Winter Storm and Heavy Snow in California, December 6 to 7, 2009

Name: Winter Storm and Heavy Snow in California, December 6 to 7, 2009
Start: 2009-12-06T10:30
End: 2009-12-07T18:00
Location: California

December 6 to 7, 2009 · NWS REV · 4 events in 3 counties and zones

A very cold and intense upper low dropped from British Columbia into western Oregon on the 6th and into northern California on the 7th. This brought heavy snow to the Sierra along with very strong winds over ridges and into the lower elevations of Mono County.

Where it happened

Every event with a place to put it; 4 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

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The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 4

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.

What happened

The episode as NWS REV wrote it up.

What forecasters said that day

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 Reno, NV wrote its last area forecast discussion before the first event at Dec 6, 2:54 AM PST, 7 hours 36 minutes earlier.

Area forecast discussion, Dec 6, 2:54 AM PST, 7 hours 36 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
254 AM PST SUN DEC 6 2009

.SHORT TERM...
COLD CORE OF SECONDARY UPPER LOW IS EVIDENT ON SATELLITE IMAGERY
THIS MORNING OVER OREGON AS OF 10Z. THIS LOW WILL CONTINUE TO DROP
SOUTH TODAY...ALONG THE TROUGH OVER THE WESTERN CONUS...AND WILL
DIG WESTWARD BY TONIGHT INTO CA AND NV. THE JET MAX DIGGING AROUND
THE BASE OF THE TROUGH HAS AN OVER WATER TRAJECTORY AND WILL
ENTRAIN A WAVE OF PACIFIC MOISTURE INTO IT AS IT APPROACHES THE
CWA. THE COLD AIR MASS COMBINED WITH MOISTURE AND EXCELLENT
DYNAMICS WILL BE PERFECT FOR GENERATING SNOW. SNOW RATIOS ARE
EXPECTED TO BE IN THE 20-30 TO 1 RANGE IN THIS STORM WITH H7
TEMPERATURES IN THE -14 TO -18 DEGREE C RANGE EVEN DOWN TO THE
LOWEST VALLEY FLOORS. THE MOIST WAVE WILL ROTATE AROUND THE BASE
OF THE WESTERN TROUGH EJECTING EASTWARD MONDAY NIGHT... TAKING THE
SNOW WITH IT.

HAVE UPGRADED ALL AREAS IN THE WATCH TO A WINTER STORM WARNING
WHICH WILL BE ISSUED SHORTLY. IN ADDITION WILL BE ISSUING A SNOW
ADVISORY FOR SURPRISE VALLEY AND NORTHERN WASHOE COUNTY. ALL OF
THE ABOVE WILL BE IN EFFECT FROM SUNDAY NIGHT THROUGH MONDAY
NIGHT. SNOW TOTALS IN THE VALLEYS OF THE WARNED AREAS WILL BE 5 TO
10 INCHES WITH 25-30 INCHES IN THE HIGHER ELEVATIONS OF THE SIERRA.
THE ADVISORY AREA WILL SEE 3 TO 5 INCHES. SEE RNOWSWREV FOR
ADDITIONAL DETAILS OF THE ADVISORY AND WARNINGS.

UPPER LEVEL WINDS WILL BE STRONG AS THIS SYSTEM DROPS SOUTH WITH
RIDGES GUSTING 55-75 MPH. LAKE LEVEL WINDS WILL BE GUSTING 30-40
MPH SO HAVE CONTINUED WITH THE LAKE WIND ADVISORY FOR TAHOE. WILL
BE ENDING THE ADVISORY 3 HOURS EARLIER...AT 7 PM PST...BECAUSE THE
WINTER STORM WARNING WILL BE STARTING AT THAT POINT.

THE SYSTEM WILL LEAVE AN EXTREMELY COLD AIR MASS IN ITS WAKE AND
THE QUESTION IS JUST HOW COLD IT BE TUESDAY AND WEDNESDAY
MORNINGS. BROUGHT LOW TEMPERATURES UP A DEGREE OR TWO TUESDAY
MORNING AS IT APPEARS THERE WILL BE SOME REMNANT CLOUDS OVER THE
AREA. WITH THE UPSTREAM SYSTEM SLOWER TO COME IN...WEDNESDAY
MORNING WILL BE CLEAR...AND WITH LIGHT WINDS AND SNOW COVER...
TEMPERATURES SHOULD PLUNGE. DROPPED TEMPS ABOUT 5 DEGREES ACROSS
THE AREA WEDNESDAY MORNING. EXPECT WIDESPREAD SINGLE DIGIT TEMPS
WITH MANY PLACES EVEN DROPPING BELOW ZERO BOTH MORNINGS. DF

