152
FXUS63 KMQT 210948
AFDMQT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
448 AM EST SAT DEC 21 2024
KEY MESSAGES
- LIGHT TO MODERATE LAKE EFFECT SNOWFALL SHIFTS TO THE NORTH
WIND SNOW BELTS THIS MORNING. BEST ACCUMULATIONS EXPECTED
OVER NORTH CENTRAL UPPER MI.
- A RARE SOUTHERLY LAKE EFFECT SNOWBAND WILL IMPACT SOUTHERN
SCHOOLCRAFT COUNTY SUNDAY, BRINGING UP TO 4 INCHES OF SNOWFALL
IN A NARROW BAND NEAR MANISTIQUE.
- CLIPPER MOVING THROUGH THE GREAT LAKES COULD BRING A
WIDESPREAD SNOW SUNDAY NIGHT INTO MONDAY, THOUGH A WIDE SPREAD
OF SNOWFALL TOTALS REMAINS POSSIBLE.
- DRIER AND WARMER CONDITIONS EXPECTED BEHIND THE EARLY WEEK
SYSTEM FOR CHRISTMAS EVE AND CHRISTMAS DAY.
SHORT TERM /THROUGH TONIGHT/
ISSUED AT 249 AM EST SAT DEC 21 2024
UPPER AIR PATTERN CONSISTS OF A DEEP 500 MB TROUGH IN THE EASTERN
U.S. AND A TROUGH OFF THE WEST COAST WITH A RIDGE OVER THE WESTERN
U.S. AND ROCKIES 06Z SAT. A SHORTWAVE EJECTS OUT OF THE WEST COAST
TROUGH INTO THE NORTHERN ROCKIES BY 12Z SUN. LAKE EFFECT SNOW WILL
CONTINUE TO SLOWLY WIND DOWN TODAY. SOUNDINGS DID SHOW INVERSION
HEIGHT BELOW 5000 FEET, BUT DGZ IN THE DEEPER MOISTURE, SO LSRS WILL
CONTINUE TO BE HIGH FOR TODAY. WILL ISSUE A SPECIAL WEATHER
STATEMENT AS A SMALL AREA OF MARQUETTE COUNTY SOUTH OF MARQUETTE TO
GWINN IN THE HIGHER TERRAIN COULD SEE UP TO 5 INCHES OF SNOW FROM
NOW UNTIL 18Z THIS AFTERNOON. DRIES OUT THIS EVENING, THEN A LAKE
MICHIGAN BAND SETS UP LATE TONIGHT WITH A SWITCH IN THE WINDS TO THE
SOUTH OVER THE EASTERN CWA. THIS JUST GETS STARTED LATE TONIGHT.
HUNG ONTO POPS LONGER OVER THE EASTERN CWA TODAY AS THE TENDENCY IS
ALWAYS TO END THEM TOO SOON, OTHERWISE DID NOT MAKE TOO MANY CHANGES
TO THE GOING FORECAST.
LONG TERM /SUNDAY THROUGH FRIDAY/
ISSUED AT 445 AM EST SAT DEC 21 2024
SUNDAY MORNING, THE UP REGION WILL BE UNDER NORTHWESTERLY FLOW AT
500MB WITH RIDGING OVER THE GREAT PLAINS AND TROUGHING OVER NEW
ENGLAND. MEANWHILE, A SURFACE HIGH HIGH OVER WESTERN QUEBEC AT
AROUND 1036 MB IS PROVIDING SOUTHERLY SURFACE FLOW WHICH IS BUILDING
AS ORGANIZING LOW PRESSURE OVER THE HIGH PLAINS IS TIGHTENING THE
PRESSURE GRADIENT. LINGERING 850MB TEMPERATURES OF -9 TO -14 C OVER
LAKE MICHIGAN AT AROUND 7 C IS PROVIDING A RARE SOUTHERLY LAKE
EFFECT SETUP. THE 00Z HREF SHOWS MEAN 6-HOURLY QPF IN A STREAK OF
AROUND 0.1" FOR SOUTHERN SCHOOLCRAFT COUNTY, AND GIVEN A SATURATED
DGZ WITH LIFT, SLRS SHOULD BE WELL INTO THE TEENS TO 20:1. THE
CURRENT FORECAST FOR THIS BAND IS FOR A TIGHT BAND OF UP TO 70%
CHANCES OF 4" OF SNOW FROM 12Z SUN TO 06Z MONDAY, THOUGH A WINTER
WEATHER ADVISORY MAY NEED TO WAIT FOR MORE CAM AVAILABILITY TO
PROPERLY LOCATE THE AREAS OF HIGHEST IMPACT. AS IS THE CASE WITH
SOUTHERLY LAKE EFFECT SETUPS, 850MB TEMPERATURES QUICKLY WARM UP BY
LATE SUNDAY, LEADING TO CHANCES OF SNOW FALLING THROUGH THE EVENING
INTO THE OVERNIGHT PERIOD.
