Flood Potential Outlook
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WATER SUPPLY AND SPRING FLOOD OUTLOOK
NATIONAL WEATHER SERVICE RENO NV
920 AM PDT THU MAY 7 2015

...WATER SUPPLY OUTLOOK FOR NEVADA AND EASTERN CALIFORNIA AS OF
MAY 7 2015...

...WELL BELOW AVERAGE TO RECORD LOW STREAM FLOW IS EXPECTED LATE
THIS SPRING AND THIS SUMMER...

ISSUED JOINTLY BY THE NATIONAL WEATHER SERVICE AND NATURAL RESOURCES
CONSERVATION SERVICE...

1/SUMMARY...WATER SUPPLY OUTLOOK...

PRECIPITATION HAS BEEN BELOW TO WELL BELOW NORMAL FOR MUCH OF NEVADA
AND EASTERN CALIFORNIA SINCE OCTOBER 2014. THE ONLY AREAS THAT HAVE
SEEN ABOVE NORMAL PRECIPITATION IN THAT TIME ARE LOCATED ACROSS
SMALL PARTS OF NORTHEAST CALIFORNIA AND FAR NORTHWEST NEVADA...
ALONG WITH SOUTHERN INYO COUNTY AND NORTHWEST AND FAR EASTERN SAN
BERNARDINO COUNTY IN EASTERN CALIFORNIA.

AFTER A SERIES OF WET STORMS IN DECEMBER LEFT A NEAR TO SLIGHTLY
ABOVE AVERAGE SNOW PACK IN EASTERN NEVADA...BUT BELOW NORMAL SNOW PACK
FOR WESTERN NEVADA AND THE EASTERN SIERRA...THE MONTH OF JANUARY WAS
WELL BELOW NORMAL IN TERMS OF PRECIPITATION AND HAD LONG STRETCHES
OF WELL ABOVE NORMAL TEMPERATURES. THIS COMBINATION OF NO
PRECIPITATION AND MILD TEMPERATURES WORKED TO DRASTICALLY DECREASE
THE SNOW PACK IN WESTERN NEVADA WHILE EASTERN NEVADA SAW DECREASES
AS WELL...JUST NOT AS SEVERE. THE DECREASED PRECIPITATION AND MILD
TEMPERATURES ALSO HELPED TO INTENSIFY DROUGHT CONDITIONS ACROSS
WESTERN NEVADA.

A SERIES OF WET...WARM STORMS MOVED THROUGH EASTERN CALIFORNIA AND
WESTERN NEVADA IN THE FIRST HALF OF FEBRUARY. THESE STORMS BOOSTED
PRECIPITATION OVER THE REGION...BUT HIGH SNOW LEVELS LIMITED
INCREASES TO THE SNOWPACK. THE WARM...WET NATURE OF THESE STORMS DID
PRODUCE RUNOFF AND INCREASED STORAGE ON AREA RESERVOIRS. A COLDER
STORM IN LATE FEBRUARY BROUGHT SNOW TO WESTERN NEVADA AND THE SIERRA
ALONG WITH SNOW AND RAIN TO SOUTHERN NEVADA...TEMPORARILY INCREASING
THE SNOWPACK. HOWEVER...THE BENEFITS OF THIS STORM LARGELY BYPASSED
EASTERN NEVADA.

ONE BRIGHT SPOT...THESE STORMS RESULTED IN AN INCREASE IN SOIL
MOISTURE ACROSS THE SIERRA AND WESTERN NEVADA. THE TRUCKEE RIVER
BASIN RECORDED ITS HIGHEST MARCH 1ST SOIL MOISTURE BASED ON TEN
YEARS OF DATA. SOIL MOISTURE HAS SINCE DECREASED AS WARMER WEATHER
HAS ACTED TO DRY SOME OF THE SOILS. SOIL MOISTURE HAS SINCE
DECREASED BUT REMAINS NEAR AVERAGE IN THE SIERRA AND WESTERN NEVADA.
IT HAS FALLEN TO ITS LOWEST IN A DECADE IN THE NORTHERN GREAT BASIN
AND EASTERN NEVADA.

