Flash Flooding and Flooding in California, March 29 to 31, 2024

Area Forecast Discussion
National Weather Service San Diego CA
221 PM PDT Fri Mar 29 2024

.SYNOPSIS...
An incoming area of low pressure will produce cold and windy
conditions across the region this weekend with areas of heavy rain
and mountain snow. This will last through Monday as the system
departs. A ridge of high pressure will come into the region by the
middle of the week with warmer and drier weather. Another trough
of low pressure will dip into the western part of the country,
which will bring us more cooler, windier and potentially wetter
weather by, of course, around next weekend.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

.SHORT TERM...(Today through Monday)....
Strong area of low pressure off the coast of the Bay Area
continues to push southeast, where clouds and showers are on the
increase in parts of the Central Coast and south of Point
Conception. Prefrontal showers will increase across the LA Basin
this evening. The main frontal band of showers will cross our area
through the night across northern areas and into the morning
across San Diego County. This first batch of rain and mountain
snow will be the heaviest for this weekend. Heaviest rainfall will
along the coastal slopes, though coastal areas will see heavy
rainfall as well. Winds out of the south will be strong as the
front passes through the region with a moderate to high chance of
seeing wind gusts over 35 MPH at the immediate coast per latest
forecast guidance.

As the low passes over Southern California, increased vorticity
and cold air aloft will aid in thunderstorm development on Sunday.
CAPE values near 200-300 J/kg, so storms may form in many areas by
this time. Isolated storm activity may occur on Saturday with the
frontal passage on Saturday, but chances are smaller. Temperatures
will also be quite cold this weekend, where many areas west of the
mountains will struggle to reach 60 degrees and mountain areas
will mainly stay in the 30s to mid 40s.

The low will slowly exit on Monday, with shower chances
diminishing closer to the mountains. When the storm departs, most
areas west of the mountains will have received over 1 inch of
rain, though there is a low to moderate chance for some areas to
see over 2 inches of rainfall. The deserts will received some
rainfall as well, near one half inch for the high desert and less
than one quarter across the lower deserts. Snow will in abundance
for areas over 5,000 feet where winter weather advisories and
winter storm warnings have been posted. Travel will be very
difficult to impossible across the San Bernardino County
mountains with heavy snow and blizzard conditions at times.
This includes Big Bear and Lake Arrowhead this weekend,
especially on Saturday, where 1 to 2 FEET of snowfall is likely.

&&

.LONG TERM...(Tuesday through End of Next Week)...
The trough of low pressure will be replaced by a ridge of high
pressure, where things will warm up very nicely compared to the
weekend. This will lead to some offshore flow and warmer
temperatures for all. Mid to upper 70s for places west of the
mountains and mid 80s in the lower deserts.

But, if you thought we were out of the woods since April is almost
here, think again...another large open wave trough will set up
across the western U.S. according to our latest ensemble model
clusters. While cooler and breezier weather looks quite likely,
there is a chance for more precipitation as we head into next
weekend (no lies sadly). Please keep an eye on the forecast for
the latest and stay safe this weekend!

&&

.AVIATION...
292025Z...Coast/Valleys...SCT locally BKN cigs 3000-5000 feet MSL
with tops to near 6000 feet MSL developing. After about 30/02z lower
clouds locally merging with higher cloud decks to around 10K ft MSL.
-RA developing north spreading south. Areas of southwest winds 20-30
kt. There is a moderate chance that the low clouds will be BKN at
30/02Z so the confidence in the cloud forecast at KSAN is moderate.

Mountains/Deserts... Mountains locally obscured til 30/02Z...
becoming increasingly obscured in clouds afterward. SCT Locally BKN
clouds 3000-5000 feet MSL with tops to near 6000 feet MSL. After
about 30/06z lower clouds locally merging with higher cloud decks to
around 10K ft MSL. -RA developing north late Fri night spreading
south becoming heavier by Sat morning. Areas of west winds 20-30 kt
with local gusts 35-45 knots will occur mainly from the mountain
crests east/north through the desert slopes and into adjacent
deserts along with moderate to strong up/downdrafts and local LLWS.

&&

.MARINE...
A Small Craft Advisory has been issued for southerly winds 20-25
knots with gusts to 30 knots and choppy seas Friday night into
Saturday afternoon. The winds will shift from south to west as a
front moves through the coastal waters Saturday morning, with weaker
winds and less chop thereafter. There will be a slight chance of
thunderstorms Saturday night through Sunday.

&&

.BEACHES...
West southwest swells of 5-7 ft at 9-13 seconds could bring surf of
7-9 feet at times Saturday evening into Sunday afternoon. This will
make for dangerous swimming conditions. The highest surf will be on
exposed west-facing beaches in San Diego County. There will be a
slight chance of thunderstorms Saturday night through Sunday.

&&

.SKYWARN...
Skywarn activation is requested.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory from 1 AM to 1 PM PDT Saturday for San Diego
     County Coastal Areas-San Diego County Valleys.

     Flood Watch from late tonight through Sunday afternoon for
     Orange County Coastal Areas-Orange County Inland Areas-
     Riverside County Mountains-San Bernardino County Mountains-
     San Bernardino and Riverside County Valleys-The Inland
     Empire-San Diego County Coastal Areas-San Diego County
     Mountains-San Diego County Valleys-Santa Ana Mountains and
     Foothills.

     Winter Storm Warning from 1 AM Saturday to 6 PM PDT Sunday for
     San Bernardino County Mountains.

     Winter Weather Advisory from 4 AM Saturday to 6 PM PDT Sunday
     for Riverside County Mountains.

     Winter Weather Advisory from 8 AM Saturday to 6 PM PDT Sunday
     for San Diego County Mountains.

     Wind Advisory until 11 PM PDT this evening for Apple and Lucerne
     Valleys-Coachella Valley-San Gorgonio Pass Near Banning.

     Wind Advisory until 11 AM PDT Saturday for San Diego County
     Deserts.

     Wind Advisory from 11 PM this evening to 11 AM PDT Saturday for
     Orange County Coastal Areas-Orange County Inland Areas.

PZ...Small Craft Advisory from 11 PM this evening to 5 PM PDT
     Saturday for Coastal Waters from San Mateo Point to the
     Mexican Border and out to 30 nm-Waters from San Mateo Point
     to the Mexican Border Extending 30 to 60 nm out including
     San Clemente Island.

&&

PUBLIC...APR
AVIATION/MARINE...Small

Preliminary Local Storm Report
National Weather Service San Diego CA
336 PM PDT Fri Mar 29 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0320 PM     Non-Tstm Wnd Gst 7 WSW Lucerne Valley    34.41N 117.05W
03/29/2024  M52 MPH          San Bernardino     CA   Mesonet

            Mesonet station SE266 Lucerne Valley
            (SCE266) southwest winds.

&&

aot