# Thursday, March 4, 2010
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AHPS 24 Hour Precipitation for the 24 hours ending March 4, 2010 - 4:00 a.m. PST Click
AHPS 24 Hour Precipitation
Ending March 4, 2010 - 4:00 a.m. PST

Tuesday's trough was even more feeble than expected south of Santa Barbara, barely managing to wet the streets and generate an official "trace" of rain in the Los Angeles area. Wednesday's upper low dug a little further south than expected, resulting in some moderate showers. Rainfall amounts were variable, generally ranging from a few hundredths in the basin to 0.25 inch or so at some mountain locations . Here are archived copies of NWS Public Information Statements with some rainfall amounts for Tuesday's trough and Wednesday's upper low.

Downtown Los Angeles (USC) recorded 0.06 inch of rain Wednesday, bringing the water year total (July 1-June 30) to 14.24 inches, which is 3.05 inches above normal for the date.

Another finicky upper low may produce some rain in Southern California this weekend. Just how much depends on the behavior of the low and it's proximity to the Southern California coast. If the low track is too far offshore, rainfall amounts could be dramatically reduced. This is well illustrated by 09z SREF plot showing the forecast probability that precipitation will exceed 0.1 inch for the 24 hr. period ending Saturday at 7:00 p.m. BUFKIT analyses of today's 18z NAM data for Santa Barbara, Van Nuys and LAX all produce about 0.3 inch of rain, mostly on Saturday.

Update 03/05/10 8:00 a.m. The models continue to have difficulty with the timing and precipitation amounts for this weekend's storm. This isn't surprising since small changes in the track of the upper low, the amount of moisture entrained, and other factors could have a big effect on the amount of rain in a particular region. Yesterday afternoon's run of the NAM generated nearly an inch of rain at Van Nuys, but this morning's 12z run of the NAM is back down to the neighborhood of 0.3 inch. Today's 09z SREF suggests the highest precipitation amounts may occur to the south of Los Angeles. Here's an SREF plot of the probability that precipitation will exceed 0.25 inch for the 24 hr. period ending 10:00 a.m. Sunday. We'll see!

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