279
FXUS63 KGRR 181927
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
327 PM EDT SUN MAY 18 2025
KEY MESSAGES
- CHILLY NIGHT TONIGHT, PATCHY FROST POSSIBLE IN THE NORTH
- UNSEASONABLY COOL AND CLOUDY THIS WEEK
- WIDESPREAD SOAKING RAIN LIKELY MIDWEEK
DISCUSSION
ISSUED AT 327 PM EDT SUN MAY 18 2025
- CHILLY NIGHT TONIGHT, PATCHY FROST POSSIBLE IN THE NORTH
A CHILLY AIRMASS HAS MOVED INTO LOWER MICHIGAN AFTER LAST WEEK'S
HEAT AND HUMIDITY - 850 MB TEMPERATURES WILL BE SAGGING INTO THE
LOW SINGLE DIGITS OVERNIGHT TONIGHT. WEAK RIDGING AT BOTH THE
SURFACE AND ALOFT MOVES INTO THE STATE TONIGHT, WHICH WILL WEAKEN
PRESSURE GRADIENTS AND TRY TO GET RID OF SOME OF THE LINGERING
CLOUDINESS. WITH AN AIRMASS THIS COLD, A CLASSIC RADIATIONAL
COOLING NIGHT WOULD PROBABLY RESULT IN THE FROST CONCERNS IN THE
NORTHERN AREAS (GENERALLY IN RURAL AREAS NORTH OF I-96).
FORTUNATELY, DESPITE WINDS DROPPING, THERE WILL STILL BE A BIT OF
WIND IN THE BOUNDARY LAYER, AS WELL AS SOME SPORADIC LINGERING
CLOUDINESS IN THESE AREAS, SO WE'RE CURRENTLY THINKING WE WON'T
RADIATE OUT ENOUGH TO PRODUCE WIDESPREAD FROST. WHILE SOME
LOCALIZED POCKETS OF FROST CAN'T BE RULED OUT, WE'LL BE HOLDING
OFF ON ANY HEADLINES FOR NOW, GIVEN THE PREVIOUSLY MENTIONED
MITIGATING FACTORS.
- UNSEASONABLY COOL AND CLOUDY THIS WEEK
MUCH OF THE UPCOMING WEEK CONTINUES TO LOOK MORE LIKE AN APRIL
WEATHER PATTERN THAN A LATE MAY WEATHER PATTERN. AN UPPER TROUGH
MOVING OUT OF THE ROCKIES TONIGHT WILL TURN INTO A WEAKLY CLOSED
UPPER LOW THAT DRIFTS OUR DIRECTION AND LINGERS THROUGH AT LEAST
MIDWEEK. WHILE 850 MB TEMPERATURES WILL REBOUND A BIT, WIDESPREAD
CLOUDINESS AND OCCASIONALLY BREEZY CONDITIONS WILL MAKE IT FEEL
NOTABLY GLOOMIER FOR MUCH OF THIS WEEK, ESPECIALLY TUESDAY THROUGH
THURSDAY. GLOBAL ENSEMBLES CONTINUE TO SUGGEST THIS UPPER LOW
WILL INTERACT/PHASE WITH A SEPARATE LOW NEAR HUDSON BAY IN THE
WED/THU TIMEFRAME AND RESULT IN ANOTHER PLUNGE OF COOLER AIR
COMING INTO MICHIGAN FROM THE NORTH FOR THE END OF THE WEEK. 850
MB TEMPERATURES MAY ACTUALLY DIP BELOW 0C ON THURSDAY, WHICH WHEN
COMBINED WITH CLOUDS AND BREEZE WILL HOLD TEMPERATURES AROUND 50
DEGREES, WHICH IS APPROXIMATELY 20 DEGREES BELOW NORMAL FOR THIS
TIME OF YEAR. AS THIS UPPER LEVEL PATTERN SLOWLY MOVES EASTWARD BY
NEXT WEEKEND, OUR WEATHER PATTERN AND TEMPERATURES WILL SLOWLY
REBOUND BACK TO SOMETHING MORE CLOSELY RESEMBLING NORMAL.
