528
FXUS63 KGRR 291150
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
750 AM EDT SAT MAR 29 2025
KEY MESSAGES
- SHOWERS AND CHANCE OF STORMS TODAY AND TONIGHT
- SEVERE WEATHER POSSIBLE SUNDAY, HIGHEST CHANCE NEAR AND SOUTH OF
M46
- ADDITIONAL SHOWER AND STORM CHANCES MID-NEXT WEEK
DISCUSSION
ISSUED AT 319 AM EDT SAT MAR 29 2025
- SHOWERS AND CHANCE OF STORMS TODAY AND TONIGHT
A WARM FRONTAL BOUNDARY SITS ACROSS THE CENTRAL PART OF THE STATE
THIS MORNING, AND IS EXPECTED TO DRIFT SOUTH TO NEAR I96 BY TONIGHT.
SHOWERS AND STORMS WILL IN INITIALLY BE LIMITED TO ALONG THE
BOUNDARY BUT EXPAND AREAWIDE AS A LOW-PRESSURE SYSTEM MOVES INTO THE
GREAT LAKES REGION LATER TODAY AND TONIGHT. CANNOT RULE OUT SOME
ISOLATED THUNDER THROUGH MID-MORNING NORTH OF I96 WHERE MARGINAL
ELEVATED INSTABILITY IS IN PLACE.
- SEVERE WEATHER POSSIBLE SUNDAY, HIGHEST CHANCE NEAR AND SOUTH OF
M46
ATTENTION THEN TURNS TO SUNDAY AS INCREASING SOUTHERLY FLOW DRIVES
THE WARM FRONTAL BOUNDARY NORTH LEADING TO WARM SECTOR DEVELOPMENT
ACROSS MUCH OF THE CWA. MUCAPE VALUES IN THE 1000-2000 J/KG RANGE
WITH SURFACE BASED CONVECTION AND 30-40 KNOTS OF EFFECTIVE SHEAR
WILL BE SUFFICIENT FOR CONVECTIVE ORGANIZATION IN THE AFTERNOON AND
EVENING. THE STORM PREDICTION CENTER CURRENTLY HAS A SLIGHT (2/5)
RISK OF SEVERE THUNDERSTORMS FOR THE SOUTHERN TWO-THIRDS OF THE AREA
WHICH ALIGNS WELL WITH EXPECTATIONS BASED ON FORECAST SOUNDINGS.
GREATEST CONCERN IS SOUTH OF M46 WHERE THE BEST SURFACE BASED
INSTABILITY WILL BE PRESENT.
ALL SEVERE HAZARDS ARE POSSIBLE IN THE FORECAST ENVIRONMENT. THERMAL
AND WIND PROFILES SUGGEST STORM CLUSTERS/A BROKEN LINE AS THE
PRIMARY MODE, SUPPORTED BY CAMS. STORM MODE AND SUFFICIENT DCAPE
SUGGEST DAMAGING WINDS AS THE PRIMARY THREAT. STEEP MID-LEVEL
LAPSE RATES WILL ALSO DRIVE A LARGE HAIL THREAT. TORNADO THREAT
IS ALSO PRESENT GIVEN THE NEARBY WARM-FRONTAL BOUNDARY
POTENTIALLY LOCALLY ENHANCING SRH. ONE LIMITING FACTOR FOR
TORNADOES HOWEVER IS THAT MODEL HODOGRAPHS HAVE CONSISTENTLY HAD
A "VEER- BACK" SIGNATURE IN THE 1-3 KM RANGE WHICH WOULD LOWER
STREAMWISE VORTICITY AVAILABILITY. ONE POTENTIAL FAILURE MODE TO
WATCH IS FOR EARLIER PRECIPITATION TO LIMIT THE AVAILABLE LOW-
LEVEL INSTABILITY, SO SKY AND PRECIPITATION COVERAGE WILL NEED TO
BE MONITORED SUNDAY MORNING.
- ADDITIONAL SHOWER AND STORM CHANCES MID-NEXT WEEK
BEHIND A COLD FRONT LATER SUNDAY INTO SUNDAY NIGHT, PRECIPITATION
WILL MIX WITH OR BRIEFLY CHANGE OVER TO SNOW AS THE SURFACE LOW
PULLS AWAY. GIVEN WARM ANTECEDENT CONDITIONS ACCUMULATIONS WILL BE
LITTLE. TUESDAY THEN WILL BE DRY AS SURFACE AND MID-LEVEL RIDGING
WILL BE PRESENT.
A LOW PRESSURE SYSTEM THEN CROSSES THE GREAT LAKES REGION NEXT
WEDNESDAY INTO THURSDAY. THE OVERALL SETUP LOOKS SIMILAR TO THIS
WEEKEND WITH WARM SECTOR SHOWERS AND STORMS FOLLOWED BY A
TRAILING COLD FRONTAL BOUNDARY. THIS WILL SUPPORT THE REGION
RECEIVING 1-2 INCHES OF RAIN BY LATE NEXT WEEK. LREF MEMBER
ENSEMBLES ARE CONSISTENT IN BRINGING A DYNAMIC KINEMATIC
ENVIRONMENT WITH THIS SYSTEM. GIVEN THE AMPLE MOISTURE RETURN
AHEAD OF THE SYSTEM CONVECTIVE ORGANIZATION POTENTIAL CANNOT BE
RULED OUT AND WILL NEED TO BE MONITORED.
AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 750 AM EDT SAT MAR 29 2025
WINDS HAVE SETTLED DOWN QUITE A BIT FROM 6-8 HOURS AGO ALTHOUGH AN
HOUR OR TWO OF LLWS IS STILL POSSIBLE. OTHERWISE WE HAVE VFR CIGS
OF 4000-6000 FT THROUGH THE MORNING THEN TRENDING MVFR FROM NORTH
TO SOUTH THIS AFTERNOON AND EVENING. CONDITIONS TURNING
PREDOMINATELY IFR LATER TONIGHT AFTER MIDNIGHT. SCATTERED SHOWERS
DEVELOPING BY AFTERNOON AND WHILE A TSTM CANNOT BE RULED OUT THE
PROBABILITY IS TOO LOW TO INCLUDE IN THE TAFS AT THIS TIME.
SOUTHWEST WINDS 10 TO 20 KTS TODAY BECOMING SOUTH 5 TO 10 KTS
TONIGHT.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 AM EDT THIS MORNING FOR LMZ844>849.
DISCUSSION...THOMAS
AVIATION...MEADE
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