996
FXUS63 KGRR 091645
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1245 PM EDT MON JUN 9 2025
KEY MESSAGES
- UPPER LOW SPAWNS AFTERNOON SHOWERS
- INCREASING CONFIDENCE IN RAIN/CONVECTION LATE WEEK
DISCUSSION
ISSUED AT 328 AM EDT MON JUN 9 2025
- UPPER LOW SPAWNS AFTERNOON SHOWERS
THE CORE REGION OF THE UPPER LOW MOVES IN THIS AFTERNOON AND
STEEPENING LAPSE RATES COMBINE WITH DEEP MOISTURE TO BRING A
DIURNAL ENHANCEMENT OF SHOWERS AND THUNDERSTORMS FROM MID
AFTERNOON INTO THE EVENING. MODEL SOUNDINGS SHOW POTENTIAL FOR PEA
SIZED HAIL WITH PERSISTENT UPDRAFTS OVER 20 KFT. SHOWERS DIMINISH
AFTER SUNSET WITH A LESSER CHANCE OF DIURNAL ENHANCEMENT ON
TUESDAY AS THE UPPER LOW MOVES OUT.
- INCREASING CONFIDENCE IN RAIN/CONVECTION LATE WEEK
LONGER RANGE MODEL GUIDANCE IS COMING INTO BETTER AGREEMENT ON THE
POTENTIAL FOR CONVECTION AND POSSIBLE MCS DEVELOPMENT THURSDAY
INTO FRIDAY ALONG A BAROCLINIC ZONE/STALLED FRONT IN THE VICINITY
OF IOWA OR SOUTHERN MINNESOTA THAT PROPAGATES EAST AND POTENTIALLY
BRINGS RAIN AND CONVECTIVE STORMS INTO LOWER MICHIGAN. THERE IS
STILL SOME SPREAD IN WHERE THIS FRONT SETS UP AND WHERE THE MCS
TRACKS, SO FORECAST CONFIDENCE IS MODERATE. THE CURRENT NBM
POPS/TIMING APPEARS TO BE A GOOD COMPROMISE OF MODEL DIFFERENCES.
AVIATION /12Z TAFS THROUGH 12Z TUESDAY/
ISSUED AT 1245 PM EDT MON JUN 9 2025
THE MAIN FOCUS OF THIS SET OF FORECASTS WILL BE ON THE CONVECTION
EXPECTED TO DEVELOP THIS AFTERNOON AND MOVE THROUGH BY MID
EVENING. MID CLOUDS HAVE MOVED OVER MOST OF THE TERMINALS EARLY
THIS AFTERNOON, ALL VFR IN NATURE SO FAR. WE ARE EXPECTING SHOWERS
AND STORMS TO BEGIN DEVELOPING TOWARD 19Z ALONG THE LAKESHORE, AND
THEN BECOMING MORE WIDESPREAD AND MOVING EAST THROUGH ABOUT 01-02Z
THIS EVENING. CONDITIONS UNDER THE CONVECTION ARE LIKELY TO DROP
TO IFR. FURTHER INLAND WILL HAVE A BETTER CHANCE OF MORE WIND GUST
POTENTIAL AS THE STORMS ORGANIZE AWAY FROM LAKE MICHIGAN.
ONCE THE STORMS MOVE EAST OF THE AREA, WE SHOULD SEE SOME CLEARING
TAKE PLACE, BUT SCATTERED CLOUDS WILL REMAIN THROUGH THE NIGHT.
THESE SHOULD BE VFR. FOG POTENTIAL IS NOT ZERO WITH THE RAINFALL
EXPECTED, BUT A PERSISTENT WIND STAYING UP THROUGH THE NIGHT
SHOULD MITIGATE THE POTENTIAL ENOUGH TO KEEP OUT OF THE FORECAST
FOR NOW.
WE WILL SEE MORE EXTENSIVE CLOUD COVER DEVELOP BY 14-15Z TUESDAY
AS WIDESPREAD CUMULUS/STRATOCUMULUS DEVELOPS. A SPRINKLE OR LIGHT
SHOWER IS NOT OUT OF THE QUESTION.
MARINE
ISSUED AT 138 AM EDT MON JUN 9 2025
WINDS AND WAVES ARE EXPECTED TO BE RELATIVELY CALM THIS WEEK WITH
WINDS MOSTLY BELOW 20 KNOTS AND WAVES MOSTLY 3 FEET OR LESS.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...OSTUNO
AVIATION...NJJ
MARINE...OSTUNO
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