300
FXUS63 KGRR 091721
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
121 PM EDT SAT MAY 9 2026
KEY MESSAGES
- THUNDERSTORMS POSSIBLE IN SE LOWER MICHIGAN THIS AFTERNOON
- FROST/FREEZE THE NEXT THREE NIGHTS
- RAIN LIKELY, CHANCE THUNDERSTORM TUESDAY
DISCUSSION
ISSUED AT 121 PM EDT SAT MAY 9 2026
- THUNDERSTORMS POSSIBLE IN SE LOWER MICHIGAN THIS AFTERNOON
ABOUT 500-750 J/KG OF MLCAPE WILL BE PRESENT AROUND JACKSON THIS
AFTERNOON WITH LITTLE INHIBITION AND MODERATELY STEEP LAPSE RATES
TO 700 MB. SOME SHOWERS OR THUNDERSTORMS MAY POP UP BUT CHANCES
ARE IFFY AS THE LOWER ATMOSPHERE WILL GENERALLY HAVE SPEED
DIVERGENCE. ANY STORMS THAT DO DEVELOP COULD PRODUCE HAIL OR GUSTY
WINDS WHILE QUICKLY MOVING EAST AND INTENSIFYING AS THEY LEAVE
OUR AREA.
- FROST/FREEZE THE NEXT THREE NIGHTS
ANOTHER COOL AIRMASS DELIVERED BY THE PERSISTENT SYNOPTIC
TROUGHING OVER THE CANADIAN SHIELD WILL BRING NIGHTLY FROST/FREEZE
POTENTIAL AS HIGH PRESSURE NOSES INTO THE REGION THROUGH MONDAY
NIGHT. MOSTLY CLEAR SKIES AND LIGHT WINDS ARE FAVORED TO SET UP
RADIATIONAL COOLING WITH OBJECT "SKIN" TEMPERATURES REACHING NEAR
THE FREEZING POINT WHILE 2-METER TEMPERATURES DIP INTO THE MID
30S. 2-METER TEMPERATURES MAY OUTRIGHT GO BELOW 32 IN THE
TYPICALLY COOLER SPOTS OF CENTRAL MICHIGAN EACH NIGHT. AFTER A
WARM AND WET MARCH AND APRIL, THE SENSITIVITY TO FREEZING
TEMPERATURES IS HIGHER THAN USUAL.
CAN'T RULE OUT ANOTHER FROST SETUP IN INTERIOR CENTRAL MICHIGAN
WED NIGHT TO THU MORNING UNDER THE 10-25 PERCENT CHANCE COOLER
SCENARIOS OF A HIGH PRESSURE SYSTEM QUICKLY MOVING IN BEHIND TUE-
WED'S LOW PRESSURE SYSTEM. BUT AFTER THAT, THE PATTERN DOES SEEM
TO SHIFT TOWARD WARMER THAN NORMAL IN THE 8-14 DAY OUTLOOK.
- RAIN LIKELY, CHANCE THUNDERSTORM TUESDAY
AN ALBERTA CLIPPER TYPE OF LOW WILL DEEPEN AS IT MOVES TOWARD
MICHIGAN ON TUESDAY. RAIN IS LIKELY IN THE MIDLEVEL WARM AIR AND
MOISTURE ADVECTION AHEAD OF THE LOW. INSTABILITY IS RATHER MEAGER
IN THE MODELS AS 700-500 MB TEMPERATURES WILL BE FAIRLY WARM
RESULTING IN MODEST LAPSE RATES, SO THUNDERSTORM CHANCES WILL BE
LESS THAN THE LIKELIHOOD OF RAIN.
AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 109 PM EDT SAT MAY 9 2026
ISOLATED THUNDERSTORMS HAVE BEGUN TO DEVELOP EAST OF THE TERMINALS
AND WILL CONTINUE EAST THROUGH THE AFTERNOON. CANNOT RULE OUT AN
ISOLATED THUNDERSTORM AT JXN THROUGH 21Z HOWEVER CONFIDENCE IS
LOW IN TERMINAL IMPACTS. GUSTY WINDS TO 30 KNOTS WILL CONTINUE
THROUGH THIS EVENING BEFORE DIMINISHING OVERNIGHT. IN ADDITION,
SKIES ARE FORECAST TO CLEAR OUT OVERNIGHT. WINDS WILL REMAIN
LIGHT INTO SUNDAY WITH SCATTERED CU DEVELOPMENT POSSIBLE BEGINNING
LATE SUNDAY MORNING.
MARINE
ISSUED AT 121 PM EDT SAT MAY 9 2026
WINDS ARE RELAXING THIS AFTERNOON AND ALLOWING 3 TO 5 FOOT WAVES
TO DIMINISH TO 2 TO 4. HIGH RESOLUTION MODELS SUGGEST A BRIEF
SURGE OF NORTHERLY WINDS NEAR BIG AND LITTLE SABLE POINTS BETWEEN
8 AND 11 PM THIS EVENING, WITH WIND SPEEDS ABOUT 15-20 KNOTS.
WAVES WILL REMAIN FAIRLY LOW SUNDAY AND MONDAY, THEN
STRENGTHENING SOUTH WINDS RELATED TO AN APPROACHING LOW PRESSURE
SYSTEM ON TUESDAY WILL BUILD UP HAZARDOUS WAVES FOR SMALL CRAFT.
HAZARDOUS CONDITIONS SHOULD CONTINUE INTO WEDNESDAY WITH WEST-
NORTHWEST WINDS.
GRR WATCHES/WARNINGS/ADVISORIES
MI...FROST ADVISORY FROM 2 AM TO 8 AM EDT SUNDAY FOR MIZ037-043>046.
FREEZE WARNING FROM 2 AM TO 8 AM EDT SUNDAY FOR MIZ038>040.
MARINE...SMALL CRAFT ADVISORY UNTIL 3 PM EDT THIS AFTERNOON FOR
LMZ846>849.
DISCUSSION...CAS
AVIATION...THOMAS
MARINE...CAS
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