MARCH WAS ANOTHER DRY AND VERY WARM MONTH. THIS DRY AND WARM WEATHER
ACTED TO DECREASE AN ALREADY BELOW AVERAGE SNOW PACK EVEN MORE. MANY
SNOTEL SITES ACROSS NORTHERN AND WESTERN NEVADA AND THE EASTERN
SIERRA OF CALIFORNIA REPORTED THEIR RECORD LOWEST SNOW WATER
EQUIVALENT READINGS SINCE SNOTEL MEASUREMENTS BEGAN IN THE EARLY
1980S. ADDITIONALLY...A FEW LONG TERM HIGH ELEVATION SNOW COURSE
SITES ALSO REPORTED NEAR RECORD LOW SNOW WATER EQUIVALENT READINGS.

STORMS IN APRIL PROVIDED NEAR TO SLIGHTLY BELOW NORMAL PRECIPITATION
ACROSS A LARGE PORTION OF THE REGION...BUT DID LITTLE TO ADD TO THE
ALREADY MEAGER SNOWPACK. THE SNOW THAT DID ACCUMULATE IN THE MIDDLE
PART OF APRIL MELTED AS TEMPERATURES AT THE END OF THE MONTH ROSE TO
WELL ABOVE NORMAL.

THE COMBINATION OF BELOW AVERAGE PRECIPITATION IN MOST AREAS AND
HIGH SNOW LEVELS IN THE STORMS THAT DID MOVE THROUGH THE AREA...
LEAVING RECORD LOW SNOW PACK IN THE REGION...HAS RESULTED IN A
FORECAST OF WELL BELOW AVERAGE RUNOFF LATE THIS SPRING INTO THE
EARLY PART OF SUMMER.

2/SNOWPACK...

SNOWPACK AS OF MAY 1ST IN THE SIERRA NEVADA AVERAGED FROM 0 PERCENT
OF NORMAL TO 19 PERCENT OF NORMAL...HISTORIC LOWS IN MANY LOCATIONS.
ACROSS NORTHERN AND EASTERN NEVADA THE SNOWPACK RANGED FROM 0
PERCENT OF NORMAL TO 36 PERCENT OF NORMAL...ALSO HISTORIC LOWS. AS
OF MAY 1ST ONLY 16 OUT OF 88 AUTOMATED STATIONS ACROSS NEVADA AND THE
EASTERN SIERRA REPORTED ANY SNOW...THE REST WERE BARE. SNOW WAS
PRESENT IN SOME HIGHER ELEVATIONS ABOVE THE MEASURING SITES...BUT
THE BASIN PERCENTAGES OF AVERAGE DO NOT ADJUST FOR THIS SITUATION.

                                 MAY 1 2015
BASIN               PERCENT OF AVERAGE
LAKE TAHOE ........................   0
TRUCKEE RIVER .....................   8
CARSON RIVER ......................   0
WALKER RIVER ......................  19
NORTHERN GREAT ....................  12
UPPER HUMBOLDT RIVER ..............   2
LOWER HUMBOLDT RIVER ..............   1
CLOVER VALLEY & FRANKLIN RIVER ....   0
SNAKE RIVER .......................  36
OWYHEE RIVER ......................   0
EASTERN NEVADA ....................   8
LOWER COLORADO RIVER ..............  NA

3/PRECIPITATION...

HEAVY PRECIPITATION IN EARLY FEBRUARY BOOSTED AVERAGES ACROSS THE
WESTERN PART OF NEVADA AND THE EASTERN SIERRA OF CALIFORNIA...BUT
MUCH OF NORTHERN AND EASTERN NEVADA MISSED THE BULK OF THIS
PRECIPITATION AND THEIR BASIN AVERAGES FELL THROUGH THE MONTH OF
FEBRUARY.

