National Weather Service Forecast Discussion

Dicussion provided by the National Weather Service Forecast Office located in San Diego, California

FXUS66 KSGX 212027

Area Forecast Discussion
National Weather Service San Diego CA
130 PM PDT Wed Aug 21 2019

High pressure over the southwest that brought the hot weather the
past two days will weaken and drift east tonight. Thursday and
Friday won`t be quite as hot as a trough of low pressure brings
stronger onshore flow and a deeper marine layer. It will feel a
little more humid this weekend as moisture moves in from the south.



High pressure aloft brought another hot day to the valleys and
deserts today where most areas were 2-5 degrees higher than
yesterday. The airmass was also exceptionally dry with single digit
humidities in the lower deserts (3% at Borrego at 1 PM). Relative
humidities were in the teens in the Inland Empire. A shallow marine
layer kept areas near the coast cooler and more humid. At 1 PM, the
San Diego Airport was 74 degrees with a RH of 73%.

Temperatures will trend lower Thursday and Friday as an unusually
deep trough for late August moves inland across the northern Great
Basin. The marine layer will gradual deepen through Friday with low
clouds reaching the western valleys Friday morning.

Saturday through Tuesday...Tropical Depression Ten-E was 540 miles
south of the of southern tip of Baja this morning. It is forecast to
slowly strengthening to Tropical Storm status tonight as it moves
west-northwest at ~15 mph. By Friday morning it briefly reaches
hurricane status 900 miles southwest of the southern tip of Baja,
then weaken back to a TS Saturday as it moves northwest over colder
waters. Track uncertainty is normally quite high with eastern
Pacific tropical systems and this one is no different. A few
ensemble member runs support an influx of moisture into SoCal for
small chances for precipitation early next week, but the majority
keep us dry.


211945Z...Coast...Patchy areas of low clouds will develop after 10Z
Thursday. Bases will be 500-900 ft MSL with local vis of 3-5 SM BR
possible where clouds intersect higher coastal terrain. Best chance
of low cloud coverage is in San Diego County. Low confidence cigs
will form at KSNA, and moderate confidence cigs will form at KCRQ.
Low clouds and vis restrictions will clear by 17Z Thursday.

Valleys/Mountains/Deserts...Mostly clear with unrestricted vis
through Thursday.


No hazardous marine conditions are expected through Monday.


A long period south-southeast swell will make its way into the area
Sunday-Tuesday. This will increase the surf to 3-5 ft with local
sets to 6 ft along south facing beaches. Elevated surf will increase
the risk for strong rip currents. Minor coastal flooding is possible
in low lying areas. Remember to always swim near a lifeguard.


Skywarn activation will not be needed this week.


CA...Excessive Heat Warning until 8 PM PDT this evening for Apple and
     Lucerne Valleys-Coachella Valley-San Diego County Deserts-
     San Gorgonio Pass Near Banning.





NWS SGX Office Area Forecast Discussion