Arctic air moving across Lake Superior in a northwest flow generated locally heavy lake effect snow in the Ironwood area on the 31st.
Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS MQT wrote it up.
Arctic air moving across Lake Superior in a northwest flow generated locally heavy lake effect snow in the Ironwood area on the 31st.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Marquette, MI wrote its last area forecast discussion before the first event at Dec 31, 5:58 AM CST, 1 hour 2 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
658 AM EST THU DEC 31 2009
UPDATED AVIATION DISCUSSION FOR 12Z TAFS
.SYNOPSIS...
00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW FAIRLY ACTIVE BUT
LO AMPLITUDE SPLIT FLOW PATTERN ACRS NAMERICA. THE NRN TIER OF THE
CONUS IS DOMINATED BY THE NRN BRANCH. A DISTURBANCE EMBEDDED IN THIS
FLOW FM NW ONTARIO INTO MN IS BRINGING SOME LGT SN TO MAINLY ERN UPR
MI THIS MRNG. ALTHOUGH THE 00Z APX/GRB RAOBS SHOW NEAR SATURATION
THRU A DEEP LYR...FLAT H85 THERMAL GRADIENT AHEAD OF ATTENDANT COLD
FNT MOVING INTO WRN LK SUP IS RESULTING IN ONLY WEAK ISENTROPIC
ASCENT. POOR SN GROWTH MICROPHYSICS WITH THE DGZ RATHER HI AND
SHALLOW ABV PER 00Z GRB/APX RAOBS IS ALSO LIMITING SN RATES. THE
AIRMASS OVER MN BEHIND THE ATTENDANT COLD FNT IS QUITE COLD...WITH
00Z INL/BIS RAOBS SHOWING TEMPS OF -18C/-17C AT TOP OF MIXED LYR BLO
INVRN BASE JUST BLO H85. SINCE THE MIXED LYR IS NOT PARTICULARLY
MOIST AT THESE RAOB SITES...CIGS ARE GENERALLY VFR...AND ONLY SOME
FLURRIES ARE FALLING ACRS NRN MN/NDAKOTA AS THE 00Z INL RAOB ALSO
DEPICTS A RATHER DRY PROFILE ABV H8. THE RAOB FM BIS SHOWS MOISTER
AIR ABV THE INVRN THAN AT INL. ANOTHER NRN BRANCH SHRTWV IS DIGGING
SE THRU SW CAN. DEEPER MSTR IS EVIDENT ON THE 00Z SDNG FM GLASGOW MT.
&&
.DISCUSSION...
MAIN FCST CONCERNS THIS PACKAGE ARE LES TRENDS/AMOUNTS/GOING
HEADLINES CONNECTED TO ARRIVAL OF COLDER AIR TO THE W AND NW.
TDAY...EXPECT LINGERING -SN OVER THE ERN CWA EARLY THIS MRNG TO BE
DIMINISHING SOON AFT 12Z WITH DEPARTURE OF DEEPER MSTR THERE.
