National Weather Service – Reno Northern Nevada 2015 Streamflow Forecast Meeting Mar 20, 2015

El Niño Status El Niño Advisory issued in early March. It’s weak, but it’s there. Oceanic and atmospheric conditions have become coupled What does that mean? Normally El Niño Conditions in winter would bring this type of response across North America. But… 2

El Niño Status A look at past events show only about 3 of the last 10 El Niño years had above average rainfall in California. There is very little correlation between El Niño and precipitation over North America during the spring months. Note over northeast Nevada there is better correlation that conditions will be dry! 3

El Niño Status 50-60% chance weak El Niño will continue through the summer and about 50% that it will continue into fall. Again no real strong correlation to expected precipitation patterns in the coming months. Impacts from El Niño tend to be weak during spring and summer

Model Solutions for early Monday morning; differences in timing GFS (upper left) is faster, colder, wetter and farther south Could produce up to a foot of snow in the Tahoe Basin above 7000 feet; lesser amounts to the south Models don’t show much chance of precipitation for the rest of March GFSECMWF GEM Upper Level Winds

Updated April 2015 Outlook Official outlook – slight favoring of above normal precip in the southeast and far eastern Nevada; equal chances of above, below and near normal elsewhere. Confidence – low to medium. Weak ENSO signal introduces a bit of uncertainty. Temperature – favors above normal with medium to high confidence (higher than average snow levels). 6

Official outlook – favoring equal chances of above, below and near normal precipitation overall; low-medium confidence Temperature – favors continued above normal with medium to high confidence. 7 Spring/Summer 2015 (May-Jul) Outlook

CNRFC Streamflow Volume Predictions Forecasts updated daily; based on current weather and historical data Start with current conditions and years worth of model data Probability distribution derived from multiple runs; 50% chance of exceedance is taken as daily forecast Upper Humboldt in better shape than the Lower Humboldt Palisade currently forecast at 30% Imlay at only 3% 8

CNRFC Streamflow Volume Predictions Forecasts updated daily; based on current weather and historical data Start with current conditions and years worth of model data Probability distribution derived from multiple runs; 50% chance of exceedance is taken as daily forecast Truckee River at Farad forecast at 48% 9

CNRFC Streamflow Volume Predictions Forecasts updated daily; based on current weather and historical data Start with current conditions and years worth of model data Probability distribution derived from multiple runs; 50% chance of exceedance is taken as daily forecast Carson River at Carson City forecast at 20% Fort Churchill forecast at 15% 10

CNRFC Streamflow Volume Predictions Forecasts updated daily; based on current weather and historical data Start with current conditions and years worth of model data Probability distribution derived from multiple runs; 50% chance of exceedance is taken as daily forecast West Walker River above Coleville forecast at 39% 11

Key Takeaways Maybe some high elevation snow in the Tahoe Basin next week. April – Maybe an increase in precipitation over southeast and eastern Nevada; no clear signal anywhere else. Seasonal forecasts for spring and summer show no clear signal in terms of precipitation. Better confidence in warmer than normal temperatures overall – increased frequency of high snow level storms in April and May. ESP Volume forecasts from CNRFC are well below average and trending down for main points 12