450
FXUS63 KGRR 131735
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
135 PM EDT SUN SEP 13 2026
KEY MESSAGES
- SLIGHT CHANCE OF RAIN TODAY
- SHOWERS AND THUNDERSTORMS POSSIBLE TUESDAY THROUGH THURSDAY
DISCUSSION
ISSUED AT 216 AM EDT SUN SEP 13 2026
- SLIGHT CHANCE OF RAIN TODAY
A COLD FRONT MOVES THROUGH TODAY ALONG WITH SOME MID-LEVEL
FRONTOGENESIS. MOISTURE IS LIMITED HOWEVER AND POP HAVE TRENDED
LOWER SINCE YESTERDAY. BEST CHANCE FOR RAIN WILL BE ACROSS THE
CENTRAL FORECAST AREA THIS AFTERNOON. COOLER AND DRIER AIR MOVES
IN BEHIND THE FRONT. WITH THE SURFACE HIGH BUILDING IN TONIGHT,
RADIATIONAL COOLING CONDITIONS WILL BE OPTIMIZED AND TEMPERATURES
WILL FALL INTO THE 40S IN MOST PLACES, WITH EVEN UPPER 30S POSSIBLE
ACROSS THE NORTHERN INTERIOR.
- SHOWERS AND THUNDERSTORMS POSSIBLE TUESDAY THROUGH THURSDAY
A SHORTWAVE TROUGH EJECTS OUT OF THE NORTHERN ROCKIES WITH A
SURFACE LOW TRACKING INTO CANADA BY TUESDAY. A TRAILING COLD
FRONT IS EXPECTED TO TOUCH OFF SHOWERS AND THUNDERSTORMS MONDAY
NIGHT AND TUESDAY. INSTABILITY AND DEEPER MOISTURE IS ACROSS
NORTHERN LOWER MICHIGAN POOLING AHEAD OF THE COLD FRONT, WHICH
SINKS SOUTH THROUGH THE FORECAST AREA ON TUESDAY. PRECIPITABLE
WATER SURGES CLOSE 2 INCHES, SO HEAVY RAIN POTENTIAL IS THERE AS
THE FRONT WILL BE MOVING SLOWLY AND MBE VECTORS ARE LESS THAN 5
KNOTS.
THE FRONT STALLS ACROSS THE SOUTHERN ZONES ON WEDNESDAY, WITH A
SHOWERS AND THUNDERSTORMS POSSIBLE INTO THURSDAY AS A SURFACE LOW
TRACKS ALONG THE FRONT ACROSS SOUTHERN LOWER MICHIGAN.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 130 PM EDT SUN SEP 13 2026
VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD AT ALL TAF
SITES. MID CLOUDS /BASES 10-12KFT/ WILL QUICKLY INCREASE NEXT FEW
HOURS, AS A FAST MOVING IMPULSE MOVES W TO E ACROSS THE LOWER
GREAT LAKES. THIS WILL ALSO YIELD A SMALL WINDOW OF LIGHT
SHOWERS, PER UPSTREAM OBS AND SHORT RANGE MODEL GUIDANCE, LIKELY
LASTING NO MORE THAN 1-2 HR AT ANY GIVEN TAF SITE BETWEEN ROUGHLY
19-00Z. GIVEN DRY AIR MASS AND HIGH CLOUD BASES, DON'T EXPECT
VSBYS IN RAIN SHOWERS TO DROP BELOW 6SM. SKIES WILL THEN CLEAR BY
EARLY THIS EVENING, AND CONTINUE FOR THE DURATION OF THE NIGHT THROUGH
18Z MONDAY.
NW BREEZES GUSTING TO 15-20 KT THIS AFTERNOON WILL QUICKLY
DIMINISH TO AROUND 5 KT THIS EVENING AS HIGH PRESSURE BUILDS
OVERHEAD, THEN BECOME E/SE 5-10 KT EARLY MONDAY AS HIGH SLOWLY
MOVES EAST OF THE AREA.
MARINE
ISSUED AT 216 AM EDT SUN SEP 13 2026
NO CHANGES TO THE MARINE HEADLINES. AFTER A BRIEF LULL, WINDS AND
WAVES WILL INCREASE AGAIN ON MONDAY NIGHT AND TUESDAY WHEN SOUTH
GALES ARE EXPECTED.
GRR WATCHES/WARNINGS/ADVISORIES
MI...BEACH HAZARDS STATEMENT UNTIL 11 PM EDT THIS EVENING FOR MIZ037-
043-050-056-064-071.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR LMZ844>849.
DISCUSSION...OSTUNO
AVIATION...SMITH
MARINE...OSTUNO
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