# Monday, December 31, 2007
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12z GFS Forecast 60 Hr. Precipitation Total For the period ending January 7, 2008 4:00 p.m. PST Click!
12z GFS Forecast 60 Hr. Precipitation Total
For the period ending January 7, 2008 4:00 p.m. PST

Los Angeles will end 2007 with precipitation for the water year close to normal, and with the Sierra snowpack at about 60% of normal. However the first week of 2008 may usher in one of the strongest Pacific storms to affect California in some time, and by Monday of next week, precipitation and Sierra snowpack totals may have increased dramatically.

If recent runs of the GFS and ECMWF verify, California -- including much of Southern California -- will be deluged with heavy precipitation in the Thursday to Sunday timeframe. A BUFKIT analysis of 12z GFS data at Van Nuys indicates rain rates of over 0.7 inch an hour Friday night, and a rainfall total for the period of more than 4 inches. A second impulse Sunday is forecast to add about another 1.0 inch to the total.

CIRA Blended TPW loops show energy and moisture associated with tropical forcing in Indonesia being transferred into the the mid-latitudes, priming the system. Additional moisture is being drawn into the system from the tropics near Hawaii, and the GFS indicates a tropical connection as the system moves into California.

Details are likely to change as the week progresses, but at this point the storm's forecast parameters are impressive. At its peak, the Van Nuys BUFKIT analysis indicates a low level jet of approximately 50 kts developing, with precipitable water values of 1.2 inches and cloud velocities exceeding 60 kts. Such a scenario -- if the forecast verifies -- could produce extraordinarily heavy, orographically enhanced rainfall in the foothills and mountains, with flash flooding and debris flows possible, particularly in areas that have been recently burned.

Please refer to your local NATIONAL WEATHER SERVICE FORECAST OFFICE for official forecasts and warnings.

More information concerning Southern California weather can be found using our WEATHER LINKS page.