Alpine, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

640
FXUS66 KSGX 250507
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
907 PM PST Wed Dec 24 2025

.SYNOPSIS...
Heavy rain will move southward across the area today along with a
slight chance of thunderstorms. The heavy rain will decrease from
the northwest this evening with scattered showers continuing
through Christmas Day. Another round of more widespread showers is
expected for Thursday night and Friday. Gusty south winds will
continue through this evening with gusts to 40 mph near the coast
and to 55 to 75 mph along the desert slopes of the San Bernardino
County mountains. Snow levels above 9000 feet this morning will
fall to around 6500 to 7500 feet on Thursday and Thursday night,
then fall to around 5500 feet for the weekend. Chances for showers
will decrease for the weekend, then may increase again around
Wednesday and Thursday of next week.

&&

Update: Most of the heaviest rain has now exited the CWA. There was
some very heavy rainfall which occurred earlier in the day for the
Lytle Creek area, and particularly for the town of Wrightwood,
where several structures were flooded. There were also reports of
portions of Highway 2 becoming impassable due to debris flow. Some
locations within this region have also reported total rainfall
amounts exceeding one foot. Given the magnitude of the amount of
precipitation received across this area, I have decided to extend
the Flood Watch for the counties of San Bernardino and Riverside
until 6 AM tomorrow morning. This is mainly also due to the
excessive rainfall taking longer to work through the local
drainage systems within urban areas. Additional rainfall overnight
may also worsen the threat of this. As far as San Diego is
concerned, conditions have continued to improve, with waters
receding within Mission Valley dropping below Action Stage, due to
this, I have decided to end the Flood Watch for San Diego County.


More showers will be possible throughout Christmas Day tomorrow as a
secondary low begins to move through and increases the chance of
rain going into the overnight hours tomorrow. These showers will
continue to be possible through Friday and going into the early
hours on Saturday. As the low exits the region on Saturday, it will
lead to much drier conditions going into the early half of next
week.

Previous discussion submitted at 230 PM:

Tonight through tomorrow night...

A very strong major shortwave trough with an associated atmospheric
river continues to bring in bouts of very heavy rain, as well as
strong and gusty winds, to all of southern California at this time.
Due to this, and given the orientation of southerly flow, some of
the locations within the southern facing slopes of the San
Bernardino Mountains is currently experiencing substantial rainfall
rates, at times of more than an inch per hour. Because of this,
there has been a few locations, as well as Wrightwood, which has
been experiencing a life-threatening situation with high rising
waters overtaking some of the urbanized areas. Per San Bernardino
County Fire, portions of Highway 2 have been inundated with flooding
and debris flow, to the amount of some of these areas becoming
impassible. Rainfall rates within some of these locations so far
have been up to 8-9 inches so far, with several more inches possible
through this evening as the heavy band of rain along the leading
front boundary associated with this system continues to slowly
transition across the region throughout this evening. Other rainfall
amounts where some of the heavier rain has already moves into Orange
County have been more on the order of a half and inch to just over
an inch of rain. Along with the threat of much more heavy rain
filling in throughout this afternoon will also come to possibility
of a few thunderstorms, whether they spawn ahead of the leading edge
of the boundary, or embedded within the heavier band of precip. In
addition to the heavy rainfall are very strong and gusty winds out
of the south-southeast direction ahead of the boundary, with some of
the higher locations, as well as along the coast, getting wind gusts
occasionally over 50 mph, and this will continue throughout the
afternoon. There will also the outlying chance of a waterspout or
two with some of these storms as they approach the shoreline.

After the first initial wave moves through, winds will switch around
to a more westerly direction and showers will become more
intermittent. Going into the overnight hours, winds should begin to
decouple a bit a weaken. Additional rainfall amounts may still
exceed an inch for some of the west-facing slopes of the foothills.
As the longwave major shortwave trough positioned over the E Pacific
waters continues to propagate east with the trough axis
transitioning from more of a negative orientation to a positive
one, it will allow for a secondary shortwave to slide southward
and just off the coast of southern California. This will keep the
possibility of showers still in the forecast throughout the day on
Christmas. Winds will remain gusty out of the west, and there
will still be the slight chance of a few thunderstorms during the
day as some of these open-celled cumulus clusters move onshore.
This chance of showers will continue to increase into the
overnight hours tomorrow and into Friday morning. Snow levels will
also drop to around 5500-6500 feet tomorrow, so areas such as Big
Bear may receive a few inches of snow.

Friday through the middle of next week...

On Friday, as the secondary wave transitions over the region, there
will be some additional showers continuing throughout the day, and
then the chance will taper off by later in the evening and into
Saturday morning from northwest to southeast. There will be a break
in the chance of rain throughout the weekend into early next week as
an upper level low within the weakening longwave trough becomes cut
off well to southwest of the region and remains there until it
begins to propagate back up towards the northeast and towards
southern California. A consensus with the deterministic models still
does have this influencing the region with increasing chances of
precipitation by next Tuesday into Wednesday, although this is still
quite far out in the forecast, and especially with it being cut off
to be considered reliable at this time, and is therefore subject to
change. However, we will continue to monitor this for the
possibility of it bringing a return to unsettled weather right
around the turn of the new year.

&&

.AVIATION...
250430Z....Coasts/Valleys...Rain has mostly ended but -SHRA will be
possible through 12z. Bases are varying quite a bit, ranging from
1800ft to 3500ft MSL, and remain very patchy. Gusts up to 25-30 kts
at times possible through 12z. MVFR/low end VFR conditions will
continue through Thursday morning. Low clouds will scatter out or
rise more efficiently after 12z, with most locations returning to
VFR by 16-18z. Still, lingering FEW-BKN clouds with bases at or
above 5000ft MSL expected, especially for Orange County into
Thursday afternoon. Low level clouds develop again Thursday evening
generally after 02z Fri, with bases anywhere from 1500-3500ft MSL.

.Mountains/Deserts...-SHRA may continue through 12z with MVFR CIGs
and brief IFR in any heavier RA. Otherwise, bases generally above
3500ft MSL. 35-45 kt gusts downwind of mtns and into the High Desert
through Thursday with gusts locally to 55 kts through passes. Mod-
strong up/downdrafts near mtns and into the High Desert. Scattering
out of low clouds Thursday morning with generally VFR thereafter.

&&

.MARINE...
Southerly winds are weakening, but both winds and seas will remain
hazardous to small craft through early Thursday morning. Gusts up to
20-25 kts possible.

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.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Flood Watch until 1 AM PST Thursday for San Diego County Coastal
     Areas-San Diego County Deserts-San Diego County Mountains-
     San Diego County Valleys.

     High Surf Advisory until 11 AM PST Saturday for Orange County
     Coastal Areas-San Diego County Coastal Areas.

     Wind Advisory until 10 PM PST this evening 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.

     Flood Watch until 6 AM PST Thursday 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 Gorgonio Pass near
     Banning-Santa Ana Mountains and Foothills.

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

PZ...Small Craft Advisory until 4 AM PST Thursday for Coastal Waters
     from San Mateo Point to the Mexican Border and out to 10 nm-
     Waters from San Mateo Point to the Mexican Border Extending
     10 to 60 nm out including San Clemente Island.


&&

$$

PUBLIC/UPDATE...Stewey
AVIATION/MARINE...Zuber