683
FXUS63 KGRR 140451
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1151 PM EST SAT DEC 13 2025
KEY MESSAGES
- LAKE EFFECT SNOW TONIGHT INTO TOMORROW
- ARCTIC LOWS FOR THE NEXT FEW MORNINGS
- WARMER WEATHER WITH RAIN POSSIBLE THURSDAY
DISCUSSION
ISSUED AT 322 PM EST SAT DEC 13 2025
- LAKE EFFECT SNOW TONIGHT INTO TOMORROW
THE ARCTIC FRONT WILL CONTINUE TO MOVE SOUTHWARD INTO SOUTHERN
CANADA THIS EVENING INTO EARLY MONDAY. STRONG NW FLOW WILL KEEP
LAKE EFFECT BANDS GOING AS A MID LEVEL THERMAL TROUGH DEEPENS DUE
TO THE ARCTIC AIR MASS MOVING OVERHEAD. THAT THERMAL TROUGH WILL
FURTHER INCREASE THE LAKE INSTABILITY. THAT INSTABILITY CAN BE
INFERRED BY SEEING THE 80 J/KG OF CAPE ALONG THE SHORE LINE. USING
THE 925MB-850MB OMEGA AS A PROXY THE BANDS BECOME MORE LAMINAR AS
THEY MOVE ON SHORE. WHILE THE ENTIRETY OF THE LAKESHORE WILL SEE
SNOW OVERNIGHT, THE GREATEST INTENSITY WILL BE HOLLAND SOUTHWARD.
THE LAKE EFFECT WILL INTENSIFY LATE TONIGHT INTO EARLY TOMORROW
MORNING. THE LAKE EFFECT WILL FINALLY BE DAMPENED AS "WARMER AIR"
IN THE LOW TO MID LEVELS FORM A THERMAL RIDGE. LAKE EFFECT SHOWERS
SHOULD LINGER THROUGH SUNDAY MORNING AND INTO THE EARLY
AFTERNOON, BUT WILL BE LIGHT.
WHILE THERE WILL BE SOME SNOW INLAND SNOW BANDS, WILL BE HARD
PRESSED TO INFILTRATE PAST THE US 131 CORRIDOR. AS SAID IN
PREVIOUS DISCUSSIONS, TEMPERATURES THIS COLD CREATE SNOW THAT IS
MORE CRYSTALLINE AND NOT LARGE DENDRITES. COUPLE THAT ICY
SNOWFALL, ALONG WITH THE FACT THAT THE COLDER TEMPS MAKE SALT LESS
EFFECTIVE AND YOU HAVE A RECIPE FOR TREACHEROUS ROADWAYS.
- ARCTIC LOWS FOR THE NEXT FEW MORNINGS
AS MENTIONED ABOVE, AN ARCTIC AIR MASS IS MOVING OVERHEAD. THE
850MB TEMPERATURES WILL DROP AS LOW AS -25C. THAT SHOULD
CORRELATE TO T TEMPERATURES IN THE LOW SINGLE DIGITS INLAND, WITH
THE POTENTIAL FOR TEMPS TO DROP BELOW ZERO. THE STRONG NW FLOW
WILL CONTINUE THROUGH THE FIRST HALF OF THE EVENING WITH WIND
GUSTS UPWARDS OF 35 MPH. WINDS WILL FINALLY SUBSIDE AFTER MIDNIGHT
AS THE GRADIENT WEAKENS. ANY WINDS ALONG WITH THE FRIGID TEMPS
WILL COUPLE FOR WIND CHILLS BELOW ZERO. HOWEVER, AS THE STRONGEST
WINDS AND COLD TEMPS WILL NOT COINCIDE, THEY SHOULD NOT REACH ANY
ADVISE CRITERIA. IF IT DOES HAPPEN IT WILL ONLY BE FOR A BRIEF
PERIOD EARLY SUNDAY MORNING. THAT SAID WIND CHILLS OF -5 TO -14
ARE POSSIBLE EARLY SUNDAY MORNING.
THE ARCTIC LOW WILL MOVE EASTWARD AND "WARMER" AIR WILL ADVECT IN
SUNDAY INTO MONDAY. GUSTY WINDS WILL RESUME SUNDAY AFTERNOON WITH
GUSTS UPWARDS OF 25 MPH. LOWS INTO MONDAY ARE EXPECTED TO BE
"WARMER" BUT RANGE BETWEEN 5 TO 12 DEGREES.
