791
FXUS63 KGRR 210730
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
330 AM EDT TUE OCT 21 2025
KEY MESSAGES
- SHOWERS WITH GUSTY WINDS THIS MORNING
- SHOWERS WITH A CHANCE OF STORMS THIS AFTERNOON INTO TOMORROW
- COOLER WEATHER WITH CHANCES FOR SHOWERS AHEAD
DISCUSSION
ISSUED AT 330 AM EDT TUE OCT 21 2025
- SHOWERS WITH GUSTY WINDS THIS MORNING
LATEST RADAR SHOWS BANDS OF SHOWERS MOVING INLAND FROM THE WEST.
WESTERLY FLOW AND WARM LAKE WATERS IS ALLOWING FOR HEAVIER
PRECIPITATION ALONG THE LAKESHORE WITH GUSTY WINDS UPWARDS OF 30
MPH. THE RADAR IS IN FAIR AGREEMENT WITH THE MODELS. SO THE
OCCLUDED FRONT AND THE RESULTANT SHOWERS WILL MOVE EASTWARDS
OVERNIGHT, EXITING MICHIGAN AROUND SUNRISE. RAINFALL THROUGH THIS
MORNING SHOULD BE AROUND A QUARTER OF AN INCH.
- SHOWERS WITH A CHANCE OF STORMS THIS AFTERNOON INTO TOMORROW
THE OVERALL FORECAST AND CONCEPTUAL MODEL FOR THIS PATTERN REMAINS
CONSISTENT. A LARGE UPPER LEVEL BAROTROPIC LOW WILL MOVE THROUGH
THE UPPER MIDWEST TODAY. THAT LOW WILL BRING SUCCESSIVE
BOUNDARIES AROUND IT AND THROUGH LOWER MICHIGAN. WITH THE STRONG
GRADIENT AND A LOW AROUND 994MB, GUSTY WINDS ARE EXPECTED THROUGH
THIS AFTERNOON AND INTO WEDNESDAY. SHORT WAVE, MID LEVEL
INSTABILITY SHOULD AID THIS GRADIENT. THAT INCREASE OF INSTABILITY
IS REFLECTED IN LATEST HRRR AND HREF WITH CAPE POTENTIALLY UPWARDS
OF 400 TO 500 J/KG. THAT SHOULD BE ENOUGH, COUPLED WITH THE LAKE
ENHANCEMENT AND SHEAR, TO ALLOW FOR STORMS THIS AFTERNOON. THE
COLD AIR ALOFT, ALONG WITH STRONG WINDS MIXING TO THE SURFACE
MEANS SMALL HAIL DEVELOPMENT REMAINS POSSIBLE.
BEST MOISTURE SHOULD ARRIVE TONIGHT WITH STRONG NORTHWESTERLY
FLOW CONTINUING TONIGHT INTO WEDNESDAY. WIDESPREAD SHOWERS WILL
CONTINUE TONIGHT INTO TOMORROW HEAVIEST PRECIPITATION ALONG THE
LAKESHORE. THOUGH PRECIP UPWARDS OF A HALF AN INCH TO AN INCH
REMAIN POSSIBLE WEST OF THE US 127 CORRIDOR.
- COOLER WEATHER WITH CHANCES FOR SHOWERS AHEAD
THE STRONG UPPER LEVEL LOW WILL CONTINUE TO DOMINATE THE PATTERN
THROUGH MOST OF THE WEEK. MID LEVEL TROUGHS AND MOISTURE WILL
CONTINUE TO KEEP RAIN SHOWERS IN THE FORECAST THROUGH THURSDAY.
850 MB TEMPS AS LOW AS -3C THURSDAY EVENING. THE SHOWERS WILL
FINALLY TAPER OFF LATE THURSDAY INTO FRIDAY AS THE STRONG LOW
TREKS INTO EASTER CANADA AND THROUGH MAINE.
