# Thursday, January 03, 2008
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HPC 5 Day Precipitation Forecast for the period ending January 8, 2008 4:00 a.m. PST Click!
HPC 5 Day Precipitation Forecast
For the period ending January 8, 2008 4:00 a.m. PST

Forecast details have changed, but the main message is the same regarding a deep trough and 504 mb H5 low developing off the west coast. Strong, deep-layered, moist southwesterly flow is forecast to produce copious precipitation Friday night into Saturday, with lesser amounts preceding and following this period.

HPC's quantitative precipitation forecast issued this morning for the 5 day period ending Tuesday morning indicates totals as high as 11 inches (water equivalent) in the Sierra Nevada, and up to about 8 inches in the mountains of Ventura and Los Angeles. The 12z runs of the NAM and GFS generate about 3 inches of rain at Los Angeles between now and Sunday afternoon -- a little more forecast by the NAM and a little less by the GFS.

BUFKIT analysis of 12z NAM data for Van Nuys continues to indicate a low level jet of approximately 50 kts developing overnight Friday, 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.

A new wrinkle, just introduced by the 12z GFS, is a more southerly track of a shortwave progged for mid-week next week, with a chance of rain developing Wednesday into Thursday. We'll see!

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

Update 01/06/08 1:00 P.M. Archived copy of a NWS Public Information Statement with preliminary rainfall totals for the ongoing rain event.

Update 01/05/08 9:00 A.M. Rain event progressing more or less as expected with storm totals so far generally ranging from about 1 to 5 inches in the basin and valleys, to 3 to 7 inches or more in the foothills and mountains. San Marcos Pass, near Santa Barbara has recorded nearly 9 inches of rain, and OPIDS Camp, near Mt. Wilson, has recorded about 8 inches of rain. Here is an archived copy of a NWS Public Information Statement with preliminary rainfall totals for the storm, and an AHPS Precipitation Analysis of California precipitation for the 24 hr. period ending 4:00 a.m. this morning.

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