THERE IS A SMALL CHANCE MONDAY WITH COLDER AIR NEAR THE SURFACE
AND SLIGHTLY WARMER AIR ALOFT, THAT FREEZING DRIZZLE WILL BE
POSSIBLE MONDAY AFTERNOON. BUFKIT SOUNDINGS DO HINT AT THIS,
THOUGH FOR RIGHT NOW THERE ISN'T ENOUGH MOISTURE. HOWEVER, WITH
AN UNSATURATED DGZ DURING THAT TIMEFRAME AND THE ABOVE CONDITIONS
FREEZING DRIZZLE REMAINS POSSIBLE AND WILL HAVE TO SEE HOW THAT
UNFOLDS.
- WARMER WEATHER WITH RAIN POSSIBLE THURSDAY; SNOW INTO FRIDAY
THE ROLLER COASTER OF WEATHER WILL CONTINUE THROUGH THE WEEK AS
A MID LEVEL TROUGH MOVING THROUGH CANADA WILL COUPLE WITH A RIDGE
BUILDING OVER THE PLAINS TO ADVECT WARM SOUTHERLY FLOW INTO THE
REGION THROUGH THE LATTER HALF OF THE WEEK. OUR FRIGID TEMPS WILL
SKY ROCKET INTO THE LOW 40S BY WEDNESDAY. A MORE ORGANIZED LOW
SHOULD MAKE ITS WAY THROUGH THE REGION THURSDAY INTO FRIDAY. THAT
LOW COULD BRING SLIGHTLY ANOMALOUS PWATS. THE QUESTION IS WHERE
THE MOISTURE WILL BE. IF THE QPF REMAINS IN THE WARM SECTOR, THEN
HEAVIER RAIN IS LIKELY. AS SAID IN PREVIOUS AFD'S IT LOOKS TO BE A
CLASSIC THAW AND REFREEZE TYPE OF EVENT. SO A RAIN/SNOW WINTRY
MIX IS TRENDING THURSDAY INTO FRIDAY. WITH RAIN FOLLOWED BY A
TRANSITION PERIOD AND THEN SNOW, AS COLD AIR, AS LOW AS -15C,
MOVES THROUGH THURSDAY NIGHT INTO FRIDAY MORNING. THERE IS SOME
QUESTIONS ON TIMING AND INTENSITY SO STAY TUNED.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 1151 PM EST SAT DEC 13 2025
LAKE EFFECT SNOW SHOWERS HAVE EXPANDED IN COVERAGE AND INTENSIFIED
AS EXPECTED, ESPECIALLY TOWARD THE LAKESHORE. SOME OF THESE
HEAVIER SNOW SHOWERS ARE MAKING IT INLAND, AND CAUSING SOME
TEMPORARY LOWER CONDITIONS INTO THE UPPER END OF IFR. THE SNOW
SHOWERS ARE STARTING TO MIGRATE CLOSER TO THE LAKESHORE AS THE
FLOW BECOMES MORE FROM THE NNW. THIS IS EXPECTED TO BRING SOME
GRADUAL PARTIAL CLEARING TO ALL OF THE SITES FROM NE TO SW.
THE SNOW SHOWERS WILL MOVE BACK INLAND ON SUNDAY AS THE FLOW BACKS
A BIT BACK TO THE WNW. THIS WILL BRING AT LEAST MVFR BACK IN, WITH
SOME IFR POSSIBLE ONCE AGAIN, MAINLY CLOSER TO THE LAKESHORE.
INLAND LOCATIONS COULD SEE A BRIEF DROP IN VSBYS UNDER SOME
ISOLATED HEAVIER SNOW SHOWERS. WINDS WILL PICK UP AFTER SUNRISE
WITH GUSTS OF 18 TO 25 KNOTS LIKELY. THOSE WINDS WILL THEN
DIMINISH TOWARD SUNSET SUNDAY.
GRR WATCHES/WARNINGS/ADVISORIES
MI...WINTER WEATHER ADVISORY UNTIL 11 AM EST SUNDAY FOR MIZ037-038-
043-050-056-064-071-072.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EST SUNDAY FOR LMZ844>849.
DISCUSSION...CERU
AVIATION...NJJ
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