ATTENTION THEN TURNS TO THE UPSTREAM LOW PRESSURE COMING OUT OF THE
PLAINS. A ROBUST 500MB TROUGH WILL SWEEP INTO THE UPPER MIDWEST
AROUND 12Z MONDAY SUPPORTED BY JET-LEVEL LIFT FROM THE RIGHT-
ENTRANCE REGION OF A 80-100 KT 250MB JET AND 850MB WAA, RESULTING IN
A ~1015MB LOW PRESSURE PASSING THROUGH THE UP BY 18Z MONDAY PER THE
00Z GEFS, UK ENSEMBLE, AND SREF, THOUGH THE CANADIAN, GERMAN, AND
EURO ENSEMBLES HAVE A SLIGHTLY SOUTHERLY TRACK FROM THAT. EITHER
WAY, 90TH PERCENTILE NAEFS VAPOR TRANSPORT THANKS TO THE 850MB
HAVING A WESTERN GULF OF MEXICO CONNECTION WILL PROVIDE PLENTY OF
MOISTURE, WHICH COINCIDENT WITH STRONG SYNOPTIC FORCING WILL PROVIDE
A HIGH CEILING FOR SNOWFALL POTENTIAL FROM A CONCEPTUAL STANDPOINT.
HOWEVER, THE NBM IS NOT FULLY ONBOARD WITH A WINTER STORM, AS MEAN
DAILY SNOWFALL IN THE 07Z NBM IS AROUND 1-2 INCHES. BUMPING UP QPF
WITH THE 90TH PERCENTILE OF THE NBM BRINGS SOME 3-6 INCH SNOW TOTALS
IN THE EASTERN THIRD OF THE UP MONDAY, THOUGH THE SPREAD IN THE
POTENTIAL SOLUTIONS REDUCES CONFIDENCE IN A WINTER STORM SOMEWHAT.
ANOTHER THING THAT WILL REDUCE SNOW TOTALS WILL BE DWINDLING SLRS AS
WARM ADVECTION PROVIDES WARMER LOW-LEVEL TEMPERATURES. FOR NOW,
EXPECTING SLRS A SHADE ABOVE 10:1 FOR THIS SYSTEM, BUT IT COULD BE
TRACK-SENSITIVE TOO.
AFTER THE LOW DEPARTS, THE MIDWEEK PERIOD LOOKS WARM AND DRY AS
ANOMALOUS RIDGING MOVES OVER THE AREA (500MB HEIGHT ANOMALY OF +27
DAM OVER NORTHERN ONTARIO BY MIDDAY CHRISTMAS). NBM HIGHS CLIMB INTO
THE MID 30S AROUND CHRISTMAS, SO WHILE THE WARM AIR MIGHT BE TOO
LATE TO ERASE THE SNOWPACK ENTIRELY (THUS, A WHITE CHRISTMAS SEEMS
PROBABLE (75+%) AT THE WFO), THERE WILL BE AT LEAST SOME SNOWMELT ON
CHRISTMAS. THE NEWS DOES NOT IMPROVE FOR WINTER RECREATION
ENTHUSIASTS AS NBM HIGHS CLIMB TO THE 40S BY NEXT WEEKEND. ENSEMBLES
ARE NOT IN MUCH AGREEMENT ON THE TIMING OF ANY SYSTEMS TO BREAK UP
THE WARM AND DRY PATTERN, THOUGH ENSEMBLE SOUNDING PLOTS DO SHOW AT
LEAST A FEW SOLUTIONS WITH A WARM NOSE, SO 15% CHANCES OF LIGHT
FREEZING RAIN IS KEPT IN THE FORECAST FOR THE LATE WEEK INTO THE
WEEKEND TIMEFRAME, HOWEVER, THE PROBABILITIES OF 0.05" OR MORE OF
FREEZING RAIN BY FRIDAY NIGHT ARE ONLY 5-10% IN THE INTERIOR WEST.
