296
FXUS63 KGRR 141734
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
134 PM EDT WED MAY 14 2025
KEY MESSAGES
- HAIL AND HIGH WINDS THURSDAY EVENING THEN GUSTY WINDS ON FRIDAY
INTO SATURDAY
DISCUSSION
ISSUED AT 328 AM EDT WED MAY 14 2025
ANOTHER DAY OF MOSTLY AFTERNOON SHOWERS AND THUNDERSTORMS TODAY
AS THE UPPER LOW RESULTS IN SOME DIURNAL ENHANCEMENT OF THE
SHOWERS. COASTAL FOG IS POSSIBLE NEAR LAKE MICHIGAN THIS AFTERNOON
IF WINDS COME ONSHORE.
THE MAIN FORECAST CONCERN REMAINS THE SEVERE WEATHER POTENTIAL
THURSDAY EVENING. AN UPPER TROUGH MOVES EAST WITH CYCLOGENESIS
ACROSS THE DAKOTAS AND THE SFC LOW DEEPENING TO NEAR 980 MB AS IT
MOVES INTO MINNESOTA. AN ADVANCING COLD/OCCLUDED FRONT MOVES INTO
THE MOIST AND UNSTABLE AIR MASS ACROSS LOWER MICHIGAN TRAVERSING
THE FORECAST AREA ROUGHLY BETWEEN 8 PM AND 2 AM.
SHEAR PROFILES SHOW POTENTIAL FOR ORGANIZED SEVERE WITH
SUFFICIENT MID LEVEL LAPSE RATES FOR DEEP UPDRAFTS AND LOW LEVEL
HELICITY SUFFICIENT FOR ROTATING UPDRAFTS. MAIN THREATS ARE LARGE
HAIL, DAMAGING DOWNBURSTS AND TRANSIENT TORNADOES. THE SEVERE
THREAT WINDS DOWN AFTER MIDNIGHT AS THE DEEP MOISTURE EXITS TO THE
EAST.
FRIDAY SHOULD BE BREEZY WITH A GOOD AMOUNT OF SUNSHINE, THOUGH
ENSEMBLE MEMBERS ARE FAR FROM SETTLED WHETHER THIS WILL BE A DAY
WITH GUSTS AROUND 30 MPH OR 40-45 MPH. A SHORTWAVE TROUGH ROUNDING
THE BASE OF THE LOW AND A PROXIMATE COLD FRONT MAY TOUCH OFF A
QUICK ROUND OF SHOWERS LATE FRI EVENING, PERHAPS THUNDERSTORMS IN
SOUTHERN MICHIGAN GIVEN THE POTENTIAL FOR INSTABILITY REBUILDING
TO 500-1000 J/KG.
SATURDAY DOES HAVE THE POTENTIAL TO BE ANOTHER BREEZY DAY,
THOUGH THE MAGNITUDE OF PEAK GUSTS IS STILL QUESTIONABLE AMONG THE
ENSEMBLES, DEPENDENT ON THE PRESSURE GRADIENT BETWEEN THE LOW OVER
THE NORTHERN GREAT LAKES AND THE HIGH OVER THE SE US.
CANADIAN SFC HIGH BUILDS IN EARLY NEXT WEEK WITH POTENTIAL FOR
SCATTERED FROST SUNDAY NIGHT AND MONDAY NIGHT.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 131 PM EDT WED MAY 14 2025
SCATTERED SHOWERS ARE ONGOING ACROSS WEST MICHIGAN, WITH ISOLATED
THUNDERSTORMS POSSIBLE AT ALL TERMINALS. CONFIDENCE IN DIRECT
IMPACTS TO A TERMINAL IS LOW, BUT IFR CONDITIONS ARE POSSIBLE IF A
STORM DOES IMPACT A TERMINAL. WILL MONITOR TAFS AND AMEND AS
NEEDED.
TONIGHT, INCREASING DEWPOINTS WILL LEAD TO AREAS OF MVFR FOG,
PARTICULARALLY AT MKG, LAN, AND JXN, AND POSSIBLY MVFR CIGS AS
WELL. THE LIKELY TIMEFRAME IS 09Z-13Z BEFORE ANY FOG MIXES OUT
BRINGING MVFR CONDITIONS THROUGH THE REMAINDER OF THE PERIOD.
MARINE
ISSUED AT 328 AM EDT WED MAY 14 2025
NO CHANGES TO THE FOG ADVISORY, ALTHOUGH IT MAY NEED TO BE
EXTENDED IF WINDS ARE NOT STRONG ENOUGH TO DISPERSE IT THIS
AFTERNOON. DEW POINTS IN THE UPPER 50S AND 60S WILL CONTINUE
THROUGH TONIGHT SO FOG WILL CONTINUE, BUT INCREASING WINDS ON
THURSDAY COULD MITIGATE DENSE FOG.
STRONG THUNDERSTORMS ARE POSSIBLE THURSDAY EVENING THEN WINDS
BEHIND THE STORMS ON FRIDAY OF 20 TO 25 KNOTS WILL BUILD WAVES
GREATER THAN 4 FEET INTO SATURDAY.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...DENSE FOG ADVISORY UNTIL 8 PM EDT THIS EVENING FOR LMZ844>849.
DISCUSSION...OSTUNO
AVIATION...THOMAS
MARINE...OSTUNO
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