Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/25/25

Area Forecast Discussion

National Weather Service San Diego CA

 158 PM PST Fri Jan 24 2025

.SYNOPSIS... For the weekend into early next week, a cold low
pressure system from the north is expected to much cooler weather
with widespread showers and mountain snow for Saturday night through
Tuesday. Dry and warmer weather is expected for the remainder of the
work week.

&&

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

Southwesterly flow aloft is bringing in some subtropical moisture in
the form of cirrus clouds across the region. We continue to monitor
an area of low pressure that is starting form across Northern
California. As this occurs, the pressure gradient will tighten,
leading to increased winds over our area on Saturday.
Southerly winds will strengthen, becoming breezy for areas along
the coast and western valleys and higher across mountains and
deserts. Areas near the desert slopes of the mountains may see
wind gusts near 55 mph, closer to 40-45 MPH at times across the
deserts. Temperatures will also take a tumble on Saturday, where
the coast to the mountains will see temperatures 5 to 10 degrees
cooler than today.

Latest hi-res WRF and HRRR guidance shows us scattered light showers
starting around Saturday afternoon for areas around Orange County
into the Inland Empire. This will push eastward across parts of
Riverside and San Diego County overnight. Model guidance shows
better agreement in the storm system potentially stalling, giving
greater amounts of precipitation to northern San Diego County into
Orange County. There is low confidence in the exact path of this,
but it`s movement will be pertinent to who sees the most rainfall.
The movement will be slow with this system, where heaviest rainfall
will occur later on Sunday into Monday. This will mostly be a light
to moderate rain event, so looking quite beneficial overall. Most
areas west of the mountains will see total amounts over one half
inch with high confidence, over one inch with moderate confidence.
Desert areas will also see rainfall during this event, most areas
seeing near one quarter of an inch, likely more than one half of an
inch across the high desert. Confidence remains low on any chances
for thunderstorms around Sunday night or Monday morning, but they
cannot be ruled out.

As stated above, this system will be a cold one. High temperatures
by Sunday and Monday will be 10-15 degrees below average widespread
50s west of the mountains, 40s into the high desert. Winter Storm
Warnings are now in effect for the Riverside and San Bernardino
County mountains along with a Winter Weather Advisory for San
Diego County mountains above 4,500 feet from late Saturday
afternoon through Monday afternoon. The snowfall forecast
confidence is moderate, with heaviest snow falling by Sunday into
Monday as snow levels lower near 3,500 feet, locally near 3,000
feet in northern areas. Areas over 6,000 feet will see around
12-18 inches, 3-6 above 4,000 feet in the SBD/RIV Co mountains.
Snowfall may even occur across higher elevations of the high
desert, but accumulation for larger population centers there will
be slim.

Small waves of energy within the area of low pressure may slow the
system further into Tuesday, where chances of precipitation start
to shrink but still are present. After this time, drier and warmer
weather will occur across the area through the work week. Models
diverge in solutions by next weekend, but uncertainty remains on
if the storm door squeaks open a bit further as we head into the
month of February.

&&

.AVIATION... 242145Z....Mostly clear skies today with some high
clouds. Onshore flow is established this afternoon with light winds
overnight. Increasing south to southwesterly winds Saturday morning,
gusts up to 20-25 mph possible along the coasts and valleys, and up
to 30 to 40 mph for the mountains and adjacent foothills. Low clouds
are expected to increase Saturday afternoon after 18-21 with bases
near 2000-3000ft MSL.

NWS San Diego is aware of limited communications of observations
from KTRM since January 8th. We are working with the FAA to address
this issue.

&&

.MARINE...
There is a slight chance of thunderstorms Sunday evening, any of
which could produce locally gusty and erratic winds, lightning, and
briefly hazardous conditions. Otherwise, prevailing winds and seas
are not expected to generate hazardous marine conditions today
through Wednesday.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Winter Storm Warning from 4 PM Saturday to 4 PM PST Monday for
     Riverside County Mountains-San Bernardino County Mountains.

     Winter Weather Advisory from 4 PM Saturday to 4 PM PST Monday
     for San Diego County Mountains.

     Wind Advisory from 10 AM Saturday to 6 AM PST Sunday for Apple
     and Lucerne Valleys-San Diego County Deserts.

PZ...None.

&&

$$

PUBLIC...APR
AVIATION/MARINE...Munyan