Hurrricane Hilary Photo credit: CIRA/NOAA

LOS ANGELES (CNS) – With Hurricane Hilary strengthening to Category 4 status in the Pacific Ocean off the coast of Baja California as it makes its way toward Southern California, a first-of-its-kind tropical storm warning was issued today for a wide swath of the region including Catalina Island and northern Los Angeles County.

The watch, which indicates that “tropical-storm-force winds are possible somewhere within this area within the next 48 hours,” is the first ever issued in Southern California, according to the National Weather Service. A tropical storm has not made landfall in California since 1939, forecasters said.

In Los Angeles County, the watch is in effect for Catalina Island, the Antelope Valley foothills, Santa Clarita Valley, San Gabriel Mountains and the Golden State (5) and Antelope Valley (14) freeway corridors. The watch also covers Orange County coastal and inland areas and the Santa Ana Mountains and foothills.

The NWS noted that the hurricane will weaken as it moves north, devolving into a tropical storm as it reaches Southern California over the weekend, but it will still pack a punch, with heavy rain likely to prompt flash flooding in some mountain and foothill areas, along with powerful winds Sunday into Monday.

Forecasters warned that the storm could have major impacts, including:
   — flooding that might prompt evacuation orders;
   — heavy rain that could turn small streams, creeks, canals, arroyos, and ditches into “dangerous rivers,” leading to potentially destructive runoff in mountain valleys that could raise the risk of rock slides, mudslides and debris flows; and
   — flooding of streets and parking lots that will make driving conditions dangerous and potentially prompt road and bridge closures.

According to the NWS, some moisture from the storm could potentially reach eastern Los Angeles County on Saturday, with a slight chance of showers and thunderstorms Saturday afternoon and evening that could reach into some valley areas.

But NWS forecasts anticipate the bulk of the moisture arriving in the area between Sunday and Monday, bringing humid conditions with “widespread shower activity.”

With the amount of moisture in the storm system, there is a potential for a “tremendous amount of precipitation,” forecasters said, adding that “locally heavy rainfall seems to be a distinct possibility.”

About 2 to 4 inches of rain is expected over most areas, with localized amounts reaching as high as 6 inches.

The NWS issued a flood watch that will be in effect from Sunday afternoon through Monday evening across the entirety of Los Angeles County, noting that “excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations.” A flood watch will be in effect from late Saturday night through Monday evening for Orange County coastal and inland areas, along with the Santa Ana mountains and foothills.

The rain is expected to be accompanied by strong winds, although their strength is dependent on the exact path of the storm and its strength by the time it makes landfall. But forecasters said there is a chance of a “wet Santa Ana pattern” of offshore winds as the storm pushes through. Initial forecasts show some areas possibly seeing gusts of up to 60 mph.

Coastal areas will also be dealing with high surf that could create some flooding concerns in beach communities. Forecasters said surf of 4 to 7 feet is possible at southeast- and south-facing beaches, along with strong rip currents — with Catalina Island “most vulnerable” to the strong swells.

Hilary is unlikely to still be packing hurricane strength by the time it reaches Southern California, but it could still be classified as a tropical storm. The NWS noted that the only time a tropical storm made landfall in California in the 20th Century was in September of 1939.

Conditions are expected to improve by Tuesday and beyond, but “enough moisture will remain to possibly continue afternoon and evening showers and thunderstorms across the interior portion of the area, especially the mountains and desert,” according to the NWS.

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