Extended Streamflow Guidance
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1
000
FGUS66 KRSA 052304
ESGNV

ESGNV

SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE
CALIFORNIA-NEVADA RIVER FORECAST CENTER SACRAMENTO CA
1200 PM PST THU MAR 5 2015

...BELOW AVERAGE RISK FOR SPRING SNOWMELT FLOODING EXPECTED
FOR NEVADA AND THE EAST SIDE SIERRA NEVADA THIS SPRING...

THE SPRING FLOOD POTENTIAL OUTLOOK IS BELOW AVERAGE FOR ALL BASINS
IN NEVADA AS WELL AS WATERSHEDS EAST OF THE CREST OF THE SIERRA
NEVADA MOUNTAINS.  LOW SOIL MOISTURE CONDITIONS DUE TO PROLONGED
DROUGHT AND/OR BELOW NORMAL SNOWPACKS ARE MINIMIZING THE
POTENTIAL FOR SPRING SNOWMELT FLOODING.  THE REGION IS FORECAST
TO ENDURE ITS FOURTH CONSECUTIVE YEAR OF WELL BELOW AVERAGE SPRING
RUNOFF.

MOUNTAIN SNOWPACK CONDITIONS ARE CURRENTLY MUCH BELOW AVERAGE IN
THE REGION.  IT WILL TAKE SEVERAL STRONG STORM SYSTEMS BETWEEN NOW
AND THROUGH APRIL TO TURN THINGS AROUND.  IT APPEARS UNLIKELY THAT
SNOWPACKS CAN RECOVER FROM THE CURRENT DEFICIT THIS LATE INTO THE
WET SEASON.  NOTE THAT FLOODING COULD STILL RESULT FROM HEAVY
RAINFALL ALONE OR COMBINED WITH SNOWMELT ANYTIME DURING THIS
SPRING.

1.  PRECIPITATION
STORM SYSTEMS DURING FEBRUARY DID BOOST THE MONTHLY AVERAGE TO
ABOVE NORMAL FOR MUCH OF THE STATE BUT WATER YEAR TOTALS
(OCT 1, 2014 TO FEBRUARY 28, 2015) ARE STILL MUCH BELOW
AVERAGE.  EXCELLENT DECEMBER PRECIPITATION FELL IN MANY PORTIONS OF
NORTHWESTERN, NORTHEASTERN, SOUTH CENTRAL, AND EXTREME SOUTHERN
NEVADA BUT IT WAS EXTREMELY DRY IN NW, NE AND SOUTH CENTRAL
NEVADA DURING JANUARY.


                         FEBRUARY 2015           WATER YEAR 2015
BASIN                 PERCENT OF AVERAGE        PERCENT OF AVERAGE
LAKE TAHOE                    106                        60
TRUCKEE RIVER                  89                        61
CARSON RIVER                   93                        53
WALKER RIVER                   89                        52
NORTHERN GREAT                 56                        87
UPPER HUMBOLDT RIVER           43                        74
LOWER HUMBOLDT RIVER           53                        79
EASTERN NEVADA                 27                        57
LOWER COLORADO RIVER           47                        60

2.  SNOWPACK
MEASUREMENTS RECORDED FROM NATURAL RESOURCES CONSERVATION SERVICE
(NRCS) SNOTEL SENSORS SHOW THAT ACCUMULATED WATER EQUIVALENT IS
WORSE THAN THAT AT THIS TIME LAST YEAR FOR THE EAST SIDE SIERRA
NEVADA AND THE HUMBOLDT RIVER WATERSHEDS:

                           PCT OF MEDIAN SNOWPACK
BASIN              MARCH 1 2014    MARCH 1 2015    MARCH 4 2015
TRUCKEE                 32              30              34
CARSON                  56              38              38
WALKER                  44              39              40
MONO LAKE*              55              33
OWENS RIVER*            45              16
UPPER HUMBOLDT          87              57              59
LOWER HUMBOLDT          44              30              33
EASTERN NEVADA          71              40              33

*DATA FROM CALIFORNIA COOPERATIVE SNOW SURVEYS.

