High Wind Watch 6, NWS San Diego, CA

Area Forecast Discussion
National Weather Service San Diego CA
1000 AM PDT Wed Sep 7 2022

.SYNOPSIS...
Strong high pressure to the north will continue the heat wave
through Thursday in the mountains and deserts and through Friday
at the coast and in the valleys. A tropical system from the
south will bring strong gusty east winds Friday through Saturday
and periods of showers and isolated thunderstorms late Friday
through Sunday with the greatest potential of heavier rainfall and
flooding from the mountain crests east into the deserts. Cooler
weather is likely next week as a trough of low pressure approaches
from the Pacific.

&&

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

Patchy stratus was occurring along the immediate coast this morning,
especially in San Diego County. A gulf moisture surge resulted in
low clouds as well in the deserts and desert mountain slopes in San
Diego and Riverside County Mountains. Otherwise, skies were sunny.
Another very warm profile (26 deg C at 850 mb in this morning's NKX
sounding), combined with east flow just above the surface will
result in another hot day today with up to around 109 in the Inland
Empire, though a little cooler in the mountains and deserts where
moisture has increased. Temperatures should be over 100 in Inland
Orange County.

Hurricane Kay is currently around 200 miles southwest of Cabo and
should reach a point about 150 miles southwest of San Diego Friday
night as a weakening tropical storm. The current NHC track forecast
is having Kay move west once it reaches about 31 deg N and
eventually southwest as a tropical depression around Sunday.

The impacts here will include the strong east winds which will be
enhanced by the mountains--in fact, the local WRF has a mountain
wave as strong east winds in the 850-700 MB interact with a bit of a
stable layer above that and the mountain crest and result in wind
gusts likely over 70 MPH in parts of San Diego County, especially
the mountains Friday and across San Diego and Riverside Counties and
possibly Orange County Saturday. The Friday scenario looks more
likely with more uncertainty for Saturday winds. Coastal areas could
have gusts over 50 MPH one or both days, but uncertainty is still
high, and these winds could be local.

Due to the easterly flow and a very warm profile, there could be
major heat near the coast Friday, even though it should be a little
cooler in the mountains and deserts then. This easterly wind will
bring the downsloping which could result in very high daytime and
nighttime temperatures Thursday night, Friday and/or Friday night.
Increasing precipitable water aloft could amplify the nighttime
temperatures due to the blanketing effect from clouds or even just
the moisture without the clouds, so this could be similar to the
nocturnal heat last Saturday night with lows over 80 possible in
some near-coastal areas Thursday night or Friday night, but that is
not a certainty yet.

Of course, flooding could be a threat with heavy rain, which could
be in the 2-4 inch range from the mountains east into the deserts.
Heavy rain is most likely late Friday through Saturday, but
lingering moisture, especially if Kay remains nearby, could bring
more rain Sunday. With so much easterly flow, heavy rain is looking
less likely west of the mountains, but enough moisture aloft could
still result in periodic showers there.

A trough of low pressure developing over the Pacific and approaching
California from the west will likely bring cooler weather next week.
There could be more of a marine layer then, including if some of
Kay's moisture is still in the area.

&&

.AVIATION...
071630Z...FEW low clouds with bases 200-700 ft MSL with FEW-SCT high
clouds AOA 10000 ft MSL. Low clouds around 3000 feet MSL could
produce cigs briefly in vcnty KTRM and KPSP through 18Z. Patchy
coastal cloud coverage with bases 300-600 ft MSL could impact
coastal TAF sites at times after 07Z through 16Z Thursday.

&&

.MARINE...
Remnants of Kay will bring strong easterly winds and southeast swell
Friday through Saturday, along with a chance of thunderstorms.
Easterly winds, wind waves, southeast swell, and thunderstorms could
make conditions hazardous. Winds and seas diminish Saturday and
Sunday, but the chance of thunderstorms continues.

&&

.BEACHES...
South swells will bring elevated surf and a high rip current risk to
Orange County through Thursday. Southeast swell from Kay should
bring higher surf and stronger rip currents, but most likely strong
longshore currents, to Orange County Friday and Saturday.

&&

.FIRE WEATHER...
Excessive heat will continue through early Friday, keeping the
fire weather threat elevated. Offshore flow will strengthen
slightly this morning, then weaken into Thursday. The intense
heat this week will result in large mixing heights, and increase
the potential for plume dominated fires should any new starts
occur. A tropical system from the south will bring strong gusty
east winds Friday and Saturday and showers and isolated
thunderstorms late Friday into Sunday with widespread wetting
rainfall likely, especially in the mountains and deserts.

&&

.HYDROLOGY...
Bands of elevated moisture from Hurricane Kay could reach far
southern California as early as Thursday. More widespread
precipitation from showers and isolated thunderstorms from the
moisture from tropical cyclone Kay is expected from late Friday
into the weekend with the greatest potential for heavier rainfall
on the east slopes of the mountains. Heavy rainfall could develop
on Friday night into Saturday with an increasing flood threat,
especially for the east slopes of the mountains into the adjacent
deserts.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions. Skywarn
activation may be needed for Friday night into the weekend.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning until 8 PM PDT Friday 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.

     Excessive Heat Warning until 8 PM PDT Thursday 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.

PZ...None.

&&

PUBLIC/FIRE WEATHER/HYDROLOGY...Maxwell
AVIATION/MARINE/BEACHES...CO