584
FXUS63 KGRR 042330
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
630 PM EST TUE FEB 4 2025
KEY MESSAGES
- LIGHT WINTRY MIX LIKELY FOR WEDNESDAY NIGHT
- WINDY CONDITIONS THURSDAY
- CONFIDENCE GROWS WITH AND IMPACTFUL STORM SATURDAY
DISCUSSION
ISSUED AT 141 PM EST TUE FEB 4 2025
- LIGHT WINTRY MIX LIKELY FOR WEDNESDAY NIGHT
A DISORGANIZED MID TO UPPER LEVEL WAVE TRACKS EASTWARD INTO THE
GREAT LAKES REGION DURING THIS TIME. OVERALL THIS SYSTEM IS SHOWN
TO REMAIN WEAK AS IT PASSES THROUGH. THERE WILL BE A LOW LEVEL JET
LIFTING NORTHWARD INTO THE MI/IN BORDER SO SOME DECENT LOW LEVEL
LIFT IS POSSIBLE OVER SOUTHERN PARTS OF LOWER MI, ESPECIALLY
WEDNESDAY NIGHT. HOWEVER, THE MOISTURE PROFILE DOES NOT FAVOR DEEP
SATURATION FOR ANY PROLONGED PERIOD OF TIME. INITIALLY THE DGZ
SATURATES WEDNESDAY AFTERNOON AND EVENING, BUT THE LOW LEVELS ARE
SHOWN TO BE RELATIVELY DRY. THEN, BY THE TIME THE LOW LEVELS
SATURATE, THE DGZ DRIES OUT. SURFACE TEMPERATURES REMAIN BELOW
FREEZING SO ONCE THE DGZ DRIES OUT FREEZING RAIN/DRIZZLE IS
LOOKING LIKELY, WITH WEDNESDAY NIGHT THE MAIN PERIOD FOR THIS TO
HAPPEN. DESI HREF PROBABILITIES FOR FREEZING RAIN SUGGEST THE
SOUTHERN PARTS OF THE CWA, NEAR AND SOUTH OF I-96, HAVE A
RELATIVELY HIGH PROBABILITY FOR SEEING LIGHT FREEZING RAIN.
OVERALL QPF VALUES ARE SHOWN TO REMAIN UNDER A TENTH OF AND INCH
IN THIS MIXED PRECIPITATION SCENARIO AND QPF TRENDS HAVE BEEN
LOWERING WITH TIME. STILL, WITH A RELATIVELY HIGH RISK FOR
LIGHT FREEZING RAIN/DRIZZLE, IMPACTS ARE LOOKING LIKELY FOR
WEDNESDAY NIGHT AND INTO THE THURSDAY MORNING COMMUTE.
- WINDY CONDITIONS THURSDAY
A TIGHTENING PRESSURE GRADIENT SETS UP THURSDAY INTO THURSDAY
NIGHT. THE WINDS UP AROUND 850 INCREASE TO 55 TO 60 KNOTS. BASED
ON THE MIXING HEIGHTS, THERE'S A POTENTIAL FOR PARTS OF THE REGION
TO SEE SURFACE GUSTS REACHING INTO WIND ADVISORY LEVELS. ENSEMBLE
WIND GUST VALUES FROM THE VARIOUS MODELS HAVE INCREASED TO 40 TO
50 MPH FOR MUCH OF THE REGION, PEAKING 21Z THU - 00Z FRI. WE WILL
INCREASE THE WINDS WITH THIS FORECAST.
- CONFIDENCE GROWS WITH AND IMPACTFUL STORM SATURDAY
A FAST MOVING STRONGER WAVE TRACKS EASTWARD THROUGH THE REGION
SATURDAY INTO SATURDAY NIGHT. THIS SYSTEM IS SHOWN TO FEATURE A
COUPLED UPPER JET, GULF MOISTURE AND MID LEVEL FGEN. WEAKNESS IN
THE STABILITY ABOVE 850 MB IS SHOWN AS WELL. AS A RESULT, THE QPF
WILL BE HIGHER. QPF ENSEMBLE MEAN VALUES ARE RUNNING AROUND A
HALF INCH FOR THE AREA NORTH OF I-96 WITH LESSER AMOUNTS FURTHER
SOUTH. THIS IS LIKELY DUE TO THE FACT THAT THE DGZ DRIES OUT OVER
SOUTHERN PARTS OF THE CWA DURING THE LATE AFTERNOON INTO THE
EVENING HOURS. THE 850 MB THERMAL RIDGE REACHES INTO SOUTHERN
LOWER MICHIGAN DURING THE AFTERNOON AND EVENING, WHICH WILL LIKELY
RESULT IN MIXED PRECIPITATION THERE, BUT THE COLD AIR REMAINS
OVER NORTHERN ZONES SO A SWATH OF HEAVIER SNOW IS LOOKING LIKELY.
ENSEMBLE SNOW AMOUNTS FOR GRAND RAPIDS SHOW A WIDE SPREAD OF
VALUES SO THERE IS STILL A LOT OF UNCERTAINTY WITH THE DETAILS,
BUT GREATER CONFIDENCE FOR HIGHER QPF VALUES FOR THIS WINTER
SYSTEM EXISTS.
AVIATION /00Z TAFS THROUGH 00Z THURSDAY/
ISSUED AT 630 PM EST TUE FEB 4 2025
LITTLE TO NO IMPACT EXPECTED FOR THE TERMINALS OVER THE NEXT 24
HOURS. MVFR TO VFR LOW CLOUDS THIS AFTERNOON HAVE MOVED OUT OF ALL
OF THE TERMINALS AS OF PRESS TIME. WE EXPECT THAT ONLY MID AND
HIGH CLOUD CEILINGS WILL REMAIN, WITH FEW-SCT CLOUDS AROUND
3000-3500 FT AGL POSSIBLE FOR THE NEXT FEW HOURS. MID AND HIGH
CLOUDS WILL PERSIST THROUGH ALL OF WEDNESDAY. WINDS WILL BE FROM
THE N, AND SWITCH TO NE/E ON WED.
WE WILL SEE IMPACTS MOVE IN JUST AFTER THIS FORECAST PERIOD IN THE
FORM OF SNOW AND LIGHT FREEZING RAIN. THAT WILL BE ACCOUNTED FOR
IN SUBSEQUENT FORECASTS.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR LMZ844>849.
DISCUSSION...MJS
AVIATION...NJJ
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