- WIDESPREAD SOAKING RAIN LIKELY MIDWEEK
PREVIOUS DISCUSSIONS NOTED THE NORTHWARD JOG OF THE RAIN SHIELD
ASSOCIATED WITH THE UPPER LOW ON TUE/WED. THIS NORTHWARD MOVEMENT
HAS NOT CONTINUED, BUT HAS ALSO NOT MOVED BACK SOUTHWARD, SO
CONFIDENCE IS INCREASING THAT WE'RE LOOKING AT A FAIRLY WIDESPREAD
0.50" TO 1.00" GENERAL RAIN EVENT MIDWEEK. THIS WON'T FALL FAST
ENOUGH TO CAUSE ANY FLOODING CONCERNS, BUT WILL CONTINUE OUR TREND
OF FAIRLY MOIST SOILS.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 145 PM EDT SUN MAY 18 2025
WE ARE CONTINUING A THEME OF PERSISTENT MVFR CEILINGS INTO THE
OVERNIGHT HOURS FOR OUR MOST INLAND TERMINALS (LAN/JXN/BTL). BY
21Z THIS AFTERNOON, THERE COULD BE A SIGNIFICANT CUTOFF BETWEEN
MVFR AT THOSE LOCATIONS AND VFR/NO CEILINGS IMMEDIATELY WEST AT
GRR/AZO. THE GOOD NEWS IS THERE'S A LOW CHANCE OF CEILINGS
DROPPING BELOW 2000 FT AGL (FUEL ALT THRESHOLD) AT ANY OF THE
TERMINALS WHICH IS CERTAINLY MORE OPTIMISTIC THAN YESTERDAY.
MKG STANDS THE BEST CHANCE OF REMAINING PREDOMINANTLY VFR THROUGH
THE PERIOD DUE TO THE CURRENT CLEARING EFFECTS OF A LAKE BREEZE
THAT WILL EVENTUALLY YIELD TO N-NE BACKGROUND GRADIENT FLOW THIS
EVENING.
MARINE
ISSUED AT 327 PM EDT SUN MAY 18 2025
LATEST WAVEWATCH III GUIDANCE INDICATES THAT SIGNIFICANT WAVE
HEIGHTS COULD MAKE A RUN TOWARDS 4 FEET EARLY TONIGHT OFF THE SABLE
POINTS. THE LARGER WAVES WOULD BE SHORT-LIVED IN THE OUTER EXTENT OF
THE NEARSHORE ZONES AND QUICKLY SHUNTED WESTWARD AS THE OVERALL WIND
FLOW TRANSITIONS FROM NORTHWEST TODAY (AS CURRENTLY DEPICTED IN LDM
AND MEEM4 AND LDTM4 COASTAL STATIONS) TO NORTH-NORTHEAST AND WEAKER
BEGINNING EARLY TONIGHT. GIVEN THE SMALL AREAL AND TEMPORAL EXTENT
OF THIS THREAT DO NOT PLAN TO ISSUE A SMALL CRAFT ADVISORY (SCA).
FARTHER SOUTH THIS AFTERNOON, FAIRLY BRISK ONSHORE FLOW APPROACHING
20 KNOTS IS CURRENTLY NOTED AROUND MUSKEGON, GRAND HAVEN, AND
HOLLAND BUT THIS SHOULD SIMILARLY BE SHORT LIVED AND UNABLE TO GROW
WAVES MUCH BEYOND THE CURRENTLY OBSERVED 2-3 FOOT RANGE.
MORE APPRECIABLE CHANCES FOR A SCA ARRIVE TUESDAY AS STRONG EASTERLY
FLOW OVERSPREADS MUCH OF SOUTHERN LAKE MICHIGAN. WAVE GROWTH IN THE
NEAR SHORE WILL BE FETCH-LIMITED OF COURSE, BUT SUSTAINED SPEEDS
ABOVE 20 KNOTS WILL STILL MAKE CONDITIONS HAZARDOUS.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...AMD
AVIATION...TJT
MARINE...TJT
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