967
FXUS63 KGRR 141130
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
630 AM EST SAT DEC 14 2024
KEY MESSAGES
- LIGHT ICING EVENT TONIGHT/SUNDAY MORNING
- MORE RAIN MONDAY
- COOLER WITH SNOW SHOWERS LATE WEEK
DISCUSSION
ISSUED AT 300 AM EST SAT DEC 14 2024
- LIGHT ICING EVENT TONIGHT/SUNDAY MORNING
SHORT RANGE MODELS CONTINUE TO ADVERTISE A COMPACT SHORT WAVE
PUSHING A SURFACE LOW ACROSS THE MISSOURI VALLEY TOWARD LOWER
MICHIGAN TONIGHT. WE MAY SEE A LITTLE SUN THIS MORNING, BUT CLOUDS
WILL INCREASE THROUGHOUT THE DAY AS THE LOW MOVES CLOSER. BUFKIT
RH PROFILES SHOW LOW LEVEL RH INCREASING SIGNIFICANTLY AROUND 00Z.
STRONG LIFT AS NOTED BY WIND BARBS PERPENDICULAR TO THE ISENTROPIC
PRESSURE SURFACES WILL SATURATE THE BOUNDARY LAYER QUICKLY BY
EARLY EVENING, LEADING TO CONDENSATION PRESSURE DEFICITS FALLING
TO LESS THAN 10 MB ACROSS THE WESTERN CWA BY 03Z. PRECIPITATION
SHOULD DEVELOP SHORTLY AFTER 00Z IN THE SOUTHWEST CWA AND
SPREADING NORTHEASTWARD THROUGHOUT THE EVENING. THE WARM AIR
ADVECTION PUSH WILL SEND SURFACE TEMPERATURES ABOVE FREEZING FROM
SOUTHWEST TO NORTHEAST DURING THE NIGHT. GIVEN CURRENT SURFACE
TEMPERATURES WELL BELOW FREEZING...INCLUDING ROAD
TEMPERATURES...WE'LL LIKELY SEE A 3-6 HOUR PERIOD OF FREEZING RAIN
BEFORE THE TRANSITION TO RAIN. THE EXCEPTION TO THAT COULD BE THE
NORTHEAST CWA WHERE THE COLDER AIR IS MORE ENTRENCHED. IN THAT
AREA, THE FREEZING PRECIPITATION MAY LINGER INTO SUNDAY MORNING.
COLLABORATION WITH SURROUNDING OFFICES SUGGESTED HOLDING OFF ON
HEADLINES AT THIS TIME.
- MORE RAIN MONDAY
THE NEXT SYSTEM WILL SEE A COLD FRONT MOVE ACROSS THE NORTHERN
PLAINS SUNDAY NIGHT AND MONDAY WITH DECENT UPPER SUPPORT. ANOTHER
ROUND OF RAIN IS LIKELY LATE MONDAY AND MONDAY NIGHT. A STRONG
FEED OF WARMER AIR WILL PRECLUDE ANY FREEZING PRECIPITATION WITH
THIS SYSTEM. A THIRD TO TWO THIRDS OF AN INCH OF RAIN IS POSSIBLE
WITH THIS.
- COOLER WITH SNOW SHOWERS LATE WEEK
FAST ON THE HEELS OF THE MONDAY SYSTEM WILL BE A PHASING OF A WAVE
MOVING ACROSS THE CENTRAL ROCKIES AND A DEEP TROUGH MOVING SOUTH
FROM CANADA. THE NORTHERN INFLUENCE OF THIS SYSTEM WILL MEAN
COLDER AIR TO WORK WITH AND WE'LL SEE LIGHT SNOW AND MIXED
RAIN/SNOW WEDNESDAY. H8 TEMPERATURES WILL FALL TO -16C BY THURSDAY
AFTERNOON, ENOUGH TO GENERATE SOME LAKE EFFECT SNOW SHOWERS
BEGINNING THURSDAY NIGHT. HIGHS WILL FALL INTO THE 30S WITH THIS
SYSTEM. HOWEVER, YET ANOTHER LOW IS PROGD TO DRAG A COLD FRONT
THROUGH THE REGION FRIDAY AND THAT WILL SEND HIGHS INTO THE 20S BY
NEXT SATURDAY, ALONG WITH SOME LIGHT SNOW.
AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 627 AM EST SAT DEC 14 2024
A SMALL AREA OF IFR CEILINGS IS IMPACTING JXN AT THE MOMENT. THESE
LOWER CEILINGS SHOULD SCATTER OUT IN THE NEXT HOUR OR TWO.
SOUTHEAST WINDS ARE EXPECTED THROUGHOUT THE DAY WITH GUSTS AROUND
20 KNOTS. CEILINGS WILL GRADUALLY LOWER INTO THIS EVENING WITH
RAIN MOVING IN FROM THE SOUTHWEST AFTER 00Z. WITH THE COLD GROUND
TEMPERATURES EXPECT 3-6 HOURS OF FREEZING RAIN OVER ANY ONE
LOCATION TONIGHT RESULTING IN A LIGHT GLAZE OF ICE. AS
TEMPERATURES WARM ABOVE FREEZING WE'LL SEE A TRANSITION TO RAIN
THAT WILL CONTINUE THROUGH SUNDAY. CEILINGS BY SUNDAY MORNING WILL
BE AROUND 1000 FEET.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 AM EST SUNDAY FOR LMZ844>849.
DISCUSSION...04
AVIATION...RAH
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