slight east track shift - west of the mountains should see slightly less rain (1.5-3.5 in. total)
Area Forecast Discussion
Issued by NWS San Diego, CA
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FXUS66 KSGX 192103
AFDSGX
Area Forecast Discussion
National Weather Service San Diego CA
203 PM PDT Sat Aug 19 2023
.SYNOPSIS...
Hurricane Hillary off the southern Baja California coast will move
northward over the coming days. Subtropical moisture will
continues to increase today, where mountains and deserts have the
best chance to see rain and thunderstorms this afternoon. This
activity will spread westward this evening over the coastal and
inland valley areas with light to moderate rainfall. The largest
impacts from Hilary will be felt on Sunday, as the system moves
into San Diego County and points north. Expect stronger and
shifting winds, and widespread heavy rain as she passes Sunday
afternoon and night. Bands of heavy rain and flooding are
expected, with dangerous and potentially catastrophic impacts
across the desert mountain slopes and deserts. The rain and wind
will taper off quickly on Monday. It will be relatively cool on
Monday, followed by mostly dry and warmer weather next week west
of the mountains and a chance for more monsoonal storms over the
mountain and desert areas.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
* Tropical Storm Warning in effect for all of Southern California.
* Flood Watch in effect through Monday afternoon for all of Southern
California.
* Unnecessary travel is discouraged on Sunday due to the high
flooding potential.
* High Wind potential for the mountains and deserts on Sunday.
Hurricane Hilary continues to move north-northwest and is located
approximately 270 miles west-northwest of Cabo San Lucas.
Subtropical moisture from Hilary`s wrath continue to stream into
Southern California, where mid-level clouds and isolated
thunderstorms are occurring across the region in the mountains and
deserts. The forecast remains on track this afternoon with precipitable
water and CAPE values are increasing through this afternoon into
Sunday. This will provide enough moisture and instability for
showers and storms to fire off this afternoon across the mountains
and deserts. Locally heavy downpours will result in flooded
roads. Showers and storms will overspread westward to encompass
all of our region tonight, where light to moderate rain is
expected.
A trough of low pressure off the Central California coast with a
large and in charge high pressure system over the Great Plains,
will funnel and accelerate the storm system over our area.
Hilary`s track will place the storm system making landfall in
northern Baja California on Sunday morning and then moving over
San Diego County and points northward through the day on Sunday.
This is when we can expect the heaviest rain, highest winds, and
largest impacts overall. Plentiful moisture with PWAT ensemble
values above 2.5 inches will aid in bouts of heavy rainfall across
the region as Hilary`s rain bands move through the area late
Sunday morning through Sunday night. Historical rainfall totals
with high rain rates will be expected across the mountains and
deserts, with some areas seeing over 2 inches of rain per hour.
This will cause major flooding, especially for mountain desert
slopes, canyons and the lower deserts. West of the mountains will
see heavy showers and thunderstorms at times where localized
flooding is expected. Hilary`s slightly eastward track this
morning has shifted some of this areas rainfall down to 1.5 to
3.5 inches in total.
The National Hurricane Center is forecasting Hilary to degrade to
a tropical storm by the time it reaches Southern California. Winds
around the counterclockwise flow of the storm will first start out
from the north and east starting in San Diego County late Sunday
morning and pushing northward through the afternoon hours. The
center of the storm will pass across our region early Sunday
evening, where winds will shift from the south and west. The
strongest winds will occur Sunday afternoon and evening. Most
areas west of the mountains will see wind gusts 35-45 MPH, locally
higher near 60 MPH for the coastal slopes and foothills. Depending
on the exact track, Hilary`s track looks to have lighter winds in Orange
County near 30-40 MPH. Mountain and desert areas will see very
gusty winds near 40-60 MPH, with some passes and canyons over 70
MPH at times. Winds will taper off Sunday night into Monday.
The system will lift out of the area on Monday, leaving residual
showers and clearing from south to north with well below (around 20
degrees) average temperatures inland. Monsoonal flow will
continue through much of next week, where a small chance of
storms remains each afternoon and early evening each day across
the mountains and deserts.
&&
.AVIATION...
192000Z...Coasts...SCT015 BKN150 through 05Z. 05Z-12Z...SCT-BKN020-
040 BKN100 with scattered SHRA. Sunday...periods of rain with the
heaviest rain 18Z-24Z with vis 1-3SM and CIGs below 1000 FT in the
strongest cells. Strong winds Sunday afternoon and evening with gust
potential of 30 kts at SAN/CRQ and SNA.
Valleys/Mountains/Deserts...Scattered SHRA/TSRA over the mountains
and deserts tonight and Sunday. The strongest SHRA/TSRA arrive
Sunday afternoon and evening with heavy rain reducing VIS to less
than 1SM and CIGs to less than 1000 FT. Strong ESE Sunday afternoon
shifting south or west Sunday evening. Gusts of 50-70 kts over the
mountains and gusts of 40-50 kts elsewhere. Wind gusts may exceed 35
kts at PSP Sunday. Conditions steadily improve Monday morning.
&&
.MARINE...
Winds from Hilary increase to 15-30 kt from the NNE on Sunday with
gusts to 35 kt. Winds shift to the WSW Sunday night, then weaken
Monday morning and shift southerly. Short-period steep seas of 8 to
13 feet. Wind speeds and sea heights will be highly dependent on the
storm track.
&&
.BEACHES...
160 degree SSE swells from Hilary will bring high surf to south
facing beaches Sunday and Monday. Highest surf will be on the south-
facing beaches in Orange County with surf of 5 to 10 feet. Strong
longshore currents at all San Diego and Orange County beaches. There
is a chance of lightning at the beaches Sunday.
&&
.SKYWARN...
Skywarn activation is requested through Monday morning. Thank you
for any reports you are able to send us, spotters!
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Tropical Storm Warning for Apple and Lucerne Valleys-Coachella
Valley-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 Deserts-San Diego County Mountains-San Diego County
Valleys-San Gorgonio Pass Near Banning-Santa Ana Mountains
and Foothills.
Flood Watch from late tonight through late Sunday night for
Orange County Coastal Areas-Orange County Inland Areas-San
Bernardino and Riverside County Valleys-The Inland Empire-
San Diego County Coastal Areas-San Diego County Valleys-
Santa Ana Mountains and Foothills.
Beach Hazards Statement from Sunday morning through late Monday
night for San Diego County Coastal Areas.
Flood Watch through Monday afternoon for Apple and Lucerne
Valleys-Coachella Valley-Riverside County Mountains-San
Bernardino County Mountains-San Diego County Deserts-San
Diego County Mountains-San Gorgonio Pass Near Banning.
High Surf Advisory from 8 AM Sunday to 2 AM PDT Tuesday for
Orange County Coastal Areas.
PZ...Tropical Storm Warning 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...Moede
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National Weather Service
San Diego, CA Weather Forecast Office
11440 W. Bernardo Court, Suite 230
SAN DIEGO, CA 92127
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