Winter Snowpack Measurements Dismal; Is There Hope Ahead?

Wendilyn Grasseschi
Times Reporter

The state Department of Water Resources March 2 snow survey of the season results were, if not dismal, at least close.

Without at least one more large, atmospheric river type of storm, California is headed for a very dry year, putting the state in extreme fire danger yet again.

Statewide snow survey measurements continue to reflect the overall dry conditions, with measurements from DWR’s electronic snow survey stations showing that statewide, the snowpack’s ‘snow water equivalent,’ called the SWE (the mount of actual water in the snow), is at about 61 percent of the March 2 average, and only 54 percent of the April 1 average. April 1 is typically when California’s snowpack is the deepest and has the highest SWE.

That means the state has about three weeks to make up the missing 40 percent of the snowpack; not impossible but getting statistically more difficult each passing day, with only one more official snowpack measurement on or around April 1. After that date, the snowpack tends to lessen due to melting and fewer cold storms, which is why the final state measurement is taken then. The four months used by the state to measure the snowpack for allocation of the Sierra snowpack are December, January, March and April.

Closer to home, many local snowpack measurements are taken by the Los Angeles Department of Water and Power, not just the state. Those measurements come in slightly better than the state average in some places – but only in some.

For example, the snowpack on Mammoth Pass is one of the better performers, coming in at about 61 percent of normal for the date on March 2, with about 23 inches of water equivalent in the snowpack. The normal for the date would be closer to about 30 inches.

In fact, the Central Sierra where Mammoth is located is in the best shape in the state, mostly due to Mammoth’s epic storm at the end of January that skews the average for the entire region.

And even in the Central Sierra, the snowpack is variable.

The further south and north the snowpack is measured from Mammoth, the worse the numbers drop off.

Rock Creek south of Mammoth came in at about 59 percent of normal but the Southern Sierra area plummeted to about 44 percent of normal for the date, or less than half of what the snowpack should be now.

The Southern Owens Valley areas fared even worse, with rain and snow coming in overall at about 30 percent of normal for the date, with numbers measured between 18 percent of normal in Bishop to 40 percent just south of Bishop.

Long Valley, the enormous area between Mammoth and Toms Place, came in at about 65 percent of normal for the date.

Although there is still some time for a ‘Miracle March’ series of strong, wet storms, time is indeed running out to make up this large deficit, which follows on the heels of a very dry 2020 in most parts of the state.

“As California closes out the fifth consecutive dry month of our water year, absent a series of strong storms in March or April we are going to end with a critically dry year on the heels of last year’s dry conditions,” said DWR Director Karla Nemeth. “With back-to-back dry years, water efficiency and drought preparedness are more important than ever for communities, agriculture and the environment.”

Dry conditions require coordination among state, federal and local entities, she said, and state water leaders are preparing to address the current dry conditions adaptively, guided by lessons learned during previous droughts.

What is next?

According to local forecaster Howard Sheckter, there is some slowly growing hope for a wetter pattern next week, when a large trough is expected to set up over the West Coast. However, he said, it is too early to know if the pattern change will allow wetter storms to break through like the large atmospheric river storm did in late January. One or two such storms could bring the Sierra to normal.

As of this week, he said, a pattern shift that has blocked almost every storm from arriving onshore in the state is finally backing off.

“It’s March, and what we would normally expect over this part of the hemisphere is a weakening Hudson Bay Low, i.e. the Polar Vortex,” he said. “That means the feature that often provides blocking in the wrong place for California is now absent! This will give California the opportunity to play catch up on our subnormal snowpack over the next two weeks. Looking at the precipitation portion of the European ensembles (models) out through the 17th, the model gives the crest up to four feet of snow through that period and the climate models keep it coming beyond that time frame.

“(That said), keep in mind, without a substantial atmospheric river, we are not going to get heavy amounts and so far, none is indicated,” he said.

Another forecaster, Bryan Allegretto, who forecasts for Open Snow and focuses on the Tahoe region, but also includes the Mammoth area at times, also said there are several storms possible in the next week or so that might... emphasis on the word ‘might,’ help.

“I did take a peek at the snow levels and all of the systems currently forecast for next week... (all the) ensemble mean runs are in agreement that we could have a fairly wet four-to-five-day period,” he said.

How wet?

“Looking at the deterministic model runs, they are showing three to four inches of total precipitation along the crest. So, not big storms or a 100-inch week or anything over the top. But, if we see several systems move through next week the snow could start to add up to a few feet through the end of the week. Hopefully, the forecast holds!

"The long-range models are still trying to show a brief break in the action the weekend of the 13th,” he said. “But the trend for the third week of March is for the trough to be over to just off the West Coast. That would be a better position than next week's trough for wetter systems. Hopefully, we will be playing some catch-up here in March with snowfall. Let's hope these positive trends for March continue!”