Big Bear Lake, California Weather Forecast Discussion

215
FXUS66 KSGX 271544
AFDSGX
Area Forecast Discussion
National Weather Service San Diego CA
844 AM PDT Sat Sep 27 2025
.SYNOPSIS...
Showers and thunderstorms are expected through this evening, with
the highest chances in the mountains and deserts. Areas of flash
flooding possible where heavy rain/thunderstorms develop. Isolated
showers and potentially thunderstorms have the potential to drift
into the inland valleys this afternoon. Slight chances of
thunderstorms continue for Sunday afternoon in the mountains, with
dry conditions expected Monday. High temperatures remain well below
normal with a deep marine layer through early next week. Gradual
warming expected Wednesday through the end of next week.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Visible satellite at 9 AM was showing widespread cloud coverage at
various levels from the coastal waters to the deserts. Radar was
showing a few light showers over the mountains and deserts, with
thunderstorms in Imperial County, eastern Riverside County, and
eastern San Bernardino County. Mid-level moisture will continue to
wrap around the north and west side of the low and into Southern
California today. As destabilization occurs late this morning and
afternoon, stronger showers and thunderstorms are expected to
develop over the mountains and high desert, drifting into the inland
valleys, Orange County, and lower deserts at times. Latest high
resolution guidance maintains hourly rainfall rates of 0.50-1 inch
per hour over the mountains and locally into the low deserts this
afternoon. A Flood Watch is in effect for the San Diego, San
Bernardino, and Riverside mountains as well as the San Gorgonio
Pass, Coachella Valley, and San Diego County deserts from 11 am to 7
pm today. Main concern is the potential for debris flows over the
burn scars and flooding of low-water crossings in the deserts. Any
shower that drifts west into the valleys is expected to have peak
rain rates of 0.20-0.30 inches per hour, if a thunderstorm develops
west of the mountains those rates will likely be exceeded.
The low pressure system will weaken and begin to move east on
Sunday. Enough moisture and instability will remain over the area to
leave a 10 to 20 percent chance of showers and thunderstorms for the
mountains Sunday afternoon. Rainfall rates on Sunday are expected to
be lower than Saturday, with high resolution guidance showing
rainfall rates below 0.50 inch an hour. Dry conditions are expected
by Monday.
Minor warming is expected through Monday, although temperatures will
remain several degrees below normal. An incoming short-wave trough
of low pressure will begin to influence our weather on Tuesday,
bringing cooler conditions with increased cloud coverage and breezy
winds in the mountains and deserts. High temperatures on Tuesday
will mostly be 5 to 10 degrees below average for inland areas to
locally 10 to 15 degrees below average for the higher elevations of
the mountains. This will be followed by slow warming through the
rest of the week with high temperatures on Friday still a few
degrees below average for inland areas. For now the forecast is dry
beyond Sunday, though there is the potential for tropical moisture
to become entrained in the southwesterly flow and into So Cal around
Wednesday, but considerable spread remains the precipitable water
ensemble forecasts.
&&
.AVIATION...
271530Z....Coasts/Valleys/Foothills...OVC clouds with bases
generally 3000-4000 ft MSL are covering the coastal basin this
morning with additional FEW-BKN clouds locally between 1500-2000 ft
MSL. Gradual scatter out for most areas 17-20Z. 20-30% chance for
SHRA/TSRA 19Z-02Z for the inland valleys and western mtn foothills,
including the Inland Empire. TSRA passing over a site will bring
gusty, erratic winds and brief heavy rain leading to reduced vis 2-5
SM. Low clouds 2000-3500 ft MSL redevelop for inland valleys and
foothills after 00Z, then expand to cover the coastal basin after
28/05Z. Below the main cloud layer, several additional FEW-BKN cloud
layers are possible locally down to 1500 ft MSL.
Mountains/Deserts...TSRA are being observed throughout SE California
this morning, drifting into the desert slopes and mountains in the
coming hours. Additional scattered SHRA/TSRA (40-60% chance) will
develop across mountains and deserts 18Z-03Z, including a 30% chance
for TSRA at KPSP/KTRM. TSRA passing over a site will bring gusty,
erratic winds, reduced cigs/vis with brief heavy rain, and frequent
lightning.
&&
.MARINE...
Slight (5%) chance for a stray thunderstorm to develop over waters
through tonight. Otherwise, no hazardous marine conditions are
expected through Wednesday.
&&
.BEACHES...
Slight (5%) chance for a stray thunderstorm to develop at the
beaches through tonight.
South swell from Hurricane Narda will arrive this weekend. 4-5 feet
swell with a period of 12-14 seconds will produce elevated surf and
a high rip current risk Sunday through Tuesday, especially for south
facing beaches, where sets could reach 8 feet, and strong alongshore
currents at all beaches. More information can be found in our Beach
Hazards Statement, which is in effect from 6 AM Sunday until 11 PM
Tuesday.
&&
.SKYWARN...
Skywarn activation is requested.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement from Sunday morning through Tuesday
     evening for Orange County Coastal Areas-San Diego County
     Coastal Areas.
Flood Watch until 7 PM PDT this evening for 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...CO
AVIATION/MARINE/BEACHES...Westerink

NWS SGX Office Area Forecast Discussion