THEN ALONG CAME MARCH AND BROUGHT WITH IT ONE OF THE DRIEST WINTER
MONTHS ON RECORD. APRIL PRECIPITATION VARIED WIDELY ACROSS NEVADA
AND THE EASTERN SIERRA...RANGING FROM 50 PERCENT OF AVERAGE TO NEAR
NORMAL IN SOME BASINS. THE SIERRA AND NORTHERN NEVADA GENERALLY
FARED BETTER THAN EASTERN NEVADA DURING THE MONTH. EVEN THOUGH APRIL
WAS FAR WETTER THAN MARCH...THE WATER YEAR AVERAGES STILL REMAIN
BELOW NORMAL IN ALL AREAS.

                                                  WATER YEAR 2015
                                    APR 2015    /THROUGH 4/30/2015/
BASIN                              PCT OF AVE        PCT OF AVE
LAKE TAHOE .........................   95  ...........   56
TRUCKEE RIVER ......................   71  ...........   54
CARSON RIVER .......................   79  ...........   50
WALKER RIVER .......................  101  ...........   50
NORTHERN GREAT .....................   50  ...........   74
UPPER HUMBOLDT RIVER ...............   80  ...........   68
LOWER HUMBOLDT RIVER ...............   74  ...........   70
CLOVER VALLEY AND FRANKLIN RIVER ...   61  ...........   81
SNAKE RIVER ........................   72  ...........   75
OWYHEE RIVER .......................   89  ...........   80
EASTERN NEVADA .....................   59  ...........   52
LOWER COLORADO RIVER ...............   NA  ...........   NA

4/RESERVOIRS...

VERY WARM TEMPERATURES DURING THE MONTH OF MARCH PRODUCED EARLY
SEASON RUNOFF THAT PROVIDED INFLOWS INTO RESERVOIRS IN THE
TRUCKEE...CARSON AND WALKER BASINS. HOWEVER...THIS INFLOW WAS OFFSET
SLIGHTLY BY EVAPORATION AND DECREED OUTFLOWS ON THE TRUCKEE BASIN.
TEMPERATURES COOLED IN APRIL AND A FEW SMALL STORMS BROUGHT RAIN AND
HIGH ELEVATION SNOWS TO THE SIERRA AND PARTS OF NORTHERN NEVADA.

OVERALL RESERVOIR STORAGE REMAINS WELL BELOW CAPACITY AND AVERAGE
FOR LATE APRIL AND EARLY MAY. MOST RESERVOIRS STATEWIDE ARE LESS
THAN 25 PERCENT OF CAPACITY...BUT THERE ARE SOME BRIGHT SPOTS.
INDEPENDENCE LAKE IN THE SIERRA...A SOURCE OF MUNICIPAL WATER FOR
RENO AND SPARKS...WAS AT 95 PERCENT OF CAPACITY WHILE LAKE MOHAVE IN
THE SOUTHERN NEVADA WAS ALSO AT 95 PERCENT OF CAPACITY. LAKE
MEAD...THE PRIMARY SUPPLY FOR LAS VEGAS...STOOD AT 38 PERCENT OF
CAPACITY

EFFECTIVE STORAGE ON LAKE TAHOE REMAINED AT 0 PERCENT DUE TO THE
LAKE`S FALLING BELOW ITS NATURAL RIM IN LATE FALL 2014. THE LEVEL OF
LAKE TAHOE ON MAY 1ST WAS 6222.87 FEET...WHICH EQUATES TO A STORAGE
DEFICIT OF 15,766 ACRE-FEET AS NO WATER CAN FLOW OUT OF THE LAKE
BELOW ITS NATURAL RIM OF 6223.0 FEET.

BASIN                        PERCENT OF CAPACITY   PERCENT OF AVERAGE
LAKE TAHOE ........................   0 ................   0
TRUCKEE RIVER .....................  19 ................  28
CARSON RIVER ......................  21 ................  30
WALKER RIVER ......................  15 ................  23
LOWER HUMBOLDT RIVER ..............   5 ................   9
OWYHEE RIVER ......................  21 ................  30
LOWER COLORADO RIVER ..............  42 ................  53

5/STREAMFLOW...

