534
FXUS63 KGRR 022218
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
618 PM EDT THU APR 2 2026
KEY MESSAGES
- THUNDERSTORMS LIKELY, SEVERE THUNDERSTORMS POSSIBLE THIS EVENING
- THUNDERSTORMS FRIDAY NIGHT TO SATURDAY
DISCUSSION
ISSUED AT 222 PM EDT THU APR 2 2026
- THUNDERSTORMS LIKELY, SEVERE THUNDERSTORMS POSSIBLE THIS EVENING
MODELS HAVE REMAINED PRETTY CONSISTENT ON THE EVOLUTION OF THE
ENVIRONMENT, WITH A WARM FRONT SURGING TOWARD I-96 LATE THIS
AFTERNOON AND STORMS DEVELOPING ALONG A PREFRONTAL TROUGH OVER IL,
IN, SOUTHERN LAKE MICHIGAN, AND SOUTHWEST MICHIGAN. ALTOGETHER,
THE GREATEST SEVERE WEATHER THREAT WILL BE BETWEEN 5 PM AND 10 PM,
BUT CAN'T RULE OUT A COUPLE MORE ISOLATED STORMS AROUND 10 PM TO
1 AM HELPING TO STIR DOWN STRONG ENVIRONMENTAL WINDS ABOVE THE
SURFACE.
CAPE IN THE RANGE OF 500-1000 J/KG WILL DEVELOP IN THE WARM
SECTOR WITH MOST UNSTABLE PARCELS JUST ABOVE THE SURFACE, AND THE
GREATEST CONCENTRATION OF CAPE WILL BE IN THE WARM LOWER
TROPOSPHERE ABOVE THE LFC TO ABOUT 4 KM. THIS LIMITS THE HAIL
POTENTIAL BUT INCREASES THE POTENTIAL FOR VORTICITY TILTING AND
STRETCHING IN A HIGHLY SHEARED 0-1 KM AND 0-3 KM LAYER. HODOGRAPHS
IN THE WARM SECTOR NEAR AND SOUTH OF I-96 ARE EXPECTED TO BE
ELONGATED AND CLOCKWISE CURVED AT LEAST IN THE 0-2 KM LAYER, WITH
LESS SHEAR ABOVE. ABOUT 45 KNOTS OF 0-3 KM SHEAR IS POSSIBLE. THE
SIGNIFICANT TORNADO PARAMETER SOUTH OF I-96 IS FAVORED TO INCREASE
TO AT LEAST 1, PERHAPS APPROACHING 2-3, BETWEEN 5 PM AND 9 PM.
MOISTURE THROUGH THE CONVECTIVE LAYER WILL BE HIGH, WITH LCLS 1000
METERS OR LOWER, INCREASING RAINFALL RATES BUT TEMPERING THE
STRENGTH OF CONVECTIVE DOWNDRAFTS AND COLD POOLS. BUT WITH LOW-
LEVEL WIND SHEAR BEING STRONG, IT WON'T TAKE STRONG DOWNDRAFTS TO
MIX DOWN LOCALLY SEVERE WIND GUSTS.
THE STORM MODE THAT EVOLVES OVER SOUTHWEST MICHIGAN THIS EVENING
COULD BE SOME MIX OF QUASI-LINEAR SEGMENTS OR SEMI-DESCRETE
SUPERCELLS. EITHER WAY, THE SMALL SCALE AND LOWER-ATMOSPHERIC
MESOCYCLONES OR MESOVORTS THAT DEVELOP IN THIS ENVIRONMENT COULD
BE CAPABLE OF PRODUCING A TORNADO OR TWO IN OUR AREA. ANY RIGHT-
MOVING MESOCYCLONES ARE CALCULATED TO MOVE NORTHEAST AROUND 55
MPH, MAKING THIS EVENING'S HAZARDS FAST-UNFOLDING IF THE
CONDITIONAL THREAT IS REALIZED.
- THUNDERSTORMS FRIDAY NIGHT TO SATURDAY
ANOTHER WAVE OF LOW PRESSURE ALONG THIS REGIONAL FRONTAL ZONE
PROVIDES ELEVATED WARM-ADVECTION THUNDERSTORMS OVERNIGHT FRIDAY
NIGHT AND SHOWERS/STORMS IN THE VICINITY OF A COLD FRONT DURING
THE DAY SATURDAY. THIS WILL BE ANOTHER HIGH-SHEAR LOW-CAPE SORT OF
ENVIRONMENT SO CAN'T RULE OUT A MARGINAL SEVERE THREAT AT THIS
POINT. THE EARLIER DAYTIME CONVECTION TIMING ON SATURDAY MAY KEEP
THE GREATER RISK FARTHER EAST.
