717
FXUS63 KGRR 281730
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
130 PM EDT SUN JUN 28 2026
KEY MESSAGES
- HEAT WAVE BEGINS MONDAY, CONTINUES THROUGH AT LEAST THURSDAY
- CHANCES FOR SHOWERS AND STORMS
DISCUSSION
ISSUED AT 244 AM EDT SUN JUN 28 2026
- HEAT WAVE BEGINS MONDAY, CONTINUES THROUGH AT LEAST THURSDAY
HEAT AND HUMIDITY BEGIN BUILDING IN MONDAY WITH HOT AND HUMID
CONDITIONS CONTINUING INTO THE END OF THE WEEK. HOTTEST DAYS
CONTINUE TO BE TUESDAY, WEDNESDAY AND THURSDAY WHEN HIGHS WILL BE IN
THE MID TO UPPER 90S AND HEAT INDEX VALUES WILL BE WELL INTO THE
100S.
MONDAY MAY NOT BE A SLAM DUNK CRITERIA HEAT WARNING DAY FOR ALL OF
THE AREA AS LINGERING CLOUDS AND SLOW BUILDING HEAT MAY LIMIT
TEMPERATURES ESPECIALLY THE FURTHER NORTH YOU GO. IN SPITE OF THAT
AND MAYBE BEING A FEW DEGREES INTO ADVISORY VS WARNING GUIDANCE
NUMBERS HERE OR THERE...THE SIGNIFICANT IMPACTS OF A PROLONGED HEAT
AND HUMIDITY STRETCH (4 DAYS OR MORE) WARRANT THE ISSUANCE OF AN
EXTREME HEAT WATCH FOR MONDAY THROUGH THURSDAY THAT IS LIKELY TO
BECOME AN EXTREME HEAT WARNING SOMETIME WITHIN THE NEXT 24 HOURS.
ANYTHING THAT CAN BE DONE TO PREPARE FOR THE HEAT AND HUMIDITY
SHOULD BE COMPLETED BY TODAY AS THE HEAT BEGINS MONDAY. THIS WOULD
INCLUDE MODIFYING SCOPE AND DURATION OF PLANNED OUTDOOR ACTIVITIES
THIS WEEK AND TAKING EXTRA PRECAUTIONS FOR ANIMALS AND VULNERABLE
POPULATIONS AMONG OTHER THINGS.
WHILE SOME RELIEF FROM THE EXTREME HEAT MAY OCCUR AFTER
THURSDAY...HOT AND HUMID CONDITIONS ARE EXPECTED TO PERSIST
THROUGH AT LEAST THE 4TH OF JULY HOLIDAY WEEKEND AND POSSIBLE MUCH
OF THE WEEK AFTER.
- CHANCES FOR SHOWERS AND STORMS
THERE MAY BE SOME STORMS THAT WORK INTO NORTHERN LOWER MICHIGAN
LATE TODAY INTO EARLY MONDAY. NON-ZERO CHANCE FOR SEVERE HAIL OR
STRONG WINGS IN A STORM OR TWO...BUT OVERALL CHANCE FOR SEVERE
WEATHER APPEARS TO BE VERY LOW WITH ELEVATED INSTABILITY.
WITH THIS MUCH HEAT AND HUMIDITY IN PLACE IT IS NOT UNCOMMON FOR US
TO SEE SOME AFTERNOON/EVENING ISOLATED STORMS OR MORE ORGANIZED
ACTIVITY AS SHORTWAVES MOVE THROUGH THE GREAT LAKES REGION. BEST
CHANCE FOR SHOWERS/STORMS AT THIS POINT STILL LOOKS TO BE THE MIDDLE
TO THE END OF THE WEEK THOUGH MODELS CONTINUE TO SHOW LIMITED
SUPPORT FOR SHOWERS/STORMS.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 130 PM EDT SUN JUN 28 2026
SATELLITE SHOWS DIURNAL CU DEVELOPMENT BETWEEN 3-4KFT WHICH WILL
LAST THROUGH THE EVENING. THEN WE SEE CIGS LOWER TO AROUND 5KFT
THROUGH THE NIGHT AS A SYSTEM APPROACHES FROM THE WEST. THE MAIN
POTENTIAL IMPACT, AND SOURCE OF UNCERTAINTY, IS THE POTENTIAL FOR
A THUNDERSTORM COMPLEX TO CLIP GRR/MKG LATE TONIGHT OR MONDAY
MORNING. SHORT RANGE MODEL GUIDANCE IS NOT IN STRONG AGREEMENT ON
WHERE OR WHEN EXACTLY STORMS WILL TRACK SO HAVE KEPT THE PROB30S
INHERITED FROM THE PREVIOUS FORECASTER. OUTSIDE OF WINDS IN
THUNDERSTORMS, LOOK FOR SOUTHEAST WINDS TO 10 KNOTS TODAY EXCEPT
FOR A WESTERLY LAKE BREEZE AT MKG. SOUTH TO SOUTHEAST WINDS ARE
EXPECTED AGAIN MONDAY WITH GUSTS TO 20 KNOTS AT MKG.
MARINE
ISSUED AT 244 AM EDT SUN JUN 28 2026
SUNDAY WILL FEATURE LIGHT EASTERLY TO SOUTHEASTERLY WINDS. MONDAY
SEES THE RETURN OF THE RISK FOR HAZARDOUS WAVES THAT PROBABLY WILL
CONTINUE THROUGH TUESDAY. SMALL CRAFT ADVISORIES AND BEACH
HAZARDS STATEMENTS ARE LOOKING MORE LIKELY FOR BOTH MONDAY AND
TUESDAY. THOSE LOOKING TO SEEK RELIEF FROM THE HEAT MONDAY AND
TUESDAY SHOULD BE AWARE THAT HAZARDOUS WAVES AND CURRENTS ARE
LIKELY TO BE ENCOUNTERED IN LAKE MICHIGAN.
GRR WATCHES/WARNINGS/ADVISORIES
MI...EXTREME HEAT WARNING FROM 2 PM MONDAY TO 8 PM EDT THURSDAY FOR
MIZ037>040-043>046-050>052-056>059-064>067-071>074.
MARINE...NONE.
DISCUSSION...04
AVIATION...THOMAS
MARINE...04
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