958
FXUS63 KGRR 142357
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
757 PM EDT WED MAY 14 2025
KEY MESSAGES
- SCATTERED SHOWERS AND STORMS INTO THIS EVENING
- ROUND OF STRONG TO SEVERE STORMS THURSDAY EVENING
- ADDITIONAL CHANCES FOR SHOWERS AND GUSTY WINDS
DISCUSSION
ISSUED AT 213 PM EDT WED MAY 14 2025
- SCATTERED SHOWERS AND STORMS INTO THIS EVENING
THIS AFTERNOON MIXED LAYER CAPE VALUES OF 500-1000 J/KG AND HIGH
PRECIPITABLE VALUES AROUND 1.4 INCHES WILL BE PRESENT. SHEAR
HOWEVER IS LACKING, THEREFORE ONLY EXPECTING GENERAL THUNDERSTORMS
WITH HEAVY DOWNPOURS AS SEEN MY THE MOIST SOUNDING PROFILES. BEST
COVERAGE COULD BE ALONG THE LAKE BREEZE AS IT WILL AID IN A SOURCE
OF LIFT THIS AFTERNOON WITH ISOLATED TO SCATTERED COVERAGE
ELSEWHERE. THUNDERSTORMS SHOULD TAPER OFF AFTER SUNSET AS THE
INVERSION BUILDS IN WITH LIGHT AND VARIABLE WINDS OVERNIGHT. THE
MOISTURE TRAPPED BELOW THE INVERSION COULD DEVELOP INTO AREAS OF
FOG INTO THURSDAY MORNING.
- ROUND OF STRONG TO SEVERE STORMS THURSDAY EVENING
DURING THE DAY, THURSDAY IS EXPECTED TO BE DRY AS WARM AIR ALOFT
PREVENTS ANY THUNDERSTORM. DEW POINTS WILL CONTINUE TO BE IN THE
60S AS WE REMAIN IN OUR MOIST ENVIRONMENT WITH PRECIPITABLE WATER
VALUES AROUND 1.5 INCHES. WARM AIR ADVECTION AHEAD OF THE
925-850MB FRONT WILL HELP ERODE OUR CAP ALLOWING FOR THUNDERSTORMS
TO TAP INTO 2000 J/KG + OF CAPE AND 30-40 KNOTS OF SHEAR THURSDAY
EVENING. THERE IS AMPLE DIRECTIONAL SHEAR IN THE LOW LEVELS
CREATING PLENTY OF SPIN IN THE ENVIRONMENT WHICH IS FAVORABLE FOR
STORMS TO ROTATE. MID LEVEL LAPSE RATES WILL ALSO BE FAVORABLE
FOR HAIL DEVELOPMENT. WITH THESE VARIABLES LARGE HAIL (30 PERCENT
CHANCE OF 2 INCH DIAMETER HAIL OR LARGER), DAMAGING WINDS, AND
TORNADOES.
THE MAIN WINDOW FOR SEVERE STORMS WILL BE BETWEEN 8PM THURSDAY TO
2AM FRIDAY FROM WEST (US 31) TO EAST (US 127). THERE IS SOME
UNCERTAINTY WITH THE SOUTHERN EXTENT DUE TO SOME DRIER AIR IN THE
MID LEVELS, EITHER WAY IF STORMS DEVELOP THEY HAVE A HIGH
PROBABILITY OF BECOMING SEVERE. WITH STORMS OCCURING OVERNIGHT,
MAKE SURE YOU HAVE A WAY TO RECEIVE WARNINGS AND THAT YOU HAVE A
PLAN TO TAKE SHELTER.
- ADDITIONAL CHANCES FOR SHOWERS AND GUSTY WINDS
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. LINGERING
SHOWERS ARE POSSIBLE THROUGH THE MORNING HOURS BEFORE DRYING OUT
DURING THE AFTERNOON.
CANADIAN SFC HIGH BUILDS IN EARLY NEXT WEEK WITH POTENTIAL FOR
SCATTERED FROST SUNDAY NIGHT AND MONDAY NIGHT.
AVIATION /00Z TAFS THROUGH 00Z FRIDAY/
ISSUED AT 757 PM EDT WED MAY 14 2025
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS CONTINUE TO POP UP
OVER MUCH OF LOWER MICHIGAN, BUT HAVE SO FAR DONE A GOOD JOB OF
STAYING VICINITY OR DISTANT THE SOUTH-CENTRAL AND SOUTHWEST
MICHIGAN TAF AIRPORTS. CONVECTION SHOULD GRADUALLY DIMINISH OVER
THE NEXT SEVERAL HOURS. SCATTERED CLOUDS OVERNIGHT WITH LIGHT
WINDS AND AREAS OF HIGHER MOISTURE NEAR THE GROUND COULD LEAD TO
PATCHY FOG DEVELOPMENT FEET BY EARLY MORNING. WENT WITH MVFR FOR
NOW FOR THE TAFS. LATEST SHORT-TERM MODEL GUIDANCE SUGGESTS IFR
IS MORE PROBABLE OVER CENTRAL MICHIGAN, NORTH OF GRR AND LAN
TOWARD MOP AND RQB. MUCH OF LATER THURSDAY MORNING THROUGH MUCH OF
THE AFTERNOON IS LIKELY TO BE VFR. THUNDERSTORMS WILL LIKELY NEED
TO BE INTRODUCED IN THE NEXT ROUTINE SET OF TAFS FOR LATE
THURSDAY EVENING (FROM 00 OR 01 Z).
MARINE
ISSUED AT 757 PM EDT WED MAY 14 2025
AREAS OF DENSE FOG CONTINUE OVER LAKE MICHIGAN AS MOIST AIR SITS
OVER THE COLD WATER. HAVE EXTENDED THE DENSE FOG ADVISORY THROUGH
NOON EDT THURSDAY AS AREAS OF DENSE FOG REMAIN OVER THE NEARSHORE
WATERS AND UP AGAINST THE SHORELINES AT SOME LOCATIONS. LATEST
SHORT TERM MODEL GUIDANCE DOES INDICATE A WEAK LAND BREEZE MAY
PUSH THE FOG SOME DISTANCE AWAY FROM SHORE TONIGHT INTO THURSDAY
MORNING, BUT THE CHANCE OF DENSE FOG DOESN'T APPEAR TO FULLY GO
AWAY UNTIL STRONGER SOUTH-SOUTHEAST WINDS DEVELOP THURSDAY
AFTERNOON.
THUNDERSTORMS ARE LIKELY THURSDAY EVENING AS A COLD FRONT MOVES
ACROSS THE LAKE. STRONG TO SEVERE STORMS ARE POSSIBLE, WITH SEVERE
STORMS CAPABLE OF GUSTS IN EXCESS OF 40 KNOTS AND LARGE HAIL.
SOUTHERLY WINDS FRIDAY VEER TO WESTERLY BY SATURDAY WITH WINDS OF 15-
20 KNOTS. GUSTS TO 30 KNOTS AND WAVES IN EXCESS OF 4 FEET ARE LIKELY
TO BRING CONDITIONS HAZARDOUS TO SMALL CRAFT.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...DENSE FOG ADVISORY UNTIL NOON EDT THURSDAY FOR LMZ844>849.
DISCUSSION...RAH
AVIATION...CAS
MARINE...CAS/THOMAS
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