The National Weather Service outlook for the winter of 2005-2006 calls for average precipitation and warmer than normal temperatures in the western United States. What Laver does not mention is that it is precisely because there is currently no El Niño or La Niña conditions in the Pacific, the likelihood for flood-producing "Pineapple Express" storms in California is about twice as likely now as in an average winter at Tahoe.

These "neutral" (no El Niño or La Niña) conditions often influence the track of the jet stream, causing it to dramatically curve past Alaska before dipping down to Hawaii where it taps into sub-tropical moisture on its way to the West Coast. The Pineapple Express pattern can bring one to two weeks of stormy wet weather, followed by extended periods dominated by high pressure with generally dry conditions. This wet-dry pattern repeats itself every 45 to 60 days.

Such neutral conditions were in play in January 1997 when a barrage of sub-tropical storms generated the worst flooding in history for California and Nevada. Flooding along the Truckee, Carson, and Walker rivers in western Nevada caused $650 million in damage. A 2001 analysis by Jan Null, a Consulting Meteorologist and owner of Golden Gate Weather Services, reveals that in the past 30 years, San Francisco has had 18 severe storms that have dumped two inches or more of rain in 24-hours. Indicative of the increased chances for torrential rain this 2005-06 winter, twelve of these 18 storm events occurred during neutral years.

Floods are common on the volatile Truckee River which has had 20 major floods in the last 145 years, giving a statistical chance of a serious flood every 10 years or so. Since 1950 a handful of reservoirs have been built in the Truckee River watershed, which have boosted flood protection for downstream communities, but the system is still not foolproof. Fifty-five years ago, Boca Reservoir stood alone as flood protector on the Truckee River. In 1950, record setting rains before Thanksgiving overwhelmed the small solitary dam. Torrents of water poured over Boca's spillway and added to the destructive flow rushing downstream. Damage in Floriston, Reno, and Sparks was extensive.

Storms came unusually early in 1950. During September and October, precipitation in the northern Sierra exceeded 300 percent of normal. By November the soil was saturated and snow lay four feet deep in the upper elevations. On November 13, 1950 a moisture-laden, monster storm plowed in from the Pacific Ocean. A strong jet stream energized this potent weather system and forced the saturated air mass over the Sierra. Heavy snow fell in the mountains, but that soon turned to rain as the tropical nature of the storm grew more dominant. When this weather pattern stalled over Northern California, the stage was set for disaster. For nine consecutive days, heavy rain drenched the Sierra. The tropic-like downpours quickly melted the high elevation snow pack in what hydrologists call a "wet mantle" flood event, where rain and melting snow combine to generate exceptional runoff.

On the Sierra west slope, nearly 27 inches of rain fell at Blue Canyon. The normally peaceful, Yolo River, exploded into a raging torrent. Floodwaters four feet deep flowing over Highway 40 closed the road at Cisco, 25 miles west of Truckee. About 500 feet of Highway 50 was washed out near Twin Bridges. Both of these vital, trans-Sierra highways were shut down for 10 days.

Donner Lake soon hit flood stage and washed out the bridge over Donner Creek on southbound Highway 89, while Truckee's school closed when high water flooded the furnace. North of Truckee, Highway 89 was underwater and the Feather River Canyon was clogged by rockslides.

A massive mudslide near Emigrant Gap and a washout at Floriston forced Southern Pacific to cancel all trains over the Sierra. The luxury streamliner, City of San Francisco, was caught between the blockades and spent the night parked at Norden on Donner Pass. Two years later (1952) this upscale passenger train would be trapped in snow for three days near Yuba Gap. Only United Airlines could offer transport from Reno to California.

More than 10 inches of rain fell in Tahoe City in one week. Alex Cushing, a founder of the Palisades Tahoe ski area, and about 30 workers were trapped in the valley when Squaw Creek washed out both bridges into the valley.

Lake Tahoe's surface elevation rose 15 inches but still remained two and a half feet below the legal maximum. In Truckee more than 11 inches of rain doused the town. Water inundated buildings and back yards of homes close to the river. In Tahoe City ponderous pines toppled over in the saturated soil. A summer home owned by Alice Griffith was destroyed when a giant tree, six feet in diameter, lost its moorings.

Tahoe dam's seventeen gates remained closed but the Truckee River drew strength from countless feeder streams. Mountain watersheds damaged by over-cutting timber or animal over-grazing allowed even more water to race down the slopes. Gushing Pole Creek joined forces with the Truckee River and added to the powerful current. This confluence helped destroy the Big Chief bridge in the Truckee Canyon and flood dozens of cabins and summer homes along the river between Lake Tahoe and Truckee.

In California the widely destructive floods in the Central Valley were the greatest since before the turn of the century. Levee systems from Marysville to Bakersfield failed when rivers draining the Sierra ran amok. California Governor, Earl Warren, proclaimed a state of emergency. Some 670,000 acres of farmland were flooded, 25,000 people were evacuated and property damage exceeded $33 million.

The situation was critical along the Truckee River. At first, Boca Reservoir absorbed the incredible runoff, but the incessant storms proved overwhelming for its limited capacity. On November 19 a super-saturated storm cell slammed against the mountains where it burst like a water-filled balloon. The downpour dumped 3.12 inches of rain on Carson City in just 24 hours, a record that still stands. Boca Reservoir topped out and 5,000 cubic-feet of water per second began pouring uncontrolled over the spillway. That additional flow rushed into the Truckee River and reinforced the flood crest surging down from the mountains.

Down river, the floodwaters washed out 800 feet of Highway 40. At Verdi, the Highland Ditch was dynamited to release floodwaters into nearby fields. Everyone could see that the Truckee River flood-control system had over-loaded. Reno residents and business owners were now vulnerable to the unchecked onslaught of the rampaging Truckee. Muddy water four feet deep swept through Reno's downtown district and National Guard Troops were called out to join emergency workers sandbagging the beleaguered city. Despite the flood, tourists still found their way into downtown casinos. Gamblers at the Mapes and Riverside casinos were seen playing slots dressed in rubber hip boots.

Finally on November 22, the day before Thanksgiving, the deluge ended, but downtown Reno looked like a war zone. Streets were piled high with muddy office furniture, equipment, and Christmas goods that had been stored in the flooded basements. There had been no warning to move supplies to higher ground. Deep water still covered the rich farmlands of the Carson Valley, but it was subsiding. Only one fatality could be directly attributed to the flood, but the monetary loss for western Nevada was $6 million.

The Thanksgiving Flood of 1950 prompted the Bureau of Army Engineers and the Bureau of Reclamation to plan the construction of additional reservoirs in the Truckee watershed. Current flood control utilizes the Prosser Creek, Boca, Martis, and Stampede reservoirs. Gates on Donner Lake and Lake Tahoe provide some control on those watersheds. But even with this hydrologic safety net, sometimes little can be done to control the wild and unpredictable Truckee River.

Weather historian, Mark McLaughlin's, award-winning books are available at Truckee-Tahoe bookstores or on his website at www.thestormking.com.