPERATURES OF 36
DEGREES OR COLDER IN THE 60 TO 90 PERCENT RANGE ARE FROM OCEANA TO
ISABELLA COUNTY AND NORTHWARD. HOWEVER IMPACTS IN THIS AREA ARE
NOT EXPECTED AS THE GROWING SEASON HAS NOT PROGRESSED ENOUGH.
SOUTH OF THIS AREA PROBABILITIES FROM THE NBM DROP BUT ARE LARGELY
IN THE 40 TO 60 PERCENT RANGE. IN COLLABORATION WITH NEIGHBORING
OFFICES WE'LL CONTINUE TO MONITOR TRENDS BEFORE ISSUING ANY
ADVISORIES.
- THUNDERSTORM POTENTIAL MONDAY NIGHT AND TUESDAY
SOUTHWEST FLOW WILL BRING A SURGE OF INSTABILITY, MOISTURE, WARM
AIR ADVECTION, AND LIFT TO THE REGION. ENSEMBLES ARE IN PRETTY
GOOD AGREEMENT OF ELEVATED CAPE VALUES AROUND 1500 J/KG MONDAY
NIGHT WITH AROUND 40 KNOTS OF SHEAR AND PRECIPITABLE WATER VALUES
AROUND 1.5 INCHES. THE TIMING COULD STILL CHANGE, BUT OVERALL
WE'RE LOOKING AT LATE MONDAY NIGHT INTO EARLY TUESDAY MORNING FROM
WEST TO EAST. THE MAIN CONCERN WOULD BE HEAVY RAINFALL AND HAIL
WITH THIS INITIAL ROUND.
TUESDAY AFTERNOON'S SEVERE THREAT IS CONDITIONAL ON HOW FAST THE
ENVIRONMENT RECOVERS FROM THE INITIAL ROUND OF STORMS AND HOW
QUICKLY THE FRONT MOVES THROUGH. THERE IS A BIT MORE VARIABILITY
IN HOW MUCH CAPE IS AVAILABLE BASED ON THE ENSEMBLES WHICH IS
LIKELY TIED TO THE PROGRESSION OF THE COLD FRONT. HIGHER
CONFIDENCE EXISTS IN CAPE OF 1000 J/KG OR MORE TOWARD THE
I-94/US-127 AREA AND FARTHER EAST. IF THE ENVIRONMENT IS ABLE TO
RECOVER AND STORMS CAN TAP INTO THESE INSTABILITY VALUES ALONG
WITH AROUND 50 KNOTS OF SHEAR, ALL HAZARDS WILL BE POSSIBLE. STAY
UP TO DATE WITH THE FORECAST WITH THE POTENTIAL FOR SEVERE
WEATHER MONDAY NIGHT INTO TUESDAY.
AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 143 PM EDT SAT APR 26 2025
WHAT WAS MVFR CLOUD COVER HAS NOW CLIMBED ABOVE 3,000 FT AND IS
SCATTERING OUT THIS AFTERNOON. BROKEN SKY CONDITIONS MAY PERSIST
FOR A FEW MORE HOURS IN MID MICHIGAN INCLUDING LAN AND JXN. CLEAR
SKIES ARE LIKELY TONIGHT WITH LIGHT WINDS.
MARINE
ISSUED AT 351 AM EDT SAT APR 26 2025
GUSTY NORTHERLY WINDS AND HIGH WAVES CONTINUE AND SUBSIDE TONIGHT
AS HIGH PRESSURE BUILDS INTO THE REGION. LIGHT AND VARIABLE WINDS
ARE EXPECTED THROUGH THE WEEKEND BEFORE WINDS BUILD FROM THE
SOUTH MONDAY BRINGING A RETURN TO SMALL CRAFT ADVISORY CONDITIONS
INTO TUESDAY. THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT AND TUESDAY
AFTERNOON WITH THE POTENTIAL FOR STORMS TO BE SEVERE.
GRR WATCHES/WARNINGS/ADVISORIES
MI...FROST ADVISORY FROM 2 AM TO 8 AM EDT SUNDAY FOR MIZ050>052-
056>059-064>067-071>074.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR LMZ844>849.
UPDATE...MEADE
DISCUSSION...RAH
AVIATION...CAS
MARINE...RAH
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