222
FXUS63 KMQT 211803
AFDMQT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
103 PM EST SAT DEC 21 2024
KEY MESSAGES
- LAKE EFFECT SNOW STREAMING INTO MARQUETTE AND ALGER COUNTIES
WILL TAPER OFF THIS AFTERNOON AND EVENING. UNTIL THEN, SOME
ISOLATED HAZARDOUS DRIVING CONDITIONS WILL BE POSSIBLE DUE TO
QUICKLY CHANGING VISIBILITIES AND LIGHT SNOW ACCUMULATIONS ON
SOME ROADWAYS.
- 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 103 PM EST SAT DEC 21 2024
GOES WATER VAPOR AND RAP ANALYSIS POSITIONS UPPER MICHIGAN WITHIN
NORTHWEST FLOW ALOFT BETWEEN MID-UPPER LEVEL TROUGHING TO OUR EAST
AND BROAD RIDGING TO OUR WEST. AT THE SURFACE, HIGH PRESSURE RIDGING
STRETCHING FROM NORTHERN ONTARIO SOUTH ACROSS LAKE SUPERIOR AND
UPPER MICHIGAN TOWARD THE MIDDLE MISSISSIPPI RIVER VALLEY HAS KEPT
WINDS LIGHT AND MOSTLY NORTHERLY ACROSS THE AREA. WITH 850MB TEMPS
ANALYZED BETWEEN -18 AND -15C AND LAKE SUPERIOR NEAR +4-6C (PER
SPC MESOANALYSIS AND GLERL RESPECTIVELY), IN ADDITION TO THE MIXED
LAYER EXTENDING TO NEAR 5K FEET THROUGH THE DGZ, THE ENVIRONMENT HAS
SUPPORTED HIGH SNOW RATIO LAKE EFFECT SNOW SHOWERS PRESSING SOUTH
INTO UPPER MICHIGAN. KMQT AND CASMR RADARS LIMIT ACTIVITY MAINLY TO
MARQUETTE COUNTY AND POINTS EASTWARD, BUT WEBCAMS HAVE SHOWN SOME
LIGHT OFF AND ON SHOWER ACTIVITY IN THE WESTERN COUNTIES. THE
STRONGEST BANDS HAVE BEEN FOCUSED ALONG THE LAKESHORE OF MARQUETTE
COUNTY DOWN TO NEAR GWINN WHERE WEAK CONVERGENCE HAS SUPPORTED
PERIODIC RADAR REFLECTIVITIES BETWEEN 30 AND 35 DBZ. THESE HIGHER
SIGNATURES HAVE BEEN MAINLY LOCATED SOUTHEAST OF THE RADAR IN A
NARROW CORRIDOR APPROXIMATELY FROM HARVEY SOUTH TO LITTLE
LAKE/GWINN BETWEEN SANDS/KSAW/GWINN AND SKANDIA/CARLSHEND. I SUSPECT
THESE LOCATIONS COULD HAVE OBSERVED A COUPLE INCHES OF SNOW THIS
MORNING, PARTICULARLY WHERE TERRAIN HAS SUPPORTED ADDITIONAL LIFT,
AND THE MOST RESTRICTIVE VISIBILITIES.
THROUGH THE REMAINDER OF THE AFTERNOON, HIGH PRESSURE WILL SLOWLY
MIGRATE THROUGH THE REGION, ENABLING FLOW TO BECOME SOUTHERLY.
GUIDANCE APPEARS TO HAVE DELAYED THIS WIND SHIFT A LITTLE, SO SNOW
SHOWERS MAY CONTINUE IN THE NORTHERN WIND SNOW BELTS INTO THE EARLY
EVENING HOURS. AT THAT POINT, SOUTHERLY FLOW WILL HELP LIFT SHOWER
ACTIVITY OVER LAKE SUPERIOR FOR THE OVERNIGHT PERIOD. IF THE SHOWERS
ARE A LITTLE SLOWER TO DIMINISH, ADDITIONAL SNOW OF AN INCH IS
GENERALLY EXPECTED WITH LOCALIZED SNOW AMOUNTS NEAR 3 INCHES NOT
BEING RULED OUT. WILL NEED TO MONITOR CAM, RADAR, AND SATELLITE
TRENDS THOUGH AFTER PUBLISHING THIS TO DETERMINE IF ANOTHER SPECIAL
WEATHER STATEMENT IS NEEDED FOR MARQUETTE COUNTY.
AFTER ACTIVITY ENDS, THE OVERNIGHT PERIOD SHOULD BE MOSTLY DRY WITH
LOWS FALLING INTO THE SINGLE DIGITS. ISOLATED SPOTS IN THE INTERIOR
WEST MAY DIP CLOSE OR JUST BELOW ZERO. JUST PRIOR TO 12Z, SOUTHERLY
FLOW WILL HELP TO SUPPORT LAKE EFFECT SNOW OFF OF LAKE MICHIGAN/BAY
OF GREEN BAY BY MORNING. RECENT CAMS ARE SUPPORTING A WIDER RANGE OF
WHERE SHOWERS MAY BE EXPERIENCED. AT THIS POINT, LIGHT SNOW SHOWERS
STREAMING NORTH MAY END UP AS FAR WEST AS ESCANABA BEFORE SUNRISE.
IF THIS DOES OCCUR, THE THOUGHT IS FOR THESE TO MIGRATE EAST INTO
SCHOOLCRAFT/MACKINAC COUNTIES. ANY SNOW EXPERIENCED PRIOR TO SUNRISE
WOULD LIKELY AMOUNT TO AN INCH OR TWO OF FLUFFY SNOW.
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 /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 1214 PM EST SAT DEC 21 2024
LAKE EFFECT CLOUD AND SNOW SHOWERS WILL CONTINUE TO PRESS SOUTH INTO
CENTRAL UPPER MICHIGAN, BRINGING SHOWERS TO KSAW THIS AFTERNOON.
BEFORE ACTIVITY ENDS LATER THIS AFTERNOON, EXPECT TEMPORARY LIFR
CONDITIONS AS THESE SHOWERS MOVE OVER THE TERMINAL.
OTHERWISE, ALL TERMINALS WILL TREND TOWARD VFR THIS EVENING AND
OVERNIGHT WITH LIGHT WINDS. BY MORNING, ANOTHER SYSTEM APPROACHING
THE AREA FROM THE WEST WILL WORK TO INCREASE THE PRESSURE GRADIENT
OVER THE AREA. THIS WILL RESULT IN GUSTY SOUTHERLY OF 20-25KTS WINDS
AT ALL TERMINALS SUNDAY.
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...JTP
LONG TERM...GS
AVIATION...JTP
MARINE...GS
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