712
FXUS63 KGRR 261820
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
220 PM EDT FRI JUN 26 2026
KEY MESSAGES
- PREDOMINANTLY DRY THIS WEEKEND
- MAJOR TO EXTREME HEAT RISK NEXT WEEK
- CHANCES FOR SHOWERS AND STORMS NEXT WEEK
DISCUSSION
ISSUED AT 220 PM EDT FRI JUN 26 2026
- PREDOMINANTLY DRY THIS WEEKEND
RADAR CURRENTLY SHOWS RAIN SHOWERS CROSSING SOUTHERN LAKE MI AND
MOVING EAST TOWARDS THE I-94 CORRIDOR. SHOWERS GENERALLY FROM
I-94 SOUTHWARD WILL BE POSSIBLE THIS AFTERNOON AND EVENING.
AFTER THIS, FORECAST CERTAINTY FOR A DRY WEEKEND IS VERY GOOD (90
PERCENT) THANKS TO A AMPLIFYING UPPER RIDGE OVER THE UPPER
MISSISSIPPI VALLEY REGION. THIS WILL SUPPLY SYNOPTIC SCALE
SUBSIDENCE TO THE WESTERN GREAT LAKES AND THIS WILL BE COMPLEMENTED
BY A LACK OF LOW LEVEL FORCING FOR ASCENT. TEMPERATURES WILL GRADUALLY
WARM.
- MAJOR TO EXTREME HEAT RISK NEXT WEEK
EXPECTATIONS FOR DANGEROUS HEAT NEXT WEEK HAVE NOT CHANGED MUCH.
AFTERNOON HEAT INDICES SHOULD EASILY EXCEED 100F STARTING TUESDAY
AND THIS SHOULD LAST THROUGH AT LEAST THURSDAY. THE HOTTEST DAY
MAY BE THURSDAY, WITH HEAT INDICES EXCEEDING 105F FOR MOST AREAS
EAST OF US-131. IN FACT, THE SOUTHERN US-127 CORRIDOR, INCLUDING
JACKSON AND LANSING, COULD EXCEED 110F.
TO COMPOUND THE RISK, AND AS NOTED PREVIOUSLY, DEWPOINTS IN THE 70S
WILL KEEP MINIMUM TEMPERATURES IN THE MID 70S. THE PROLONGED HEAT
AND HUMIDITY WILL TEST THE RESILIENCE OF VULNERABLE POPULATIONS NOT
HAVING ACCESS TO PROPER AIR CONDITIONING, SO NOW IS A GOOD TIME TO
START PLANNING FOR CHECKING UP ON THOSE AT RISK.
HEAT SAFETY TIPS AND RESOURCES CAN BE FOUND BY VISITING:
WEATHER.GOV/HEAT
- CHANCES FOR SHOWERS AND STORMS NEXT WEEK
PRECIPITATION CHANCES ARE CHALLENGING BECAUSE WITH THE HEAT AND
HUMIDITY COMES PERSISTENT AND SUBSTANTIAL CONDITIONAL INSTABILITY.
EVEN FOR THE OVERNIGHT HOURS, SOUTHERN LOWER MI COULD SEE MUCAPE
EASILY REMAINING ABOVE 2000 J/KG. THIS IS PLENTY SUFFICIENT FOR
CONVECTIVE MAINTENANCE OF UPSTREAM MCSS OVER WI THAT DEVELOP THE
PRIOR EVENING/AFTERNOON AND MOVE INTO THE AREA. FOR THIS REASON, OUR
NORTHWESTERN ZONES WILL MAINTAIN AT LEAST A SLIGHT CHANCE OF SHOWERS
AND THUNDERSTORMS THROUGH THE PERIOD. NOCTURNAL MCSS ARE NOTORIOUSLY
DIFFICULT TO MODEL, BUT GIVEN THEIR TENDENCY TO PROPAGATE TOWARDS
THE GREATEST INSTABILITY, IT IS HIGHLY PLAUSIBLE THAT EVEN AREAS
ALONG AND SOUTH OF I-96 COULD SEE ACTIVITY ROLLING IN FROM THE
NORTH-NORTHWEST ALMOST ANY DAY OF THE WEEK, MOST LIKELY DURING
THE OVERNIGHT OR EARLY MORNING HOURS. SO, OUR CURRENTLY ADVERTISED
LOW POPS DURING THIS TIME DO COME WITH A BIT OF A CAVEAT.
