FGUS75 KREV 082206
ESFREV
NVZ001>037-CAZ070>073-180000-
HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE RENO NV
210 PM PST TUE FEBRUARY 8 2005
...WATER SUPPLY AND SPRING FLOOD POTENTIAL OUTLOOK FOR NEVADA AND
THE EASTERN SIERRA NEVADA...
ISSUED JOINTLY BY THE NATIONAL WEATHER SERVICE AND NATURAL RESOURCES
CONSERVATION SERVICE...
1/ SUMMARY...
WATER SUPPLY...NEVADA AND THE EASTERN SIERRA CAN BE BROKEN INTO
THREE BANDS OF VERY DIFFERENT WATER SUPPLY CONDITIONS. NORTHERN
NEVADA AND EXTREME NORTHEASTERN CALIFORNIA HAVE DRY CONDITIONS...
WITH BELOW AVERAGE SNOWPACK AND STREAMFLOW FORECASTS. CENTRAL
NEVADA RECEIVED ABOVE AVERAGE SNOW...WITH RECORD BREAKING
SNOWPACK IN EASTERN NEVADA. SNOW IN THE EASTERN SIERRA NEVADA
INCREASES DRAMATICALLY FROM NORTH TO SOUTH...WITH SEVERAL AREAS
ALREADY HAVING AN ENTIRE YEARS WORTH OF SNOW...WITH TWO MONTHS OF
WINTER LEFT. STREAMFLOW IS EXPECTED TO BE ABOVE AVERAGE FOR THE
EASTERN SIERRA. SOUTHERN NEVADA SAW A PHENOMENALLY WET JANUARY...
RESULTING IN FLOODING ON THE VIRGIN AND MUDDY RIVERS. WHILE LOCAL
AREAS CONTRIBUTE LITTLE FLOW TO THE COLORADO RIVER...CONDITIONS IN
THE UPPER WATERSHED ARE SUCH THAT FLOWS ARE EXPECTED TO BE ABOVE
AVERAGE...GOOD NEWS FOR THE LAS VEGAS AREA. THE EXCITEMENT OVER
THE MOSTLY EXCELLENT WATER SUPPLY FORECASTS IS TEMPERED BY RECENT
HISTORY. THE AREA HAS SEEN SEVERAL EARLY...WET STARTS TO THE
SEASON ONLY TO HAVE THE STORMS STOP...TEMPERATURES INCREASE AND
WATER SUPPLIES DWINDLE. A RETURN TO DRIER CONDITIONS AFTER MID
JANUARY HAS CAUSED CONCERN THAT WE ARE SLIPPING BACK INTO THIS
PATTERN. THE NEXT TWO MONTHS WILL TELL THE TALE FOR THE REGIONS
SUMMER WATER SUPPLY.
FLOOD POTENTIAL...DUE TO THE WETTER THAN AVERAGE CONDITIONS IN ALL
BUT THE EXTREME NORTH...THE FLOOD POTENTIAL FOR THE EASTERN SIERRA
AND ALL OF NEVADA...WITH THE EXCEPTION OF THE EXTREME NORTH...IS FOR
ABOVE AVERAGE FLOOD POTENTIAL. THE FLOOD POTENTIAL DESIGNATION IS
BASED ON ABOVE AVERAGE SNOWPACK...PRECIPITATION...STREAMFLOW
FORECASTS AND SOIL MOISTURE IN THESE AREAS. THERE IS AMPLE RESERVOIR
STORAGE THROUGHOUT NEVADA AND THE EASTERN SIERRA...SO FLOOD POTENTIAL
FOR AREAS BELOW MAJOR RESERVOIRS IS LOWER. FLOOD POTENTIAL IN
EXTREME NORTHERN NEVADA IS BELOW AVERAGE.
2/ SNOWPACK...
FEBRUARY 1 SNOWPACK CONDITIONS FOR NEVADA AND EASTERN CALIFORNIA
RANGED FROM RECORD BREAKING IN THE EAST...TO DRY IN THE FAR NORTH.
THE EXCEPTIONAL SNOWFALL CONTINUED INTO EARLY JANUARY IN MUCH OF
THE REGION...LEAVING WELL ABOVE AVERAGE AMOUNTS IN THE CENTRAL
SIERRA NEVADA AND RECORD BREAKING AMOUNTS IN EASTERN NEVADA NEAR
ELY. UNFORTUNATELY...THE STORM TRACK CONTINUED TO MISS THE FAR
NORTHERN PORTION OF THE STATE...WHERE DRY CONDITIONS PREVAIL. THE
HIGHEST FEBRUARY 1 SNOWPACK VALUE WAS IN EASTERN NEVADA AT 211
PERCENT OF AVERAGE ...WHILE THE OWYHEE RIVER BASIN WAS THE LOWEST
AT 73 PERCENT OF AVERAGE.
