Flood Potential Outlook
Issued by NWS Los Angeles, CA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2
FGUS76 KLOX 180018 CCA

Hydrologic Outlook...CORRECTED
National Weather Service Los Angeles/Oxnard CA
518 PM PDT Sat Mar 17 2018


A strong pacific storm system will tap into a long fetch of
deep subtropical moisture, bringing 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 1.50 to 4.00 inches across coastal and valley areas,
to between 3.00 and 6.00 inches across south and southwest
facing foothills and mountains.

There is the potential for a prolonged period of moderate to
heavy rainfall with this system, with the highest rainfall
intensities expected to occur sometime between late Tuesday night
and early Thursday. During this time, rainfall rates will likely
exceed USGS thresholds, bringing a threat of significant flash
flooding and debris flows in recent burn areas. These burn areas
potentially include the Thomas, Whittier, Creek, and La Tuna burn
scars. There is some uncertainty in the positioning of heaviest
rainfall with this system, but areas under the heaviest rainfall
are projected to see rainfall rates ranging between 0.50 and 0.75
inch per hour, with a chance of reaching as high as 1.00 inch per
hour in isolated locations.

In addition to the flash flooding 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. There is
the potential for widespread urban roadway flooding as well as
rockslides and mudslides, especially near canyon roadways. As a
result, there could be significant travel delays and road
closures. Also, there is the potential for flooding of creeks and
small steams.

As we draw closer to this event, Flash Flood Watches will likely
be needed, especially for many of the recent burn areas. Pay
close to the latest updates and follow instructions from your
local emergency officials.



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.