High Wind Watch 5, NWS San Diego, CA

Area Forecast Discussion
National Weather Service San Diego CA
932 AM PST Mon Nov 4 2024

.SYNOPSIS...
Dry conditions are expected this week with periods of Santa Ana
winds today and again Wednesday and Thursday. Gusty north to
northeast winds currently impacting portions of the San Bernardino
county mountains into the Inland Empire below the Cajon Pass and for
the Santa Ana mountains and portions of inland Orange County will
weaken into this afternoon. For the middle of the week, another
round of gusty and more widespread northeasterly to easterly Santa
Ana winds are expected. Below average temperatures are expected for
much of this week, with a gradual warming to near normal for the
weekend. Areas of frost are possible in wind sheltered valleys and
the High Desert Thursday and Friday morning.

&&

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

Areas of gusty north to northeast winds have been observed last
night into this morning. So far peak wind gusts have topped out at
62 mph at a few locations in the San Bernardino coastal mountain
slopes. Elsewhere gusts have been in the 35 to 50 mph range. A peak
wind gust summary has been headlined on our weather.gov/sandiego
website. Relative humidity values have decreased substantially since
Sunday morning with a lot of valley and mountain locations running
50 to 70 percent drier than yesterday. Conditions are expected to
continue to dry out into the afternoon.

High temperatures will warm west of the mountains today and for
inland areas on Tuesday with much greater cooling for inland areas
on Wednesday. A gradual warming trend is expected for Thursday into
the weekend. Overnight low temperatures are expected to remain below
average for the deserts, mountains, and wind sheltered valley
locations for most of this week. Wind sheltered locations in the
valleys and High Desert may get cold enough for frost to develop
particularly Thursday and Friday mornings.

For the middle of next week the latest guidance continues to show an
area of low pressure digging into the Great Basin. Ensemble
solutions with more influence from the ECMWF have the low stronger
and a little further west, which would bring stronger winds compared
to solutions from the GFS. While there is still some spread in
solutions latest guidance is indicating this mid-week Santa Ana wind
event will be just as strong, potentially stronger, than the
current event, with more widespread coverage in the gusty winds.
Another concern with the mid-week event is the air mass is
expected to be much drier than what is currently being observed.
Current thinking is gusty northeast winds will develop on
Wednesday with more impact for the coastal slopes and foothills of
the San Bernardino mountains into the Inland Empire and for the
Santa Ana mountains into inland Orange County. Winds look to turn
more easterly for late Wednesday into Thursday which would be more
of an impact to the Riverside and San Diego County mountains,
potentially into the San Diego county valleys. The strongest winds
look to be late Wednesday into Thursday. Periods of critical fire
weather conditions are expected for the coastal slopes and
foothills of the San Bernardino mountains into the Inland Empire
and for the Santa Ana mountains into inland Orange County. Near-
critical fire weather conditions are expected for the Riverside
and San Diego County mountains and San Diego valleys. More
information about wind speeds and relative humidity values can be
found in the Fire Weather discussion below.

&&

.AVIATION...
041700Z...Clear skies with unrestricted VIS today and tonight. Areas
of gusty north to northeast winds 20-30 kts at times through 22Z
from foothills into valleys, inland Orange County and lower desert.
MDT-strong up/downdrafts and LLWS VCNTY KSNA, KONT, KSBD and KPSP.
Winds switching to N/NW and calming most areas after 20Z from west
to east.

&&

.MARINE...
No hazardous marine conditions are expected through Friday.

&&

.FIRE WEATHER...

Areas of gusty north to northeast winds will continue through the
morning, weakening into Monday afternoon. Strongest winds have
likely already occurred, but gusts to 35 to 45 mph are possible on
the coastal slopes of the western San Bernardino County
Mountains, below the Cajon Pass into the Inland Empire, the Santa
Ana mountains, and portions of inland Orange County. Daytime
relative humidity values are expected to fall to 12 to 15 percent
this afternoon for the Inland Empire and foothills of the San
Bernardino mountains. Relative humidity for the Santa Ana
mountains and inland Orange County will be 15 to 20 percent. Winds
are expected to continue to weaken into this afternoon.

Another Santa Ana wind event is expected for the middle of the
week. Latest guidance is showing winds starting to increase by
early Wednesday morning, with gusty northeast winds expected to
continue into Thursday afternoon. Critical fire weather
conditions are expected for the Santa Ana mountains, portions of
inland Orange County, the Inland Empire, and coastal slopes of the
San Bernardino County mountains. Preliminary forecast shows the
potential for wind gusts 35 to 45 mph, with more frequent gusts of
55 to 65 mph in wind prone locations. Relative humidity values
are expected to fall to 10 to 15 percent in windy areas, with the
potential to see areas with relative humidity values as low as 8
percent. For San Diego and Riverside county mountains and San
Diego valleys, winds look to increase later in the day Wednesday
into Thursday. Peak gusts there currently look to be in the 40 to
50 mph range. Dry conditions are also expected in San Diego County
with falling relative humidity. Near critical fire weather
conditions are expected for San Diego and Riverside county
mountains and portions of the valleys.

Winds are expected to weaken through the day Thursday with the
potential for weaker northeast to east winds to linger into Friday
morning.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Red Flag Warning until 6 PM PST this evening for San Bernardino
     County Mountains-Including The Mountain Top And Front
     Country Ranger Districts Of The San Bernardino National
     Forest-San Bernardino and Riverside County Valleys  -The
     Inland Empire.

     Wind Advisory until 4 PM PST this afternoon for Orange County
     Coastal Areas-Orange County Inland Areas-San Bernardino
     County Mountains-San Bernardino and Riverside County
     Valleys-The Inland Empire-Santa Ana Mountains and Foothills.

     Fire Weather Watch from late Tuesday night through Thursday
     afternoon for Orange County Inland Areas-San Bernardino
     County Mountains-Including The Mountain Top And Front
     Country Ranger Districts Of The San Bernardino National
     Forest-San Bernardino and Riverside County Valleys  -The
     Inland Empire-Santa Ana Mountains-Including The Trabuco
     Ranger District of the Cleveland National Forest.

PZ...None.

&&

PUBLIC/FIRE WEATHER...CO
AVIATION/MARINE...CSP