FEB 1 2004 FEB 1 2005
PERCENT OF PERCENT OF
BASIN AVERAGE SNOWPACK AVERAGE
SNOWPACK
LAKE TAHOE .......................... 106 ................ 158
TRUCKEE RIVER ....................... 117 ................ 140
CARSON RIVER ........................ 105 ................ 158
WALKER RIVER ........................ 109 ................ 190
NORTHERN GREAT ...................... 103 ................ 80
UPPER HUMBOLDT RIVER ................ 109 ................ 114
LOWER HUMBOLDT RIVER ................ 128 ................ 94
CLOVER VALLEY & FRANKLIN RIVER ...... 104 ................ 91
SNAKE RIVER ......................... 127 ................ 91
OWYHEE RIVER ........................ 135 ................ 73
EASTERN NEVADA ...................... 86 ................ 211
3/ PRECIPITATION...
IN JANUARY...DRY CONDITIONS PREVAILED IN THE NORTH...AVERAGE TO
ABOVE AVERAGE AMOUNTS FELL OVER THE MID SECTIONS...AND FLOOD
PRODUCING PRECIPITATION FELL IN THE SOUTH. JANUARY PRECIPITATION
WAS HIGHEST IN THE LOWER COLORADO RIVER BASIN AT A WHOPPING 1071
PERCENT OF AVERAGE. THE LOWEST WAS IN THE NORTHERN GREAT BASIN AT
62 PERCENT OF AVERAGE. PRECIPITATION VALUES FOR THE 2005 WATER
YEAR...WHICH BEGAN OCTOBER 1 2004...WERE SIMILAR. WATER YEAR
PRECIPITATION IS HIGHEST IN THE LOWER COLORADO RIVER BASIN AT
810 PERCENT OF AVERAGE AND THE LOWEST IN THE OWYHEE RIVER BASIN AT
85 PERCENT OF AVERAGE.
JANUARY 2005 2005 WATER YEAR
BASIN PERCENT OF AVERAGE PERCENT OF AVERAGE
PRECIPITATION PRECIPITATION
THRU FEB 1 2005
LAKE TAHOE ....................... 123 ................ 136
TRUCKEE RIVER .................... 119 ................ 140
CARSON RIVER ..................... 130 ................ 145
WALKER RIVER ..................... 188 ................ 181
NORTHERN GREAT ................... 62 ................ 96
UPPER HUMBOLDT RIVER ............. 148 ................ 142
LOWER HUMBOLDT RIVER ............. 89 ................ 111
CLOVER VALLEY AND FRANKLIN RIVER . 100 ................ 115
SNAKE RIVER ...................... 90 ................ 101
OWYHEE RIVER ..................... 89 ................ 85
EASTERN NEVADA ................... 173 ................ 272
LOWER COLORADO RIVER ............ 1071 ................ 810
4/ RESERVOIRS...
RESERVOIR STORAGE VALUES IN NEVADA AND EASTERN CALIFORNIA CONTINUES
TO SHOW THE STRAIN FROM SEVERAL DRY YEARS. RESERVOIR STORAGE IS
HIGHEST ON THE TRUCKEE AND CARSON RIVER BASINS AT 70 PERCENT OF
AVERAGE...WHILE LAKE TAHOE IS LOWEST AT JUST 2 PERCENT OF
AVERAGE.
BASIN ...FEB 1 2005...
PERCENT OF PERCENT OF
RESERVOIR CAPACITY AVERAGE STORAGE
LAKE TAHOE.................... 1 ................ 2
TRUCKEE RIVER ................ 38 ................ 70
CARSON RIVER ................. 41 ................ 70
WALKER RIVER ................. 28 ................ 56
LOWER HUMBOLDT RIVER ......... 10 ................ 21
OWYHEE RIVER ................. 20 ................ 36
LOWER COLORADO RIVER ......... 60 ................ 71
5/ STREAMFLOW...
FEBRUARY 1 STREAMFLOW FORECASTS FOR NEVADA AND EASTERN CALIFORNIA
RANGE FROM BELOW AVERAGE IN THE NORTH TO ABOVE AVERAGE FOR THE
REST OF THE REGION. FORECASTS ARE THE HIGHEST FOR THE WALKER
RIVER BASIN AT 150 PERCENT OF AVERAGE AND LOWEST IN THE OWYHEE
RIVER BASIN AT 58 PERCENT OF AVERAGE.
NOTE...THESE FORECASTS ARE FOR THE MOST PROBABLE OUTCOME...THE
BEST ESTIMATE THAT CAN BE PRODUCED GIVEN CURRENT CONDITIONS. THERE IS
A 50 PERCENT CHANCE THAT ACTUAL STREAMFLOW VOLUME WILL BE LESS THAN
THESE FORECAST VALUES...AND A 50 PERCENT CHANCE THAT THEY WILL EXCEED
THEM. FORECASTS ARE BASED ON THE OUTCOME OF SIMILAR PAST SITUATIONS.
