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Thursday January 17, 2019

Assignment: Predict the 24 hr precipitation amount (inches) for Lake Tahoe, CA (KTVL)

California has been receiving a series of strong storms recently, and Thursday should be a day of very heavy precipitation in the Sierra Nevada Mountains. The NWS forecast discussion from Reno says this: "Our best recommendation is to prepare for heavy accumulations down to lake level starting Wednesday night and continuing through early Friday morning. Above 7000 feet, it`s game on! 2+ inches of liquid is anticipated with 2 to 6 feet of snow forecast. Avalanche danger will be on the rise, and the Sierra Avalanche Center has issued an Avalanche Watch for the Tahoe Basin." So let's forecast Thursday's 24-hour precipitation amount (liquid equivalent) for Lake Tahoe, California and see if they really get more than 2 inches of water and several feet of snow. The observing site is near the lake shore, with an elevation of a little under 7000 feet.

Question: The high temperature forecast for Lake Tahoe is in the 40's and the heaviest snow is expected during the day. How can there be heavy snow with the temperature in the 40's?

Forecasts for Lake Tahoe, CA (KTVL)
Forecaster Precip24, inches (error) Comment Day Score
OBSERVED 0.37 Precip24 FINAL.
PERSISTENCE 0.55 (0.18) 4.4
GFS-MOS-00-DAY00 1.5 (1.13) 2.7
GFS-MOS-18-DAY01 1.5 (1.13) 2.7
GFS-MOS-12-DAY01 1.5 (1.13) 2.7
GFS-MOS-00-DAY01 1.86 (1.49) 2.1
GFS-MOS-18-DAY02 1.86 (1.49) 2.1
GFS-MOS-06-DAY02 1.86 (1.49) 2.1
GFS-MOS-06-DAY01 2.16 (1.79) 1.5
NAM-MOS-12-DAY01 2.22 (1.85) 1.4
NAM-MOS-00-DAY01 2.22 (1.85) 1.4
GFS-MOS-12-DAY02 2.22 (1.85) 1.4
NAM-MOS-00-DAY00 2.34 (1.97) 1.2
NAM-MOS-12-DAY02 3 (2.63) 0.1