THUNDERSTORM CHANCES CLIMB SOMEWHAT THURSDAY/FRIDAY AND INTO THE
FOURTH OF JULY WEEKEND AS SEVERAL OF THE DETERMINISTIC SOLUTIONS
SHOW THE UPPER RIDGE BREAKING DOWN DUE TO CANCELLING EFFECTS OF AT
LEAST ONE MINOR SHORTWAVE TROUGH MOVING THROUGH. FROM A QPF
STANDPOINT, SUCCESSIVE RUNS OF THE ECMWF ENSEMBLE AND AI GUIDANCE
HAVE NOT BEEN PARTICULARLY CONSISTENT. HENCE, PREDICTABILITY REMAINS
VERY LOW. IT IS PLAUSIBLE THAT THE HEAT AND HUMIDITY CONTINUE
UNABATED INTO THE HOLIDAY WEEKEND WITHOUT TEMPERATURES BEING
MITIGATED MUCH BY PRECIPITATION. ON THE OTHER HAND, NIGHTTIME
PRECIPITATION COULD GIVE AFTERNOON DEWPOINTS A BOOST INTO THE
UPPER 70S, THUS GREATLY INCREASING THE DAYTIME HEAT RISKS.
GIVEN INCREASED EXPOSURE/VULNERABILITY TO MULTIPLE HAZARDOUS
WEATHER CONCERNS DURING NEXT WEEKEND, WE WILL BE WATCHING THIS
VERY CLOSELY IN THE COMING DAYS.
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 133 PM EDT FRI JUN 26 2026
AREAS OF MVFR ARE DIMINISHING THIS AFTERNOON AS STRATUS DECK WITH
CEILINGS 1500 TO 2500 FEET IS BREAKING UP. SO THE TREND WILL BE
TOWARD VFR CONDITIONS BY LATE AFTERNOON.
SHOWERS MOVING ACROSS SOUTHERN LOWER MICHIGAN THROUGH LATE
AFTERNOON SHOULD NOT BE HEAVY ENOUGH TO LOWER VISBYS. INDEED,
MUCH OF THE RAIN COULD BE EVAPORATING ALOFT WHILE FALLING THROUGH
A LATER OF DRY AIR BELOW CLOUD BASE. THIS COULD CAUSE SOME PATCHY
TURBULENT DOWNDRAFTS FROM AZO TO JXN THIS AFTERNOON.
MARINE
ISSUED AT 220 PM EDT FRI JUN 26 2026
NO CONCERNS THIS WEEKEND, ALTHOUGH LOCALIZED MARINE FOG IS NOT OUT
OF THE QUESTION. BY SUNDAY NIGHT, DEWPOINTS ARE EXPECTED TO HAVE
CLIMBED TO THE MID/UPPER 60S F, WHICH SHOULD EXCEED NEARSHORE
WATER TEMPERATURES. HOWEVER, STRENGTHENING OFFSHORE FLOW MIGHT
KEEP THE INCIPIENT FOG THREAT SHUNTED OUT MORE TOWARDS MID-LAKE.
WAVE GROWTH WILL ALSO BE UNDERWAY SUNDAY NIGHT AS WELL WITH THE
STRONGER WINDS. AREAS NORTH OF MUSKEGON WILL LIKELY REQUIRE SMALL
CRAFT ADVISORY HEADLINES THROUGH AT LEAST MONDAY.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...TJT
AVIATION...OSTUNO
MARINE...TJT
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page