223
FXUS63 KGRR 041050
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
650 AM EDT SAT JUL 4 2026
KEY MESSAGES
- THUNDERSTORM CHANCES BOTH TODAY AND SUNDAY
- PERIOD OF QUIETER WEATHER EXPECTED MONDAY AND TUESDAY
- CHANCE FOR SHOWERS/STORMS MID WEEK
DISCUSSION
ISSUED AT 423 AM EDT SAT JUL 4 2026
- THUNDERSTORM CHANCES BOTH TODAY AND SUNDAY
A FAIRLY DIFFUSE SURFACE PATTERN IS IN PLACE TODAY WITH LIGHTER
WINDS AND HIGH DEW POINT AIR REMAINING ACROSS THE ENTIRE AREA.
MULTIPLE MCS'S IN THE PAST 24 HOURS DRIVEN BY CONVECTIVELY
INDUCED MESO VORTS HAVE PUSHED AN OUTFLOW WELL SOUTH OF THE AREA
INTO ILLINOIS AND INDIANA. THE UPPER PATTERN IS ZONAL WITH NO
SIGNIFICANT SHORTWAVES MOVING THROUGH THE FLOW. CONVECTION TODAY
WILL BE DRIVEN BY DIURNAL HEATING AND ADDITIONAL CONVECTIVE VORT
MAXIMA. THE MAIN FEATURE OF NOTE IS CONVECTION IN IOWA AND
NORTHERN MISSOURI THAT THE HREF PICKS UP ON AND MOVES A SHORTWAVE OUR
DIRECTION THROUGH THE COURSE OF THE DAY. FEEL CONVECTION TODAY
WILL BE 1) HEAT OF THE DAY DRIVEN DEVELOPING OVERHEAD AND 2) WHAT
CAN DEVELOP AND ADVECT IN FROM THE SW AND W. THE MAIN SIGNAL IN
THE HREF IS HEAT OF THE DAY CONVECTION THAT DEVELOPS IN EASTERN
LOWER MICHIGAN THAT MIGRATES WESTWARD INTO CENTRAL AND EASTERN
PORTIONS OF OUR AREA INCLUDING MOP/AMN AND LAN. GIVEN LIGHTER DEEP
LAYER SHEAR TODAY, LESS THAN 30 KNOTS, AGREE WITH THE SPC OUTLOOK
THAT WE ARE LOOKING AT GENERAL THUNDER. SEVERE THREAT IS OVERALL
LOW. HEAVY RAIN WILL REMAIN POSSIBLE TODAY WITH HIGH DEW
POINT/PWAT AIR AND LIKELY SLOW MOVING THUNDERSTORMS.
A SIMILAR DAY ON SUNDAY IS EXPECTED WITH MAINLY DIURNALLY DRIVEN
CONVECTION. LOW DEW POINT AIR SLIDES IN FROM THE NORTH THROUGH THE
DAY AND WE FEEL THE BEST CHANCES FOR STORMS WILL BE IN THE
SOUTHEAST HALF OF THE FORECAST AREA CLOSER TO A WEAK LOW MOVING
THROUGH IN/OH. AGAIN, GENERAL THUNDER OUTLOOK ON SUNDAY WITH LOW
SEVERE WEATHER RISK.
- PERIOD OF QUIETER WEATHER EXPECTED MONDAY AND TUESDAY
AFTER AN ACTIVE WEATHER PERIOD MONDAY AND TUESDAY WILL SEE QUIET
WEATHER WITH RIDGING BUILDING IN AT THE SURFACE. GFS BUFKIT
OVERVIEWS AT GRAND RAPIDS ARE NEARLY DEVOID OF MOISTURE IN THE
VERTICAL PROFILE. CONFIDENCE IS HIGH THAT WE SHOULD BE DRY BOTH
DAYS.
