277
FXUS63 KGRR 181815
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
215 PM EDT MON MAY 18 2026
KEY MESSAGES
- SEVERE LINE OF STORMS MOVING OUT THIS EVENING
- MORE STORMS ON TUESDAY
- FROST/FREEZE WEDNESDAY NIGHT ACROSS THE NORTH
DISCUSSION
ISSUED AT 215 PM EDT MON MAY 18 2026
- SEVERE LINE OF STORMS MOVING OUT THIS EVENING
A LINE OF STORMS THAT WAS WELL FORECAST BY THE HI-RES ARW WILL BE
MOVING ACROSS THE SOUTHERN HALF OF THE FORECAST AREA THIS
AFTERNOON AND MOVING OFF TO THE EAST THIS EVENING. DOWNDRAFT CAPE
VALUES OF OVER A 100 J/KG IN THE AIRMASS THE LINE IS MOVING
THROUGH MEANS DOWNBURSTS WITH SEVERE WIND GUSTS TO 60 MPH ARE THE
MAIN THREAT WITH THIS LINE. SCATTERED STORMS WITH ISOLATED SEVERE
WINDS AND/OR HAIL ARE POSSIBLE ACROSS THE NORTH.
THE SEVERE THREAT WINDS DOWN THIS EVENING AS THE LINE OF STORMS
MOVES OFF THE THE EAST WITH LITTLE TO NO ADDITIONAL QPF EXPECTED
OVERNIGHT WITH THE ATMOSPHERE BEING EFFECTIVELY STABILIZED.
- MORE STORMS ON TUESDAY
SURFACE COLD FRONT MOVES SOUTHEAST ACROSS THE FORECAST AREA ON
TUESDAY AFTERNOON ATTENDED BY SCATTERED STRONG TO SEVERE STORMS AS
SURFACE BASED CAPE APPROACHES 1500 J/KG. BEST CHANCE FOR SEVERE
WEATHER WILL BE ACROSS THE SOUTHEAST FORECAST AREA WHERE
INSTABILITY IS GREATEST. DEEP LAYER SHEAR GREATER THAN 40 KNOTS
WILL ALSO AID THE CAUSE. THE COLD FRONT WILL MOVE SOUTHEAST OF THE
FORECAST AREA DURING THE EVENING, ENDING THE THREAT WITH A MUCH
COOLER AIRMASS MOVING BACK IN.
- FROST/FREEZE WEDNESDAY NIGHT ACROSS THE NORTH
CANADIAN SURFACE HIGH BUILDING IN ON WEDNESDAY AND WEDNESDAY
NIGHT WITH DEW POINTS DROPPING INTO THE 20S AND 30S WILL LEAD TO
MIN TEMPS COLD ENOUGH FOR FROST/FREEZE HEADLINES ACROSS ABOUT THE
NORTHERN THIRD OR HALF OF THE FORECAST AREA. TEMPERATURES
MODERATE BY THE END OF THE WEEK AS LOW PRESSURE MOVES UP FROM THE
SOUTH BRINGING RAIN BY FRIDAY INTO SATURDAY.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 215 PM EDT MON MAY 18 2026
A LINE OF SEVERE THUNDERSTORMS WITH SURFACE WIND GUSTS TO 50
KNOTS WILL BE MOVING THROUGH AZO AND BTL BETWEEN 18 AND 19Z AND
JXN BY 20Z. THE NORTHERN END OF THE LINE WILL CLIP GRR AND LAN
WITH SURFACE WIND GUSTS OF 45 TO 50 KNOTS POSSIBLE. THE STORMS
THIS AFTERNOON COULD BRING BRIEF IFR CONDITIONS WITH HEAVY RAIN
REDUCING VISIBILITIES LESS THAN 2 MILES.
THE STORMS WILL MOVE OFF TO THE EAST AND THIS EVENING SHOULD SEE
A LULL IN THE THUNDERSTORMS UNTIL LATE TUESDAY MORNING OR
AFTERNOON. LLWS TO 40 KNOTS IS EXPECTED LATE TONIGHT INTO TUESDAY
MORNING.
MARINE
ISSUED AT 215 PM EDT MON MAY 18 2026
NO CHANGES TO THE SCA. WINDS AND WAVES WILL REMAIN HAZARDOUS TO
SMALL CRAFT THROUGH TUESDAY. A COLD FRONT MOVES THROUGH LATE
TUESDAY AND NORTHWEST WINDS COULD GUST TO 25 KNOTS INTO WEDNESDAY
BEFORE DIMINISHING WEDNESDAY NIGHT AS HIGH PRESSURE BUILDS IN.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 2 AM TO 8 PM EDT TUESDAY FOR LMZ844-
845.
SMALL CRAFT ADVISORY UNTIL 8 PM EDT TUESDAY FOR LMZ846>849.
DISCUSSION...OSTUNO
AVIATION...OSTUNO
MARINE...OSTUNO
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