020
FXUS63 KGRR 020601
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
201 AM EDT WED APR 2 2025
KEY MESSAGES
- WINTER WEATHER TONIGHT
- SEVERE WEATHER TOMORROW
UPDATE
ISSUED AT 1006 PM EDT TUE APR 1 2025
NO CHANGES WILL BE MADE TO THE GOING HEADLINES THIS EVENING. THIS
EVENING'S UPDATE WILL ONLY HAVE ONE MINOR CHANGE TO THE GOING
FORECAST. THAT CHANGE IS TO DELAY PRECIPITATION BY A FEW HOURS
BASED ON LATEST RADAR TRENDS, OBSERVATIONS UPSTREAM, AND LATEST
MODEL GUIDANCE ROLLING IN.
WE CURRENTLY ONLY HAVE MID AND HIGH LEVEL MOISTURE IN PLACE THIS
EVENING, WITH FAIRLY DRY AIR REMAINING IN PLACE AT THE SFC WITH AN
EASTERLY WIND. PRECIPITATION IS BLOSSOMING AS EXPECTED OUR TO OUR
SW OVER IL. WE HAVE ECHOES OVER OUR AREA, BUT IT IS ALL VIRGA THUS
FAR.
LATEST DATA SHOWS THAT OUR EARLIER THINKING OF SNOW BEGINNING, TO
SLEET/FREEZING RAIN FOR I-96 AND NORTH, TURNING TO ALL RAIN
WEDNESDAY MORNING IS STILL ON TRACK. WHILE THE I-96 CORRIDOR MAY
SEE A LITTLE SNOW, A LITTLE FREEZING RAIN, IT WILL BE VERY BRIEF,
AND SHOULD NOT CAUSE ANY SIGNIFICANT IMPACTS BEFORE IT WARMS
ENOUGH TO CHANGE IT TO RAIN.
NORTH OF I-96, IT IS STILL LOOKING LIKE A CLASSIC SETUP OF
FREEZING RAIN FOR A FEW HOURS, AND ICE ACCUMULATIONS UP TO A
QUARTER OF AN INCH LIKELY. THUS, THE ADVISORY REMAINS JUSTIFIED.
DISCUSSION
ISSUED AT 352 PM EDT TUE APR 1 2025
- WINTER WEATHER TONIGHT
A WINTER WEATHER ADVISORY HAS BEEN ISSUED FOR AREAS NORTH OF I-96
TONIGHT THROUGH NOON ON WEDNESDAY FOR A WINTRY MIX OF SNOW
CHANGING TO SLEET AND FREEZING RAIN. ICE ACCUMULATIONS MAY
APPROACH A QUARTER INCH ACROSS PARTS OF OSCEOLA, CLARE AND
ISABELLA COUNTIES BY LATE WEDNESDAY MORNING BEFORE TEMPERATURES
GET ABOVE FREEZING.
WARM ADVECTION/ISENTROPIC ASCENT INCREASES THIS EVENING WITH SNOW
EXPECTED TO BREAK OUT AFTER MIDNIGHT GENERALLY NORTH OF I-96.
THERMAL PROFILES SHOW THAT SNOW WILL MIX WITH SLEET AND FREEZING
RAIN BY DAYBREAK WITH GENERALLY 1 TO 3 INCHES OF SNOW ACROSS THE
ADVISORY AREA. ELEVATED INSTABILITY DURING THE MORNING COULD LEAD
TO SOME HEAVIER PRECIP RATES, WITH ICE PELLETS AND HEAVY FREEZING
RAIN CAUSING TRAVEL IMPACTS, PRIMARILY ACROSS THE HIGHER
ELEVATIONS OF OSCEOLA AND CLARE COUNTIES. WE WILL HAVE TO WATCH
PRECIP TRENDS DURING THE MORNING FOR THE POTENTIAL FOR HEAVY
FREEZING RAIN CAUSING POWER OUTAGES.
DEW POINTS ARE STARTING OUT IN THE TEENS TONIGHT AND WILL TAKE A
WHILE TO GET ABOVE FREEZING ON WEDNESDAY WITH THE SURFACE HIGH
ADVECTING COLD, DRY AIR INTO THE NORTHERN FORECAST AREA.
EVENTUALLY THE LOW LEVEL COLD ADVECTION GOES NEUTRAL AND RAIN
RATES AND DIURNAL WARMING BEGINS THE MELTING PROCESS.
- SEVERE WEATHER TOMORROW
AS THE WINTER WEATHER THREATS WIND DOWN NORTH OF I-96, THE SEVERE
WEATHER THREAT RAMPS UP SOUTH OF I-96. THE CONVECTIVE ALLOWING
MODELS SHOW TWO MAIN BATCHES OF CONVECTION, ONE AROUND 12Z AND
ANOTHER AROUND 00Z, OR A BIT LATER.
