FGUS66 KRSA 011901
ESGCA1

SPRING FLOOD POTENTIAL OUTLOOK NATIONAL WEATHER SERVICE CALIFORNIA-
NEVADA RIVER FORECAST CENTER SACRAMENTO CA 
1100 AM PST FRI MAR 1 2024

…LOW FLOOD THREAT DUE TO SPRING SNOWMELT ACROSS CALIFORNIA …

The potential for flooding due to spring snowmelt in the California 
Nevada River Forecast Center’s domain is fairly low given that the 
state-average snowpack is slightly below normal.  The upcoming storm 
could push snowpack conditions to slightly above normal, but even 
under those conditions, the chance of flooding due to pure snowmelt 
is fairly low.  In California, the areas with the highest risk of 
snowmelt flooding are in mountainous areas of the Cascades and the 
Sierra Nevada.
   
Note that flooding in California could also result from heavy 
rainfall alone, or combined with snowmelt anytime during the spring.

CURRENT BASIN CONDITIONS

SNOWPACK The Northern Sierra & Trinity regions are currently 95% of 
average for this time of year.  The Central and Southern Sierra are 
75-80% of normal.  Statewide, snowpack is 82% of normal.  These 
percentages are expected to increase due to a significant winter 
storm expected during the first couple of days of March.
  
PRECIPITATION

Precipitation totals for the current water year are near normal in 
the far northern portions of California, similar to the snowpack. 
Precipitation in the Central and Southern Sierra are slightly below 
normal, and roughly 75-80% of normal.

SEASONAL (APRIL-JULY) RUNOFF FORECASTS

The seasonal runoff forecasts for the  northern areas, including the 
Klamath and Upper Sacramento, are near normal.  The other portions 
in the Northern and Central Sierra covering the Feather down through 
the Stanislaus are projected to be above normal ranging from 110-
120% of normal.  The Southern Sierra is also expected to have above 
normal seasonal runoff ranging from 110% to 115% of normal.  These 
projections are elevated compared to the current precipitation and 
snowpack conditions mainly because the seasonal runoff forecasts 
incorporate the forecasted snow totals expected from the early March 
storm.

FLOOD EXCEEDANCE PROBABILITIES

Flood potential due to pure snowmelt is fairly low this spring. The 
Merced River has the highest chance of exceeding flood stage during 
the snowmelt season with a 10-25% chance.  It is important to note 
that potential for large springtime rainfall events resulting in 
river flooding is still present and should be monitored throughout 
the spring.  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 due to pure snowmelt is fairly 
low given the near normal snowpack conditions.  Refer to the long 
range outlook product for flood exceedance probabilities at 
particular locations (http://water.weather.gov/ahps/long_range.php) 
for the March through May period.  Flooding due to rainfall is still 
a risk for much of the spring season.  Consult the CNRFC homepage 
for near-term flood threats:  https://cnrfc.noaa.gov/.

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