ARRIVAL OF COLDER AIR BLO H85 IN THE NW FLOW BEHIND THE COLD FROPA
WL LEAD TO INCRSG LES OVER THE W TDAY WITH BOTH GFS/NAM SHOWING H85
TEMPS FALLING TO -18C TO -20C OVER WRN LK SUP BY 00Z...BUT OBSVD DRY
AIR IN THE MIXED LYR MIGHT LIMIT SN RATES. ON THE OTHER HAND...THE
SN GROWTH MICROPHYSICS SHOULD BE EXCELLENT WITH CONSIDERABLE UVV
FCST IN THE DGZ CORRESPONDING TO THE -17C/-18C TEMPS OBSVD UPSTREAM
AT 00Z NEAR THE TOP OF THE MIXED LYR. BOTH MODELS SHOW THE SHARPEST
H95 CNVGC IN GOGEBIC/ONTONAGON COUNTIES THRU THE DAY WITH SLOWLY
VEERING H925 FLOW FM WNW TO NNW MEETING MORE WLY LAND BREEZE FLOW OF
ARCTIC AIR OFF NW WI...AND THESE AREAS SHOULD BE THE FOCUS FOR THE
MOST IMPRESSIVE LES. ALTHOUGH THE KEWEENAW ALSO SHOULD SEE SOME
SHARPER LLVL CNVGC THRU THE MRNG...THE VEERING FLOW THERE TO NNW IN
THE AFTN SHOULD TEND TO LIMIT DURATION OF HEAVIER SN THERE. FOR FCST
INVRN HGT IN THE 5-7K FT AGL RANGE SHOWN ON FCST SDNGS...LES CHART
SUGS 3-6/12HRS...BUT EXCELLENT SN GROWTH MIGHT TEND TO MAKE THESE
NUMBERS CONSERVATIVE IN AREAS OF MORE PERSISTENT CNVGC OVER THE FAR
W. OVER THE E...LES SHOULD BEGIN TO PICK UP IN THE AFTN WITH ARRIVAL
OF COLDER AIR LATER THAN IN THE W. BUT SINCE NEITHER NAM NOR GFS
SHOW ANY PERSISTENT LLVL CNVGC THERE...ALSO REFLECTED BY LOCAL
WRF-ARW...LES AMOUNTS SHOULD NOT GET OUT OF HAND THERE TDAY.
CONSIDERING THE COLD...RATHER STABLE AIRMASS UPSTREAM...TENDED
TOWARD THE LO END OF MOS GUIDANCE FOR TEMPS AWAY FM LK MODERATION.
AS SHRTWV NOW IN WRN CAN DROPS ESEWD INTO MN LATE TNGT...LLVL CYC
FLOW IS PROGGED TO VEER FM NNW TO A MORE STEADY STATE N AFT MIDNGT.
WITH COLD DENSE LLVL ARCTIC AIR UPSTREAM...PREFER THE RUC13 MORE
EMPHATIC WNW LAND BREEZE SFC FLOW OVER THE W HALF INTERIOR... WHICH
RESULTS IN FOCUSED H95 CNVGC IN GOGEBIC/ONTONAGON AND ERN MQT/WRN
ALGER COUNTIES. PCPN INTENSITY OVER THE NCNTRL MAY BE ENHANCED BY
MOISTENING OFF LK NIPIGON. SN/WATER RATIOS WL REMAIN ON THE
IMPRESSIVE 25-30:1 SIDE IN AREAS EXPERIENCING UPSLOPE FLOW...WITH
SHARP LLVL UVV TIED TO THE TERRAIN LOCKED IN PRIME DGZ. WSHFT TO THE
N SHOULD RESULT IN MORE LK MODERATION OF TEMPS. GOING FCST MINS SEEM
ON TRACK.
ON FRI...SHRTWV IN MN IS PROGGED TO DIG SE THRU WI...DEEPENING UPR
TROF OVER THE GREAT LKS. THIS TRACK SHOULD MAINTAIN H925 N WIND...
WHICH GUIDANCE SHOWS BACKING A BIT MORE NNW IN THE AFTN WITH PASSAGE
OF SHRTWV TO THE SE. GOGEBIC/ONTONAGON AND ERN MQT/WRN ALGER SHOULD
REMAIN THE FOCUS FOR THE HEAVIER LES...WHICH SHOULD BE EVEN MORE
INTENSE WITH MID LVL MOISTENING ACCOMPANYING THE DPVA/MID LVL
QVECTOR CNVGC COINCIDENT WITH THE SHRTWV ACTING AS AN ENHANCEMENT
FACTOR. OVERALL...THE HEAVIEST LES SHOULD FALL IN THE 06Z-18Z FRI PD
WITH STEADY STATE N FLOW AND INCRS IN MID LVL MOISTENING/INVRN BASE
COINCIDENT WITH DIGGING SHRTWV. SN/WATER RATIOS REMAIN HI IN THE
PRIME UPSLOPE AREAS. HEAVIER LES MAY TEND TO SHIFT A BIT TO THE E IN
THE AFTN WITH THE BACKING WIND FLOW.
