LOS ANGELES (CNS) – An infusion of monsoonal moisture from Arizona and
Baja California threatens to trigger showers and slow-moving thunderstorms in
the Southland today, raising the possibility of flash flooding in the San
Gabriel mountains and the Antelope Valley, forecasters said.

If today’s “moist and unstable conditions” produce thunderstorms, it
will occur this afternoon and this evening, according to a National Weather
Service advisory. Because the winds in the upper atmosphere are light,
thunderstorms will  be slow-moving, “increasing the potential for heavy
rainfall and associated flash flooding,” it said.

“The greatest probability of flash flooding in our forecast area will
be the eastern San Gabriel mountains, the washes and arroyos across the
Antelope Valley, as well as the Lockwood Valley area in the Ventura County
mountains.”

In Los Angeles County, a flash flood watch, issued by the NWS to
indicate the advent of conditions ripe for flash flooding, will be in effect
from noon through this evening in the Antelope Valley and the San Gabriel
Mountains.

“Excessive runoff from heavy downpours may cause rapid filling and
overflowing of normally dry washes and small creeks and low-lying areas,”
according to the NWS advisory. “In addition there is a threat of rock and mud
slides below steep terrain in the mountains.”

The NWS also issued a small craft advisory, warning of winds of up to
between 15 and 25 knots per hour, gusting to 30 knots.

Temperatures will remain a few degrees above normal today but short of
the heat wave-levels recorded between Aug. 5 and Wednesday, NWS forecasters
said.

The Antelope Valley should be around four degrees above normal today but
the Western San Fernando Valley is likely to experience temperatures 8-10
degrees higher than they should be, said NWS meteorologist Curt Kaplan.

The NWS forecast highs today under partly cloudy skies of 77 in Avalon;
80 in Newport Beach; 82 at LAX; 91 in downtown L.A. and Anaheim; 94 in San
Gabriel; 96 in Burbank; 97 in Pasadena; 101 in Saugus; 102 in Palmdale and
Woodland Hills; and 103 in  Lancaster.

Saturday’s highs will be up to five degrees lower in some areas and go
down some more over succeeding days, according to an NWS forecast.

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