537
FXUS63 KGRR 301540
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1140 AM EDT SUN MAR 30 2025
KEY MESSAGES
- SEVERE THUNDERSTORMS POSSIBLE TODAY
- ADDITIONAL PRECIPITATION MID-WEEK
UPDATE
ISSUED AT 1139 AM EDT SUN MAR 30 2025
THE STORM PREDICTION CENTER HAS INCREASED THE SEVERE STORM RISK
ACROSS THE AREA TODAY AS THE SLIGHT RISK (LEVEL 2 OUT OF 5) WAS
MOVED NORTHWARD AS WAS THE ENHANCED RISK (LEVEL 3 OUT OF 5). THE
THREAT IN THOSE TWO RANGES NOW COVERS MOST OF THE SOUTHWEST
QUARTER OF LOWER MICHIGAN, WITH THE HIGHEST RISK BEING IN THE
SOUTH ALONG AND NEAR I-94.
AT 1100AM A SURFACE LOW WAS CENTERED IN NORTHEAST IOWA WITH A COLD
FRONT EXTENDING SOUTH INTO MISSOURI AND A WARM FRONT SITUATED TO
THE EAST ACROSS LAKE MICHIGAN AND THROUGH THE LOWER PENINSULA. IN
OUR AREA THE WARM FRONT IS POSITIONED FROM NEAR HOLLAND EASTWARD
INTO THE SOUTHERN METRO AREA OF GRAND RAPIDS THROUGH SOUTHERN
IONIA COUNTY TO NEAR DEWITT IN SOUTHERN CLINTON COUNTY. IN THE
OPEN WARM SECTOR OF THIS SYSTEM (ILLINOIS, INDIANA AND SOUTHERN
LOWER MICHIGAN) DEW POINTS HAVE SURGED INTO THE LOWER TO MIDDLE
60S WITH CLEARING NOW TAKING PLACE OVER PORTIONS OF ILLINOIS AHEAD
OF THE COLD FRONT. THE OPEN WARM SECTOR SHOULD PUSH NORTHWARD IN
OUR FORECAST AREA TO PORTIONS OF CENTRAL LOWER MICHIGAN
POTENTIALLY.
INSTABILITY HAS BEEN ON THE INCREASE THIS MORNING OFF TO OUR SOUTH
GIVEN THE RISING DEW POINTS AND NOW DAYTIME HEATING. 1000 J/KG
MOST UNSTABLE CAPE VALUES HAVE PUSHED AS FAR NORTH AS SOUTHERN
LAKE MICHIGAN OFF SHORE OF MUSKEGON. 2000 J/KG MUCAPE VALUES HAVE
DEVELOPED INTO SOUTHERN ILLINOIS. WE EXPECT 1000-2000 J/KG MUCAPE
VALUES TO REACH AT LEAST THE I-96 CORRIDOR IF NOT POINTS A BIT
FURTHER NORTH. SO, PLENTY OF INSTABILITY WILL BE IN PLACE. LIFT
WILL BE PROVIDED BY THE APPROACHING SURFACE LOW AND COLD FRONT AND
MORE SO THE MID LEVEL UPPER WAVE THAT DRIVES IN THIS AFTERNOON
AND EVENING. DEEP LAYER SHEAR (0-6KM) WILL BE IN THE 40-55 KNOT
RANGE AS THE STORMS SWEEP THROUGH, SO ALL INGREDIENTS WILL BE IN
PLACE FOR THE POTENTIAL OF SEVERE WEATHER.
WE EXPECT A BROKEN LINE OF STORMS TO SWEEP NORTHEAST THROUGH THE
AREA, LIKELY DURING THE 300PM TO 900PM TIME FRAME. THE MAIN THREAT
GIVEN SEASONABLY STRONG WINDS THROUGH THE DEPTH OF THE PROFILE
WILL BE DAMAGING WINDS. HAIL WITH THE STRONGEST CORES HAS THE
POTENTIAL TO REACH SEVERE LEVELS AS WELL, IN EXCESS OF 1 INCH.
ISOLATED TORNADOES WILL BE POSSIBLE TOO GIVEN ALL THE
AFOREMENTIONED PARAMETERS. ROTATING STORMS WITHIN THE LINE WILL BE
MONITORED FOR THIS THREAT, ESPECIALLY ONES ABLE TO INTERACT WITH
THE NORTHWARD RETREATING WARM FRONT THAT WILL LIKELY BE NORTH OF
I-96 AS THE LINE MOVES IN WHILE RACING NORTHEAST. MOST CONVECTION
ALLOWING MODELS WITHIN THE HREF ARE NOT SHOWING WIDESPREAD
UPDRAFT HELICITY SWATHS, BUT THE ARW AND FV3 HAVE BEEN. THEY HAVE
BEEN CONSISTENT IN SHOWING A LONG DURATION ROTATING UPDRAFT
THROUGH OUR AREA (FROM SW TO NE) AND THEREFORE WE WILL BE
MONITORING FOR THAT POSSIBILITY.
BOTTOM LINE...SEVERE WEATHER THREAT IS ELEVATED TODAY GIVEN THE
PARAMETER SPACE WILL ALL HAZARDS POSSIBLE. MAIN THREAT TIME 3-9 PM
ACROSS THE ENTIRE AREA.
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 /12Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 752 AM EDT SUN MAR 30 2025
WIDESPREAD IFR/LIFR CONDITIONS IN LOW STRATUS AND LIGHT
RAIN/DRIZZLE PERSISTING THIS MORNING WITH WARM FRONT STALLED IN
THE VICINITY. CONDITIONS TRENDING TOWARD MVFR THIS AFTERNOON FROM
SOUTH TO NORTH AS THE WARM FRONT LIFTS NORTHWARD.
THE THUNDERSTORMS CURRENTLY IN SRN WI/NRN IL ARE EXPECTED TO
IMPACT MKG AND POSSIBLY GRR FOR A COUPLE HOURS ROUGHLY 14-16Z.
OTHERWISE THE PRIMARY RISK FOR STORMS OCCURS BETWEEN 21Z AND 01Z
AND SOME OF THE STORMS COULD BE SEVERE WITH STRONG WIND GUSTS
AND/OR HAIL.
WINDS INCREASING OUT OF THE SOUTH TO 15-25 KTS THIS AFTERNOON,
VEERING SOUTHWEST BEHIND A COLD FRONTAL PASSAGE THIS EVENING THEN
WESTERLY OVERNIGHT. RAIN CHANCES DECREASE SUBSTANTIALLY AFTER THE
STORMS DEPART TO THE EAST TONIGHT BUT MVFR TO IFR CIGS EXPECTED
TO LINGER IN 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.
UPDATE...DUKE
DISCUSSION...THOMAS
AVIATION...MEADE
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