Alpine, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

027
FXUS66 KSGX 252257
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
257 PM PST Thu Dec 25 2025

.SYNOPSIS...
Light isolated showers in the San Bernardino
Mountains this afternoon become more widespread and heavier
overnight into Friday morning. Highest precipitation favored in
the northern mountains, with lighter totals closer to San Diego.
Shower activity weakens late Friday night, fully tapering off
Saturday morning. Drier and warmer weather early next week with a
possible Santa Ana event peaking Monday. Showers could return from
the south some time the latter half of next week centered around
New Year`s Day.

&&

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

Aviation discussion updated.

Today through Saturday...

Today features a lull between the moderate to heavy rainfall
observed across the region yesterday and a secondary surge of
moisture set to move through late tonight into Friday afternoon.
Very isolated showers remain possible through this afternoon for the
San Bernardino Mountains with relatively light accumulations through
midnight. The more defined band of precipitation will move through
the region beginning after midnight, spreading moderate rainfall
eastward, which may be heavy at times in the mountains. While
rainfall rates within this band of only 0.4-0.6"/hr expected, of
particular concern is the overly saturated portions of the San
Bernardino Mountains and adjacent drainage basins spreading into the
Inland Empire and High Desert regions. 4-8" of rainfall observed
yesterday (and locally up to 10") will likely lead to lower
intensities of rainfall required to lead to further instances of
flash flooding, landslides, and debris flow. With this, a Flood
Watch has been issued for the San Bernardino Mountains and adjacent
areas into the northern Inland Empire and High Deserts from midnight
Friday morning until 4 PM Friday afternoon. Behind the main band of
rain, light showers remain possible through Friday evening and
overnight, eventually tapering off by Saturday morning.

Expected additional rainfall totals from this band of rain is about
1-3 inches (and locally up to 4") for the San Bernardino Mountains,
1-1.5 inches for Orange County and portions of the Inland Empire
adjacent to the San Bernardino Mountains, with about 0.25-0.75"
for San Diego County coasts/valleys and the remainder of the
Inland Empire. Snow levels will generally remain between
7500-8000ft for a bulk of the precipitation tomorrow
morning/afternoon, through snow levels will rapidly fall to around
5000ft by Saturday morning as the upper low moves overhead. 2-3
inches of snow is possible near 7000ft with 8-12 inches possible
near mountain peaks.

Sunday through Late Week...

Much drier conditions expected come the beginning of next week after
this weekend`s system departs. However, a potent inside slider upper
trough helps to strengthen the offshore gradient, with a Santa Ana
Wind event looking more likely for Sunday into Tuesday. CW3E WRF
ensemble means suggest this could be a moderate strength event with
a ~60% chance of a moderate to strong event. Given the recent
rainfall, there is not as high of a fire concern, but the potential
for strong wind gusts through and below mountain passes is worth
noting. Weak upper level ridging coinciding with the downsloping
offshore winds will trend temperatures up to 5 to 10 degrees above
normal.

Attention quickly turns to cut-off low out in the south-central
Pacific that could bring the next shot of rain to southern
California. Global ensembles diverge significantly on the resolution
of this storm system, so uncertainty for this event is quite high.
Keep an eye on the forecast to see how this pans out, but early
indications hint that this will be a much less intense event than
yesterday`s atmospheric river.


&&

.AVIATION...
252245Z....Coasts/Valleys...FEW-BKN clouds with bases 3000-6000 ft
MSL expected, especially for the Inland Empire this afternoon. Low
level clouds develop again this evening generally after 02z Fri,
with bases anywhere from 1500-3500ft MSL. Low clouds may rise above
3000 ft MSL briefly Friday morning ahead of the incoming
precipitation. Moderate up/downdrafts downwind of the Santa Anas
into the Inland Empire through Friday morning.

.Mountains/Deserts...35-45 kt gusts along desert slopes of the
San Bernardino County mtns and into the High Desert through this
afternoon with gusts locally to 55 kts through passes. Mod
up/downdrafts near mtns and into the High Desert. Winds weaken some
this evening, but gusts 25-40 kts last through the period.

.Region-wide...A band of moderate to locally heavy rain moves into
the region from the west starting around 12Z Fri, though exact
timing is still uncertain, and moves across the area through the
daytime. A few hours of MVFR to locally IFR cigs/vis are expected as
the rain moves through. SCT -SHRA in the wake of the main band will
create intermittent cig/vis reductions into Saturday night.

&&

.MARINE...
South to southwest winds strengthen slightly again late Thursday
into Friday, with gusts intermittently exceeding 20 kts. Winds then
turn northwest and gradually decrease late Friday into Saturday.

&&

.Beaches...
Westerly swell will arrive tonight leading to surf building 5 to 8
feet Friday-Saturday. Highest surf for west-facing beaches. A Surf
Advisory is in effect now through Saturday afternoon.

&&

.HYDROLOGY...
Isolated light showers remain possible through this
afternoon across the San Bernardino County mountains, with
expected rainfall generally insignificant, but up to 0.25"
possible through midnight. More widespread showers and a more
defined band of rainfall is expected to push through the region
tonight into Friday. Maximum rainfall rates with this band of
0.4-0.6"/hr expected. Total additional rainfall of 1-3 inches (and
locally up to 4") for the San Bernardino Mountains, 1-1.5 inches
for Orange County and portions of the Inland Empire adjacent to
the San Bernardino Mountains, with about 0.25-0.75" for San Diego
County coasts/valleys and the remainder of the Inland Empire.
Given the 4-8" (locally up to 10") that fell in the San Bernardino
Mountains, resulting in widespread flash flooding and numerous
instances of debris flow in the mountains and surrounding
drainages, a Flood Watch is now in effect for the San Bernardino
Mountains, High Desert, and portions of the northern Inland Empire
adjacent to the mountains from midnight tonight through 4PM
Friday afternoon.

Rainfall will trend down in intensity Friday afternoon, but
additional light precipitation remains possible into Saturday
morning before clearing out completely late Saturday morning. Snow
levels fell below 7000 feet briefly today, but rise back to 7500-
8000 feet for most of the duration of the precipitation before
falling back to near 5000 feet by Saturday morning. 2-3 inches of
snow is possible near 7000ft with 8-12 inches possible near mountain
peaks.


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory until 11 AM PST Saturday for Orange County
     Coastal Areas-San Diego County Coastal Areas.

     Flood Watch from midnight PST tonight through Friday afternoon
     for Apple and Lucerne Valleys-San Bernardino County
     Mountains-San Bernardino and Riverside County Valleys-The
     Inland Empire.

     High Wind Warning until 3 PM PST this afternoon for Apple and
     Lucerne Valleys-San Bernardino County Mountains.

PZ...None.

&&

$$

PUBLIC...Munyan
AVIATION/MARINE/BEACHES...KW