An active polar jetstream will transport a series of disturbances over the region this weekend into next week. The shortwaves will combine with the moist airmass and orographic lifting to produce periods of heavier precipitation especially in the mountains and foothills, with higher amounts in San Bernardino county. The graphic displays forecast storm total rainfall for Friday through Tuesday evening.
.. Strong Pacific storm systems will bring high rain amounts to
Southern California through at least Wednesday...
Deep moist flow out of the Pacific will bring periods of rain
through next Wednesday. Heaviest precipitation will occur
Sunday... Tuesday and Wednesday... but steady long-lasting rain of
light to moderate intensity will be likely during other times.
This weekend... southwestern California will be at the south edge
of the deep moisture... so Orange and San Bernardino counties will
generally receive more rainfall than San Diego and Riverside
counties. Strong upslope flow will result in the mountains
receiving large amounts of precipitation... with up to 8 inches
possible in the San Bernardino County mountains through Sunday
night. The moisture plume will be directly over Southern
California Tuesday and Wednesday... so the entire region will
likely have heavy rainfall then.
Total rainfall estimates for the period Friday night through
Sunday night are as follows:
San Diego County coast 1.00 to 1.50 inches
San Diego County valleys 1.50 to 2.00 inches
Orange County coast 1.50 to 2.50 inches
inland Empire 1.25 to 3.00 inches (highest north)
San Diego County mountains 2.00 to 5.00 inches
Riverside County mountains 2.50 to 5.00 inches
Santa Ana Mountains 3.00 to 6.00 inches
San Bernardino County mtns 4.00 to 8.00 inches
Note that mountain totals will be highly variable. For the deserts...
San Diego County deserts around one-half inch
Coachella Valley less than one inch Apple and Lucerne valleys around one inch
Heavy rainfall accumulations are expected... but they will be due to
long durations and not due to heavy intensities. Therefore... the
flash flood threat will be fairly low over the weekend... though this
could change with the heavy rain next Tuesday or Wednesday. Some low
lying spots... especially along streets... could have minor flooding
this weekend. Streams and washes which might normally be dry could
have water flowing through them.
Through Tuesday... snow levels will be above 8000 feet... and
confined to the highest peaks of San Bernardino and Riverside
counties. However... a brief period heavy snow down to 6500 feet
is possible Tuesday night into Wednesday as a cold front comes
through.
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