329
FXUS63 KGRR 011047
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
647 AM EDT TUE SEP 1 2026
KEY MESSAGES
- SMALL CHANCES FOR SHOWERS AND STORMS TODAY
- ADDITIONAL SHOWER AND STORM CHANCES WEDNESDAY THROUGH FRIDAY
- ABOVE NORMAL TEMPERATURES THROUGH THE 7 DAY FORECAST
DISCUSSION
ISSUED AT 354 AM EDT TUE SEP 1 2026
- SMALL CHANCES FOR SHOWERS AND STORMS TODAY
LIGHT SOUTHWEST FLOW IS IN PLACE THIS MORNING ALONG WITH DEW
POINTS AROUND 70F. UPSTREAM A COLD FRONT IS SITUATED FROM THE U.P.
SOUTHWEST ACROSS WISCONSIN AND INTO IOWA. WE REMAIN IN THE WARM
SECTOR TODAY WITH BUILDING INSTABILITY. MUCAPE VALUES EVEN AT THIS
EARLY HOUR RANGE FROM 2,000 J/KG IN SOUTHWEST LOWER MICHIGAN TO
AROUND 4,000 J/KG IN IOWA. THE FRONT REMAINS UPSTREAM TODAY AND
ONLY SLOWLY SAGS INTO THE AREA TONIGHT WHILE LOSING DEFINITION.
ALOFT, IT IS DIFFICULT TO PICK OUT MUCH OF ANY SHORTWAVE ACTIVITY
UPSTREAM EARLY THIS MORNING AND MODEL DATA MOVING THROUGH THE DAY
SHOWS LITTLE ENERGY ALOFT EITHER. THE BOTTOM LINE IS A THREAT FOR
SOME ISOLATED SHOWERS AND STORMS IS CERTAINLY THERE TODAY/TONIGHT,
BUT THERE IS LITTLE TO TRULY PINPOINT TIMING OR AREAS. CONFIDENCE
IN MORPHOLOGY OF STORMS TODAY IS LOW AS IS THE THREAT FOR STORMS
AT ALL. WOULD NOT BE SURPRISED TO SEE SOME ISOLATED ACTIVITY
DURING THE HEAT OF THE DAY TODAY, BUT HAVE KEPT THE FORECAST DRY.
WE DO HAVE SOME SMALL POPS AROUND 20 PERCENT THIS EVENING BASED ON
A CONSENSUS OF SHORT TERM MODELS AND BLENDS. SPC HAS THE AREA IN
A MARGINAL RISK TODAY, WHICH IS RELATED TO AN INCREASE IN WIND
FIELDS AT 850MB AND 500MB AFTER 00Z. AGAIN, WE WILL NEED A
KICKER/LIFTING MECHANISM AND AT THIS POINT THAT COMPONENT IS
NEBULOUS.
HAVE HELD OFF ON ANY HEAT HEADLINE TODAY AS INDEX VALUES ARE
MARGINAL ONLY IN THE FAR SOUTH. WE COULD SEE HEAT INDEX VALUES
APPROACH 100 FROM AZO OVER TO JXN THIS AFTERNOON, BUT MOST AREAS
SHOULD HOLD IN THE 90S FOR MAXIMUM APPARENT TEMPERATURES TODAY.
- ADDITIONAL SHOWER AND STORM CHANCES WEDNESDAY THROUGH FRIDAY
THE SURFACE FRONT WILL REMAIN IN THE AREA ON WEDNESDAY WHICH MAY
PROVIDE A FOCUS FOR SHOWERS AND THUNDERSTORMS. MULTIPLE SHORTWAVE'S
ARE FORECAST TO BE MOVING THROUGH THE GENERALLY ZONAL FLOW ALOFT
ON WEDNESDAY AS WELL. STRONG INSTABILITY WILL REMAIN IN PLACE ON
WEDNESDAY MAKING FOR BETTER CHANCES FOR SHOWERS AND STORMS. SPC
HAS SOME OF OUR FAR EASTERN AREAS TOWARDS THE U.S. 27/127 CORRIDOR
IN A SLIGHT RISK FOR SEVERE WEATHER. CANNOT RULE THIS OUT GIVEN
STRONG WINDS ALOFT REMAINING IN PLACE.
