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KPBS Drought Tracker Update: Warm Temps Keeping Snowpack Thin

DATA SOURCES: Rainfall data comes from a weighted average of 96 weather stations throughout the state. Snowpack data represents the average of three different multi-station measures of the northern, central and southern Sierra snowpack. Scripps Institution of Oceanography researchers, through the California Nevada Applications Program RISA and the Center for Western Weather and Water Extremes, helped compile the data.

An update from the newly relaunched KPBS Drought Tracker shows Thursday night's storm coming in the midst of a wet season that has so far brought California increased rain — but paltry snow — compared to previous drought years.

Thursday night's forecast shows rain coming into San Diego County. Up to an inch of rain is expected in some coastal areas, and more is predicted to fall in the mountains.

An update from the newly relaunched KPBS Drought Tracker shows the storm coming in the midst of a wet season that has so far brought California increased rain — but paltry snow — compared to previous drought years.

Since the state's wet season officially began on Oct. 1, California has seen a bit more rain than in many previous drought years. As of Thursday morning, average rainfall throughout the state has added up to 45 percent of what normally falls by April 1, a date used to mark the official end of the wet season.

But the Sierra Nevada snowpack has stayed pretty thin. On average, it's only 14 percent of the way toward a normal April 1 snowpack measurement.

These numbers come from data compiled by a team at the Scripps Institution of Oceanography. Scripps climate researcher David Pierce says you can blame the lack of snow on high temperatures.

"Because of temperature, the precipitation we've had — which has been already even a bit above normal — hasn't been driving much increase in snowpack," said Pierce. "We care about that in California because we depend on the snowpack as a natural reservoir of our winter water."

The northernmost parts of California are now drought-free, but according to the U.S. Drought Monitor, nearly three quarters of California remains in a state of moderate drought or worse.

Last year, a strong El Niño was expected to bring above-normal rain and snow to the parched state. But that didn't quite pan out.

This year, climatologists are seeing a weak La Niña pattern of cooling waters in the tropical Pacific Ocean. Pierce says La Niñas are typically associated with drier conditions in California, but this year's pattern probably won't have a strong impact.

"It's a slight nudge to the probabilities in the direction of a drier winter than usual," said Pierce. "But it's not a strong push."

As the state grapples with its sixth year of drought, we'll be periodically updating the KPBS Drought Tracker. Come April 1, we'll know if statewide rain and snow levels have exceeded 100 percent of normal, which would help put a dent in the drought.

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