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This is the National Weather Service in Reno with an informational online weather briefing
about the weather events that occurred in the Sierra and Western Nevada during 2012.
An unusually dry start to winter continued through much of January with almost no snowpack
in the Sierra until a winter storm finally arrived during the third week of January.
January 2012 was warmer than normal. The average temperature for the month was 38.9 degrees,
which is an exceptional 5.3 degrees above normal. The average temperature for all but
three days was above normal at Reno international airport. A number of record high temperatures
were broken in Reno during January and the record high was tied or exceeded at least
9 days at South Lake Tahoe airport in CA. The second major wildfire outside of the usual
fire season occurred on January 19th in the northern portion of Washoe Valley. The Washoe
Drive fire was spread rapidly by gusty winds into portions of Pleasant Valley south of
Reno, and destroyed 33 homes before being contained two days later at 3177 acres. Here
is a view from the NWS Reno office on the north end of Reno. Strong winds created blowing
dust which combined with the smoke from the Washoe Drive Fire to limit visibility in Reno.
Eventually by late January some snowfall gave the Sierra snowpack a boost, but it still
remained well below average. The graph above shows the snow water equivalent (SWE) from
the 2011-2012 water year through February 1st, the average water year (includes 1971-2000),
and the 2010-2011 water year. The Snow Water Equivalent for this past water year through
February 1st was approximately 5 inches, compared to over 20 inches this time in 2010-2011.
An unsettled weather pattern developed across the Western U.S. towards the last half of
March, which allowed more storm systems to impact the region. Generally, storms that
moved across the Sierra and Western Nevada during the end of March brought strong gusty
winds, snow to the northern Sierra and Tahoe basin, and rain to Western Nevada valleys.
Snowstorms during this time frame brought recovery to the snowpack, but the large deficit
could not be overcome, resulting in a snowpack well below seasonal average.
The snowfall from March and April gave the Sierra snowpack a boost, but it remained well
below average. On April 1, Eastern Sierra snowpack totals ranged from 55 to 65 percent
of normal in the Truckee and Tahoe basins, and only 40-45 percent of normal for the Carson
and Walker river basins. The last significant snowfall in the Sierra occurred in mid April.
Record high temperatures occurred in late April, which included Reno reporting its first
ever 90 degree temperature for the month of April on the 22nd. By the end of April, snowpack
in the Sierra had decreased to 20-30 percent of normal, except near 45 percent of normal
for the Truckee River basin.
Dry conditions prevailed for most of May. After a cool start, temperatures warmed across
western Nevada well into the 80s during the 2nd and 3rd week of the month. Around Memorial
Day weekend, a cold system produced wetting rain and light snow over much of western Nevada
and eastern California, with a few inches of snow in the Sierra. Warm and dry temperatures
returned quickly by the end of the month. The highest temperature for the month in Reno
was 92 degrees which occurred on the 31st.
The most significant event, besides Memorial Day weekend snow, was the “TRE” fire in
southeast Douglas county. It burned 2 homes in the Topaz Ranch Estates subdivision, 17
additional structures, and over 7000 acres between the 22nd and 26th.
June started out with above normal temperatures with record highs in the mid to upper 90s
in the lower elevations and some isolated thunderstorms. A cold front moved through
the first week of June bringing gusty winds and blowing dust to western Nevada, while
wetting rain impacted eastern California. The picture above is courtesy of Susie, a
storm spotter in Fernley. Temperatures cooled significantly with highs in the 50s on June
5th, which was about 40 degrees cooler than the highs on June 1st. The remainder June
and into July was relatively dry with warmer temperatures. During mid-July, a large area
of high pressure remained across the region resulting in a period of hot temperatures
for some western Nevada valleys with heat advisories in effect. July of 2012 tied for
the eighth warmest July on Record at Reno since 1888. The highest temperatures at Reno
for July was 103 degrees which occurred on the 12th.
August brought thunderstorms which resulted in several new fire starts, including the
Chips and Rush fires. The Rush fire consumed over 315,000 acres in eastern Lassen and western
Washoe counties during the middle of August. The number of acres burned in the Rush fire
alone, exceeded the combined total acreage burned from all of the large fires recorded
in the Reno county warning area between 2007-2011! A severe thunderstorm produced over
4 inches of hail in Truckee-Glenshire on August 15th, while successive thunderstorms produced
heavy rains over the Ray May fire burn scar that resulted in rocks and mud across
highway 395. August 2012 was also the warmest month on record for Reno, since records
began in 1888. 2012 was the 3rd warmest summer (June, July, August) on record in Reno.