ADDITIONAL SHOWER AND THUNDERSTORM ACTIVITY IS EXPECTED ON
THURSDAY AND FRIDAY AS WELL BEFORE HIGH PRESSURE BUILDS IN FOR THE
WEEKEND. THAT SAID, QUITE A FEW ENSEMBLE MEMBERS OF BOTH THE GFS
AND THE ECMWF INDICATE PRECIPITATION POTENTIAL INTO THE WEEKEND AS
WELL. SUFFICE IT TO SAY, FORECAST CONFIDENCE IN PRECIPITATION IN
THE COMING DAYS IS NOT HIGH OWING TO TRANSIENT WEAKER SHORTWAVES
ALOFT AND A WEAK SURFACE PATTERN MOST DAYS.
- ABOVE NORMAL TEMPERATURES THROUGH THE 7 DAY FORECAST
WE ARE EXPECTING ABOVE NORMAL TEMPERATURES THROUGH MUCH OF THE
PERIOD WITH THE WARMEST DAYS BEING TODAY AND WEDNESDAY. A SLOW
COOLING TREND IS NOTED INTO EARLY NEXT WEEK. IT WILL TAKE UNTIL
NEXT MONDAY BEFORE WE SEE TEMPERATURES APPROACHING NORMALS FOR
THIS TIME OF YEAR.
AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 646 AM EDT TUE SEP 1 2026
VFR WEATHER PREVAILS ACROSS THE AREA FOR THE MOST PART AS WE
APPROACH 11Z. THERE IS A POCKET OF STRATUS ACROSS CENTRAL LOWER
MICHIGAN NEAR BIG RAPIDS (RQB) BUT THIS SHOULD REMAIN NORTH OF THE
TAF SITES BEFORE DISSIPATING THIS MORNING. THERE IS SOME LIGHT FOG
IN PLACE AT TIMES NEAR/AT THE TAF SITES, BUT THIS SHOULD DISSIPATE
AROUND 13Z OR SO.
WE EXPECT SOME CUMULUS DEVELOPMENT TODAY WITH BASES AROUND 4,000
TO 5,000 FEET. ADDITIONALLY, SOME CIRRUS DEBRIS CLOUDS FROM
UPSTREAM STORMS WILL DRIFT IN FROM THE WEST AS WELL. BOTTOM LINE
VFR WEATHER IS EXPECTED.
THE QUESTION WITH THE PRIOR SET OF TAFS REMAINS IN THIS SET. THAT
IS, WILL WE SEE SHOWERS AND STORMS THIS AFTERNOON AND EVENING.
THERE IS AN INCREASE IN THE LOW LEVEL JET THIS AFTERNOON AND
TONIGHT SO CANNOT RULE OUT SOME ISOLATED ACTIVITY. CONFIDENCE AT
THIS POINT IS TOO LOW TO INCLUDE. CURRENT FEELING IS WE STAY DRY
AT THE TAF SITES DURING THE DAYLIGHT HOURS, BUT CAN ENVISION SOME
SCATTERED SHOWERS AND STORMS TONIGHT. LATER FORECASTS WILL INCLUDE
SHRA/TSRA IF CONFIDENCE INCREASES.
MARINE
ISSUED AT 354 AM EDT TUE SEP 1 2026
AS FORECAST, WAVES SUBSIDED BELOW ADVISORY LEVELS YESTERDAY
EVENING. SUB ADVISORY CONDITIONS ARE NOW EXPECTED THE NEXT COUPLE
OF DAYS AT LEAST. THE PRESSURE GRADIENT WILL BE FAIRLY SLACK IT
APPEARS AS A WEAK BOUNDARY SAGS INTO THE AREA TODAY AND REMAINS
NEAR THROUGH THE END OF THE WORK WEEK. WITHOUT A LOW OF SOME
DEPTH AND/OR A BUILDING HIGH WINDS WILL REMAIN ON THE LIGHTER
SIDE. WAVES LOOK TO BE 2 FEET OR LESS THE NEXT FEW DAYS. THE
CAVEAT HOWEVER AS ALWAYS IS THUNDERSTORMS. WE ARE EXPECTING AT
LEAST SOME PERIODIC THUNDERSTORM ACTIVITY THROUGH FRIDAY WHICH
WILL BRING A LOCAL UPTICK IN WAVE ACTION AS THE STORMS AND
ASSOCIATED LOCALIZED WIND MOVE THROUGH.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...DUKE
AVIATION...DUKE
MARINE...DUKE
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