- CHANCE FOR SHOWERS/STORMS MID WEEK
OUR NEXT CHANCE FOR RAIN AFTER THE WEEKEND WILL BE IN THE
WEDNESDAY AND THURSDAY TIME FRAME. AT THIS POINT THERE IS MODEL
DISPARITY BETWEEN THE GFS AND THE ECWMF. THE GFS BRINGS A FRONT
THROUGH QUICKER FROM THE NORTHWEST ON WEDNESDAY WHEREAS THE ECMWF
HOLDS OFF UNTIL INTO THURSDAY. AT THIS POINT A BIT EARLY TO TELL
THE CORRECT PATH GIVEN WE ARE TALKING ABOUT A WAVE IN ZONAL FLOW
OUT ON DAY 5 AND 6. CONFIDENCE IS LOW IN TERMS OF TIMING OF THE
WAVE AND ITS ASSOCIATED COLD FRONT. THE FRONT WILL BRING A ROUND
OF SHOWERS AND STORMS WHEN IT MOVES THROUGH.
AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 649 AM EDT SAT JUL 4 2026
RAIN HAS LARGELY MOVED OFF TO THE EAST OF THE TAF SITES AS WE
APPROACH 12Z, BUT THERE STILL ARE SOME ISOLATED SHOWERS THAT
REMAIN. VCSH SHOULD COVER THAT THREAT. NEXT ITEM OF NOTE ARE AREAS
OF MVFR CEILINGS (AND SOME IFR) FLOATING THROUGH THE REGION THIS
MORNING. THESE CEILINGS ARE DUE TO TIME OF DAY AND A VERY MOISTURE
RICH AIR MASS. EXPECTATION IS FOR POCKETS OF LOWER CEILINGS TO BE
AROUND THROUGH ABOUT 1530Z AND THEN THEY SHOULD HAVE MIXED OUT.
FOCUS THEN SHIFTS TO THE POTENTIAL OF THUNDERSTORMS THIS AFTERNOON
AND EVENING. LATEST MODEL GUIDANCE IS TRYING TO SHOW THE HIGHEST
CONCENTRATION TO THE NORTHEAST OF THE TAF SITES UP TOWARDS MT
PLEASANT AND SAGINAW AND THEN TO THE SOUTHWEST TOWARDS CHICAGO.
FEEL THERE IS AT LEAST A CHANCE OF SCATTERED ACTIVITY THIS
AFTERNOON AND EVENING (20Z THROUGH 03Z) SO HAVE KEPT THE PROB30
GROUND IN THE TAFS DURING THAT TIME FRAME.
MARINE
ISSUED AT 423 AM EDT SAT JUL 4 2026
WIND AND WAVE CONDITIONS ARE EXPECTED TO REMAIN BELOW ADVISORY
LEVELS THROUGH THE REMAINDER OF THE HOLIDAY WEEKEND. WAVES WILL
GENERALLY BE 1-2 FEET OR LESS THROUGH SUNDAY NIGHT. RIDGING WILL
BUILD IN FROM THE NORTH IN THE LATTER HALF OF THE WEEKEND WHICH
WILL ACTUALLY PIVOT THE WINDS FROM WHAT HAVE BEEN SOUTHWESTERLY
FOR SOME TIME TO A NORTH AND EAST OFF SHORE FLOW. THE ONLY
EXCEPTION TO THE LOWER WAVES/WINDS WILL BE IN AND NEAR
THUNDERSTORMS WHERE CONDITIONS MAY BRIEFLY REACH ADVISORY LEVELS.
THE MAIN TIME FRAME WHERE THAT COULD OCCUR WOULD BE THIS AFTERNOON
AND EVENING AND STORMS REDEVELOP IN THE HEAT OF THE DAY. CHANCES
FOR STORMS OVER THE LAKE THOUGH ARE RELATIVELY LOW TODAY AS
COMPARED TO ADJACENT LAND AREAS. BOTTOM LINE, FAIRLY HIGH CHANCES
FOR GOOD WEATHER ON THE BIG LAKE TODAY.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...DUKE
AVIATION...DUKE
MARINE...DUKE
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