Following the warmest August on record, September 2012 also broke the record for the warmest
September since 1888 in Reno, Nevada. The average temperature for September was 70.7
degrees, which is 5.3 degrees above normal and exceeded last year’s record September
of 70.6 degrees. The graph above shows the normal high temperature in September in the
black line and the daily high temperature for September 2012 in the red line. September
2012 was also relatively dry with only 0.08 inch of precipitation recorded at the Reno/Tahoe
International Airport. This follows a very dry summer making 2012 the ninth driest summer
on record at Reno.
October 2012 was the 5th warmest October on record for Reno, with most of the month warm
and dry. Temperatures in Reno reached 90 degrees on the first two days of the month, and reached
at least 70 degrees on 24 out of the 31 days in October. The exceptions to the warm and
dry pattern are shown on the slide. A low pressure system which stalled over southern
California on October 10th-12th brought the first measurable snow of the season to higher
elevations of Mono county including Mammoth Lakes, and rain to the Lake Tahoe Basin and
portions of western Nevada. A much stronger storm brought the first significant snow of
the season to the Sierra and northeast California on October 22nd and 23rd. Up to 30 inches
of snow fell above 7000 feet, with up to 18 inches near the west shores of Lake Tahoe.
For western Nevada, precipitation was limited, as gusty winds of 40-50 mph were the main
impact from this storm.
This visible satellite image from November 11th shows three narrow areas (white patches
on image) where heavy snowfall occurred on November 9th-10th . Area #1 (red oval) includes
Susanville and Janesville which received heavy snow from a convective snow band, that had
originated from thunderstorms which formed over north central California. Area #2 (yellow
oval) includes lake effect snow which occurred southeast of Pyramid Lake including Nixon,
Nevada highway 447 and a small portions of Interstate 80 northeast of Fernley. Area #3
(blue oval) includes lake effect snow which occurred east-southeast of Lake Tahoe including
Carson City, northern Douglas county and central Lyon county.
Here are a couple of images from the lake effect snow event. The picture on the right
is from Carson City courtesy of storm spotter Robert Sandberg. The MODIS visible satellite
image on the left shows snow fields from the lake effect snow east of Lake Tahoe and southeast
of Pyramid Lake. A heavy rain pattern developed across the
eastern Pacific in late November and early December. A series of warm storm systems combined
with an atmospheric river event brought periods of heavy precipitation and strong gusty winds
to the Sierra and western Nevada. Snow levels were fairly high through the series of storms
so much of the precipitation fell as rain and resulted in rises in many area rivers.
The potential for flooding in the Reno industrial area was forecast. Fortunately lower snow
levels and a slightly shorter period of precipitation resulted in a lack of significant flooding
along the Truckee river. There was a rapid rise on the Susan river that caused moderate
flooding in Susanville California. Here are some of the five day storm totals
from this atmospheric river event. Some areas along the Sierra crest received more then
10 inches of rain. A series of cold low pressure systems tracked
into California and Nevada in mid to late December bringing periods of gusty winds and
snow to the Sierra as well as some rain and snow showers to western Nevada. This active
and unsettled pattern brought at least 4-7 feet of snow to the Sierra and some snow accumulations
down to western Nevada valley floors. Abundant heavy snow in the Sierra produced an unstable
snowpack which created dangerous avalanche conditions. Several avalanches occurred in
the backcountry and at local ski resorts resulting in two fatalities.
This graphic compares the precipitation in December 2011 with the precipitation for December
2012. The image on the left represents the total liquid precipitation that fell during
December 2011. The image on the right is the total liquid precipitation that fell over
the last 30 days of 2012 ending on December 28th. The images show the stark contrast between
the exceptionally dry December of 2011 and the very wet December of 2012. Tahoe City
received no measureable snowfall in December 2011. In December 2012 Tahoe City received
42 inches of snowfall. As of December 28th the snow water equivalent a measure of the
total water in the snowpack in the Truckee River basin is 204% and 169% in the Lake Tahoe
Basin. Thank you for all of your reports, photos,
and comments during the past year! Participation from our community and partners is essential
and it helps us to improve our forecasts. We at the National Weather Service in Reno
look forward to working with you all in the New Year.