Hydrologic Outlook

CAC001>115-081930-

Hydrologic Outlook
National Weather Service Sacramento CA
1118 AM PST Thu Mar 7 2019

...ELEVATED FLOOD THREAT DUE TO SPRING SNOWMELT ACROSS PORTIONS OF
CALIFORNIA...

THE POTENTIAL FOR FLOODING DUE TO SPRING SNOWMELT IN THE CALIFORNIA
NEVADA RIVER FORECAST CENTER`S DOMAIN IS ELEVATED DUE TO ABOVE
NORMAL SNOWPACK. IN CALIFORNIA, THIS ELEVATED RISK IS FOR MANY
LOCATIONS IN THE MOUNTAINOUS AREAS OF THE CASCADES AND THE SIERRA
NEVADA. SOME OF THE LOWER ELEVATION REGULATED SYSTEMS, LIKE THE SAN
JOAQUIN RIVER AND ITS TRIBUTARIES, WILL LIKELY BE UNDER ADDITIONAL
STRESS THROUGHOUT THE SPRING DUE TO HIGHER THAN NORMAL RELEASES FROM
THE LARGE RESERVOIRS AS THEY MANAGE INFLOWS FROM THE ABOVE NORMAL
SNOWMELT VOLUMES. FLOWS ARE EXPECTED TO REMAIN ABOVE NORMAL IN THE
SAN JOAQUIN SYSTEM WELL INTO THE SNOWMELT SEASON, PUTTING CONTINUOUS
STRESS ON THE FLOOD CONVEYANCE SYSTEM.

NOTE THAT FLOODING IN CALIFORNIA COULD ALSO RESULT FROM HEAVY
RAINFALL ALONE, OR COMBINED WITH SNOWMELT ANYTIME DURING THE SPRING.

CURRENT BASIN CONDITIONS

SNOWPACK

EVERYWHERE FROM THE NORTHERN PORTIONS OF IN THE KLAMATH BASIN DOWN
TO THE TULARE BASIN IN THE SOUTHERN SIERRA NEVADA IS EXPERIENCING
ABOVE AVERAGE SNOWPACK. PERCENT OF NORMAL NUMBERS ARE FAIRLY
SIMILAR THROUGHOUT THIS REGION.

SEASONAL PRECIPITATION

PRECIPITATION TOTALS FOR THE CURRENT WATER YEAR ARE ABOVE NORMAL TO
MUCH ABOVE NORMAL FOR THE ENTIRE STATE OF CALIFORNIA. THE WATER
YEAR ACCUMULATIONS STARTED OFF FAIRLY DRY, BUT THE PRODUCTIVE MONTHS
OF JANUARY AND FEBRUARY HAVE PUSHED WATER YEAR TOTALS TO ABOVE
AVERAGE THROUGHOUT CALIFORNIA.

SEASONAL (APRIL-JULY) RUNOFF FORECASTS

THE SEASONAL RUNOFF FORECASTS ARE VERY SIMILAR TO THE SNOWPACK
CONDITIONS. ABOVE NORMAL TO MUCH ABOVE NORMAL RUNOFF VOLUMES CAN BE
EXPECTED DURING THE APRIL-JULY PERIOD THROUGHOUT THE CASCADES AND
SIERRA NEVADA.

FLOOD EXCEEDANCE PROBABILITIES

FLOODING DURING THE SPRING SNOWMELT SEASON IS DEFINITELY MORE
PROBABLE THIS YEAR DUE TO THE ABOVE NORMAL SNOWPACK. CONSULT THE
AHPS LONG RANGE FLOOD RISK MAP FOR THE LATEST POINT EXCEEDANCE
PROBABILITIES: HTTP://WATER.WEATHER.GOV/AHPS/LONG_RANGE.PHP.

SUMMARY

RISK OF CALIFORNIA FLOODING DURING THE SNOWMELT SEASON IS ELEVATED
THIS YEAR FOR MUCH OF THE CASCADES AND SIERRA NEVADA. FLOOD
CONVEYANCE SYSTEMS BELOW MAJOR RESERVOIRS IN THE SAN JOAQUIN WILL
BE UNDER ADDITIONAL STRESS THROUGHOUT THE SPRING. FLOODING
ANYWHERE IN THE STATE COULD ALSO RESULT FROM HEAVY RAINFALL, OR
THE COMBINATION OF RAIN AND SNOWMELT AT ANY TIME DURING THE
SPRING. REFER TO THE LONG RANGE OUTLOOK PRODUCT FOR FLOOD
EXCEEDANCE PROBABILITIES AT PARTICULAR LOCATIONS FOR THE MARCH
THROUGH MAY PERIOD. FOR SHORT TERM HYDROLOGIC FORECASTS AND
GENERAL WATER RESOURCE INFORMATION, PLEASE SEE THE CNRFC HOMEPAGE
AT: HTTP://WWW.CNRFC.NOAA.GOV.

CNRFC/BW
STO/CM


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