830
FXUS63 KGRR 210516
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
116 AM EDT THU MAY 21 2026
KEY MESSAGES
- FROST EXPECTED ALONG AND NORTH OF M-20
- PERIODS OF RAIN FRIDAY THROUGH THE WEEKEND
- WARMING UP NEXT WEEK WITH SLIGHT CHANCES (20 PERCENT) FOR RAIN
DISCUSSION
ISSUED AT 143 PM EDT WED MAY 20 2026
- FROST EXPECTED ALONG AND NORTH OF M-20
COLDER TEMPERATURES MOVE IN TONIGHT WITH 925 MB TEMPERATURES
AROUND 4 TO 5 C AND A WEAK INVERSION IN PLACE. LOWS TONIGHT DROP
INTO THE LOW 30S TO LOW 40S FROM NORTH TO SOUTH. THE BEST
POTENTIAL FOR FROST WILL BE ALONG AND NORTH OF M-20 WHERE THERE IS
A HIGHER PROBABILITY (60 TO 90 PERCENT) OF TEMPERATURES FALLING
BELOW 37 F. THEREFORE THIS AREA HAS BEEN INCLUDED IN THE FROST
ADVISORY.
FURTHER SOUTH TEMPERATURES ARE EXPECTED TO BE LARGELY ABOVE 37 F,
BUT SOME ISOLATED LOW LYING AREAS COULD BRIEFLY FALL BELOW BEFORE
SUNRISE. WINDS FURTHER SOUTH ARE LESS LIKELY TO BE CALM AND
THEREFORE WILL HELP KEEP TEMPERATURES WARMER. ANY INCREASE IN
CLOUD COVER WOULD ALSO KEEP TEMPERATURES FROM FALLING LOWER.
- PERIODS OF RAIN FRIDAY THROUGH THE WEEKEND
HIGH PRESSURE STICKS AROUND FOR ONE MORE DAY THURSDAY. SOME
SHOWERS MAY TRY TO MOVE IN FROM THE WEST THURSDAY AFTERNOON, BUT
DRY AIR SHOULD KEEP ANYTHING FROM REACHING THE GROUND.
UPPER LEVEL DIVERGENCE WILL BE PRESENT FRIDAY INTO SATURDAY WITH
A SHORTWAVE MOVING THROUGH. THERE ARE SOME DIFFERENCES WITH THE
TIMING AND LOCATION OF THE LOW AS IT MOVES THROUGH. OVERALL THE
BEST CHANCES LOOKING AT THE CLUSTER ANALYSIS WILL BE FRIDAY NIGHT
INTO SATURDAY. THERE WILL BE SOME INSTABILITY WHICH COULD RESULT
IN SOME EMBEDDED THUNDERSTORMS OVERNIGHT INTO SATURDAY. THE BEST
CHANCE FOR ANY THUNDER WILL BE SOUTH OF I-96. ANOTHER SHORTWAVE
MOVES THROUGH SUNDAY BRINGING MORE CHANCES FOR RAIN AND
THUNDERSTORMS. THE BEST CHANCES (40 TO 50 PERCENT) ARE ALONG AND
EAST OF A KALAMAZOO TO ALMA LINE.
- WARMING UP NEXT WEEK WITH SLIGHT CHANCES (20 PERCENT) FOR RAIN
UPPER LEVEL RIDGING BUILDS IN FOR NEXT WEEK WITH WARMING
TEMPERATURES AND SOME SLIGHT CHANCES (20 PERCENT) FOR RAIN AND
THUNDERSTORMS. THESE SHOWERS AND STORMS COULD BE MORE OF THE
AFTERNOON POP UP VARIETY AS THERE ISN'T ANY GREAT SOURCE OF LIFT
FOR ANYTHING MORE WIDESPREAD. TEMPERATURES WILL WARM EACH DAY WITH
HIGHS IN THE UPPER 70S TO MID 80S AND LOWS IN THE 50S.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 115 AM EDT THU MAY 21 2026
THE MAJORITY OF THE TIME DURING THIS 24 HOUR FORECAST PERIOD, THE
AREA WILL BE MAINLY UNDER THE INFLUENCE OF MID/HIGH CLOUDS BASED
AROUND 12-15K FT AGL. THE EXCEPTION TO THIS IS AN AREA OF LOW
CLOUDS THAT HAS FORMED EAST OF KLAN AND KJXN EARLY THIS MORNING.
THE HI-RES MODELS HAVE CAUGHT ON TO THIS FOR A FEW RUNS NOW. WE
HAVE BROUGHT THIS LOW CLOUD COVER IN THE MVFR CATEGORY TO THE I-94
CORRIDOR FOR 2-4 HOURS THIS MORNING. THE I-96 TERMINALS MAY SEE
SOME OF THIS LOW CLOUD COVER, BUT WILL KEEP THEM VFR WITH SCT
LOWER CLOUDS. THESE LOWER CLOUDS SHOULD MOVE WEST OF THE AREA AND
DISSIPATE AS THEY MOVE INTO DRIER AIR BY 11Z OR SO. WINDS FROM THE
NE WILL DOMINATE THROUGH THIS ENTIRE PERIOD.
MARINE
ISSUED AT 143 PM EDT WED MAY 20 2026
NORTHERLY WINDS AND WAVES CONTINUE TO BUILD THIS AFTERNOON WITH
HIGH SWIM RISK CONDITIONS AND SMALL CRAFT ADVISORY CONDITIONS
EXPECTED FROM GRAND HAVEN AND TO THE SOUTH. WINDS AND WAVE HEIGHTS
WILL DECREASE TONIGHT WITH WINDS BECOMING MORE EASTERLY INTO
THURSDAY. WINDS FURTHER OFFSHORE WILL REMAIN FROM THE NORTH BEFORE
SHIFTING TO THE NORTHEAST THURSDAY NIGHT. FRIDAY WINDS BUILD ONCE
MORE TO SMALL CRAFT ADVISORY LEVELS AS A LOW PRESSURE SYSTEM
TRACKS TOWARD THE AREA. RAIN AND A FEW THUNDERSTORMS WILL BE
POSSIBLE FRIDAY NIGHT INTO SATURDAY WITH THE BEST CHANCES FOR
LIGHTNING SOUTH OF GRAND HAVEN.
GRR WATCHES/WARNINGS/ADVISORIES
MI...FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR MIZ037>040-
043>046.
BEACH HAZARDS STATEMENT UNTIL 2 AM EDT EARLY THIS MORNING FOR
MIZ056-064-071.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT EARLY THIS MORNING FOR
LMZ844>846.
DISCUSSION...RAH
AVIATION...NJJ
MARINE...RAH
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