Frost Advisory 4, NWS San Diego, CA

323 
WWUS76 KSGX 251231
NPWSGX

URGENT - WEATHER MESSAGE
National Weather Service San Diego CA
431 AM PST Sat Feb 25 2017

...Patchy frost for portions of the inland valleys early this
morning...

...Periods of strong gusty west winds for the mountains for
tonight into Monday evening. 

.With clear skies...light winds...and a dry air mass... 
temperatures in portions of the inland valleys will fall into the 
lower to mid 30s early this morning with areas of frost. A pair of
low pressure systems from the northwest will bring periods of
gusty west winds for the mountains and the northern Coachella
Valley for tonight into Monday evening.

CAZ055-056-058-065-251615-
/O.NEW.KSGX.WI.Y.0012.170226T0000Z-170228T0600Z/
San Bernardino County Mountains-Riverside County Mountains-
San Diego County Mountains-San Gorgonio Pass Near Banning-
Including the cities of Crestline, Big Bear City, Big Bear Lake, 
Wrightwood, Julian, Pine Valley, and Desert Hot Springs
431 AM PST Sat Feb 25 2017

...WIND ADVISORY IN EFFECT FROM 4 PM THIS AFTERNOON TO 10 PM PST
MONDAY...

The National Weather Service in San Diego has issued a Wind
Advisory, which is in effect from 4 PM this afternoon to 10 PM
PST Monday. 

* WINDS...Areas of west winds 20 to 30 mph with gusts to 45 mph.
  Local gusts to 55 mph...mainly late Sunday night into Monday
  evening.

* TIMING...One round of stronger winds is expected for tonight
  with a second round of stronger and more widespread winds for
  Sunday night into Monday evening.

* LOCATION...Strongest winds near mountain ridge tops onto the
  desert slopes of the mountains...and across the northern
  Coachella Valley below the San Gorgonio Pass. 

* IMPACTS...Driving will be hazardous for high profile vehicles.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Wind Advisory means that winds of 35 mph are expected. Winds
this strong can make driving difficult...especially for high
profile vehicles. Use extra caution.

&&

$$

CAZ048-050-251600-
/O.CON.KSGX.FR.Y.0004.000000T0000Z-170225T1600Z/
San Bernardino and Riverside County Valleys-The Inland Empire-
San Diego County Valleys-
Including the cities of Corona and Escondido
431 AM PST Sat Feb 25 2017

...FROST ADVISORY REMAINS IN EFFECT UNTIL 8 AM PST THIS MORNING...

* LOCATION...wind sheltered valleys

* TEMPERATURE...lower to mid 30s.

* IMPACTS...Damage to sensitive vegetation if left uncovered.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Frost Advisory means that widespread frost is expected.
Precautions should be taken to protect sensitive outdoor plants.
Make sure pets left outdoors have adequate shelter.

&&

$$

17

Area Forecast Discussion
National Weather Service San Diego CA
742 AM PST Fri Feb 24 2017

.SYNOPSIS...
Continued dry and cool through Saturday with patchy frost possible
in the valleys again Saturday morning. For Sunday and Monday...
cooler with periods of rain and snow showers as a pair of low
pressure systems moves south along the Coast. High pressure aloft
and weak offshore flow will bring dry and warmer weather again
Wednesday through Friday with periods of weak offshore flow.

&&

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

Skies were mostly clear across SoCal this morning, except for a few
high clouds. It was a chilly start to the day with little cloud
cover and light winds. Temperatures fell to near freezing in some
valley areas this morning. The Miramar sounding had a 5 degree C
inversion based near 4500 FT MSL and indicated a very dry atmosphere
with a PW of only 0.33 inch. Surface pressure gradients from the
coast to the deserts were nearly neutral at 7 AM PST. This has
resulted in mostly light winds across the forecast area.

Look for a slow increase in high clouds on Saturday, and a few
degrees warmer after a chilly start, with possible frost again in
the valleys. No forecast changes this morning

From previous discussion...

A low pressure system will move southward along the central
California coast on Saturday night and move inland across Southern
California on Sunday. The current forecast leans towards the
ECMWF...but confidence remains low on the timing and amounts of any
precipitation. Based on the ECMWF timing...some lighter
precipitation could reach areas bordering Los Angeles County late
Saturday night with generally light to possibly locally moderate
precipiation moving through southwest California on Sunday. A second
low pressure system moving southward along the West Coast could
bring another round of light to possibly moderate precipitation late
Sunday night into Monday.

Confidence is low with the timing and amounts of any precipitation,
but rainfall could range from around one-quarter inch near the
coast, to one-half to three-quarters of an inch in the mountains
through early Tuesday, with local amounts exceeding one inch on the
south slopes of the San Bernardino County mountains. The most
widespread precipiation is expected for Sunday...and again for late
Sunday night into Monday morning. Snow levels will lower to around
5000 feet on Sunday...and 4000 to 4500 feet on Monday.

In addition to any precipitation...these low pressure systems are
expected to bring cooling with gusty west to northwest winds in
the mountains and deserts. Periods of advisory strength winds are
possible near the mountain ridge tops onto the desert slopes of
the mountains for Saturday night into early Sunday...and again
Sunday night into Monday morning. Some showers could linger into
early Tuesday.

Slight warming for Tuesday...then greater warming for Wednesday
through Friday with periods of mostly weak offshore flow.

&&

.AVIATION...
241540Z...P6SM vis through Saturday morning. FEW-SCT clouds AOA
20000 ft msl becoming SCT-BKN by 25/1200 UTC.

&&

.MARINE...
Another storm may bring a period of showers and gusty winds sometime
Sunday and Monday, but confidence in timing and expected impacts
remains low at this time.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.

&&

PUBLIC...JAD
AVIATION/MARINE...Harrison