800
FXUS63 KGRR 300549
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
149 AM EDT THU APR 30 2026
KEY MESSAGES
- PRECIPITATION ENDING LATE TONIGHT, THEN POSSIBLE FROST/FREEZE
- AFTERNOON SHOWERS THURSDAY AND FRIDAY, FROST/FREEZE POTENTIAL
- UNSETTLED EARLY NEXT WEEK WITH GREATER RAIN CHANCES
DISCUSSION
ISSUED AT 243 PM EDT WED APR 29 2026
- PRECIPITATION ENDING LATE TONIGHT, THEN POSSIBLE FROST/FREEZE
AN EXTENSIVE AREA OF PRECIPITATION WAS CROSSING SOUTHWEST LOWER
MI EARLY THIS AFTERNOON AND IS EXPECTED TO DISSIPATE/EXIT BY LATE
TONIGHT. THERE IS A WELL DEFINED UPPER PV MAX DRIVING THIS
PRECIPITATION. ADDITIONAL PRECIPITATION IS NOTED OVER WI WITH
SEPARATE AND SOMEWHAT WEAKER UPPER PV SUPPORT. HOWEVER, CAM
GUIDANCE SUGGESTS THIS IS CHIEFLY FORCED BY DIURNAL DESTABILIZATION
AND IT WILL LIKELY NOT MAKE IT INTO LOWER MI.
AFTER DISCUSSION WITH APX, DECIDED TO GO WITH A FREEZE WARNING FOR
INTERIOR NORTHERN COUNTIES AND A FROST ADVISORY EXTENDING SOUTH
TOWARDS I-96 OVERNIGHT. THERE IS A LOT OF BUST POTENTIAL WITH
THIS FORECAST BECAUSE THERE ARE QUESTIONS ABOUT HOW QUICKLY WE
WILL LOSE CLOUDINESS OVERNIGHT. ALSO, WE WILL NOW BE DEALING WITH
A BIT MORE SOIL MOISTURE THAN BEFORE, MEANING SLIGHTLY MORE
RESILIENCE AGAINST FALLING AIR TEMPERATURES.
- AFTERNOON SHOWERS THURSDAY AND FRIDAY, FROST/FREEZE POTENTIAL
WITH A SEASONABLY DEEP UPPER LOW OVER THE WESTERN GREAT LAKES AND
COLD TEMPERATURES ALOFT, THERE REMAINS THE CHANCE FOR AT LEAST
SOME AFTERNOON SHOWERS, MAINLY OVER INTERIOR LOWER MI, THANKS TO
DIURNAL SURFACE INSOLATION YIELDING FAVORABLE LAPSE RATES FOR
MODERATELY DEEP MOIST CONVECTION. THUNDER IS NOT EXPECTED PER SPC
OUTLOOKS AND INSTABILITY PROGS.
TEMPERATURES IN THE LOWER TROPOSPHERE LOOK TO BE COLDER FRIDAY AND
SATURDAY MORNINGS. ADDITIONALLY, THERE IS GREATER POTENTIAL FOR
CLOUDS CLEARING AT NIGHT. HENCE, WE EXPECT A GROWING THREAT FOR
NIGHTTIME FROST/FREEZE CONDITIONS AS WE GO INTO THE LATTER PART OF
THE WEEK AND INTO THE WEEKEND.
- UNSETTLED EARLY NEXT WEEK WITH GREATER RAIN CHANCES
GUIDANCE IS COMING INTO BETTER AGREEMENT REGARDING A STRONG UPPER PV
MAX PIVOTING INTO THE WESTERN GREAT LAKES ON THE PERIPHERY OF A
BROADER UPPER LOW. THIS LOOKS FAVORABLE CHIEFLY FOR RAIN SHOWERS
GIVEN THE ARRIVAL OF BEST UPPER FORCING IN THE MORNING HOURS WHEN
CONDITIONAL INSTABILITY TENDS TO BE AT ITS MINIMUM.
AS NOTED PREVIOUSLY, WE WILL SEE INCREASINGLY GULF-SOURCED LOWER
TROPOSPHERIC MOISTURE AS WE MOVE INTO THE MIDDLE OF NEXT WEEK. THIS
WILL ALLOW CONDITIONAL INSTABILITY TO DEVELOP AND INCREASE THE
CHANCES FOR THUNDERSTORMS. BY LATE IN THE WEEK, DEEP SOUTHWESTERLY
FLOW LOOKS LIKE IT COULD SET UP SOMEWHERE OVER THE EASTERN U.S. AND
THIS WILL DEFINITELY NEED TO BE WATCHED SINCE BOTH CONVECTIVE AND
HYDROLOGIC HAZARDS COULD BE IN PLAY WHEREVER THIS OCCURS.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 149 AM EDT THU APR 30 2026
WE CONTINUE TO SEE LOWER CONDITIONS VARYING FROM MVFR TO IFR OVER
THE EAST WHERE THE RAIN REMAINS EARLY THIS MORNING. AREAS TO THE
WEST HAVE SEEN IMPROVEMENT TO VFR WHERE THE RAIN HAS STOPPED.
AREAS THAT HAVE PARTIALLY CLEARED OUT ARE LIKELY TO SEE STRATUS
REDEVELOP. AREAS TO THE EAST MAY SEE A BRIEF BREAK IN THE
STRATUS, AND HAVE HANDLED THIS WITH A TEMPO GROUP DUE TO THE
SHORT DURATION OF ANY CLEARING. NOT EXPECTING MUCH FOG TO DEVELOP
DUE TO ENOUGH OF A WIND TO KEEP THINGS MIXED UP A BIT.
WE WILL SEE THE STRATUS MIX OUT BY MID MORNING, WITH ONLY SOME
CLOUDS LINGERING AROUND 6K FT OR SO. WINDS WILL PICK UP A BIT FOR
THE AFTERNOON AS SOME BETTER WINDS ALOFT WILL MIX DOWN. CLOUDS AT
6K FT WILL THICKEN UP AS A WAVE RIDES BY JUST TO OUR SOUTH. THIS
COULD BRING SOME LIGHT RAIN TO THE I-94 TERMINALS AFTER 00Z FRI.
MARINE
ISSUED AT 243 PM EDT WED APR 29 2026
WAVES COULD MAKE A BRIEF RUN TO AROUND 3 FEET TONIGHT OVER OUR FAR
SOUTHERN MARINE ZONES. HOWEVER, THIS IS NOT TERRIBLY SIGNIFICANT
AND NO CONCERNS ARE NOTED AT THIS TIME.
GRR WATCHES/WARNINGS/ADVISORIES
MI...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR MIZ038>040-045.
FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR MIZ044-046-051-
052-057>059-065-066.
MARINE...NONE.
DISCUSSION...TJT
AVIATION...NJJ
MARINE...TJT
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