CORE OF COLDEST H85 AIR...WITH TEMPS CLOSE TO -25C...IS FCST TO DIP
INTO WRN UPR MI ON FRI NGT BEHIND THE SHRTWV PASSAGE TO THE SE. THE
ARRIVAL OF THIS COLD CORE MAY TEND TO LOWER SN/WATER RATIOS A BIT AS
FCST SDNGS SHOW DGZ DESCENDING CLOSER TO AND EVEN BLO THE SFC. THEN
AGAIN...A MORE STEADY STATE 350 DEGREE H925 FLOW MAY KEEP THE
HEAVIER LES BANDS OVER THE SAME LOCATIONS...GOGEBIC/ONTONAGON AND
ERN MQT/WRN ALGER COUNTIES. SN INTENSITY LATE FRI NGT MAY BEGIN TO
DIMINISH OVER THE FAR W WITH APRCH OF HI PRES RDG/LOWERING INVRN
BASE TO 4K FT AGL BY 12Z SAT. THIS TREND WL CONT ON SAT WITH FCST
H925 FLOW TENDING MORE DIFFLUENT OVER THE W AND INVRN BASE SINKING
TO AOB 3K FT MSL CLOSER TO RDG AXIS IN MN. HEAVIER LES WL LINGER
OVER THE NCNTRL...WHERE INVRN BASE IS PROGGED TO REMAIN AT 4K FT.
GOING FCST POPS APPEAR TO HAVE THESE TRENDS IN HAND.
BUMPED UP TEMPS A FEW DEGREES SAT NGT WITH ARRIVAL OF ATLANTIC MSTR/
HIER H85 TEMPS WRAPPING ARND DEEP LO PRES IN SE CAN. BUMPED UP POPS
A BIT OVER THE ERN ZNS TO ACCOUNT FOR THIS MOISTENING.
FOR THE HEADLINES...OPTED TO MAINTAIN GOING WARNINGS FOR GOGEBIC...
ONTONAGON...AND HOUGHTON COUNTIES. ALTHOUGH THE HEAVIEST SNOW MAY
TEND TO MISS HOUGHTON COUNTY TO THE WEST WITH 340-360 DEGREE FLOW...
THIS COUNTY IS CLOSE ENOUGH TO FCST HEAVIEST SN TO AVOID DOWNGRADE.
BARAGA COUNTY WL BE SHADOWED...SO REPLACED LES WARNING THERE WITH AN
ADVY. SINCE NNW FLOW IS NOT IDEAL FOR KEWEENAW COUNTY...REPLACED
WATCH WITH AN ADVY THERE. ERN MQT/WRN ALGER COUNTIES ARE FAVORED FOR
EXPECTED NNW FLOW...SO REPLACED WATCH WITH A WARNING FOR THOSE
COUNTIES STARTING THIS EVNG. RAN HEADLINES THRU 12Z SAT...WHEN DGZ
WL BE SUBSIDING.
&&
.AVIATION /FOR THE 12Z TAF ISSUANCE/...
ARCTIC AIRMASS FLOWING OVER THE WARMER WATERS OF LK SUPERIOR
RESULTS IN LK EFFECT SNOW SHOWERS THROUGH THE PERIOD. EXPECT MOST
PERSISTENT SHSN AT KCMX THROUGH EARLY THIS EVENING WITH FAVORABLE
WNW WINDS. HEAVIER SHSN AFFECT KSAW TONIGHT AS WINDS BECOME NNW/N.
