566
FXUS63 KGRR 061855
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
255 PM EDT WED AUG 6 2025
KEY MESSAGES
- POP-UP SHOWERS AND STORMS TODAY AND TOMORROW
- BECOMING HOT AND HUMID WITH ADDITIONAL RAIN CHANCE NEXT WEEK
DISCUSSION
ISSUED AT 255 PM EDT WED AUG 6 2025
- POP-UP SHOWERS AND STORMS TODAY AND TOMORROW
AN AXIS OF 500 J/KG OF MLCAPE AND HIGHER PRECIPITABLE WATER
VALUES AROUND 1.4 INCHES IS PRESENT ALONG AND EAST OF THE US 127
CORRIDOR. IT IS IN THIS AREA THAT WE ARE SEEING ISOLATED SHOWERS
AND THUNDERSTORMS DEVELOP. WINDS AT THE SURFACE AND ALOFT ARE
LIGHT RESULTING IN LITTLE TO NO MOVEMENT OF THESE SHOWERS AND
STORMS THEREFORE THEY WILL LIKELY COLLAPSE ON THEMSELVES AND MAY
PRODUCE A OUTFLOW BOUNDARIES WHERE ADDITIONAL SHOWERS AND STORMS
MAY DEVELOP. AS WE HEAD TOWARD SUNSET WE'LL GRADUALLY LOSE OUR
INSTABILITY WITH SHOWER AND THUNDERSTORM CHANCES COMING TO AN END.
THURSDAY WILL BE QUITE SIMILAR TO TODAY ALTHOUGH THERE WILL BE A
SHORTWAVE TROUGH MOVING THROUGH WITH SOME POSITIVE VORTICITY
ADVECTION WITH ADDITIONAL CHANCES (20 TO 30 PERCENT) FOR SHOWERS
AND THUNDERSTORMS DURING THE AFTERNOON. WINDS TOWARD THE SURFACE
AND MID LEVELS WILL AGAIN BE ON THE LIGHTER SIDE, EXPECT ANY
SHOWER OR STORM THAT DEVELOPS TO BE SLOW MOVING. ANOTHER SHORTWAVE
TROUGH AND ASSOCIATED POSITIVE VORTICITY ADVECTION RIDE THE RIDGE
THURSDAY NIGHT WHICH MAY SPARK OFF ANOTHER ROUND OF SHOWERS AND
THUNDERSTORMS WITH THE BEST CHANCES 40 PERCENT OR GREATER
NORTHWEST OF GRAND RAPIDS. DRY CONDITIONS ARE THEN EXPECTED FOR
MOST OF THE DAY FRIDAY.
- BECOMING HOT AND HUMID WITH ADDITIONAL RAIN CHANCE NEXT WEEK
DEW POINTS INCREASE INTO THE UPPER 60S TO LOW 70S BY FRIDAY AND
CONTINUE THROUGH THE WEEKEND. WITH HIGHS IN THE MID 80S TO MID 90S
HEAT INDICES WILL MAINLY BE IN THE 90S WITH VALUES SATURDAY
APPROACHING 100. THESE CONDITIONS WON'T LAST LONG THOUGH AS A
DEEPER MID LEVEL TROUGH MOVES THROUGH THE REGION FOR THE FIRST
HALF OF NEXT WEEK. THIS SYSTEM WILL BRING WITH IT CHANCES FOR RAIN
AND STORMS ALONG WITH COOLER AIR WITH HIGHS DROPPING BACK INTO
THE LOW TO MID 80S.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 135 PM EDT WED AUG 6 2025
SCATTERED / AREAS OF BROKEN CUMULUS CLOUD BASES BETWEEN 4,000 AND
6,000 FEET THROUGH SUNSET TODAY. SCATTERED SHOWERS ARE DEVELOPING
EAST OF LAN/JXN, INCLUDING A THUNDERSTORM CELL IN VICINITY OF
DETROIT. HREF MODELS INDICATE 30 PERCENT POTENTIAL FOR SHOWERS
LATER THIS AFTERNOON TO AFFECT LAN AND JXN. ANY HEAVIER SHOWERS
COULD HAVE LOWERED VISIBILITY UNDER MODERATE RAIN, AND SOME
LOCALIZED LLWS DUE TO WEAK-MODERATE DOWNDRAFTS. SOME MIST/FOG
POTENTIAL AGAIN TONIGHT BETWEEN 09 AND 13 Z, THOUGH IT APPEARS
LESS OF A THREAT THAN LAST NIGHT AS THERE MAY BE VARIOUS VFR CLOUD
LAYERS PRESENT.
MARINE
ISSUED AT 255 PM EDT WED AUG 6 2025
A LIGHT BREEZE OVER THE LAKE TODAY AND THURSDAY, VARYING IN
DIRECTION WITH THE DAYTIME LAKE BREEZE AND NIGHTTIME LAND BREEZE
CIRCULATIONS. SCATTERED THUNDERSTORMS MAY BE PRESENT OVER LAKE
MICHIGAN THURSDAY NIGHT TO EARLY FRIDAY MORNING ACCORDING TO SOME
SHORT-TERM MODELS, AIDED BY BETTER FLOW OF MOIST AIR ABOVE THE
MARINE LAYER VIA SOUTHWEST WINDS. FRIDAY THROUGH THE WEEKEND, SOUTH-
SOUTHEAST WINDS 10-20 KNOTS MAY BUILD 2 TO 4 FOOT WAVES AND MODERATE
SWIM RISK FOR BEACHES NORTH OF GRAND HAVEN.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...RAH
AVIATION...CAS
MARINE...RAH
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