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Friday January 25, 2019

Assignment: Predict the 24 hr precipitation amount (inches) for Sitka, AK (PASI)

Since there is hardly a drop of precipitation expected on Friday in the entire conterminous U.S. (the lower 48 states), we have to travel to Alaska to see some action. The National Weather Service says that "the weekend forecast remains wet with an atmospheric river impacting the Panhandle between Friday and Saturday." An atmospheric river is just a strong, fairly narrow flow of high moisture that can stay over one area for days, dumping heavy precipitation over the same locations. The river can be seen in this plot as a high moisture band (green and blue colors) flowing toward the Alaska panhandle on Friday. So let's forecast the 24-hr precipitation amount for Sitka, Alaska, which is located on the coast of the Panhandle in the high moisture band.

Question: Why do you think that there is hardly any precipitation expected in the 48 states on Friday?

Forecasts for Sitka, AK (PASI)
Forecaster Precip24, inches (error) Comment Day Score
OBSERVED 0.26 Precip24 FINAL.
CLIMATE 0.22 (-0.04) NCDC Climate Normals, 1981-2010 3.5
PERSISTENCE 0.24 (-0.02) 3.6
GFS-MOS-00-DAY01 1.32 (1.06) 0
GFS-MOS-06-DAY02 1.08 (0.82) 0.8
GFS-MOS-18-DAY02 0.96 (0.7) 1.2
GFS-MOS-12-DAY02 0.9 (0.64) 1.4
GFS-MOS-06-DAY01 0.9 (0.64) 1.4
NAM-MOS-12-DAY02 0.84 (0.58) 1.6
GFS-MOS-12-DAY01 0.84 (0.58) 1.6
NAM-MOS-00-DAY01 0.66 (0.4) 2.3
NAM-MOS-12-DAY01 0.54 (0.28) 2.7
GFS-MOS-18-DAY01 0.54 (0.28) 2.7
NAM-MOS-00-DAY00 0.54 (0.28) 2.7
GFS-MOS-00-DAY00 0.54 (0.28) 2.7