.LONG TERM...WEDNESDAY THROUGH SATURDAY...
MODELS CONTINUE TO BACK OFF ON LATE WEEK SYSTEM AND NOW DELAY
ARRIVAL UNTIL POSSIBLY THURSDAY MORNING. IN ADDITION...SYSTEM
LOOKING LESS AND LESS ORGANIZED WITH EACH RUN AND QPF ALONG SIERRA
CREST NOW DOWN TO ONLY 1-1.5 INCHES. HAVE GONE DRY NOW FOR WED...AND
WITH REINFORCING SHOT OF COLD AIR OVERNIGHT...HAVE LOWERED TEMPS
ABOUT 5 DEGREES...WITH HIGHS STRUGGLING TO REACH 30 ONCE AGAIN
THROUGHOUT WRN NV. EXPECT CLOUD COVER TO MOVE IN WED NIGHT...BUT NOT
SURE ABOUT PRECIP TIMING. GEFS A BIT FASTER THAN OPERATIONAL GFS/EC
SO HAVE LEFT POPS IN...BUT DRASTICALLY REDUCED THEM.

SYSTEM APPEARS TO HIT THU/THU NIGHT AND SAME REASONING WITH SNOW
LEVELS APPLY AS BEFORE. SFC GRADIENT REMAINS EAST SO EXPECT COLD AIR
DAMMING IN THE LEE OF SIERRA AND JUST ABOUT AN ALL SNOW EVENT. SNOW
LEVELS MAY BRIEFLY RISE FRI MORNING TO NEAR 5000 FEET...BUT THIS IS
NOW BECOMING LESS LIKELY AS THE TREND IS FOR THE SYSTEM TO TRACK
FURTHER SOUTH. KEPT THE HIGH POPS IN DURING THIS TIME...BUT DID NOT
ADJUST UPWARD. GIVEN THE TREND OF THE MODELS BACKING
OFF...CONFIDENCE IS NOW QUITE LOW WITH THIS SYSTEM DOING ANYTHING
SIGNIFICANT. NEW 06Z GFS IS ALARMING IN THAT IS ALMOST COMPLETELY
LOSES THE SYSTEM BY THE TIME IT ARRIVES. THIS WILL BE TREATED AS AN
OUTLIER RIGHT NOW...BUT GIVEN THE POTENTIAL SYSTEM SAT IT CANNOT BE
COMPLETELY DISCOUNTED EITHER.

FRI THERE IS SOME SHORT WAVE RIDGING...BUT NOW MODELS ARE IN GOOD
AGREEMENT WITH A WETTER SYSTEM FOR NEXT WEEKEND THAT COMES IN
PIECES. HAVE KEPT CHC POPS IN THE SIERRA WITH LOW CHC TO SLIGHT CHC
WRN NV OVER THE WEEKEND. REALLY HAVE NO CONFIDENCE TO GO HIGHER
DESPITE EXCELLENT MODEL AGREEMENT. MODELS WERE QUITE WET WITH THU
SYSTEM 3-4 DAYS AGO AND HAVE SIGNIFICANTLY BACKED OFF. PREFER TO
WAIT ON THIS ONE RIGHT NOW. IF IT DOES OCCUR...COULD BE IMPRESSIVE
AND WILL BE WARMER...BUT SNOW LEVELS DO NOT LOOK TO RISE ABOVE 6000
FEET WITH THAT ONE EITHER. WALLMANN

&&

.AVIATION...VFR CONDS WITH BRISK SW-W WINDS GUSTING TO 30 KT AT
KRNO/KTVL/KTRK FM 19Z THRU 03Z. WINTER STORM SET TO IMPACT THE
AREA BEGINNING AROUND 03Z FOR KTVL/KTRK AND 09-15Z FOR KRNO-
KLOL...DETAILS BELOW.

FOR KTVL/KTRK...EXPECT MVFR CIGS/VIS BY 03Z MON WITH IFR AFT 06Z.
LIFR CONDS...ABOUT 70 PCT CHC...AFT 12Z CONTINUING THRU AT LEAST 21Z
MON IN MDT-HVY SNOW. SIGNIFICANT RUNWAY ACCUMULATIONS WITH A FOOT OR
MORE POSSIBLE.

KRNO...EXPECT LGT -SN TO MOVE IN AFT 09Z WITH OCNL MVFR CIGS/VIS
THRU 15Z. THEN PDS OF IFR...90 PCT CHC...AND POSSIBLY LIFR THRU
21-00Z IN BANDS OF MDT SNOW. RUNWAY ACCUMULATION LIKELY WITH VERY
COLD TEMPS DURING SNOWFALL...IN THE 20S. AROUND 4 INCHES OR
SO...50-60 PCT PROBABILITY WITH MORE POSSIBLE.