AVIATION /00Z TAFS THROUGH 00Z SATURDAY/
ISSUED AT 615 PM EDT THU APR 2 2026
A DYNAMIC SYSTEM IS MOVING THROUGH THE AREA. A WARM FRONT IS
MOVING NORTH NEAR I-94 AND SHOWERS AND THUNDERSTORMS WILL CONTINUE
TO DEVELOP FOR THE NEXT SEVERAL HOURS. ADDITIONALLY, STRONG LOW
LEVEL FLOW AHEAD OF THE LOW OVER IOWA WILL RESULT IN LLWS THROUGH
MIDNIGHT OR SO.
THE TRAILING COLD FRONT WILL PASS OVER THE TERMINALS AROUND 12Z
FRIDAY PUTTING AN END TO THE PRECIPITATION. CIGS/VSBYS WILL SLOWLY
LIFT LATE MORNING AND EARLY AFTERNOON.
MARINE
ISSUED AT 222 PM EDT THU APR 2 2026
CONSIDERED A GALE WARNING FOR THIS EVENING/TONIGHT, BUT THE
THREAT OF GALES WILL PROBABLY BE CONVEYED WITH SPECIAL MARINE
WARNINGS IN THE VICINITY OF THUNDERSTORMS. SOUTH-SOUTHWEST WINDS
STRENGTHEN THIS EVENING, BUT THE STABLE AND COOL MARINE AIR LAYER
IS LIKELY TO SUBDUE THE POTENTIAL FOR HOURS OF WIDESPREAD GALES.
INSTEAD, GALES MAY BE MORE SPURIOUS AND THUNDERSTORM-RELATED.
HAZARDOUS WAVES FOR SMALL CRAFT LINGER INTO PART OF THE DAY FRIDAY
WHILE GRADUALLY DIMINISHING. HAZARDOUS CONDITIONS FOR SMALL CRAFT
ARE AGAIN LIKELY SATURDAY AND SUNDAY.
HYDROLOGY
ISSUED AT 222 PM EDT THU APR 2 2026
THE 3RD (OF 4) ROUNDS OF RAIN THIS WEEK IS UNDERWAY, AND IS SO
FAR UNFOLDING ABOUT AS EXPECTED. AN ADDITIONAL 0.5 TO 1.0 INCHES
OF RAIN HAS FALLEN ACROSS THE MUSKEGON RIVER AND LOWER GRAND RIVER
WATERSHEDS. WATER LEVELS ARE BEGINNING TO RISE. AN ADDITIONAL 0.5
TO 1.0 FOR THE REMAINDER OF TODAY, PLUS ANOTHER 0.5 OR SO ON
SATURDAY (ROUND 4) IS RAISING THE POSSIBILITY OF SOME MINOR
FLOODING DEVELOPING ALONG THE MUSKEGON RIVER. IT'S ALSO POSSIBLE
THAT SOME OF THE MOST VULNERABLE FLOOD LOCATIONS IN THE GRAND
BASIN COULD APPROACH FLOOD STAGE, NAMELY IN COMSTOCK PARK AND ALSO
ALSO THE MAPLE RIVER NEAR MAPLE RAPIDS, BUT THIS WILL DEPEND ON
HOW THE REST OF TODAY'S RAIN UNFOLDS. A FLOOD WATCH IS IN EFFECT
FOR PARTS OF THE MUSKEGON RIVER, WITH FLOODING POSSIBLE BY THIS
WEEKEND.
THANKFULLY THE RAIN RATE TODAY IS FAIRLY MODERATE, WITH LOCALLY
HEAVY DOWNPOURS, BUT NOT ENOUGH TO CAUSE SUBSTANTIAL TRAVEL
IMPACTS OR OTHER TYPES OF URBAN FLOODING.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 PM EDT FRIDAY FOR LMZ844>849.
DISCUSSION...CAS
AVIATION...04
MARINE...CAS
HYDROLOGY...AMD
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