The last time it rained at least a shower or two every day was, curiously, the last big El Nino years of 1997-1998. The current season is starting to bring home those familiar wet winter memories.
The system that passed through the region Monday night and Tuesday (Dec. 21-22) brought the first widespread rainfall event of the season that dumped more than one inch of the wet stuff. Three Rivers rain gauges were brimming on the morning of December 22 with 1.55 inches (at 1,000 feet elevation), and that was after recording another half-inch of rain on the evening of December 18. Another quarter-inch was recorded the morning of December 23.
The 1.55 inches of rainfall was widespread across the entire region and accompanied by a welcomed, albeit short-lived, warming trend. The subtropical system stalled out for a time over the area and brought a steady rain that lasted all night.
Forecasters are saying that the current pattern is a trend that is likely to continue for Central and Southern California as the storm track that has brought cold moisture so far this season from the Gulf of Alaska begins to dig southward into California. As those jet streams move south, they will be fueled by tropical moisture, and that creates the potential for some monster storms with rainfall, heavy at times, and snow accumulations measured in feet, not inches, for the Sierra Nevada.
Areas in the Pacific Northwest such as Portland, Ore., and North Bend, Wash., have received rain for 21 consecutive days, washing out bridge approaches, flooding creeks, and causing major rockslides that have highway crews working around the clock to keep roads open and rural communities, such as Vernonia, Ore., from being totally cut off. It’s only the first week of winter and some folks in the Pacific Northwest, where they are used to wet weather, are already saying enough is enough.
If and when the region gets a break, it will be at California’s expense. And storm damage from an El Nino season can be expensive. Damage to California coastal, low-lying properties and roadways was in the hundreds of millions of dollars in 1997-1998. The silver lining, however, will be the refilling of the state’s vital reservoirs and water supply that have been sitting below 30 percent — a cause and effect of four years of consecutive drought.
The intermittent warm rainfall early in the week also caused a welcome rise in the flow of the Kaweah River. At its most muddy, chocolate-brown stage, the flow in the Middle Fork of the Kaweah peaked at 1,150 cubic feet per second on Tuesday, Dec. 22; contrast that flow to 100 cfs on the previous day.
That rapid rise pales compared to the peak flows in the springs of 1995 and 1998 when the thunderous Kaweah River ran for several days between 4,000 and 5,000 cfs. All that high water is a bit problematic for riverfront property owners but translates to a miracle season for whitewater rafting outfitters.
Consider these benchmark statistics at the end of 2015 and ponder what might be in store for 2016. Keep in mind the last significant flood of the Kaweah River occurred on January 2-3, 1997. At 11 p.m. on the evening of Jan. 2 the peak flow of the Kaweah River at the Middle fork reached 56,595 cfs.
The current storage at Lake Kaweah (Dec. 23, 2015) is 26,675 acre-feet or just slightly under 15 percent capacity. Mean inflow of 789 cfs (all Kaweah tributaries) is typical for this time of year. Current snowpack at elevations above 7,000 feet in the nearby mountains (Lodgepole, Mineral King) is hovering around three feet.
Three Rivers has already eclipsed 10 inches of rainfall in the current season; 1.27 of that total was recorded in July 2015 storms. The entire season of 2014-2015 was 11.21 inches.
During the last major El Nino of 1997-1998, Three Rivers received a total of 37.14 inches; a single storm on March 3, 1998, produced 2.50 inches.
The forecast for the extended holiday period shapes up with more rain and snow. The foothills around Three Rivers could experience snow down to the 2,000 foot level. Daytime temperatures in the Giant Forest are of Sequoia National Park will be in the 30s; in the foothills high temperatures will struggle to even make the mid 50s.