811
FXUS63 KGRR 201743
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
143 PM EDT WED MAY 20 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 /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 143 PM EDT WED MAY 20 2026
VFR PREVAILS THIS AFTERNOON NOW THAT STRATOCUMULUS CLOUDS HAVE
GONE SCATTERED/BROKEN ABOVE 3,500 FEET. THE LOWER ATMOSPHERIC
CLOUDS WILL CONTINUE TO DISSIPATE GOING INTO THIS EVENING, THOUGH
SOME MODELS SUCH AS THE HRRR WANT TO HANG ON TO MOISTURE AND
CLOUDS AROUND 3,000 FEET FOR A PERIOD BETWEEN 02-08 Z TONIGHT,
MOVING FROM JXN TOWARD AZO.
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 FROM 1 AM TO 9 AM EDT THURSDAY FOR MIZ037>040-
043>046.
BEACH HAZARDS STATEMENT THROUGH LATE TONIGHT FOR MIZ056-064-071.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT THURSDAY FOR LMZ844>846.
DISCUSSION...RAH
AVIATION...CAS
MARINE...RAH
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