IN ITS WAKE A COLDER PERIOD IS AHEAD OVERALL, WITH TEMPS
DROPPING BELOW NORMAL. MIN TEMPERATURES COULD BE NEAR FREEZING BY
SATURDAY MORNING. THERE IS SOME QUESTION ON THE TRACK OF THE
SYSTEM THROUGH THIS WEEKEND, BUT WITH SOME INSTABILITY PRESENT
THERE IS A CHANCE OF RAIN SHOWERS THROUGH THE WEEKEND.
AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
ISSUED AT 126 AM EDT TUE OCT 21 2025
LIGHT SHOWERS HAVE BEGUN TO MOVE THROUGH THE REGION AS FRONTAL
BANDS APPROACH. EXPECT PERIODS OF MVFR CIGS AND VSBYS UNTIL 10Z
WITH IMPROVING CONDITIONS BY 12Z. ANOTHER ROUND OF LOWER CLOUDS
WITH SHOWERS WILL MOVE IN DURING THE LATE AFTERNOON TIMEFRAME
WITH AREAS OF MVFR CONDITIONS. THERE IS A CHANCE FOR AN ISOLATED
STORMS SO HAVE INCLUDED PROB30 GROUPS TO REPRESENT THIS POTENTIAL.
SOUTH/SOUTHWEST LLWS OF 40 KNOTS WILL CONTINUE FOR THE NEXT FEW
HOURS. THE LOW LEVEL JET CAUSING THIS SHEAR WILL MOVE EASTWARD
AFTER 10Z, ENDING THE THREAT OF LLWS. GUSTY WINDS HAVE BEGUN TO
MIX DOWN TO THE SURFACE WITH WIND GUSTS OF 20 TO 25 KTS ALREADY AT
MKG AND AZO. THESE WINDS WILL BEGIN TO INFILTRATE THE OTHER TAF
SITES OVERNIGHT. EXPECT GUSTY WINDS TO INCREASE TO UPWARDS OF
35KTS AND CONTINUING THROUGH TUESDAY. THERE WILL BE IMPROVING
CONDITIONS LATE TUESDAY WITH MORE SHOWERS TUESDAY NIGHT INTO
WEDNESDAY WITH MVFR CIGS AND VSBYS EXPECTED.
MARINE
ISSUED AT 330 AM EDT TUE OCT 21 2025
SMALL CRAFT CONDITIONS ARE BECOMING WIDESPREAD ACROSS THE NEAR
SHORE, WITH PERIODS OF GALES THROUGH THE FAR SOUTHERN ZONES. THIS
IS EXPECTED AND ANY GALE CONDITIONS ARE ACCOMPANYING THE FRONT AS
IT MOVES ONSHORE. SMALL CRAFT CONDITIONS ALONG WITH THE SMALL
CRAFT ADVISORY WILL CONTINUE THROUGH 8 AM.
CONDITIONS WILL RAMP UP THIS MORNING WITH FREQUENT GALES BY THIS
AFTERNOON AND WILL RUN THROUGH WEDNESDAY EVENING. FORECAST HASN'T
CHANGED TO MUCH. A TIGHT PRESSURE GRADIENT, ALONG WITH COLD AIR
ADVECTION WILL COMBINE TO BRING 30 TO 40 KNOT WINDS THROUGH THE
NEAR SHORE. EXPECT STRONG WAVE ACTION TODAY INTO TOMORROW ALONG
WITH A CHANCE OF WATERSPOUTS. THE BEST CHANCE FOR WATERSPOUTS WILL
BE LATE WEDNESDAY AFTERNOON AND EVENING WHEN THE WINDS THROUGH
THE LOW/MID LEVELS DECREASE BELOW 35 KNOTS.
AS THE LOW MOVES EASTWARD THE WINDS WILL SLACKEN. HOWEVER, WINDS
AND WAVES SHOULD REMAIN DANGEROUS TO SMALL CRAFT THROUGH THURSDAY.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT THIS MORNING FOR LMZ844>849.
GALE WARNING FROM 8 AM THIS MORNING TO 2 AM EDT THURSDAY FOR
LMZ844>849.
DISCUSSION...CERU
AVIATION...CERU
MARINE...CERU
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