003
FXUS63 KGRR 110611
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
211 AM EDT TUE AUG 11 2026
KEY MESSAGES
- UNSETTLED WITH SEVERAL CHANCES OF SHOWERS AND THUNDERSTORMS
THROUGH THURSDAY
- MORE WIDESPREAD RAINFALL POTENTIAL THIS WEEKEND
DISCUSSION
ISSUED AT 144 PM EDT MON AUG 10 2026
- UNSETTLED WITH SEVERAL CHANCES OF SHOWERS AND THUNDERSTORMS
THROUGH THURSDAY
PERSISTENT WEST-NORTHWEST FLOW WITH SEVERAL EMBEDDED SHORTWAVES WILL
KEEP A FRONTAL BOUNDARY STALLED SOUTH OF THE AREA OVER THE NEXT
SEVERAL DAYS. EACH SHORTWAVE WILL DRIVE THE POTENTIAL FOR SHOWERS
AND THUNDERSTORMS UNTIL LATE THURSDAY INTO FRIDAY A PATTERN SHIFT
FORCES THE FRONT SOUTH.
FIRST CHANCE IS THIS AFTERNOON WHERE THE NAMNEST, WHICH IS BEST
HANDLING ONGOING CONVECTION, SUGGESTS AN ISOLATED POP-UP
THUNDERSTORM OR TWO. COVERAGE GIVEN LITTLE MESOSCALE FORCING WILL BE
WIDELY ISOLATED WITH MANY IF NOT ALL STAYING DRY.
NEXT CHANCE ARRIVES TONIGHT WITH THE LOW-LEVEL JET JUST SOUTH OF THE
AREA. THIS FOCUSES THE BEST CONVECTIVE POTENTIAL SOUTH OF THE AREA,
THOUGH A FEW SHOWERS AND STORMS ARE POSSIBLE CLOSER TO THE FRONT
ALONG AND SOUTH OF THE I-94 CORRIDOR.
ATTENTION THEN TURNS TO TUESDAY AFTERNOON WHERE A COMPLEX OF STORMS
IS FORECAST TO EITHER JUST MISS US TO THE SOUTH, OR IMPACT OUR
SOUTHWEST FORECAST AREA. BEST CHANCE IF IT DOES REACH US IS SOUTH OF
A GRAND HAVEN TO LANSING LINE. WITH AMPLE DEEP LAYER SHEAR (40+
KTS) AND MUCAPE VALUES NORTH OF 2000 J/KG, THIS COMPLEX MAY HAVE
THE POTENTIAL FOR DAMAGING WINDS IF IT IMPACTS OUR FORECAST AREA.
THIS MATCHES THE SIGNAL SEEN IN SEVERAL DIFFERENT MACHINE LEARNING
GUIDANCE TOOLS. HOWEVER, STORM TRACK DEPENDS HIGHLY ON HOW STORMS
EVOLVE TONIGHT SO CONFIDENCE IN ANY SEVERE WEATHER THREAT IS LOW.
WEDNESDAY AND THURSDAY WILL FEATURE ADDITIONAL AFTERNOON/EVENING
THUNDERSTORM CHANCES AS WEAK SHORTWAVES INTERACT WITH THE FRONT
SOUTH OF THE AREA. BEST CHANCE WILL BE SOUTH OF I-96, PARTICULARLY
NEAR I-94. THE FRONT THEN IS DRIVEN SOUTH FRIDAY ENDING THE
UNSETTLED PATTERN BRIEFLY. THERE ALSO MAY BE LOCALLY HEAVY RAIN
WITH ANY OF THESE ROUNDS, WITH ISOLATED MAXIMUM TOTALS AOA 2
INCHES SHOWN IN HREF/REFS LPMM GUIDANCE.
