450
FXUS63 KGRR 072249
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
649 PM EDT THU MAY 7 2026
KEY MESSAGES
- FROST/FREEZE POSSIBLE AGAIN TONIGHT ACROSS THE NORTH
- A FEW SHOWERS POSSIBLE SATURDAY WITH A COLD FRONT PASSAGE
- COOL SUNDAY THROUGH WEDNESDAY - UNSETTLED CONDITIONS TUESDAY
DISCUSSION
ISSUED AT 310 PM EDT THU MAY 7 2026
SECONDARY SHORTWAVE PERTURBATION WORKING ACROSS WISCONSIN IN
ADVANCE OF A STRONGER CLOSED WAVE NORTHWEST OF LAKE SUPERIOR WILL
PASS OVER WEST MICHIGAN THIS EVENING. SHOWERS ARE EXPANDING IN
COVERAGE WITH THE MATURING DIURNAL BOUNDARY LAYER BENEATH THIS
FORCING FEATURE. MANY OF THE SHOWERS WILL NOT SURVIVE THE LAKE
TRANSIT - HOWEVER, THE WAVE WILL BE REINTRODUCED TO A MATURE
BOUNDARY LAYER DOWNSTREAM OF THE LAKE - ESPECIALLY ALONG AND
SOUTH OF THE I-96, WHERE MORE INSOLATION HAS PRIMED DEEPER MIXING.
NET RESULT WILL BE A FEW HOURS OF POTENTIAL FOR SCATTERED SHOWERS
THIS EVENING - MAINLY ALONG THE I-94 CORRIDOR.
SUBSIDENCE KICKS IN QUICKLY IN THE WAKE OF THIS WAVE, WHICH WILL
SUPPORT CLEARING SKIES - WITH THE EARLIEST CLEARING OCCURING
ACROSS THE NORTHERN COUNTIES OF THE FORECAST AREA. GOOD OUTGOING
RADIATIVE FORCING AND A DECOUPLED SURFACE LAYER WILL ONCE AGAIN
ALLOW TEMPERATURES WILL DROP TO AROUND FREEZING - MAINLY ALONG AND
NORTH OF US-10. SURFACE MOISTURE AVAILABILITY WITH THE RECENT AGGRESSIVE
SEASONAL GREEN UP WILL PUT THE BRAKES ON THE TEMPERATURE FALL.
FROST/FREEZE HEADLINES LAY OUT THE BEST CHANCES FOR IMPACTFUL COLD
CONDITIONS. THE NEAR SURFACE RIDGING WILL LINGER THROUGH FRIDAY
PROVIDING THE REGION WITH A QUIET AND SEASONABLE WEATHER.
LONGWAVE TROUGHING ALOFT IS THE THEME THROUGHOUT THE FORECAST
PERIOD. A SHORTWAVE HANDOFF FROM THE CLOSED LOW OVER ALASKA TO THE
TROUGH COMPLEX OVER HUDSON BAY WILL BE THE NEXT WEATHER MAKER FOR
THE REGION ON SATURDAY. STILL SOME SOLUTION VARIANCE ASSOCIATED
WITH THE TIMING AND WAVE ALIGNMENT WITHIN THE NORTHWEST FLOW OVER
CENTRAL CANADA ON FRIDAY. GENERAL CONSENSUS IS THE ESTABLISHED
LONGWAVE TROUGH WILL BE DEEPER THAN PRIOR CYCLES AND THE
SHORTWAVE WILL SLING THROUGH THE GREAT LAKES EARLIER ON SATURDAY.
LOOK FOR A LITTLE MORE MOVEMENT IN THE FORECAST TIMING OF THE
FRONTAL PASSAGE AND THE ASSOCIATED SHOWER CHANCES. THE BEST
CHANCE FOR SHOWERS WILL BE ACROSS MID-MICHIGAN AND POINTS EAST,
WHERE GREATER DESTABILIZATION CAN OCCUR AHEAD OF THE COLD FRONT.
COOL WEATHER WILL THEN SETTLE IN FOR SUNDAY THROUGH WEDNESDAY. A
REASONABLY STRONG SYSTEM IN THE NORTHWEST FLOW IS EXPECTED IN THE
TUESDAY TIME WINDOW. THE TRAJECTORY OF BEST FORCING IS STILL OUT
OF FOCUS AT THIS TIME - SO ELEVATED CHANCES FOR SHOWERS WILL BE
THE GOING MESSAGE.
AVIATION /00Z TAFS THROUGH 00Z SATURDAY/
ISSUED AT 649 PM EDT THU MAY 7 2026
WIDESPREAD CUMULUS PERSIST WITH CLOUD BASES PREDOMINANTLY IN THE
6-10KFT RANGE AT PRESENT. ISOLATED SHOWERS ARE LIKELY TO IMPACT
AZO/BTL/JXN FOR THE NEXT HOUR OR TWO, HOWEVER RESTRICTIONS ARE NOT
ANTICIPATED GIVEN THE DRY AMBIENT AIRMASS. LIGHT AND VARIABLE
WINDS AND INCREASED DEWPOINTS OVERNIGHT MAY LEAD TO A WINDOW FOR
LIGHT FOG DEVELOPMENT BETWEEN ROUGHLY 08Z-13Z. HIGHEST CONFIDENCE
IS ALONG I-94, HOWEVER CONFIDENCE IS TO LOW TO INCLUDE
RESTRICTIONS WITH THIS PACKAGE (20% CHANCE OF MVFR CONDITIONS).
GOING INTO THE DAY FRIDAY, HIGH CLOUDS WILL PERSIST THROUGH THE
REST OF THE TAF PERIOD. WINDS WILL INCREASE FROM THE SOUTHWEST TO
7-10 KNOTS DURING THE AFTERNOON FRIDAY.
MARINE
ISSUED AT 310 PM EDT THU MAY 7 2026
WEAK SURFACE HIGH PRESSURE WILL CONTINUE TO SUPPORT ONSHORE FLOW
CONDITIONS WITH WAVE GENERALLY LESS THAN 2 FEET THROUGH FRIDAY.
STRONGER SOUTHERLY FLOW IS EXPECTED BY EARLY SATURDAY MORNING AS
THE NEXT SYSTEM APPROACHES THE REGION. EVEN WITH THE RELATIVELY
STABLE MARINE BOUNDARY LAYER, GUSTS WILL CLIMB TO AROUND 20 KNOTS
AND SUPPORT A BUILDING WAVE FIELD, HIGHER FROM GRAND HAVEN NORTH
TO MANISTEE.
GRR WATCHES/WARNINGS/ADVISORIES
MI...FROST ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM EDT FRIDAY FOR
MIZ037-038-043>046.
FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT FRIDAY FOR
MIZ039-040.
MARINE...NONE.
DISCUSSION...MANN (DTX)
AVIATION...THOMAS
MARINE...MANN (DTX)
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