Flood Potential Outlook
Issued by NWS Los Angeles, CA

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FGUS76 KLOX 192132
ESFLOX
CAZ034>041-044>046-051>054-059-087-088-547-548-192330-

Hydrologic Outlook
National Weather Service Los Angeles/Oxnard CA
230 PM PDT Sun Mar 18 2018

...STRONG PACIFIC STORM REMAINS ON TRACK TO BRING POTENTIAL
FLOODING CONCERNS TO SOUTHWEST CALIFORNIA TUESDAY THROUGH THURSDAY
NIGHT...

A strong storm system originating from the Pacific Ocean will tap
into a long fetch of deep subtropical moisture and bring the
potential for a very wet and long duration storm event for
Southwest California Tuesday through Thursday night. This
atmospheric river event will likely bring the highest rainfall
totals to some portions of Southwest California, so far this season.
Preliminary storm total estimates range from 5.00 and 10.00 inches
across southwest facing foothills and mountains, and 2.00 to 6.00
inches elsewhere.

A prolonged period of moderate to heavy rainfall could occur with
this system, with the highest rainfall intensities expected to occur
sometime between late Wednesday afternoon through Thursday morning.
Rainfall rates will likely exceed USGS thresholds and bring a threat
of significant flash flooding and mud and debris flows to recent
burn areas. These burn areas include the Thomas, Whittier, Creek,
and La Tuna burn scars. Peak rainfall rates are projected to range
between 0.50 and 0.75 inch per hour. Isolated rainfall rates as high
as 1.00 inch per hour cannot be ruled.

In addition to the flash flooding and mud and debris flow risk in
recent burn areas, there will be other flooding threats in non-
burn areas due to the long duration and intensity of this storm.
Widespread urban roadway flooding is possible as well as
rockslides and mudslides, especially near canyon roadways. As a
result, there could be significant travel delays and road closures
across the region between Tuesday and Thursday night. Creeks and
small streams could also be running and it is always advised to
remain out of arroyos and barrancas.

As we draw closer to this event, Flash Flood Watches will likely
need to be issued, especially for the recent burn areas. Pay
close attention to the latest forecasts and updates on this storm
system. Please follow instructions from your local emergency
officials.

$$

Hall/RK


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