PERCENT OF AVERAGE
MOST PROBABLE FORECAST
BASIN /50 PERCENT CHANCE OF EXCEEDANCE/
LAKE TAHOE ................................. 122
TRUCKEE RIVER .............................. 131
CARSON RIVER ............................... 136
WALKER RIVER ............................... 150
NORTHERN GREAT ............................. 72
UPPER HUMBOLDT RIVER ....................... 116
LOWER HUMBOLDT RIVER ....................... 113
CLOVER VALLEY AND FRANKLIN RIVER ........... 123
SNAKE RIVER ................................ 62
OWYHEE RIVER ............................... 58
EASTERN NEVADA ............................. 144
LOWER COLORADO RIVER ....................... 115
6/ FLOOD POTENTIAL OUTLOOK...
CURRENTLY...DUE TO THE WETTER THAN NORMAL CONDITIONS IN ALL BUT
THE EXTREME NORTH...THE FLOOD POTENTIAL FOR MOST OF NEVADA AND THE
EASTERN SIERRA IS ABOVE AVERAGE. THIS FLOOD POTENTIAL DESIGNATION
IS BASED ON ABOVE AVERAGE SNOWPACK...PRECIPITATION...STREAMFLOW
FORECASTS AND SOIL MOISTURE IN THESE AREAS. THERE IS AMPLE
RESERVOIR STORAGE THROUGHOUT NEVADA AND THE EASTERN SIERRA...SO
FLOOD POTENTIAL FOR AREAS BELOW MAJOR RESERVOIRS IS LOWER. FLOOD
POTENTIAL IN EXTREME NORTHERN NEVADA IS BELOW AVERAGE.
DUE TO THE ABOVE AVERAGE FLOOD POTENTIAL...THOSE LIVING IN THE
EASTERN SIERRA AND ALL BUT EXTREME NORTHERN NEVADA SHOULD CLOSELY
MONITOR WEATHER AND RIVER FORECAST CONDITIONS THROUGH THE SNOWMELT
PERIOD THIS SPRING...ESPECIALLY WHEN WINTER STORMS ARE BEING
FORECAST. FLOODING COULD RESULT IF THERE ARE VERY WET...WARM
WINTER STORMS WITH HIGH SNOW LEVELS. FLOODING COULD ALSO OCCUR
DURING THE SNOWMELT PERIOD IN THE SPRING AND EARLY SUMMER IF THE
SNOWPACK REMAINS SIGNIFICANTLY ABOVE AVERAGE AND VERY WARM WEATHER
OR LATE SEASON HEAVY RAINFALL OCCURS. SPRING SNOWMELT FLOODING IS
UNLIKELY ON RIVERS BELOW MAJOR RESERVOIRS.
7/ LONG RANGE WEATHER OUTLOOK FOR NEVADA AND THE EASTERN SIERRA...
THROUGH FEBRUARY 22...NORMAL TEMPERATURES ARE EXPECTED OVER MOST
OF THE REGION...ALTHOUGH ABOVE NORMAL TEMPERATURES ARE EXPECTED IN
SOUTHERN NEVADA. PRECIPITATION IS EXPECTED TO BE BELOW NORMAL IN
THE EXTREME NORTH AND ABOVE NORMAL SOUTH OF A LINE FROM ABOUT LAKE
TAHOE TO PIOCHE NV THROUGH FEBRUARY 18. FROM FEBRUARY 18 TO
22...NORMAL PRECIPITATION IS EXPECTED REGION-WIDE.
THE LONG RANGE OUTLOOK FOR THE MONTHS OF MARCH THROUGH MAY IS FOR
ABOVE NORMAL TEMPERATURES OVER THE ENTIRE REGION...ESPECIALLY IN
SOUTHERN NEVADA. PRECIPITATION IS EXPECTED TO BE SOMEWHAT ABOVE
NORMAL SOUTH OF A LINE FROM ABOUT MONO LAKE CALIFORNIA TO ELY NV.
8/ FOR MORE DETAILED WATER SUPPLY AND STREAMFLOW FORECAST
INFORMATION FOR THE EASTERN SIERRA AND NEVADA...
PLEASE REFER TO THE FOLLOWING WEB SITES
NATIONAL WEATHER SERVICE RENO NEVADA...
http://www.wrh.noaa.gov/rev
NWS CALIFORNIA NEVADA RIVER FORECAST CENTER...
http://www.wrh.noaa.gov/cnrfc/
NATURAL RESOURCES CONSERVATION SERVICE...
http://www.nv.nrcs.usda.gov/snow/index.html
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/