171
FXUS63 KGRR 162328
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
728 PM EDT THU OCT 16 2025
KEY MESSAGES
- LIGHT RAIN TONIGHT AND TOMORROW
- WET AND WINDY WEATHER AHEAD
- MORE UNSETTLED WEATHER NEXT WEEK
DISCUSSION
ISSUED AT 330 PM EDT THU OCT 16 2025
- LIGHT RAIN TONIGHT AND TOMORROW
AN UPPER LEVEL RIDGE WILL CONTINUE TO BUILD AND MOVE OVER THE
GREAT LAKES REGION THROUGH TOMORROW. HOWEVER, MID LEVEL MOISTURE
STEMMING FROM AN INFILTRATING LOW WILL BRING A SHORT SAVE TROUGH,
THROUGH THE MID AND LOWER LEVELS. THIS WILL BRING ENOUGH
INSTABILITY THAT SHOULD ALLOW FOR ISOLATE SHOWERS ALONG AND NORTH
OR THE I 96 CORRIDOR.
WARM AIR ADVECTION WILL CONTINUE OUT AHEAD OF THE APPROACHING
LOW. THIS WILL KEEP TEMPERATURES IN THE UPPER 60S TO LOW 70S. THAT
IS AROUND 10 DEGREES ABOVE NORMAL.
THERE SHOULD BE A BREAK IN PRECIPITATION FRIDAY AFTERNOON.
HOWEVER THAT BREAK IN RAIN WILL BE SHORT LIVED.
- WET AND WINDY WEATHER AHEAD
THE TREND IS YOUR FRIEND AND THIS CASE IS NOT THE EXCEPTION TO
THE RULE. LATEST MODELS CONTINUE TO SHOW A COLD FRONT APPROACHING
FROM THE WEST, MOVING SLOWLY TO THE EAST. AS IT MOVES ACROSS THE
GREAT LAKES IT WILL DRAPE ACROSS MICHIGAN FROM THE NORTHEAST TO
THE SOUTHWEST BEGINNING EARLY SATURDAY MORNING. CAPE VALUES REMAIN
FAIRLY LOW, BUT CAN'T RULE OUT THUNDER ALONG THE LEADING EDGE OF
THE FRONTAL BOUNDARY SATURDAY. THE BIGGEST AREA OF MOISTURE HAS
SHIFTED TO THE EAST AND SOUTH. THE FRONT SHOULD STALL AS THE RIDGE
SLOWLY SHIFT EASTWARD WHICH WILL ALLOW PERIODS OF SHOWERS
SATURDAY.
THE HEAVIEST RAIN SHOWERS WILL MOVE THROUGH THE AREA SATURDAY
NIGHT INTO SUNDAY, ESPECIALLY THROUGH SOUTHERN LOWER MICHIGAN. THE
LOW CONTINUES TO TRACK THROUGH THE STATE, BRINGING WET AND WINDY
WEATHER THROUGH SUNDAY. TWO DAY TOTALS HAVE QPF UPWARDS OF 1 TO 2
INCHES, HOWEVER THAT IS OVER A 48 HOUR PERIOD. HEAVIEST RAIN IS
MOST LIKELY MAINLY ALONG THE LAKE SHORE AND ALONG A SWATH ALONG
THE I 69 CORRIDOR.
WHILE THE MOISTURE, TEMPERATURE BOUNDARIES WILL ALLOW FOR GUSTY
WINDS THROUGH THIS PERIOD. SATURDAY SHOULD HAVE GUSTY UPWARDS OF
30 MPH. SUNDAY SHOULD HAVE A STRONGER GRADIENT WITH WIND GUSTS
UPWARDS OF 40 MPH POSSIBLE SUNDAY AND MONDAY AFTERNOON.
- MORE UNSETTLED WEATHER NEXT WEEK
WITH THE LARGE UPPER LEVEL LOW MOVING SLOWLY ALONG THE UPPER
GREAT LAKES REGION, SHORT WAVES AND COLD NORTHWESTERLY FLOW SHOULD
BRING PERIODS OF SHOWERS THROUGH THE AREA THROUGH MID NEXT WEEK.
