Arrowhead Highlands, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

872
FXUS66 KSGX 030341
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
841 PM PDT Wed Apr 2 2025

.SYNOPSIS...
A low pressure system over the western states will continue the cool
weather with periods of showers through early Friday. Shower
activity will increase again tonight through Thursday evening
with the greatest coverage and accumulation over the mountains.
Dry and warmer for the weekend into next week, with high
temperatures rising to around average over the weekend and 10 to
15 degrees above average for inland areas for the middle of next
week.

&&

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

Evening update...
Showers are generally confined to areas around the San Bernardino
Mountains, with only isolated very light showers further south. A
few lightning strikes have been observed in a heavier shower along
the northern slopes of the San Bernardino Mountains south of
Lucerne Valley. A spotter even reported large snowflakes falling
and sticking to the ground in Lucerne Valley with this
thunderstorm.

The broad upper level trough over the southwest US will continue
to amplify tonight as a weak short wave drops south on the back
side of the trough. Shower activity will increase tonight,
especially across San Diego County. With the trough amplifying and
colder air aloft moving in, snow levels will fall to around
4000-4500 ft tonight, rising to around 5500 ft Thursday afternoon.
The colder air aloft will also lead to increasing instability
tomorrow afternoon as daytime heating occurs, with ensemble mean
CAPE of around 100-300 J/kg along and west of the mountains, good
enough for Southern CA. The NBM has a 15-20% chance of
thunderstorms tomorrow afternoon, and even if thunder doesn`t
occur, there will certainly be enough instability for another
round of scattered showers. Showers will generally end by late
Thursday evening. While NBM precipitation probabilities are less
than 10% on Friday, hi-res guidance is suggesting another round of
showers on Friday as the low lingers nearby and we get another
burst of afternoon instability, mainly over the mountains.

Through Thursday, additional rainfall accumulations of up to 0.20"
for the coasts and valleys, and up to around 0.40" in the
mountains, is expected. Given how scattered the showers will be,
some areas may receive little or no rain/snow. Additional snow
accumulations will be around 1-3 inches with locally higher
amounts above 7500 ft. Otherwise continued cool conditions through
Friday with high temperatures well below normal. Noticeable
warming will begin on Saturday as the upper trough begins to shift
east.

Previous discussion...
By Sunday, daytime high temperatures rise to above seasonal
averages as the upper level low pressure trough moves east and
a ridge of high pressure moves over the region from the west. A
weak trough of low pressure moves inland to the north but will
have minimal impacts for SoCal. A more robust high pressure ridge
begins to build over the west on Tuesday and by Wednesday,
temperatures will rise to as much as 18 degrees above seasonal
averages in the inland valleys.


&&

.AVIATION...
030300Z...Coast/Valleys/Coastal Mountain Slopes...SCT to
occasionally BKN clouds based between 2500-4500 feet MSL, with tops
reaching 7000 feet, will continue to fill in throughout the night.
Cigs below 3000 feet MSL and -SHRA most likely far inland against
the west-facing slopes, mainly in San Diego County. West-northwest
winds gusting 15-25 kts near the coast are currently diminishing,
and will continue to do so throughout the night. Clouds will lower
and become more widespread, more widespread -SHRA return. Cloud
bases will locally lower to 2000-3500 feet MSL, lowest in any
isolated -SHRA developing through the morning, most likely near
mountains and in San Diego County. Bases rise again to mostly above
3000 ft MSL after 13Z Thu. Partial scattering will occur late
Thursday morning into the afternoon, but clouds and -SHRA will
linger along the coastal slopes and in San Diego County. -SHRA
tapering off by 05Z Thu. There will be some CIGs redeveloping after
05Z Thu, mostly for the coastal an inland valleys of San Diego
County, with bases around 1500-3000ft MSL.

Desert Mountain Slopes/Deserts...Mostly clear skies tonight. Some
bases around 4000-5000ft MSL could provide some isolated -SHRA and
possibly even -TSRA over the mountains tomorrow afternoon. Westerly
winds are continuing to weaken, with gusts now below 35 kts for most
locations. They will further decrease and gradually become calm
overnight.

&&

.MARINE...
Winds and seas are continuing to gradually diminish from the inner
coastal to the outer coastal waters this evening through early
Thursday. See the Small Craft Advisory for details. Winds and seas
will further decrease going into tomorrow and beyond, and no
additional hazardous marine conditions are expected through Sunday.

&&

.BEACHES...
Surf of 3 to 6 feet, with local sets to 7 feet, in San Diego County
may still generate dangerous rip currents, and hazardous swimming
conditions, through this evening. Surf will gradually subside
overnight and into Thursday. The High Surf Advisory is in effect
through 10 PM PDT this evening and contains more details, which will
likely be allowed to expire, given that conditions are currently
improving, and are expected to continue to do so.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory until 11 PM PDT this evening for San Diego
     County Coastal Areas.

PZ...Small Craft Advisory until 7 AM PDT Thursday for Waters from San
     Mateo Point to the Mexican Border Extending 10 to 60 nm out
     including San Clemente Island.


&&

$$

PUBLIC...SS
AVIATION/MARINE/BEACHES...Stewey