STREAMFLOW FORECASTS THROUGH JULY FOR ALL OF NEVADA AND EASTERN
CALIFORNIA AS OF MAY 1ST ARE FORECAST TO BE MUCH BELOW
AVERAGE....WITH MORE THAN HALF OF ALL LOCATIONS FORECAST TO HAVE
LESS THAN 10 PERCENT OF AVERAGE FLOW. ALL LOCATIONS SAW DECLINES IN
STREAMFLOW FORECASTS FROM APRIL 1ST TO MAY 1ST.

MAY 1ST STREAMFLOW FORECASTS FROM THE NRCS WERE HIGHEST ON FRANKLIN
CREEK AT 23 PERCENT OF AVERAGE.  ON THE VIRGIN RIVER IN SOUTHERN
NEVADA...THE FORECAST WAS FOR 22 PERCENT OF AVERAGE.  THE OWYHEE
RIVER BELOW WILDHORSE RESERVOIR AND THE TRUCKEE RIVER AT FARAD BOTH
HAD FORECASTS OF 16 PERCENT OF AVERAGE....THE ONLY OTHER SITES ABOVE
15 PERCENT OF AVERAGE.

BELOW ARE FORECASTS FOR SELECTED RIVER POINTS ACROSS NEVADA AND
EASTERN CALIFORNIA. SOME CONTAIN BOTH THE NRCS FORECAST AND NWS
FORECAST PROVIDED BY THE ENSEMBLE STREAMFLOW PREDICTION SYSTEM AT
THE CALIFORNIA-NEVADA RIVER FORECAST CENTER. THE FORECASTS MAY
DIFFER SLIGHTLY BASED ON FORECAST METHODOLOGY.

                      PERCENT OF AVERAGE APRIL TO JULY STREAMFLOW
                        MOST PROBABLE FORECAST AS OF MAY 1 2015
                          (50 PERCENT CHANCE OF EXCEEDANCE)
BASIN                                 NRCS    NWS
LAKE TAHOE RISE ......................  6 ... -6  .. 0.06 FOOT RISE (NRCS)
TRUCKEE RIVER ........................ 16 ... 20  .. FARAD
CARSON RIVER .........................  3 ...  2  .. CARSON CITY
WEST WALKER RIVER .................... 12 ... 23
EAST WALKER RIVER ....................  6 ...  8
NORTHERN GREAT .......................  7 ... NA  .. MCDERMITT
UPPER HUMBOLDT RIVER ................. 13 ... 20  .. PALISADE
LOWER HUMBOLDT RIVER .................  1 ...  3  .. IMLAY
CLOVER VALLEY AND FRANKLIN RIVER ..... 23 ... NA
SNAKE RIVER .......................... 10 ... 21@
OWYHEE RIVER ......................... 16 ... 14@
EASTERN NEVADA .......................  7 ... NA  .. ELY
LOWER COLORADO RIVER ................. 22 ... 19* .. LITTLEFIELD
SUSAN RIVER........................... NA ... 19  .. SUSANVILLE
MIDDLE FORK FEATHER RIVER............. NA ...  1  .. PORTOLA

NA - FORECAST EITHER NOT AVAILABLE OR NOT PRODUCED FOR THIS LOCATION
     AT THE TIME OF THE REPORT
*  - VIRGIN RIVER NWS FORECAST PROVIDED BY CBRFC IN SALT LAKE CITY
@  - SNAKE AND OWYHEE RIVER NWS FORECASTS PRODUCED BY NWRFC IN
     PORTLAND

6/ DROUGHT STATUS...

