302
FXUS63 KGRR 171758
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
158 PM EDT FRI JUL 17 2026
KEY MESSAGES
- SMALLER RAIN CHANCES INTO THIS EVENING AND SATURDAY
- GOOD RAIN CHANCES LATE MONDAY INTO EARLY WEDNESDAY
DISCUSSION
ISSUED AT 158 PM EDT FRI JUL 17 2026
- SMALLER RAIN CHANCES INTO THIS EVENING AND SATURDAY
THE WILDFIRE SMOKE REMAINS AT THE FOREFRONT OF WEATHER RELATED ITEMS
THIS AFTERNOON. IT CONTINUES TO HOLD IN FOR THE TIME BEING, BUT
CONFIDENCE IS INCREASING PER COORDINATION WITH MICHIGAN EGLE THAT
THERE WILL BE A TEMPORARY IMPROVEMENT LATER TODAY THROUGH SATURDAY
MORNING AS STRONGER WINDS FROM THE SW LIKELY PUSH THE SMOKE OUT.
THIS OCCURS AS THE FRONT DROPPED THROUGH ON WEDNESDAY MOVES BACK
NORTH AS A WARM FRONT AS A LOW MOVES THROUGH THE AREA.
WE WILL SEE WARMER AIR AND ADDITIONAL LOW LEVEL MOISTURE MOVE BACK
IN, AND CREATE SOME INSTABILITY FOR A FEW SHOWERS/STORMS LATE THIS
AFTERNOON AND THIS EVENING. MU CAPES ARE EXPECTED TO PUSH 2,000 J/KG
EARLY THIS EVENING. ANY MESOSCALE BOUNDARY COULD TOUCH OFF A
SHOWER/STORM. DEEP LAYER SHEAR IS VERY WEAK, UNDER 20 KNOTS. THIS
WILL FAVOR PULSE TYPE STORMS WITH LOCALLY HEAVY RAINFALL FOR 20-30%
OF THE AREA.
WE SHOULD SEE A BREAK THEN TONIGHT AND FIRST THING SATURDAY MORNING.
BY LATE MORNING, THE FRONT WILL STEADILY START PUSHING THROUGH THE
FORECAST AREA, AND START TO DEVELOP SCATTERED TO NUMEROUS
SHOWERS/STORMS ALONG IT. MU CAPES ARE FORECAST TO INCREASE TO ALMOST
2500 J/KG BY EARLY AFTERNOON. THE FRONT IS EXPECTED TO BE NEAR GR
AROUND NOON, AND THEN PUSH OUT OF THE AREA BY 3 PM PER THE LATEST
CONSENSUS OF GUIDANCE. DEEP LAYER SHEAR ALONG AND AHEAD OF THE FRONT
CONTINUES TO BE WEAK, 20 KNOTS OR LESS. DCAPES ARE SHOWN BY FORECAST
SOUNDINGS TO APPROACH 1000 J/KG, SO CAN'T RULE OUT SOME ISOLATED
MICROBURSTS WITH SOME OF THE BETTER STORMS. THE STORMS SHOULD JUST
GET GOING BETTER AS THEY LOOK TO EXIT THE AREA.
THE STORM POTENTIAL WILL END WITH THE PASSAGE OF THE FRONT, WITH NW
WINDS SPREADING IN. THESE WINDS HAVE THE POTENTIAL TO BRING SOME
ADDITIONAL SMOKE IN FROM THE MN AND WRN ONTARIO FIRES, BUT HOW MUCH
IS THE BIG QUESTION. THE MICHIGAN EGLE HAS EXTENDED THE AIR QUALITY
ALERT FOR THE STATE THROUGH SATURDAY WITH THIS IN MIND, EXPECTING
THAT UNHEALTHY FOR SENSITIVE GROUPS WILL AT LEAST BE AFFECTED.
- GOOD RAIN CHANCES LATE MONDAY INTO EARLY WEDNESDAY
WE WILL SEE SHORT WAVE RIDGING ALOFT SETTLE IN ON SUNDAY, WITH THE
GENERAL FLOW FROM THE WNW. THIS WILL BRING IN COOLER WEATHER, ALONG
WITH THE POTENTIAL OF SOME SMOKE. DRY CONDITIONS WILL CONTINUE INTO
THE FIRST HALF OF MONDAY.