THE FIRST ROUND OF STORMS DURING THE MORNING IS ELEVATED AND THE
PRIMARY THREAT IS MINOR FLOODING OF POOR DRAINAGE AREAS THAT ARE
STILL SATURATED FROM THE RAIN ON SUNDAY, ALONG WITH SMALL HAIL.
THIS MOVES EAST DURING THE AFTERNOON AND THE CONDITIONAL
PROBABILITY FOR SEVERE WEATHER FROM THE LATER ROUND OF STORMS WILL
DEPEND ON HWO MUCH AIR MASS RECOVERY OCCURS DURING THE AFTERNOON.
THE CURRENT THINKING IS THAT THERE WILL BE SEVERAL HOURS DURING
THE LATE AFTERNOON INTO THE EARLY EVENING WHEN SFC HEATING IS
POSSIBLE. THE SHEAR PROFILES AND HODOGRAPHS SHOWN BY MOST MODEL
GUIDANCE ACROSS THE SOUTHERN HALF OF THE FORECAST AREA AT THAT
TIME ARE FRIGHTENING WITH OVER 65 KNOTS OF DEEP LAYER SHEAR AND
0-1 KM HELICITY IN THE 400 TO 500 RANGE! ANY DEEP UPDRAFTS
OCCURRING AT THAT TIME CERTAINLY HAVE THE POTENTIAL FOR
SIGNIFICANT SEVERE WEATHER. THE CAMS INDICATE A LINEAR MODE OF
CONVECTION TOMORROW EVENING, WITH THE POTENTIAL FOR DISCRETE CELLS
AS WELL.
AS AN ASIDE, TOMORROW MARKS THE 48TH ANNIVERSARY OF THE LAST F4
TORNADO IN MICHIGAN.
HEAVY RAIN COULD ALSO CAUSE SOME MINOR FLOODING BY TOMORROW
EVENING. SEE HYDRO SECTION BELOW FOR DETAILS.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 200 AM EDT WED APR 2 2025
A BAND ON SNOW IS CURRENTLY MOVING THROUGH NORTHERN PORTIONS OF
THE AREA IMPACTING MOP, RBQ, LDM AND NORTH WITH ACCUMULATIONS
AROUND 1 TO 2 INCHES OVER THE NEXT FEW HOURS. RAIN AND SNOW
SHOWERS WILL THEN EXPAND OVER THE AREA EARLY THIS MORNING WITH A
WINDOW OF FREEZING RAIN POSSIBLE EARLY THIS MORNING FOR MKG, GRR,
AND LAN. FREEZING RAIN ACCUMULATIONS ARE MORE LIKELY NORTH OF
THESE SITES.
ANY FROZEN PRECIPITATION TRANSITIONS TO RAIN THIS MORNING WITH
SOME EMBEDDED THUNDERSTORMS. CEILINGS WILL GRADUALLY DROP TO LIFR
VALUES WITH BRIEF PERIODS OF LIFR POSSIBLE. THERE IS SOME
UNCERTAINTY IN THE TIMING OF THUNDERSTORMS THROUGHOUT THE DAY, BUT
A LULL IS POSSIBLE WEDNESDAY AFTERNOON BEFORE THUNDERSTORMS
RETURN IN THE EVENING.
LOW LEVEL WIND SHEAR WILL BE PRESENT THROUGHOUT THE DAY INITIALLY
FROM THE SOUTHEAST AND THEN BECOMING SOUTHWESTERLY WEDNESDAY
EVENING AS THE WARM FRONT MOVES NORTH OF THE AREA. SURFACE WINDS
CURRENTLY FROM THE EAST GUSTING TO AROUND 25 KNOTS WILL INCREASE
WITH GUSTS AROUND 30-35 KNOTS THIS MORNING BEFORE SHIFTING TO THE
SOUTHWEST WEDNESDAY EVENING.
GRR AIRPORT DSS UPDATE:
THERE IS A SLIGHT TIME ADJUSTMENT FOR THE WINDOW OF FREEZING RAIN
THAT WAS PROVIDED EARLIER. THE BEST WINDOW FOR ANY FREEZING RAIN
WILL BE BETWEEN 5-8AM BEFORE WARMER TEMPERATURES CAUSE A
TRANSITION TO RAIN. OTHERWISE NO OTHER CHANGES TO THE PREVIOUS
FORECAST.
EAST TO SOUTHEAST WINDS GUSTING AROUND 25 KNOTS CONTINUE WITH
GUSTS INCREASING TO AROUND 30 KNOTS WEDNESDAY MORNING.