KLOL...MAINLY VFR HERE...BUT PDS OF IFR CIGS/VIS FM 15-21Z IN
LGT-MDT SNOW. LGT RUNWAY ACCUMS POSSIBLE. WALLMANN

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...WINTER STORM WARNING FROM 7 PM THIS EVENING TO 7 PM PST MONDAY
     FOR NVZ002.

     WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 4 PM PST
     MONDAY FOR NVZ005.

     WINTER STORM WARNING FROM 10 PM THIS EVENING TO 7 PM PST MONDAY
     FOR NVZ003.

     LAKE WIND ADVISORY FROM 10 AM THIS MORNING TO 7 PM PST THIS
     EVENING FOR NVZ002.

CA...WINTER STORM WARNING FROM 7 PM THIS EVENING TO 7 PM PST MONDAY
     FOR CAZ071-072.

     WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 4 PM PST
     MONDAY FOR CAZ070.

     WINTER STORM WARNING FROM 10 PM THIS EVENING TO 7 PM PST MONDAY
     FOR CAZ073.

     LAKE WIND ADVISORY FROM 10 AM THIS MORNING TO 7 PM PST THIS
     EVENING FOR CAZ072.

&&

HTTP://WEATHER.GOV/RENO

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

2 heavy snow, 1 high wind, 1 winter storm. Local standard time, as filed.

High Wind, Mono

When: December 6, 10:30 AM PST to 6:10 PM PST
Where: Mono forecast zone
Measured: 81 kt (93 mph) measured gust
Reported by: Mesonet
Coordinates: 37.939, -118.887 (the zone’s center; the record gives no point)

Some areas near the Sierra crest and along highway 395 experienced remarkably strong winds. The Mammoth Mountain ski area gusted to 142 mph between 1300PST and 1400PST. Along highway 395, the Mammoth airport AWOS gusted to 93 mph at 1410PST while the Bridgeport RAWS gusted to 66 mph between 1300PST and 1400 PST.

In Lee Vining, a couple of car windows were broken by flying debris and an unsecured dumpster. Also, a road information sign was blown down onto a roadway. A wind gust to 56 mph was recorded at 1302PST.

Winter Storm, Greater Lake Tahoe Area

When: December 6, 5:00 PM PST to December 7, 1:00 PM PST
Where: Greater Lake Tahoe Area forecast zone
Reported by: COOP Observer
Coordinates: 38.935, -120.458 (the zone’s center; the record gives no point)

A storm total of 2 to 3 feet of snowfall fell west of highway 89 and along the Sierra Crest, with 1 to 2 feet east of highway 89 and south of Lake Tahoe. Here are some specific snowfall reports: Alpine Meadows Ski Area with 33-42 inches, 25 inches at the Truckee Airport, 18-20 inches for Tahoe City, and 13-15 inches for South Lake Tahoe.

In addition to heavy snowfall, wind gusts of 35-45 mph were recorded on the 6th between 1100PST and 1800PST with a 58 mph gust at the South Lake Tahoe airport at 1156PST. Winds over the Sierra Crest gusted to between 90-100 mph.

Heavy Snow, Lassen/Eastern Plumas/Eastern Sierra

When: December 6, 5:00 PM PST to December 7, 11:00 AM PST
Where: Lassen/Eastern Plumas/Eastern Sierra forecast zone
Reported by: Trained Spotter
Coordinates: 40.086, -120.650 (the zone’s center; the record gives no point)

Storm total snowfall reports ranged from 6 to 13 inches. Here are some specific snowfall reports: 13 inches in Portola, 7-9 inches in Susanville, and 7 inches in Doyle.

Heavy Snow, Mono

When: December 7, 4:00 AM PST to 6:00 PM PST
Where: Mono forecast zone
Reported by: Mesonet
Coordinates: 37.939, -118.887 (the zone’s center; the record gives no point)

This storm featured an intense, fairly short period of snowfall which affected areas mainly west of highway 395 and near the Sierra Crest with much less snowfall along and east of highway 395. Here are some snowfall totals: An estimated 24 inches at the Leavitt Lake SNOTEL, 13-16 at the Mammoth Lakes Ski Area and Mammoth Pass. Lesser amounts further east include the Mammoth Lakes Ranger Station with 10 inches and the Bridgeport CO-OP with 5 inches.

What these are

High Wind: Sustained non-thunderstorm winds of 40 mph or more for an hour, or gusts of 58 mph or more.
Winter Storm: A storm that brought snow, sleet or freezing rain at warning levels, usually over several hours or days.
Heavy Snow: Snowfall reaching the local warning threshold without the other hazards of a winter storm.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in California in 2009 Every state in 2009 This day in weather history Warnings in California, December 2009

Sources

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: 204637, 203627, 203628, 204508.