AS OF APRIL 28 2015...THE UNITED STATES DROUGHT MONITOR CLASSIFIED
MUCH OF WESTERN NEVADA...INCLUDING CHURCHILL...PERSHING...STOREY...
CARSON CITY...DOUGLAS...MINERAL...WESTERN LANDER AND SOUTHERN WASHOE
COUNTIES IN NEVADA ALONG WITH FAR NORTHWEST ESMERALDA COUNTY AS IN
EXCEPTIONAL DROUGHT /LEVEL 4 OF 4 LEVELS OF DROUGHT/. IN CALIFORNIA
ALL OF LASSEN...PLUMAS... SIERRA...NEVADA...PLACER...EL DORADO...
ALPINE AND MONO COUNTIES WERE CLASSIFIED IN EXCEPTIONAL DROUGHT...
ALONG WITH THE WESTERN AND NORTHERN PARTS OF INYO COUNTY. MUCH OF
THE REMAINDER OF EASTERN CALIFORNIA AND WESTERN NEVADA WAS
CLASSIFIED AS IN EXTREME DROUGHT /LEVEL 3 OF 4 LEVELS OF DROUGHT/.
IN EASTERN AND SOUTHERN NEVADA...PARTS OF ELKO...EUREKA AND NYE
COUNTIES WERE CLASSIFIED AS HAVING EXTREME DROUGHT WHILE THE
REMAINDER OF EASTERN AND SOUTHERN NEVADA WAS CLASSIFIED AS HAVING
MODERATE TO SEVERE DROUGHT. FAR SOUTHEAST INYO COUNTY AND MUCH OF
SAN BERNARDINO COUNTY WERE ALSO NOTED AS HAVING MODERATE TO SEVERE
DROUGHT...EXCEPT AREAS ALONG THE COLORADO RIVER WHICH WERE
CLASSIFIED AS ABNORMALLY DRY.

POSSIBLE IMPACTS FROM DROUGHT IN NEVADA AND EASTERN CALIFORNIA
INCLUDE...

HIGH FIRE DANGER THIS SPRING AND SUMMER...AS TEMPERATURES WARM AND
FUELS DRY.

LIKELY WATER SUPPLY DEFICITS...RESERVOIR STORAGE REMAINS VERY LOW
AND WATER SUPPLY MAY BECOME AN ISSUE THROUGHOUT THE REGION THIS
SPRING AND SUMMER. WATER SUPPLY CONCERNS WOULD BE HIGHEST ON BASINS
WITHOUT RESERVOIR STORAGE.

7/ LONG RANGE WEATHER OUTLOOK FOR NEVADA AND EASTERN CALIFORNIA. THE
OUTLOOK FOR MAY IS FOR ABOVE NORMAL TEMPERATURES FOR ALL OF NEVADA
AND EASTERN CALIFORNIA. ALL OF NEVADA AND EASTERN CALIFORNIA HAVE
EQUAL CHANCES OF ABOVE...BELOW OR NEAR NORMAL PRECIPITATION.

THE OUTLOOK FOR THE MONTHS OF JUNE THROUGH AUGUST IS FOR EQUAL
CHANCES OF ABOVE...BELOW AND NEAR NORMAL PRECIPITATION ACROSS
WESTERN NEVADA AND EASTERN CALIFORNIA. EASTERN NEVADA HAS A BETTER
CHANCE FOR SLIGHTLY ABOVE AVERAGE PRECIPITATION AS THE MONSOON
DEVELOPS...BUT THERE IS LOW CONFIDENCE IN THIS OUTCOME. TEMPERATURES
DURING THIS PERIOD ARE EXPECTED TO BE ABOVE NORMAL FOR THE ENTIRE
REGION.

8/ FOR MORE DETAILED WATER SUPPLY AND STREAMFLOW FORECAST
INFORMATION FOR NEVADA AND EASTERN CALIFORNIA...PLEASE REFER TO THE
FOLLOWING WEB SITES /NOTE...ALL LETTERS IN WEB SITE ADDRESSES ARE
LOWER CASE/...

NWS CALIFORNIA NEVADA RIVER FORECAST CENTER...
HTTP://WWW.CNRFC.NOAA.GOV/WATER_SUPPLY.PHP

NEVADA NATURAL RESOURCES CONSERVATION SERVICE...
HTTP://WWW.NV.NRCS.USDA.GOV/SNOW/

CALIFORNIA DEPT. OF WATER RESOURCES...
HTTP://CDEC.WATER.CA.GOV/

NWS CLIMATE PREDICTION CENTER LONG RANGE OUTLOOK MAPS...
HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/FORECASTS/

U.S. DROUGHT PORTAL...INCLUDING U.S. DROUGHT MONITOR...
HTTP://DROUGHT.GOV/

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