- MORE WIDESPREAD RAINFALL POTENTIAL THIS WEEKEND
FRIDAY LOOKS TO BE DRY AS SURFACE AND UPPER-LEVEL RIDGING
SUPPRESSES CONVECTIVE POTENTIAL. HOWEVER, THAT PATTERN CHANGES BY
SATURDAY. THIS WEEKEND, POTENTIALLY AS EARLY AS FRIDAY NIGHT, A
MID-LEVEL WAVE EJECTS INTO THE CENTRAL GREAT LAKES DRIVING A
SURFACE LOW ACROSS THE AREA. THIS WILL BRING MORE WIDESPREAD
PRECIPITATION UNTIL THE LOW EXITS LATE WEEKEND WITH COOLER
TEMPERATURES WITH IT.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 144 PM EDT MON AUG 10 2026
DAYTIME HEATING, COUPLED WITH A MOIST BOUNDARY LAYER AIDED BY OVERNIGHT
RAINFALL, HAS RESULTED IN A SC CLOUD DECK WITH MVFR CEILINGS /AROUND
2KFT/ AT ALL TAF SITES. WITH CONTINUED WARMING THIS AFTERNOON, EXPECT
SC TO LIFT TO VFR CU DECK /AROUND 3.5 KFT/ AFTER 19-20Z. STATIONARY
FRONT OVER THE LOWER GREAT LAKES WILL CONTINUE TO SERVE AS FOCAL FOR
SCATTERED STORMS NEXT 24 HR, WITH THE NEXT ROUND OF THUNDERSTORMS
POTENTIALLY MOVING INTO SW LOWER /INCLUDING THE AZO-BTL TAF SITES/
AFTER 02-03Z THIS EVENING. YET ANOTHER ROUND OF STORMS MAY BE
APPROACHING AZO/BTL/GRR AFTER 16Z TUESDAY, BUT WILL NOT INCLUDE IN
TAFS AT THIS TIME.
OTHERWISE, EXPECT SCT-BKN MID CLOUDS TONIGHT NORTH OF THE BOUNDARY,
ALONG WITH 2-4SM VSBYS IN FOG AFTER 06-07Z. WINDS WILL REMAIN LIGHT
THROUGHOUT TAF PERIOD, WITH WESTERLY FLOW BECOMING VARIABLE
TONIGHT.
AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
ISSUED AT 211 AM EDT TUE AUG 11 2026
VARIED AVIATION CONDITIONS ARE IN PLACE TO BEGIN THE TAF PERIOD AT
06Z. CONDITIONS RANGE FROM VFR TO LIFR WITH FOG AND STRATUS. THESE
VARIED CONDITIONS WILL REMAIN THE CASE THROUGH DAYBREAK AROUND 11Z
WITH A GRADUAL DOWNWARD TREND AND EXPANSION OF THE FOG AND
STRATUS, ESPECIALLY FOR THE I-94 TAF SITES. THE FOG AND STRATUS
WILL LIFT IN THE 12Z TO 15Z TIME FRAME.
THE NEXT FOCUS WILL BE THUNDERSTORMS THAT MAY POTENTIALLY SWEEP
THROUGH THE SOUTHWEST CORNER OF THE STATE AFTER 15Z. THESE STORMS
ARE AT PRESENT FORMING OUT OVER SOUTH DAKOTA AND NEBRASKA. THE
STORMS WILL MOVE/DEVELOP EASTWARD ALONG A WARM FRONT SITUATED FROM
IOWA TO INDIANA. NEAR AND NORTH OF THE FRONT STORMS WILL SWEEP
EAST MOST LIKELY IMPACTING AZO AND BTL, ALTHOUGH ALL TAF SITES
COULD BE IMPACTED IF THE COMPLEX COMES A BIT FURTHER NORTH IN ITS
EASTWARD PUSH. WE WILL BE WATCHING THE 15Z TO 21Z TIME FRAME AS
THE SWEET SPOT WHEN STORMS HAVE THE POTENTIAL TO MOVE THROUGH.
MVFR AND IFR CONDITIONS ARE POSSIBLE WITH THIS ACTIVITY.
MARINE
ISSUED AT 144 PM EDT MON AUG 10 2026
CONDITIONS LOOK TO REMAIN BELOW SMALL CRAFT ADVISORY/BEACH HAZARDS
STATEMENT LEVELS MUCH OF THE WEEK GIVEN WEAK GRADIENT FLOW ACROSS
THE AREA. THE ONE CAVEAT IS THAT ONE OR MORE ROUNDS OF
THUNDERSTORMS ARE LIKELY BETWEEN TONIGHT AND THURSDAY ACROSS THE
WATERS. LOCALLY HIGHER WINDS AND WAVES ARE POSSIBLE IN ANY
THUNDERSTORMS OR AS A RESULT OF THEIR OUTFLOW WINDS EVEN IF THEY
MISS OUR PART OF THE LAKE. MARINE HEADLINES MAY BE NEEDED FRIDAY
NIGHT INTO THE WEEKEND AS A MORE ROBUST SYSTEM CROSSES THE CENTRAL
GREAT LAKES.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...THOMAS
AVIATION...DUKE
MARINE...THOMAS
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