MARINE
ISSUED AT 352 PM EDT TUE APR 1 2025
REPLACED THE GALE WATCH WITH A GALE WARNING FOR LATE TONIGHT
THROUGH WEDNESDAY EVENING. SOUTHEAST WINDS WILL GUST TO 35 KNOT
GALES AT TIMES. THE OFFSHORE COMPONENT OF THE WINDS WILL KEEP THE
HIGHEST WAVES WELL OFFSHORE, WITH 4 TO 6 FOOT WAVES MOSTLY
CONFINED TO OUT BEYOND A COUPLE MILES FROM SHORE.
THERE COULD ALSO BE WINDS GUSTING OVER 40 KNOTS WEDNESDAY EVENING
AS A LINE OF THUNDERSTORMS MOVES ACROSS THE LAKE. HAIL AND EVEN
WATERSPOUTS ARE POSSIBLE WITH THESE STORMS.
A SMALL CRAFT ADVISORY WILL BE NEEDED TO REPLACE THE GALE WARNING
LATER WEDNESDAY NIGHT. CONDITIONS WILL IMPROVE ON THURSDAY AS
HIGH PRESSURE BUILDS IN AND WINDS DECREASE TO LESS THAN 25 KNOTS
DURING THE AFTERNOON.
HYDROLOGY
ISSUED AT 352 PM EDT TUE APR 1 2025
SEVERAL ROUNDS OF SHOWERS AND STORMS ARE EXPECTED TO SWEEP ACROSS
LOWER MICHIGAN BETWEEN WEDNESDAY MORNING AND LATE WEDNESDAY
EVENING. WE'RE EXPECTING MOST LOCATIONS TO RECEIVE BETWEEN 1 AND
1.5 INCHES OF RAIN DURING THIS TIME, THOUGH DEPENDING ON HOW THE
CLUSTERS OF THUNDERSTORMS EVOLVE SOME LOCATIONS COULD EASILY 2.5
INCHES OR MORE. IF THUNDERSTORMS MOVE OVER THE SAME AREAS
REPEATEDLY, WE MAY OVERWHELM LOCAL DRAINAGES AND RESULT IN SOME
GENERAL FLOODING CONCERNS AS WE GO THROUGH THE DAY WEDNESDAY.
AS THE RAIN THAT FALLS TOMORROW STARTS MAKING ITS WAY INTO OUR
RIVERS, WE'LL BE MONITORING FOR POSSIBILITY OF OVERFLOWING SOME OF
THE RIVERS. CURRENTLY, THE MUSKEGON RIVER IS THE ONLY LARGE RIVER
SYSTEM IN OUR AREA THAT IS RUNNING HIGHER THAN NORMAL - MOSTLY DUE
TO RECENT HEAVY RAINS AND SNOWMELT IN NORTHERN LOWER MICHIGAN. IF
RAIN TOTALS TOMORROW IN THIS AREA START TO SURPASS THE EXPECTED 1
INCH TOTALS, WE MAY BE LOOKING AT PUSHING SOME OF THE LOWER RIVER
AREAS (NEWAYGO AND BRIDGETON) INTO THE MINOR/NUISANCE FLOODING
CATEGORY.
MEANWHILE, MOST OF THE RIVERS IN THE GRAND AND KALAMAZOO RIVER
WATERSHEDS ARE NEAR OR SLIGHTLY BELOW AVERAGE FOR THIS TIME OF YEAR,
SO WE'VE GOT A DECENT AMOUNT OF SPACE IN THESE RIVERS TO FILL UP.
HOWEVER, IF RAIN TOTALS ACROSS A LARGE AREA START TO PASS THE 2 INCH
MARK, WE MAY EVENTUALLY START TO SEE SOME MINOR FLOODING AT A FEW
SPOTS AROUND LANSING AND DOWNSTREAM IN COMSTOCK PARK. HOWEVER, IF
RAIN TOTALS STAY IN THE 1 TO 1.5 INCH RANGE IN THIS AREA, WE'LL
BRING WATER LEVELS UP TO BANKFULL BUT THAT WILL PROBABLY BE ABOUT
IT.
GRR WATCHES/WARNINGS/ADVISORIES
MI...WINTER WEATHER ADVISORY UNTIL NOON EDT TODAY FOR MIZ037>040-
043>046-051-052.
MARINE...GALE WARNING UNTIL 11 PM EDT THIS EVENING FOR LMZ844>849.
UPDATE...NJJ
DISCUSSION...OSTUNO
AVIATION...RAH
MARINE...OSTUNO
HYDROLOGY...AMD
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