THIS WILL BRING TEMPERATURES BACK TO AROUND NORMAL, THOUGH LOWS
SHOULD REMAIN ABOVE FREEZING.
AVIATION /00Z TAFS THROUGH 00Z SATURDAY/
ISSUED AT 728 PM EDT THU OCT 16 2025
VFR CONDITIONS WILL CONTINUE THROUGH FRIDAY AFTERNOON. THERE IS A
SLIGHT CHANCE OF SHOWERS AFTER MIDNIGHT WHICH SHOULD END BEFORE
12Z. WINDS WILL BE LIGHT AND VARIABLE TONIGHT AND PICK UP FROM THE
SOUTH DURING THE MORNING WITH SOME GUSTS TO 20 KNOTS IN THE
AFTERNOON POSSIBLE, ESPECIALLY AT MKG.
MARINE
ISSUED AT 331 PM EDT THU OCT 16 2025
SMALL CRAFT ADVISORY CONDITIONS EXPECTED FRIDAY AND SATURDAY.
GALES POSSIBLE ON SUNDAY.
HIGH PRESSURE OVER THE REGION THURSDAY WILL DEPART TO THE EAST, AND
THE GRADIENT IN PRESSURE BETWEEN THE HIGH AND A LOW OVER MANITOBA /
NORTHWEST ONTARIO WILL DRIVE STRENGTHENING SOUTHERLY WINDS OVER THE
LAKE ON FRIDAY. 15 TO 25 KNOT WINDS WITH GUSTS TO 30 KNOTS ARE
EXPECTED, WITH WAVES 6 TO 10 FEET IN THE NEARSHORE, THE BRUNT OF
WHICH WILL BE FELT FROM GRAND HAVEN TOWARD MANISTEE. HAZARDOUS WINDS
AND WAVES WILL PERSIST THROUGH SATURDAY, GRADUALLY BUT NOT
COMPLETELY SUBSIDING BY EVENING.
A MORE CLASSIC AUTUMN LOW-PRESSURE SYSTEM DEEPENING OVER THE GREAT
LAKES IS LIKELY FOR SUNDAY. AS MENTIONED IN THE PREVIOUS DISCUSSION,
THE ATMOSPHERIC DISTURBANCE THAT WILL BE RESPONSIBLE FOR THIS IS
STILL OUT IN THE PACIFIC NORTHWEST REGION. SO THERE ARE STILL SOME
DETAILS TO SHORE UP WITH THE STRENGTH AND TRACK OF THE LOW, WHICH
WILL AFFECT THE DIRECTION AND STRENGTH OF THE WINDS OVER LAKE
MICHIGAN. THE ENSEMBLE AVERAGE TRACK OF THE LOW TAKES IT FROM
SOUTHERN MICHIGAN TO LAKE HURON SUNDAY MORNING, GIVING LAKE MICHIGAN
NORTHWEST WINDS WITHIN A STRONG PRESSURE GRADIENT BETWEEN THE LOW
AND THE HIGH PRESSURE RIDGE QUICKLY ARRIVING ON ITS HEELS. LAST
NIGHT'S RUN OF THE EUROPEAN ENSEMBLES RESULTED IN ABOUT 75 TO 80
PERCENT OF MEMBERS EXPRESSING GALES OVER THE SOUTHERN MID-LAKE BUOY,
AND ABOUT 20 PERCENT WITH PEAK GUSTS AT STORM FORCE. TODAY'S RUN
LOOKS SIMILAR. THIS ENSEMBLE SYSTEM CAN BE UNDERDISPERSIVE WITH ITS
SOLUTION ENVELOPE AND CAN SOMETIMES MAKE US OVERCONFIDENT, BUT
UNLESS THE FORECAST SHIFTS SIGNIFICANTLY, A GALE WATCH WILL PROBABLY
BE POSTED SOON FOR SUNDAY.AY WITH WAVES THAT WILL LIKELY PEAK IN THE
12-15 FOOT RANGE.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 5 AM FRIDAY TO 8 PM EDT SATURDAY FOR
LMZ844>849.
DISCUSSION...CERU
AVIATION...OSTUNO
MARINE...CAS
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