ALTHOUGH GENEROUS RAINFALL DURING DECEMBER HAS HELPED IMPROVE SOIL
MOISTURE, GROUNDWATER AND RESERVOIR STORAGE DEFICITS...THE
MOUNTAIN SNOW PACK HAS NOT IMPROVED SUBSTANTIALLY DUE TO PERIODS
OF WARM AND DRY WEATHER THIS WINTER.  THERE MAY BE SPRING AND
SUMMER STREAMFLOW DEFICITS WITH LITTLE SNOW SUPPORT FOR NORMAL
SNOWMELT RUNOFF.

3.  RESERVOIRS
SEASONAL AVERAGE STORAGE (OCTOBER 1, 2014 TO FEBRUARY 28, 2015)
STANDS AT BELOW TO MUCH BELOW AVERAGE.  THESE PERCENTAGES ARE
WORSE THAT AT THIS TIME LAST YEAR.  THE LAKE LEVEL AT LAKE TAHOE
IS CURRENTLY AT 6222.83 FEET OR 0.17 FEET BELOW ITS NATURAL RIM
ELEVATION OF 6223.0 FEET.

                     PCT OF AVG STORAGE      PCT OF AVG STORAGE
RESERVOIR/BASIN    OCT 1 2013-FEB 28 2014  OCT 1 2014-FEB 28 2015
TRUCKEE RIVER BASIN          72                      42
WALKER RIVER BASIN           33                      30
LAHONTAN RESERVOIR           43                      25

4.  RUNOFF
AVERAGE MONTHLY RUNOFF RANGED NEAR TO JUST ABOVE AVERAGE
FOR EAST SIDE SIERRA BASINS DURING FEBRUARY.  HOWEVER, THIS
COMES AFTER AN EXTREMELY DRY JANUARY.  THE PREDOMINANTLY DRY
CONDITIONS THIS WATER YEAR ARE REFLECTED BY BELOW AVERAGE
SEASONAL RUNOFF PERCENTAGES.

               PERCENT OF AVG RUNOFF    PERCENT OF AVG RUNOFF
BASIN              FEBRUARY 2015        OCT 1 2014-FEB 28 2015
TRUCKEE                    110                    70
CARSON                      92                    52
WEST WALKER                108                    52
HUMBOLDT                    39                    55

5.  STREAMFLOW FORECASTS
APRIL THROUGH JULY FORECASTS DERIVED FROM ENSEMBLE GUIDANCE
ARE MUCH BELOW AVERAGE FOR THE REGION AS OF MARCH 4TH:

                                APRIL-JULY 50%
                                EXCEEDENCE FCST
FORECAST POINT                      (KAF)          % AVG
TRUCKEE-FARAD**                       95             37
TAHOE APR-HIGH STAGE RISE**       0.40 FEET          31
EF CARSON-GARDNERVILLE                65             35
WF CARSON-WOODFORDS                   20             37
CARSON RIVER-CARSON CITY              28             16
CARSONRIVER-FORT CHURCHILL**          18             11
WEST WALKER BLO LTL WALKER(APR-AUG)   62             38
HUMBOLDT RIVER-PALISADE               94             42
HUMBOLDT RIVER-IMLAY                  35             19

** DENOTES MARCH 1ST FORECASTS COORDINATED WITH THE NRCS.

IN SUMMARY... THE FLOOD POTENTIAL IS BELOW AVERAGE FOR ALL
WATERSHEDS IN NEVADA AND THE EAST SIDE SIERRA NEVADA TYPICALLY
AFFECTED BY SPRINGTIME SNOWMELT...AS WELL AS OTHER WATERSHEDS
IN THE REGION WHERE SNOWMELT IS NOT A MAJOR FACTOR IN
SPRINGTIME FLOODING.

CNRFC/AT



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.