THE NEXT FORMIDABLE SHORT WAVE ALOFT, AND SFC REFLECTION WILL
APPROACH THE AREA MONDAY AFTERNOON. WE WILL SEE SHOWER/STORM CHANCES
INCREASE AS AS THE LOW LEVEL JET AHEAD OF IT NOSES INTO THE AREA.
NOT MUCH INSTABILITY INITIALLY IS WEAK. BEST CHANCE FOR THUNDER WILL
BE MONDAY NIGHT AND TUESDAY MORNING WHEN THE INSTABILITY AXIS IS
OVERHEAD. THE FRONT MOVES BY TUESDAY AFTERNOON, ENDING THE BETTER
CONVECTIVE POTENTIAL.
IT DOES LOOK LIKE SOME SHOWER POTENTIAL STICK AROUND INTO WEDNESDAY
AS THE UPPER TROUGH LINGERS OVER THE REGION UNTIL WEDNESDAY
AFTERNOON. AFTER THAT, HIGH PRESSURE WILL RETURN, AND BRING BACK
COOLER AND DRIER WEATHER FOR THE REST OF THE WEEK.
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 158 PM EDT FRI JUL 17 2026
VISIBILITY REDUCTIONS DUE TO SMOKE TO SLOWLY IMPROVE OVER THE
COURSE OF THE TAF PERIOD...BUT CURRENT EXPECTATIONS ARE AT LEAST
ANOTHER 8-12 HOURS OF IMPACTS TO TERMINAL BEFORE SMOKE BEGINS TO
MOVE OFF. SOME SHOWERS, MAYBE A RUMBLE OF THUNDER OVER THE NEXT 6
HOURS OR SO BUT ONLY CONFIDENT ENOUGH TO KEEP PROB30 IN FOR A
COUPLE LOCATIONS.
MARINE
ISSUED AT 158 PM EDT FRI JUL 17 2026
WE WILL BE HOISTING SMALL CRAFT ADVISORIES AND BEACH HAZARDS
STATEMENTS FOR THE ENTIRE LAKESHORE FROM OVERNIGHT TONIGHT THROUGH
SATURDAY NIGHT. WINDS WILL INCREASE THIS EVENING AHEAD OF THE FRONT,
BUT SHOULD REMAIN JUST UNDER CRITERIA. IT WILL BE RIGHT ALONG AND
THEN BEHIND THE FRONT THAT CRITERIA SHOULD BE MET PRETTY EASILY WITH
A DECENT GRADIENT AND A GOOD SURGE OF COOLER AIR COMING IN. WINDS
WILL EVENTUALLY TURN OFFSHORE FROM THE NE SATURDAY NIGHT. WAVES WILL
SUBSIDE AT THAT POINT.
CONDITIONS WILL SETTLE DOWN FOR A COUPLE OF DAYS FOR SUNDAY AND
MONDAY AS HIGH PRESSURE MOVES THROUGH. THE NEXT PERIOD OF HIGHER
WINDS AND WAVES WILL COME IN LATE MONDAY INTO TUESDAY ASSOCIATED
WITH THE NEXT SYSTEM TO AFFECT THE AREA.
GRR WATCHES/WARNINGS/ADVISORIES
MI...AIR QUALITY ALERT UNTIL MIDNIGHT EDT SATURDAY NIGHT FOR
MIZ037>040-043>046-050>052-056>059-064>067-071>074.
BEACH HAZARDS STATEMENT FROM LATE TONIGHT THROUGH LATE SATURDAY
NIGHT FOR MIZ037-043-050-056-064-071.
MARINE...DENSE SMOKE ADVISORY UNTIL 8 PM EDT THIS EVENING FOR LMZ844>849.
SMALL CRAFT ADVISORY FROM 2 AM SATURDAY TO 4 AM EDT SUNDAY FOR
LMZ844>849.
DISCUSSION...NJJ
AVIATION...MACZKO
MARINE...NJJ
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