DEW POINTS ALSO LOOK TO RISE TO THE FREEZING MARK BY LATE FRIDAY, SO
IF ANY SNOWPACK SURVIVES TO THAT POINT, FOG MAY NEED TO BE ADDED TO
THE FORECAST, COMPLICATING THE POST-CHRISTMAS TRAVEL FORECAST.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 1153 PM EST FRI DEC 20 2024
LOW-LEVEL NORTHERLY WINDS AHEAD OF HIGH PRES APPROACHING FROM THE NW
ALONG WITH A CHILLY AIR MASS FLOWING ACROSS LAKE SUPERIOR WILL
SUPPORT MVFR CIGS AND LAKE EFFECT -SHSN/FLURRIES THRU THIS MORNING
AT IWD/CMX/SAW. THE -SHSN WILL BE MOST FREQUENT AND A LITTLE HEAVIER
AT SAW, LIKELY RESULTING IN PREVAILING MVFR VIS AND OCNL BRIEF IFR
VIS OVERNIGHT THRU THE MORNING. ONLY OCNL FLURRIES ARE EXPECTED AT
IWD WITH NO VIS RESTRICTION OUT OF VFR. CMX WILL SEE SOME PERIODS OF
MVFR VIS DURING THE NIGHT WITH BRIEF IFR ALSO A POSSIBILITY. AS HIGH
PRES PASSES, MVFR CIGS WILL SCATTER OUT TO VFR AT IWD LATE THIS
AFTN, AT CMX AROUND 00Z AND AT SAW NEAR THE END OF THE FCST PERIOD.
MARINE
ISSUED AT 445 AM EST SAT DEC 21 2024
HIGH PRESSURE OVER LAKE SUPERIOR TODAY WILL KEEP WIND GUSTS BELOW 20
KT UNTIL LATE TONIGHT. COMPRESSING PRESSURE GRADIENT SUNDAY WILL
ALLOW FOR SOUTHERLY WINDS TO BUILD TO 25 KT OVER THE WEST HALF OF
THE LAKE AND UP TO 30 KT OVER THE EAST, WITH THE EAST ALSO CARRYING
AROUND 30% CHANCES OF A BRIEF GALE SUNDAY AFTERNOON TO EVENING.
WINDS FALL BELOW 20 KT AS WINDS VEER TO THE SOUTHWEST OVERNIGHT INTO
MONDAY, AND WITH GENERALLY HIGH PRESSURE OVER MUCH OF THE GREAT
LAKES THROUGH THIS PERIOD, WINDS WILL REMAIN BELOW 20 KT THROUGH
MUCH OF NEXT WEEK. WAVES WILL FALL BELOW 4 FEET THIS MORNING OVER
SOUTH-CENTRAL LAKE SUPERIOR. WAVES THEN INCREASE TO 4-8 FT OVER MUCH
OF THE NORTHERN HALF OF THE LAKE SUNDAY MORNING THROUGH MONDAY
MORNING. MODERATE FREEZING SPRAY IS ALSO POSSIBLE (~40%) IN EAST-
CENTRAL LAKE SUPERIOR SUNDAY MORNING.
MQT WATCHES/WARNINGS/ADVISORIES
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
SHORT TERM...07
LONG TERM...GS
AVIATION...ROLFSON
MARINE...GS
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