FGUS66 KRSA 021459
ESGNV

?ESGNV
SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE
CALIFORNIA-NEVADA RIVER FORECAST CENTER SACRAMENTO CA
700 AM PST MON MAR 2 2026

…Low threat of snowmelt flooding along Humboldt River and East
Sierra rivers that drain to Nevada…

There is a low threat of spring snowmelt flooding along the Humboldt
River and its tributaries. Snowpack is extremely below normal for
this date across the watershed. There is a low threat of spring
snowmelt flooding in the eastern Sierra along the Truckee, Carson,
and Walker rivers where snowpack conditions are currently much below
normal. Flooding can occur from snowmelt, rain, or a combination of
both at any time during the winter and spring months.

Current basin conditions

Snowpack

The snowpack across both the upper and lower Humboldt is
currently measuring just below record lows per the SNOTEL network.
What little snow does exist is confined to the highest elevations
with no low elevation snowpack. The majority of snow pillows
throughout the watershed are measuring below 50% of the to-date
average. With warm temperatures expected for the next 1-2 weeks, and
with no impactful storms on the horizon, conditions are not expected
to improve during the first 2 weeks of March.

The snowpack throughout the east Sierra is looking much worse than
it did just a week ago. After recovering to near average conditions
from a big mid-February storm, a warm storm last week brought
significant rainfall up to elevations as high as 10,000ft, causing
some of the snowpack that had built the previous week to melt. That
snow will continue to melt through early March due to abnormally
warm temperatures and a ripe snowpack. Snow pillows across the
Truckee basin are measuring around 50-70% of normal. Conditions are
a bit better further south in the Carson and Walker basins, which
did not receive as much warm rain and elevations are higher. Snow
pillows throughout these watersheds are measuring around  70-80% of
average. These will continue to drop throughout the next 1 to 2
weeks as warm temperatures and limited precipitation in the forecast
will continue to decrease the snowpack. In all east Sierra basins,
low elevation snow does exist, but amounts are lower relative to
average and will continue to decline.


Precipitation

Year-to-date precipitation totals across northern Nevada tell a much
better story than the record low snowpack. Periodic rain throughout
the year has precipitation totals slightly below average in the
upper Humboldt and near average in the lower Humboldt. In both upper
and lower Humboldt, soil moisture is currently quite high, so that
should help enhance what little runoff is expected from the low
snowpack.

Precipitation totals across the east Sierra are currently
running slightly above average. Soil moisture is currently at or
near record high for this time of year as the result of high
elevation rainfall throughout the water year, in addition to the
significant rainfall event that occurred this past week.

Seasonal (April – July) runoff forecasts

The seasonal Apirl-July runoff forecasts are extremely below normal
across the Humboldt watershed. Forecasts are mostly in the 40% range
in the upper Humboldt, with lower projections further down in the
system. There is still considerable uncertainty in the forecasts,
even this late in the season. If drier conditions prevail through
the rest of the spring and into summer, ensembles indicate runoff
could be closer to 20% of average in the upper watershed.

Seasonal runoff in the east Sierra took a big hit this past week
with the warm rain that melted some of the snowpack. The majority of
seasonal runoff forecasts are currently in the 50-70% range. Moist
soils should help enhance runoff as we head into the typical melt
season later this spring.

Flood exceedance probabilities

The risk of flooding during the spring is low with models currently
showing less than a 5% chance of minor flooding on the upper and
lower Humboldt River. There is also a similar low risk of flooding
for the east Sierra, as the snowpack is much below normal. Consult
the NWPS long-range flood risk map for the latest point exceedance
probabilities for the March through May time period:
https://water.noaa.gov/long_range

Summary

The risk of flooding during the spring is low along the Humboldt
River and its tributaries and in the eastern Sierra. Flooding can
occur from snowmelt, rain, or a combination of both at any time
during the winter and spring months. For a wide range of short- and
long-range hydrologic forecast products, and general water resource
information, please visit the CNRFC webpage at:
http://www.cnrfc.noaa.gov

CNRFC/MI