910
FXUS63 KGRR 150550
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1250 AM EST SUN DEC 15 2024
KEY MESSAGES
- FREEZING RAIN TONIGHT
- RAIN MONDAY
- SNOW CHANCES WEDNESDAY TO FRIDAY
UPDATE
ISSUED AT 949 PM EST SAT DEC 14 2024
A SWATH OF WARM AIR ADVECTION RELATED PRECIPITATION IS SPREADING
INTO SOUTHWEST LOWER MICHIGAN AT THIS TIME. THE PRECIPITATION IS A
MIX AND ASSOCIATED WITH A LOW CENTERED IN NORTHERN MISSOURI.
TEMPERATURES ALONG THE LAKE MICHIGAN SHORE ARE ABOVE FREEZING FROM
MUSKEGON SOUTHWARD, BUT DEW POINT DEPRESSIONS ARE 11-15 DEGREES AT
MKG AND BIV. SO, AS THE PRECIPITATION CONTINUES, THE AIR
TEMPERATURE WILL COOL TOWARDS THE DEW POINT AND RESULT IN SUB 32F
AIR TEMPERATURES AND FREEZING RAIN.
WE EXPECT PERIODS OF FREEZING RAIN TONIGHT ACROSS THE ENTIRE
FORECAST AREA WITH THE LEAST IMPACT DOWN TOWARDS I-94 WHERE THE
WARMER AIR WILL INFILTRATE THE QUICKEST. FROM I-96 TO THE NORTH
THE COLDER AIR WILL HANG ON THE LONGEST AND RESULT IN THE
RELATIVELY HEAVIER ICING TOTALS. TRACE AMOUNTS TO MAYBE A TENTH OF
AN INCH ARE POSSIBLE TOWARDS I-96 WITH ONE TO TWO TENTHS POSSIBLE
NORTH OF GRAND RAPIDS AND LANSING. WE EXTENDED THE WESTERN AND
SOUTHERN PORTIONS OF THE WINTER WEATHER ADVISORY THROUGH 600AM TO
ALLOW FOR SOME EXTRA TIME TO ASSESS THE SITUATION OVERNIGHT. ONE
CONCERN IS THAT SECONDARY ROADS THAT ARE ALREADY SNOW AND ICE
COVERED TO BEGIN WITH OVER WESTERN LOWER MICHIGAN WILL HANG ON TO
ICE FOR AWHILE EVEN AFTER WE BEGIN TO WARM ABOVE FREEZING LATE.
THE MAIN IMPACT GIVEN THE TOTALS WILL BE SLIPPERY TRAVEL. WE ARE
NOT EXPECTING WIDESPREAD POWER OUTAGES, BUT SOME ISOLATED OUTAGES
ARE CERTAINLY POSSIBLE OVER CENTRAL LOWER MICHIGAN NORTH OF GRAND
RAPIDS AND LANSING.
DISCUSSION
ISSUED AT 357 PM EST SAT DEC 14 2024
- FREEZING RAIN TONIGHT
WINTER WEATHER ADVISORY HAS BEEN ISSUED FOR THE ENTIRE FORECAST
AREA FOR FREEZING RAIN. CURRENT OBSERVATIONS SHOW DEW POINTS IN
THE TEENS ACROSS SE LOWER MICHIGAN AND SOUTHEAST WINDS WILL
PREVAIL THROUGH THE EVENING, ADVECTING LOWER DEW POINTS IN AS WARM
AIR OVERRUNS COLD AIR AT THE SURFACE. THIS IS THE CLASSIC
RETREATING COLD HIGH, ADVANCING LOW/WARM PUSH THAT CAN PRODUCE
SEVERAL HOURS OF ICING BEFORE SKIN TEMPS AND DEW POINTS RISE ABOVE
FREEZING AND ICE AND RESIDUAL HARD PACKED SNOW ON THE ROADS CAN
MELT OFF.
THE NORTHEAST INTERIOR ZONES SHOULD SEE ICING PERSIST WELL INTO
SUNDAY MORNING AS EAST-SOUTHEAST LOW LEVEL FLOW PERSISTS THERE. WE
HAVE THE ADVISORY GOING UNTIL 11 AM. WINDS GO SOUTHEAST THEN
SOUTH IN THE AFTERNOON AND CONDITIONS WILL FINALLY IMPROVE.
- RAIN MONDAY
A SECONDARY WAVE MOVES THROUGH ON MONDAY-TUESDAY WITH RAIN BUT IT
APPEARS THE HEAVIER PRECIP PASSES SOUTH OF LOWER MICHIGAN. POPS
WILL BE SHADED HIGHER FROM NORTH TO SOUTH AS CENTRAL AND NORTHERN
ZONES APPEAR TO GET DRY SLOTTED.
- SNOW CHANCES WEDNESDAY TO FRIDAY
COLDER AIR FILTERS BACK IN ON WEDNESDAY PERSISTING INTO THE
WEEKEND. THERMAL PROFILES SHOW IT IS COLD ENOUGH FOR SNOW, BUT
DETAILS IN INDIVIDUAL SHORTWAVE TROUGHS ARE SHOWING A LOT OF
ENSEMBLE SPREAD/UNCERTAINTY. THERE IS A SIGNAL FOR CYCLONIC FLOW
AND LAKE EFFECT SNOW WED-THU AND A CLIPPER LOW LATE IN THE WEEK OR
NEXT WEEKEND.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 1250 AM EST SUN DEC 15 2024
ONGOING FREEZING RAIN WILL CONTINUE TO SHIFT NORTHEAST OVERNIGHT
WITH SOME SNOW MIXING IN AT TIMES. A TRANSITION TO RAIN IS
EXPECTED FROM SOUTHWEST TO NORTHEAST INTO SUNDAY MORNING. TAF
SITES ARE EXPECTED TO TRANSITION TO RAIN BY 9Z. A LIGHT GLAZE OF
ICE WILL BE POSSIBLE UNTIL THEN.
CEILINGS WILL GRADUALLY LOWER OVERNIGHT INTO SUNDAY MORNING WITH
IFR CONDITIONS DEVELOPING BY MID TO LATE MORNING. THERE WILL ALSO
BE SOME LOW LEVEL WIND SHEAR INITIALLY WITH THE LOW LEVEL JET
OVERHEAD. THIS WILL TAPER OFF EARLY SUNDAY MORNING AS THE LOW
LEVEL JET SHIFTS EAST. RAIN CHANCES (20 TO 30 PERCENT) LINGER
THROUGH THE DAY.
GRR AIRPORT DSS UPDATE:
THE TRANSITION FROM FREEZING RAIN TO RAIN MAY LINGER FOR A FEW
MORE HOURS, OTHERWISE NO OTHER ADJUSTMENTS TO THE FORECAST.
GRR WATCHES/WARNINGS/ADVISORIES
MI...WINTER WEATHER ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR
MIZ037-038-043-044-050>052-056>059-064>067-071>074.
WINTER WEATHER ADVISORY UNTIL 11 AM EST THIS MORNING FOR MIZ039-
040-045-046.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 AM EST THIS MORNING FOR LMZ844>849.
UPDATE...DUKE
DISCUSSION...OSTUNO
AVIATION...RAH
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