520
FXUS63 KGRR 111910
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
310 PM EDT SAT APR 11 2026
KEY MESSAGES
- SHOWERS AND STORMS WITH INCREASING FLOOD CONCERN SUNDAY
- POSSIBLE SEVERE THUNDERSTORMS AND FLOODING MON NIGHT AND TUE
DISCUSSION
ISSUED AT 310 PM EDT SAT APR 11 2026
- SHOWERS AND STORMS WITH INCREASING FLOOD CONCERN SUNDAY
RAIN IS EXPECTED TO DEVELOP LATE TONIGHT WITH MOISTURE BROUGHT BY
A 850-700 MB JET NORTH OF AN ADVANCING WARM FRONT. INSTABILITY
WILL BE RELATIVELY MEAGER BUT INCREASE JUST ENOUGH FOR SOME
LIGHTNING BEGINNING DURING THE EARLY MORNING HOURS OF SUNDAY. THE
LONGER-DURATION RAIN AND HEAVIER TOTALS ARE MORE FAVORED NORTH OF
I-96 TOWARD CENTRAL AND NORTH-CENTRAL LOWER MICHIGAN, WITH A
CHANCE OF SHOWERS/STORMS PERSISTING THROUGHOUT MUCH OF THE DAY IN
THAT AREA.
SOUTHERN LOCATIONS WHICH ARE MORE LIKELY TO BREAK INTO THE OPEN
WARM SECTOR DURING THE DAY WITH A FEW BREAKS IN THE CLOUDS MAY
HAVE A PERIOD OF GUSTS 30-40 MPH AS TEMPERATURES SURGE INTO THE
70S. MESOSCALE MODELS DEPICT A FAIRLY ROBUST CONVECTIVELY ENHANCED
SHORTWAVE EJECTING OUT OF TX/OK AS NEARLY A CLOSED LOW SUNDAY
WHICH WILL PROVIDE AN ADDITIONAL IMPETUS FOR RAIN AND SPOTTY
THUNDERSTORMS IN LOWER MICHIGAN SUNDAY EVENING INTO MONDAY
MORNING.
THE 12Z HREF PROBABILITY MATCHED MEAN RAINFALL TOTALS THROUGH
MONDAY MORNING PAINT A LARGE AREA OF 1.5 TO 2.5 INCHES NORTH OF
MUSKEGON, GRAND RAPIDS, AND ALMA. THIS IS HIGHER THAN THE OFFICIAL
FORECAST OF ABOUT 1 TO 1.5 INCHES. FORTUNATELY RIVERS HAVE
CRESTED AND SOIL HAS AT LEAST HAD SEVERAL DAYS TO DRY OUT FROM THE
WET PATTEN SINCE THE BEGINNING OF MARCH, BUT UNFORTUNATELY THERE
IS NOT MUCH ROOM TO ABSORB ADDITIONAL RAIN. MINOR AREAL AND RIVER
FLOODING HAS THE POTENTIAL TO RETURN RELATIVELY QUICKLY IF A
WETTER SCENARIO UNFOLDS.
- POSSIBLE SEVERE THUNDERSTORMS AND FLOODING MON NIGHT AND TUE
A LARGE PLUME OF GREATER THAN 1000 J/KG OF MUCAPE WILL SPREAD
OVER MICHIGAN MONDAY NIGHT THROUGH WEDNESDAY, AND SET UP THE
POTENTIAL FOR AT LEAST A COUPLE ROUNDS OF THUNDERSTORMS AS
SHORTWAVES MOVE OVER A WAVERING FRONTAL ZONE. SPC HAS HIGHLIGHTED
LOWER MICHIGAN IN A MARGINAL RISK FOR SEVERE WEATHER MONDAY NIGHT
AND A SLIGHT RISK FOR TUESDAY-TUESDAY NIGHT. PRECIPITABLE WATER
VALUES EXPECTED AROUND OR ABOVE 1.25 INCHES WOULDN'T BE FAR FROM
THE CLIMATOLOGICAL MAXIMUM FOR THE TIME OF YEAR, MAKING FLOODING A
PERSISTENT CONCERN THIS WEEK.
AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 136 PM EDT SAT APR 11 2026
VFR CONDITIONS CONTINUE WITH EASTERLY WINDS BECOMING MORE
SOUTHEASTERLY TONIGHT. THE LOW LEVEL JET WILL ALSO MOVE INTO THE
REGION CREATING LOW LEVEL WIND SHEAR OF AROUND 40 KNOTS THROUGH
SUNDAY MORNING. SCATTERED SHOWERS WILL BE POSSIBLE LATE TONIGHT
INTO SUNDAY MORNING AS WELL WITH THE BEST CHANCES (60 PERCENT OR
GREATER) TOWARD MKG AND TO THE NORTH. IT IS THIS AREA THAT
CEILINGS ARE EXPECTED TO DIP TO MVFR WITH ONLY A 20 PERCENT CHANCE
FOR IFR CONDITIONS AT MKG SUNDAY MORNING INTO EARLY SUNDAY
AFTERNOON. THERE COULD BE SOME EMBEDDED THUNDERSTORMS WITHIN THE
SHOWERS BUT CONFIDENCE WAS NOT HIGH ENOUGH TO INCLUDE IN THE TAFS.
MARINE
ISSUED AT 310 PM EDT SAT APR 11 2026
SOUTHEAST WINDS STRENGTHEN EARLY SUNDAY MORNING, BECOMING SOUTH-
SOUTHWESTERLY DURING THE DAY. WAVES WILL BUILD THROUGHOUT THE DAY
AND STAY HAZARDOUS TO SMALL CRAFT THROUGH AT LEAST MONDAY MORNING.
SCATTERED THUNDERSTORMS MAY DEVELOP ABOVE THE COOLER MARINE AIR
ON SUNDAY. SLIGHT CHANCE ONE SUNDAY EVENING COULD STIR UP THE
LOWER ATMOSPHERE ENOUGH TO BRING DOWN A GALE FORCE WIND GUST.
ADDITIONAL HAZARDS TO SMALL CRAFT ARE LIKELY MONDAY NIGHT THROUGH
TUESDAY FROM WINDS, WAVES, AND CHANCES FOR THUNDERSTORMS.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 4 AM SUNDAY TO 4 PM EDT MONDAY FOR
LMZ844>849.
DISCUSSION...CAS
AVIATION...RAH
MARINE...CAS
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