093
FXUS63 KGRR 210838
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
338 AM EST SAT DEC 21 2024
KEY MESSAGES
- LIGHT LAKE EFFECT SNOW WINDS DOWN TODAY
- MONDAY SYSTEM TO BRING RAIN AND SNOW TO SOUTHWEST LOWER MICHIGAN
- LOW CONFIDENCE MID/LAKE WEEK WITH REGARD TO PRECIPITATION
CHANCES
DISCUSSION
ISSUED AT 337 AM EST SAT DEC 21 2024
- LIGHT LAKE EFFECT SNOW WINDS DOWN TODAY
NORTHERLY FLOW LAKE EFFECT IS ONGOING AT THIS TIME WITH A
CONNECTION TO LAKE SUPERIOR. DELTA T'S ARE TOWARDS 20C MAKING FOR
SOLID INSTABILITY. SO, BOTH FETCH LENGTH AND INSTABILITY ARE
FAVORABLE FOR LAKE EFFECT SNOW. THE ISSUE IS MOISTURE DEPTH IS
VERY SHALLOW WHICH LIMITS FLAKE SIZE AND ACCUMULATION. WINDS WILL
REMAIN OUT OF A NORTH-NORTHWEST DIRECTION WHICH FAVORS OUR
LAKESHORE COUNTIES AS WELL AS SOME OF THE U.S. 10 CORRIDOR. WINDS
WILL BE WEAKENING THOUGH AS WE MOVE THROUGH THE DAY AT THE SAME
TIME MOISTURE DEPTH BECOMES MORE SHALLOW. WE EXPECT LAKE EFFECT TO
CONTINUE THIS MORNING AND GRADUALLY TAPER THIS AFTERNOON GIVEN
WEAKER WINDS IN THE CLOUD LAYER AND THE DECREASING MOISTURE DEPTH.
EXPECTING LIGHT SNOW IN THE AFOREMENTIONED AREAS ON THE ORDER OF
A TRACE TO A HALF INCH. AN ISOLATED INCH OF SNOW IS POSSIBLE WHERE
BANDS PERSIST THIS MORNING.
- MONDAY SYSTEM TO BRING RAIN AND SNOW TO SOUTHWEST LOWER MICHIGAN
MODELS HAVE BEEN CONSISTENT IN BRINGING A SURFACE LOW OUR
DIRECTION FROM THE PLAINS STATES SUNDAY NIGHT INTO MONDAY. SUNDAY
NIGHT SHOULD BE MAINLY DRY WITH PRECIPITATION OCCURRING MAINLY
MONDAY INTO MONDAY NIGHT. THE PRECIPITATION WILL BE OF A WARM AIR
ADVECTION VARIETY AHEAD OF THE SURFACE LOW AND IT'S ASSOCIATED MID
LEVEL SHORTWAVE. AN INCH OR TWO OF LIGHT SNOW LOOKS POSSIBLE UP
TOWARDS U.S. 10 WITH EVEN LIGHTER AMOUNTS ELSEWHERE. SOME RAIN
WILL MIX IN MONDAY AFTERNOON AND EVENING
- LOW CONFIDENCE MID/LAKE WEEK WITH REGARD TO PRECIPITATION
CHANCES
A DRY DAY IS EXPECTED ON TUESDAY BEFORE LIGHT PRECIPITATION IS
STRUNG OUT IN THE FORECAST FROM WEDNESDAY THROUGH FRIDAY.
CONFIDENCE IS LOW IN THE PRECIPITATION CHANCES GIVEN DISPARITY IN
THE MAIN FEATURES IN PLAY BOTH IN TIME AND SPACE. THE GFS BRINGS A
SHORTWAVE INTO THE AREA LATE IN THE WEEK WHEREAS THE ECMWF HAS
RIDGING. OUR FORECAST IS A COMPROMISE OF THE TWO MAIN GLOBAL
MODELS WITH A LOT OF LOW CHANCE POPS IN THE 20-40 PCT RANGE DURING
THIS TIME FRAME.
WE WARM UP WEDNESDAY THROUGH FRIDAY WITH 850MB TEMPERATURES GOING
ABOVE ZERO C ON TUESDAY. PRECIPITATION TYPE IS MAINLY RAIN MID TO
LATE WEEK WHICH WILL MEAN A CONTINUED EROSION OF WHAT LITTLE SNOW
PACK THAT IS IN PLACE.
AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
ISSUED AT 1159 PM EST FRI DEC 20 2024
VFR WEATHER CONTINUING TONIGHT AND SATURDAY WITH SCATTERED TO
BROKEN CLOUDS AROUND 5000 FT. HOWEVER CAN'T RULE OUT SOME BRIEF
MVFR OR EVEN IFR VSBYS IN SNOW AT MKG THROUGH MIDDAY SATURDAY AS
LAKE EFFECT SNOW SHOWERS CONTINUE TO HUG THE COASTLINE. NORTHERLY
WINDS 5 TO 10 KTS.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR LMZ844-
845-848-849.
DISCUSSION...DUKE
AVIATION...MEADE
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