656
FXUS63 KGRR 311744
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1244 PM EST FRI JAN 31 2025
KEY MESSAGES
- LIGHT RAIN TODAY/WINTRY MIX POSSIBLE NORTH
- MIXED RAIN/SNOW SATURDAY NIGHT/SUNDAY
- WINTRY MIX POSSIBLE MID WEEK
UPDATE
ISSUED AT 1151 AM EST FRI JAN 31 2025
SURFACE LOW PRESSURE IS SITUATED ACROSS NORTHERN INDIANA AS WE
APPROACH THE NOON HOUR. A DEFORMATION ZONE IS LOCATED TO THE NORTH
OF THE LOW AND IS PRODUCING A COLD RAIN ACROSS SOUTHERN LOWER
MICHIGAN FROM ESSENTIALLY THE I-96 CORRIDOR TO THE SOUTH. THE HREF
KEEPS THE PRECIPITATION ESSENTIALLY WHERE IT IS AT THIS AFTERNOON,
EVENTUALLY DROPPING IT SOUTH OUT OF THE STATE BY 900PM. AS COLDER
AIR FILTERS IN FROM THE NORTH BEHIND THE EXITING LOW, RAIN WILL
MIX AT TIMES WITH SNOW. WE ARE NOT EXPECTING ANY ACCUMULATION
OUTSIDE OF SOME TRACE AMOUNTS FROM THE LANSING AREA SOUTH TO
JACKSON. OVERALL LITTLE CHANGE WAS MADE TO THE GOING FORECAST
WHICH HAD THINGS WELL IN HAND.
DISCUSSION
ISSUED AT 258 AM EST FRI JAN 31 2025
- LIGHT RAIN TODAY/WINTRY MIX POSSIBLE NORTH
RADAR SHOWS LIGHT RAIN SOUTH OF I-96 SLOWLY MOVING NORTHWARD
ASSOCIATED WITH THE WARM AIR ADVECTION WING OF THE CYCLONE OVER
OKLAHOMA. CONCURRENTLY, LOW PRESSURE OVER SOUTHERN ONTARIO IS
MOVING EAST AND THE COLD FRONT ASSOCIATED WITH IT IS NEAR THE
STRAITS MOVING SOUTH.
THERE'S QUITE A TEMPERATURE GRADIENT BETWEEN AREAS THAT ARE CLEAR,
LIKE CAD AT 18 DEGREES AND MBL AT 23 AND THOSE WHERE LOW CLOUDS
ARE PRESENT, SUCH AS LDM AT 32 AND RQB AT 35. THERE'S A NARROW
WINDOW IN WHICH SOME LIGHT FREEZING RAIN MAY DEVELOP AROUND 12Z
ACROSS THE NORTHEAST CWA, BUT CHANCES OF SEEING ICING SEEM TO BE
DECREASING AND THIS IS LOOKING MORE LIKE A GENERAL LIGHT RAIN
EVENT THIS MORNING.
THE RAIN SHIELD WILL CONTINUE TO MOVE NORTH THIS MORNING AT THE
SAME TIME THAT THE COLD FRONT MOVES SOUTH. THE RESULT WILL BE
LIGHT RAIN MIXING WITH AND THEN CHANGING TO LIGHT SNOW THIS
AFTERNOON AS THE LOW TO THE SOUTH MOVES THROUGH THE REGION AND
COLDER AIR FLOWS IN BEHIND THE NORTHERN STREAM COLD FRONT THAT
WILL ACCELERATE SOUTHWARD AS NORTHEAST WINDS DEVELOP IN RELATION
TO THE LOW PASSING BY TO THE SOUTH. OVERALL, SNOW ACCUMULATIONS
LOOK LESS THAN AN INCH AND TRAVEL IMPACTS AREN'T ANTICIPATED.
- MIXED RAIN/SNOW SATURDAY NIGHT/SUNDAY
A CLIPPER MOVING EAST ALONG THE US/CANADA BORDER FROM SOUTH TO
NORTHER WILL PUSH SOME LIGHT SNOW INTO THE CWA SATURDAY NIGHT VIA
SOME ISENTROPIC LIFT IN THE WARM AIR ADVECTION WING. THE AREA MOST
LIKELY TO SEE LIGHT SNOW WILL BE NORTH OF I-96. ONE TO TWO INCHES
ARE POSSIBLE THERE AND SHOULD BE EAST OF THE CWA BY SUNDAY
AFTERNOON.
- WINTRY MIX POSSIBLE MID WEEK
TONIGHT'S MODEL RUNS ARE IN A LITTLE BETTER AGREEMENT IN REGARD TO
THE POTENTIAL MID WEEK SYSTEM.
THERE SHOULD BE A DECENT AMOUNT OF LOW LEVEL COLD AIR IN PLACE
TUESDAY NIGHT AS A WARM FRONT MOVES NORTH FROM THE OHIO VALLEY. A
STRONG FEED OF MOISTURE NORTHWARD AHEAD OF LOW PRESSURE NEAR THE
MISSOURI VALLEY WILL RESULT IN PRECIPITATION DEVELOPING IN AN
ENVIRONMENT OF STRONG ISENTROPIC LIFT. INITIALLY, WE'LL SEE LIGHT
SNOW DEVELOP, BUT AS WARM TEMPERATURES PUSH IN FROM THE SOUTH,
FREEZING RAIN MAY DEVELOP TUESDAY NIGHT/WEDNESDAY. EVENTUALLY,
THE PRECIPITATION WILL TRANSITION TO JUST RAIN SOUTH OF I-96 WEDNESDAY.
IT'S TOO EARLY TO TELL YET HOW MUCH, IF ANY, ICE CAN BE EXPECTED,
BUT CERTAINLY BEARS WATCHING.
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 1244 PM EST FRI JAN 31 2025
WE ARE STARTING OUT THIS FORECAST PERIOD WITH IFR-LIFR CONDITIONS
WITH RAIN AND LOW CLOUDS AT ALL TERMINALS EXCEPT KMKG AND KGRR,
WHERE THEY ARE BOUNCING BACK AND FORTH FROM MVFR TO VFR. THE RAIN
SHOULD SLIP SOUTH OF KGRR BY 20Z. WE EXPECT THAT MVFR CEILINGS
WILL HOLD IN OVER KGRR MORE THAN NOT INTO THE EVENING HOURS BEFORE
THE GET INTO THE SOLID VFR CONDITIONS. ALL SITES WILL HAVE WIND
GUSTS OF 20-25 KNOTS UNTIL SUNSET THIS EVENING.
THE SOUTHERN SITES WILL SEE THE RAIN AND LIFR CONDITIONS LAST MOST
OF THE AFTERNOON. THEY WILL THEN GRADUALLY IMPROVE FROM NORTH TO
SOUTH LATER THIS EVENING AND OVERNIGHT AS DRIER AIR MOVES IN. ALL
SITES SHOULD GO VFR BY DAYBREAK ON SATURDAY, AND STAY VFR UNTIL
AFTER THIS FORECAST PERIOD.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
UPDATE...DUKE
DISCUSSION...04
AVIATION...NJJ
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