OVERALL AT BOTH SITES EXPECT LOW MVFR CIGS WITH IFR VSBY...THOUGH
THERE IS A POTENTIAL FOR LIFR AT KSAW TONIGHT AS CONVERGENT FLOW AT
LOW-LEVELS INTENSIFIES THE SHSN.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST/...
NO GALES THIS FORECAST PERIOD...BUT A PROLONGED PERIOD OF N/NW WINDS
25-30 KTS ARE EXPECTED THROUGH EARLY NEXT WEEK. WITH STRONG COLD AIR
ADVECTION AND VIGOROUS MIXING...CANNOT RULE OUT OCCASIONAL GALE
FORCE GUSTS. MAIN HAZARD THROUGH THE WEEKEND WILL BE HEAVY FREEZING
SPRAY AS AIR TEMPS DROP INTO THE SINGLE DIGITS TO LOWER TEENS.
HAVE ISSUED HEAVY FREEZING SPRAY WARNINGS FOR MUCH OF LAKE SUPERIOR
THROUGH SATURDAY.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
LAKE EFFECT SNOW WARNING UNTIL 7 AM EST /6 AM CST/ SATURDAY FOR
MIZ002-003-009-084.
LAKE EFFECT SNOW ADVISORY UNTIL 7 AM EST SATURDAY FOR MIZ001.
LAKE EFFECT SNOW WARNING FROM 7 PM THIS EVENING TO 7 AM EST
SATURDAY FOR MIZ005-006.
LAKE EFFECT SNOW ADVISORY UNTIL 7 AM EST SATURDAY FOR MIZ004.
LAKE SUPERIOR...
HEAVY FREEZING SPRAY WARNING FROM 7 PM FRIDAY TO 7 AM EST SUNDAY
FOR LSZ265>267.
HEAVY FREEZING SPRAY WARNING FROM 7 PM EST /6 PM CST/ THIS
EVENING TO 7 AM EST /6 AM CST/ SUNDAY FOR LSZ162-263-264.
LAKE MICHIGAN...
NONE.
&&
SYNOPSIS...KC
DISCUSSION...KC
AVIATION...JLA
MARINE...JLAHAZARDOUS WEATHER OUTLOOK...CORRECTED NATIONAL WEATHER SERVICE MARQUETTE MI 541 AM EST THU DEC 31 2009 MIZ001>007-009-084-085-011045- KEWEENAW-ONTONAGON-NORTHERN HOUGHTON-BARAGA-MARQUETTE-ALGER-LUCE- GOGEBIC-SOUTHERN HOUGHTON-NORTHERN SCHOOLCRAFT- 541 AM EST THU DEC 31 2009 /441 AM CST THU DEC 31 2009/ THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF WESTERN UPPER MICHIGAN AND CENTRAL UPPER MICHIGAN. .DAY ONE...TODAY AND TONIGHT EXPECT HEAVY LAKE EFFECT SNOWS NEAR LAKE SUPERIOR...ESPECIALLY OVER WESTERN AND NORTH CENTRAL UPPER MICHIGAN. SEE THE LATEST WINTER WEATHER STATEMENT FOR MORE DETAILS. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY HEAVY LAKE EFFECT SNOWS WILL CONTINUE NEAR LAKE SUPERIOR THROUGH SATURDAY MORNING. SEE THE LATEST WINTER WEATHER STATEMENT FOR FURTHER DETAILS. .SPOTTER INFORMATION STATEMENT... SNOWFALL REPORTS ARE GREATLY APPRECIATED. MIZ010>014-011045- IRON-DICKINSON-MENOMINEE-DELTA-SOUTHERN SCHOOLCRAFT- 541 AM EST THU DEC 31 2009 /441 AM CST THU DEC 31 2009/ THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL UPPER MICHIGAN. .DAY ONE...TODAY AND TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... THE NEED FOR WEATHER SPOTTER REPORTS IS NOT ANTICIPATED AT THIS TIME. LSZ162-240>251-263>267-011045- LAKE SUPERIOR WEST OF A LINE FROM SAXON HARBOR WI TO GRAND PORTAGE MN BEYOND 5NM-SAXON