Bulletin 120 and Water Supply Index forecasts for May 1, 2017

Unimpaired flows for the 2016-2017 water year: Region October-April Runoff (%) April Runoff (%) Sacramento Valley Index (4 rivers) 239 211 San Joaquin Valley Index (6 rivers) 307 204 Tulare Lake Basin (4 rivers) 266 229 Accumulated October – April flows for WY 2017 set a new record of 31.2 MAF for the Sacramento Valley 4 Rivers.
2415 3336 3283 (1983) SRR – Sacramento at Bend Bridge through American rivers SJR – Stanislaus through San Joaquin rivers TLR – Kings through Kern rivers Precipitation: The 93.0 inches of precipitation measured during October-April in the Northern Sierra 8-Station Index ranks as the highest total during that period in the entire record of the 8-Station Index dating back to 1921.
Precipitation for the 2016-2017 water year accumulated at the following rates of average: Hydrologic Region October-April precipitation (%) Sacramento River 198 San Joaquin River 183 Tulare Lake 177 Statewide 173 Precipitation Index Percent of Seasonal Average to Date through May 8, 2017 Northern Sierra 8-Station Index 202 (93.1 inches) San Joaquin 5-Station Index 189 (71.2 inches) Tulare Basin 6-Station Index 169 (45.9 inches) Snowpack: Snowpack is monitored using two complementary methods: automatic snow sensor (or “pillow”) readings and manual snow course measurements.
The snow sensors give us a daily snapshot of snow conditions while the manual snow course measurements provide a monthly verification of snow conditions in locations where snow has been measured in the same manner as far back as 100 years.
The snow water content in the Mokelumne, Stanislaus, Merced, San Joaquin, Kings and Kern river basins was equal to or greater than 160 percent of the April 1 average.
Of the nearly 200 snow courses that were measured during the May 1 snow survey, 16 courses recorded new May all-time records.
Courses Measured Average WC (inches) % Average April 1 % Average May 1 North Coast 9 39.1 112 160 Sacramento 65 40.9 122 169 San Joaquin Valley 55 53.6 158 192 Tulare Lake 42 41.2 157 201 North Lahontan 5 34.4 138 162 South Lahontan 7 27.6 178 207 Statewide Average (weighted) 140 181 The snowpack as of the morning of May 8, 2017 stands at the following (based on snow sensors): Region Snow Water Equivalent (inches) % of Average (Apr 1) % of Average (May 8) Northern 31.4 112 188 Central 41.9 143 204 Southern 31.7 119 171 Statewide 36.2 128 190 Weather and Climate Outlooks: The 6-day weather forecast indicates precipitation totals near 0.1 inch on Monday and Tuesday over the southern Sierra.
The forecast predicts up to 1.0 inch of precipitation over the North Coast on Thursday and up to 0.5 inch of precipitation on Friday.
The same outlook predicts increased chances of above normal temperatures eastern half of the state, elsewhere equal chances of above or below temperatures are expected.
Seasonal Drought Outlook: http://www.cpc.ncep.noaa.gov/products/expert_assessment/sdo_summary.html Weather Forecast Office California Service Area-Products: http://www.cnrfc.noaa.gov/forecasts.php El Niño Southern Oscillation (ENSO) Conditions and Weekly Discussion (including La Niña): http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf Sign up for daily email service and you’ll never miss a post!

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