794
FXUS63 KGRR 300753
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
353 AM EDT SUN MAR 30 2025
KEY MESSAGES
- SEVERE THUNDERSTORMS POSSIBLE TODAY
- ADDITIONAL PRECIPITATION MID-WEEK
DISCUSSION
ISSUED AT 350 AM EDT SUN MAR 30 2025
- SEVERE THUNDERSTORMS POSSIBLE TODAY
SCATTERED LIGHT SHOWERS AND CLOUDY SKIES ARE FAVORED TO CONTINUE
INTO THE MORNING, WITH SHOWERS DIMINISHING IN COVERAGE. A LINE OF
STORMS PRESENTLY OVER IOWA THEN ARRIVES LATE MORNING ALONG THE
NORTHERN HALF OF THE LAKESHORE, MOVING ACROSS AREAS NORTH OF I96.
THIS IS NOT EXPECTED TO BE SEVERE GIVEN FAVORABLE INSTABILITY WILL
HAVE NOT YET ARRIVED.
AS THIS IS ONGOING, INCREASING WARM AND MOIST SOUTHERLY ADVECTION
WILL LED TO THE WARM FRONTAL BOUNDARY NEAR I96 SURGING INTO CENTRAL
LOWER MICHIGAN. ACCORDINGLY, AN OPEN WARM SECTOR DEVELOPS ACROSS
LOWER MICHIGAN AS DEWPOINTS SURGE INTO THE 60S. MUCAPE VALUES ARE
FORECAST TO CLIMB INTO THE 1000-2500 J/KG RANGE BY MID AFTERNOON,
WITH THE HIGHER END OF THAT RANGE DEPENDENT ON IMPACTS OF EARLIER
PRECIPITATION AND WHETHER BREAKS IN CLOUD COVER OCCUR. A STRONG 50
KNOT LOW-LEVEL JET WILL PROVIDE 30-45 KNOTS OF DEEP LAYER SHEAR
OVERLAPPING THE INSTABILITY WHICH WOULD BE FAVORABLE FOR ORGANIZED
AND POTENTIALLY ROTATING STORMS. THE KEY NOTE HERE IS THAT SEVERE
THUNDERSTORM DEVELOPMENT WILL HINGE ON SUFFICIENT INSTABILITY,
MEANING INSTABILITY WILL NEED TO BE MONITORED THROUGH THE DAY AND AS
NOTED, AMPLE INSTABILITY DEVELOPING IS NOT 100 PERCENT CERTAIN GIVEN
DEPENDENCE ON CLOUD COVER AND EARLIER PRECIPITATION.
THE FAVORED TIMEFRAME FOR ANY SEVERE THUNDERSTORMS IS 2-10 PM SUNDAY
AFTERNOON AND EVENING, WITH CHANCES AREAWIDE BUT HIGHEST SOUTH OF
M46 WHERE BETTER SURFACE-BASED INSTABILITY WILL BE. MODE WILL BE
STORMS GROWING INTO A MIX OF SEMI-DISCRETE STORMS AND BROKEN BOWING
SEGMENTS WITH POTENTIAL EMBEDDED SUPERCELLS AS THEY TRANSIT THE
REGION.
THE PRIMARY HAZARD IS EXPECTED TO BE DAMAGING WINDS GIVEN THE STRONG
WINDS ALOFT AND SUFFICIENT LOW-LEVEL SHEAR FOR MESOVORTEX
DEVELOPMENT IN ANY BOWING SEGMENTS. A SLIGHTLY LOWER BUT STILL
NOTABLE THREAT IS LARGE HAIL GIVEN SUFFICIENT MID-LEVEL LAPSE RATES,
THE POTENTIAL FOR ROTATING STORMS, AND LOW FREEZING LEVELS. THERE IS
A TORNADO THREAT AS WELL, ALBEIT LOWER THAN WIND AND HAIL. PRIMARY
POTENTIAL LIMITING FACTOR IS THE CONTINUED EXPECTATION FOR MID-LEVEL
BACKING HODOGRAPHS TO HINDER LONG LIVED SUPERCELL DEVELOPMENT.