HARBOR WI TO BLACK RIVER MI- BLACK RIVER TO ONTONAGON MI- ONTONAGON TO UPPER ENTRANCE OF PORTAGE CANAL MI- UPPER ENTRANCE OF PORTAGE CANAL TO EAGLE RIVER MI- EAGLE RIVER TO MANITOU ISLAND MI- MANITOU ISLAND TO POINT ISABELLE MI- POINT ISABELLE TO LOWER ENTRANCE OF PORTAGE CANAL MI- LOWER ENTRANCE OF PORTAGE CANAL TO HURON ISLANDS MI INCLUDING KEWEENAW AND HURON BAYS-HURON ISLANDS TO MARQUETTE MI- MARQUETTE TO MUNISING MI-MUNISING TO GRAND MARAIS MI- GRAND MARAIS TO WHITEFISH POINT MI- LAKE SUPERIOR FROM SAXON HARBOR WI TO UPPER ENTRANCE TO PORTAGE CANAL MI 5NM OFF SHORE TO THE US/CANADIAN BORDER INCLUDING ISLE ROYALE NATIONAL PARK- LAKE SUPERIOR FROM UPPER ENTRANCE TO PORTAGE CANAL TO MANITOU ISLAND MI 5NM OFF SHORE TO THE US/CANADIAN BORDER- LAKE SUPERIOR WEST OF LINE FROM MANITOU ISLAND TO MARQUETTE MI BEYOND 5NM FROM SHORE- LAKE SUPERIOR EAST OF A LINE FROM MANITOU ISLAND TO MARQUETTE MI AND WEST OF A LINE FROM GRAND MARAIS MI TO THE US/CANADIAN BORDER BEYOND 5NM FROM SHORE- LAKE SUPERIOR FROM GRAND MARAIS MI TO WHITEFISH POINT MI 5NM OFF SHORE TO THE US/CANADIAN BORDER- 541 AM EST THU DEC 31 2009 /441 AM CST THU DEC 31 2009/ THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EASTERN LAKE SUPERIOR...CENTRAL LAKE SUPERIOR AND WESTERN LAKE SUPERIOR. .DAY ONE...TODAY AND TONIGHT HEAVY FREEZING SPRAY IS EXPECTED OVER WESTERN AND NORTH CENTRAL LAKE SUPERIOR TONIGHT. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY GALE FORCE GUSTS TO 35 KNOTS ARE POSSIBLE ACROSS CENTRAL AND EASTERN LAKE SUPERIOR LATE FRIDAY THROUGH SATURDAY AFTERNOON. HEAVY FREEZING SPRAY IS EXPECTED ACROSS MUCH OF LAKE SUPERIOR FRIDAY THROUGH SATURDAY NIGHT. .SPOTTER INFORMATION STATEMENT... THE NEED FOR WEATHER SPOTTER REPORTS IS NOT ANTICIPATED AT THIS TIME. LMZ221-248-250-011045- GREEN BAY NORTH OF LINE FROM CEDAR RIVER MI TO ROCK ISLAND PASSAGE-SEUL CHOIX POINT TO POINT DETOUR MI- 5NM EAST OF A LINE FROM FAIRPORT MI TO ROCK ISLAND PASSAGE- 541 AM EST THU DEC 31 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHERN LAKE LAKE MICHIGAN. .DAY ONE...TODAY AND TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... THE NEED FOR WEATHER SPOTTER REPORTS IS NOT ANTICIPATED AT THIS TIME. JLA/KC
The national radar mosaic for the moment the first event began.
1 lake-effect snow. Local standard time, as filed.
The observer in Ironwood measured 15 inches in the 24-hour period ending on the morning of 01/01/2010.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Michigan in 2009Every state in 2009This day in weather historyWarnings in Michigan, December 2009
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 207001.