Drought Information Statement
Issued by NWS San Francisco Bay Area, CA

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CAC001-013-041-053-055-069-075-081-085-087-097-182315-

DROUGHT INFORMATION STATEMENT
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
904 AM PST THU DEC 18 2014

SINCE THANKSGIVING, SEVERAL PERIODS OF SIGNIFICANT PRECIPITATION
HAVE FALLEN ACROSS CALIFORNIA. IN VALLEY LOCATIONS, RAIN HAS
BOOSTED TOPSOIL MOISTURE, BENEFITED WINTER GRAINS, AND HELPED TO
REVIVE RANGELAND AND PASTURES. ACCORDING TO USDA/NASS, 30% OF
CALIFORNIA`S RANGELAND AND PASTURES WERE RATED IN GOOD TO
EXCELLENT CONDITION ON DECEMBER 14, COMPARED TO JUST 15% ON
OCTOBER 26. ALSO ON DECEMBER 14, FOUR-FIFTHS (80%) OF
CALIFORNIA`S WINTER WHEAT WAS RATED IN GOOD TO EXCELLENT
CONDITION.

DURING THE THREE-WEEK PERIOD FROM THANKSGIVING DAY (NOVEMBER 27)
TO DECEMBER 17, RAINFALL TOTALS AT SELECTED CALIFORNIA LOCATIONS
INCLUDED:

LOCATION TOTAL (IN.) NORMAL (IN.) PERCENT OF NORMAL
MT. SHASTA 11.63 4.94 235%
SAN FRANCISCO 11.30 2.41 469%
REDDING 9.84 4.03 244%
SACRAMENTO 8.15 2.01 405%
SAN DIEGO 4.42 0.92 480%
LOS ANGELES 3.95 1.14 346%
BAKERSFIELD 1.87 0.60 312%

DURING CALIFORNIA`S WET SPELL, MOST OF THE PRECIPITATION HAS BEEN
PRODUCED BY "WARM" STORMS. AS A RESULT, SIERRA NEVADA SNOW LEVELS
HAVE BEEN VERY HIGH---SOMETIMES ABOVE 7,000 FEET. CONSEQUENTLY,
HIGH-ELEVATION SNOWPACK IS NEITHER DEEP NOR WELL ESTABLISHED. ACCORDING
TO THE CALIFORNIA DEPARTMENT OF WATER RESOURCES, THE AVERAGE WATER
CONTENT OF THE HIGH-ELEVATION SIERRA NEVADA SNOWPACK WAS LESS THAN
4 INCHES ON DECEMBER 17---ONLY 48% OF NORMAL FOR THIS TIME OF
YEAR. IN A TYPICAL WINTER, NEARLY 30 INCHES OF WATER BUILDS UP IN
THE SIERRA NEVADA SNOWPACK BY APRIL 1.

WITH MOST OF THE PRECIPITATION FALLING AS RAIN, SOME OF CALIFORNIA
MAJOR RESERVOIRS RECEIVED A BOOST FROM RUNOFF. IN GENERAL, THE
RUNOFF LED TO CAPACITY INCREASES (AT LEAST 6 TO 10 PERCENTAGE
POINTS) IN MAJOR RESERVOIRS ACROSS NORTHERN AND CENTRAL
CALIFORNIA. FOR EXAMPLE, THE RESPECTIVE PERCENT OF CAPACITY VALUES
FOR NOVEMBER 28 FOR TRINITY, SHASTA, OROVILLE, FOLSOM, AND SAN
LUIS LAKES WERE 23, 23, 26, 28, AND 23; ON DECEMBER 16, THEY
INCREASED TO 29, 32, 33, 38, AND 33 PERCENT. RESPECTIVE HISTORICAL
AVERAGES ON DECEMBER 16, FOR THOSE FIVE RESERVOIRS ARE 44, 53, 54,
79, AND 52 PERCENT.

THE EFFECT OF THE RECENT RAINS ON SF AND MONTEREY BAY AREA WATER
SUPPLY AND DROUGHT CONDITIONS IS THAT THE WATERSHEDS ARE NOT ONLY
WELL SATURATED, BUT DATA AND OBSERVATIONS SUGGEST GROUNDWATER
LEVELS HAVE RISEN (NOT ENOUGH TO ELIMINATE DROUGHT, THOUGH) AND
RESERVOIRS ARE FILLING. MOST BAY AREA RESERVOIRS ARE FAR FROM
REACHING FULL OR FLOOD POOL HEIGHTS, BUT MODEST TO SIGNIFICANT
ADDITIONS HAVE BEEN MADE FROM STORM RUNOFF, PARTICULARLY IN THE
NORTH BAY AND SANTA CRUZ MOUNTAINS. STREAM WINTER BASE FLOWS ARE
UP, AND SPRING FLOWS HAVE BEEN REJUVENATED IN MANY OF THE KARST
(LIMESTONE) AND LIMITED GRANITIC AQUIFERS IN THE COAST RANGE
PROVINCE. LOCAL WATER SUPPLY SYSTEMS, PARTICULARLY GROUNDWATER AND
RESERVOIR SYSTEMS, ARE FAR FROM BEING REPLENISHED, AND MORE RAIN
WILL BE NEEDED THIS YEAR AND NEXT TO RECOVER FROM THE IMPACTS OF
THE DROUGHT AND TO PROMISE ANY RESILIENCE AGAINST SUMMERTIME
DRYNESS AND LONGER (ANNUAL) DRY SPELLS.

THE LATEST U.S. DROUGHT MONITOR, ISSUED DECEMBER 18, INDICATES
THAT THERE WAS A SUBSTANTIAL REDUCTION IN D4 (EXCEPTIONAL DROUGHT)
COVERAGE IN NORTHERN AND CENTRAL CALIFORNIA. STATEWIDE, D4
COVERAGE FELL FROM 55 TO 32% -- THE SMALLEST AREA IN EXCEPTIONAL
DROUGHT SINCE EARLY-JUNE 2014. HOWEVER, OVERALL DROUGHT (D1 TO D4)
COVERAGE DECLINED ONLY SLIGHTLY, FROM 99.7 TO 98.4%. IN OTHER
WORDS, NEARLY ALL OF THE STATE REMAINS IN DROUGHT, ALTHOUGH THE
DROUGHT INTENSITY HAS DECREASED BY ONE CATEGORY IN PARTS OF
NORTHERN AND CENTRAL CALIFORNIA.

CALIFORNIA WEATHER OUTLOOK:
NORTHERN AND CENTRAL CALIFORNIA CAN EXPECT ONE MORE ROUND OF
PRECIPITATION, STARTING ON FRIDAY, DECEMBER 19. STARTING THIS
WEEKEND, HOWEVER, THE FOCUS FOR HEAVY PRECIPITATION WILL SHIFT
INTO THE NORTHWEST. AS A RESULT, THE LAST TEN DAYS OF DECEMBER
APPEAR TO BE RATHER WARM AND DRY ACROSS MOST OF CALIFORNIA,
ALTHOUGH SHOWERS MAY OCCASIONALLY GRAZE THE NORTHERN PART OF THE
STATE.

(CREDIT FOR MUCH OF THE ABOVE ASSEMBLAGE OF DATA GOES TO BRAD
RIPPEY, METEOROLOGIST, USDA.)

$$

STRUDLEY

WEATHER.GOV/SANFRANCISCO






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