Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 192119

Area Forecast Discussion
National Weather Service San Diego CA
219 PM PDT Sun May 19 2019

An unseasonably cold storm system will drop south across California
today, moving over SoCal early Monday morning with periods of
showers and possible thunderstorms. Wintery weather will revisit
the mountains as the snow level falls below 6000 feet, resulting
in accumulating snow for many resort areas north of San Diego
County. Winds will be strong and gusty over all of the mountains,
deserts, and coastal waters all the way through Tuesday. Continued
cool Monday, with showers ending in the morning. Some scattered
light showers are possible on Tuesday, otherwise it will be mostly
dry and cool ahead of the next round of showers and mountain snow
to arrive on Wednesday. A deep marine layer will remain in place
through the week due to a strong onshore flow pattern, with
daytime temperatures remaining well below normal.



At 1 PM, water vapor satellite showed an upper-level low centered
just north of San Francisco, with a trough moving south over Point
Conception and another trough just to our south over northern
Baja. The precipitation from the first trough has mostly ended,
however colder air behind and strong, moist, onshore flow is
starting to help develop isolated showers across the Coastal
Basin. No lightning has been observed yet over our area, but the
storms developing this afternoon could have a few strikes. The
greatest chance for lightning will be this evening and overnight
as the second, colder trough moves across the region. Showers
could be heavy at times, and help snow levels lower a bit more
compared to surrounding areas in the mountains. Although light
snow fell down to 6000 ft overnight, the snow level quickly rose
to 7000-7500 ft by late morning. As the second trough moves across
the region later, snow levels will crash down to 5500 ft with
accumulations possible above 6000 ft. The stronger showers tonight
could create heavy snow at times, especially above 7000 ft. The
Winter Weather Advisory remains in effect through early Monday
morning for total snow accumulations of 1 to 3 inches from 6000 to
7000 ft, 3 to 6 inches above 7000 ft, and localized amounts up to
8 inches above 8000 ft. The coastal mountain slopes could see an
additional inch to inch and a half of precipitation by Monday
morning, with lesser amounts of a tenth or two as you head to the

Winds have also picked up today with strengthening pressure
gradients. the latest highest wind gust summary is on our webpage,
and includes a gust to 56 mph at Whitewater and 70 mph in Burns
Canyon. The Wind Advisory remains in effect for the desert
mountain slopes and adjacent desert areas through late Tuesday.

Westerly winds are looking even stronger late Tuesday as another
system takes aim at California. More precipitation and lower snow
levels return, with only a brief break in the precipitation and
strong winds late Monday. Multiple waves moving around the low
could create periods of precipitation Tuesday through Thursday.
Friday looks dry at this time, then wet weather could return again
for the weekend with another system moving across the region. This
pattern will keep high temperatures well below seasonal normals
for inland areas this time of year, with some areas staying 15 to
25 degrees below normal. Several areas could break their lowest
high temperature records over the past few days. Coastal
locations will only be a few degrees below normal since they are
usually cloudy and cool this time of year anyway.


192100Z...Coast/Valleys...BKN-OVC low clouds with VRB bases 2000-
6000 FT MSL should briefly clear from terminals 19/22Z-20/03Z. MOD
confidence in SHRA returning to TAF sites late evening after 04Z
with similar cigs. Confidence is lower in KSNA seeing SHRA. Coverage
will then decrease from NW to SE...Orange County/Inland Empire
clearing around 20/14Z, with KSAN/KCRQ likely clearing 3 to 5 hrs
later. MOD confidence in period of stronger W SFC winds gusting 20-
25 kts through 20/03Z at coastal/valley TAFs.

Mountains/Deserts...OVC skies with scattered SHRA will persist over
the mtns into tomorrow morning. W winds will continue to strengthen
this afternoon, with MOD-STG UDDFTS and LLWS likely over and east of
the mtns where SFC winds are expected to range between 25-35 kts,
with gusts 40-55 kts. Clouds will obscure terrain along the coastal
slopes at times, reducing vis to 2-4 SM in BR. Strong NW winds late
afternoon and evening at KPSP/KTRM, with gusts to 30 to 35 kts. AWW
in effect 19/20Z-20/09Z for KPSP for possible gusts 35-40 kts.


WNW winds will increase in strength late tonight with gusts to 25
kts over the Outer Waters early Mon. Winds will weaken slightly Mon
evening into Tue morning, but could remain above Small Craft
Advisory thresholds over the Outer Waters, before quickly increasing
late Tue into Wed. Gusts of 30-35 kts look possible over the Outer
Waters late Tue. Winds will be accompanied by combined seas of 10-14
ft and rough conditions. A Small Craft Advisory remains in effect
through 3 PM Wednesday.

Showers along with a slight chance of thunderstorms and an isolated
waterspout will be possible late this afternoon and evening over the
coastal waters.


A slight chance of thunderstorms late afternoon and evening with an
associated risk of lightning at the beaches. Confidence is low-

Building medium-period WNW swell will generate locally elevated surf
conditions Monday into early Tuesday, with surf up to 7 FT,
especially in southern San Diego County. A Beach Hazards Statement
is in effect between 3 AM Monday and 9 AM Tuesday.


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


CA...Winter Weather Advisory until 5 AM PDT Monday for Riverside
     County Mountains-San Bernardino County Mountains.

     Wind Advisory until 11 PM PDT Tuesday for Apple and Lucerne
     Valleys-Coachella Valley-Riverside County Mountains-San
     Bernardino County Mountains-San Diego County Deserts-San
     Diego County Mountains-San Gorgonio Pass Near Banning.

     Beach Hazards Statement from late tonight through Tuesday
     morning for Orange County Coastal Areas-San Diego County
     Coastal Areas.

PZ...Small Craft Advisory until 3 PM PDT Wednesday for Coastal Waters
     from San Mateo Point to the Mexican Border and out to 30 nm-
     Waters from San Mateo point to the Mexican Border Extending
     30 to 60 nm out including San Clemente Island.



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