HOWEVER, SUFFICIENT LOW-LEVEL SHEAR AND HODOGRAPH CURVATURE EXISTS
THAT TORNADOES CANNOT BE RULED OUT BOTH IN A DISCRETE SUPERCELL OR
QLCS MESOVORTEX GENERATION IN A BOWING SEGMENT. PARTICULAR ATTENTION
IS NEEDED AS TO THE NORTHWARD EXTENT OF INSTABILITY TODAY AS IF
SUFFICIENT SURFACE-BASED INSTABILITY CAN REACH THE WARM FRONTAL
BOUNDARY, LOCALLY BACKED WINDS COULD ENHANCE SRH THERE.
TONIGHT, THE SURFACE LOW RESPONSIBLE FOR TODAYS SEVERE POTENTIAL
MOVES OFF TO THE NORTHEAST WITH COLD AIR SWEEPING IN BEHIND THE LOW.
RAIN MAY MIX WITH OR BRIEFLY CHANGE OVER TO SNOW AS THIS OCCURS WITH
LITTLE IN THE WAY OF ACCUMULATION EXPECTED.
- ADDITIONAL PRECIPITATION MID-WEEK
AFTER A DRY TUESDAY, PRECIPITATION RETURNS TO THE FORECAST BEGINNING
TUESDAY NIGHT WITH THE APPROACH OF OUR NEXT SYSTEM. THERMAL PROFILES
SUGGEST THAT SNOW AND OR FREEZING RAIN IS POSSIBLE AT ONSET,
PARTICULARLY NORTH OF I96. WARMING TEMPERATURES CHANGE
PRECIPITATION TO RAIN THURSDAY, WITH THE POTENTIAL FOR ORGANIZED
CONVECTION NOT OUT OF THE QUESTION LATER IN THE DAY GIVEN THE STRONG
DYNAMICS AND ADVECTION OF ENHANCED MOISTURE. SPECIFICS FOR THIS
SYSTEM WILL BECOME CLEARER IN THE FOLLOWING DAYS.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 152 AM EDT SUN MAR 30 2025
IFR/LIFR CONDITIONS WITH LOW STRATUS AND RAIN/DRIZZLE EXPECTED TO
CONTINUE THROUGH THE MORNING HOURS DUE TO A WARM FRONT WHICH IS
STALLED NEARBY. AZO/BTL/JXN WERE STILL MVFR TO VFR AT 06Z BUT
THE EXPECTATION IS FOR IFR TO OVERSPREAD THESES TERMINALS AS WELL
OVERNIGHT.
THE CHANCE FOR THUNDERSTORMS BEGINS AROUND 15Z, WHICH IS WHEN THE
CLUSTER CURRENTLY OVER IOWA TIMES INTO THE AREA. NO CHANGE TO THE
PREVIOUS TAFS IN THE THIS REGARD, WITH THE THREAT FOR THESE
STORMS MAINLY JUST AT MKG AND GRR. OTHERWISE THE PRIMARY WINDOW
FOR MORE WIDESPREAD CONVECTION LOOKS TO BE BETWEEN 20Z AND 24Z
SUNDAY WHEN A LINE OR CLUSTERS OF CELLS AHEAD OF THE COLD FRONT
WILL BE PASSING THROUGH. SOME OF THESE STORMS COULD BE SEVERE WITH
STRONG WIND GUSTS AND/OR HAIL.
ONCE STORMS EXIT TO THE EAST AFTER 00Z MONDAY, EXPECT MVFR TO IFR
CIGS TO LINGER IN THE THEIR WAKE.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 11 PM THIS EVENING TO 2 AM EDT TUESDAY
FOR LMZ844>849.
DISCUSSION...THOMAS
AVIATION...MEADE
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