Severe Thunderstorm Warning 1, NWS San Diego, CA

Area Forecast Discussion
National Weather Service San Diego CA
1017 AM PST Sat Feb 2 2019

.SYNOPSIS...A powerful storm centered off the northern California
Coast will drive a strong cold front across the area this
afternoon. Ahead of it, rain and wind will increase, peaking near
the front late this afternoon and evening. Scattered Showers will
linger behind the front through Sunday, becoming more numerous
Monday and Tuesday. Upslope flow onto the mountains will result in
more continuous rain and snow through the first half of next
week. Winter storm conditions are expected at times with heavy
snow accumulating above 6000 feet. Fair and a little warmer late
in the week, but another cold, wet storm system is possible by
next Saturday.

&&

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

...Update...

Satellite imagery is really impressive, showing a powerful Pacific
Storm centered off the NorCal coast. The cold front stretches
south and a heavy frontal band of showers lies along it. S-SW
winds are strengthening ahead of the frontal band with winds now
gusting into 25-35 mph range along the coast. Winds will
strengthen further ahead and along the frontal band with coastal
and even inland valley gusts of 40 mph expected and isolated
gusts to 50 mph even possible, strongest along the coast. These
winds are capable of downing trees.

Winds will blow much stronger in the mountains, especially from
the ridge tops to the high deserts with severe gusts of 60-80 mph
expected. In fact, an 81 mph gust was just recored at Burns Canyon
on the desert slopes of the San Bernardinos!

Timing of the frontal band (heaviest rainfall) still is into
Orange County at or shortly after the noon hour then to San Diego
in the 3-4 PM time frame. This band will produce widespread
rainfall amounts of 0.5-1.5" as is passes by, lasting 1-2 hours as
it is progressive.

The rainfall amounts/intensity expected is enough to push the San
Diego River into minor flood at Mission Valley, so a Flood Warning
for the river was just issued. Flood stage is 11.3 FT and a crest
to 11.3 FT is forecast.

Latest rainfall amounts, wind gusts, and storm reports are
headlined on our webpage weather.gov/sandiego

...Previous Discussion (Issued at 230 AM PST Sat Feb 2 2019)...

Satellite imagery early this morning shows an intense low pressure
center wrapping up off the northern CA coast. A sheet of clouds
extends south, covering much of CA. Radar this morning shows large
areas of weak echoes moving east off the water, and area rain gages
have been recording periods of light precipitation much of the
night. The freezing level is above 7000 feet and likely climbing due
to strong south flow. The sfc pressure gradient KSAN-KSFO was 15 MBS
at 1 AM PST supporting wind gusts over our mts to about 40 MPH. That
gradient is forecast to strengthen to about 20 MBS by morning which
should support the high winds called for today.

The deep storm west of SFO will peak this morning, then weaken
rapidly into Sunday morning as it drifts toward the Coast. The
strong front trailing south of the storm center will sweep across
SoCal later today proceeded by gusty south winds, and accompanied by
a period of moderate to heavy rainfall. Behind the front later
tonight, wind will drop off from the west and scattered showers are
expected to continue.

The hemispheric pattern will remain a stormy one for us though, as
several more waves deepen the mean trough along the West Coast with
more surges of precipitation and gusty onshore winds. Another wave
comes through Sunday night, followed by another Mon night through
Tue night. Precip is likely to continue on and off into Wednesday
before a break in the pattern allows us to dry out for a couple of
days late next week.

Winter Storm...This is going to be a messy situation and will likley
be revised for the San Bernardino Mts. The initial surge tonight
will see very strong and possibly damaging winds, rapidly falling
freezing levels, heavy fog, and low liquid to snow ratios. The snow
level should initially fall to around 5000 feet Sunday morning, but
rise to near 6000 feet again during the day. Another sharp fall is
likely again from Tue morning through Wed morning from 5500 to near
3000 feet. The current Winter Storm Warning begins late this
afternoon and goes through Sunday evening (above 6000 ft.) but
winter weather will linger through Wednesday and we will likley have
to reissue, redefine, and extend the winter weather products.

High winds...Winds will increase through the morning from the south
and should peak this afternoon. The wind field just a couple
thousand feet off the sfc is forecast to exceed 50 Kts. This will be
a significant wind for the area. Strongest will be on the ridges and
north slope of the San Bernardino Mts with peak gusts of 75 to 80
MPH. West of the mts, a peak gusts of 40 to even 50 MPH will be
possible just about anywhere, which is likley to cause palm fronds
to fall and may even topple diseased and lop-sided, shallow rooted
trees. Secure loose objects on patios that are likely to become
airborne and dangerous.

Rainfall/Hydrology...Rainfall rates of 1/2 to one inch per hour are
likley in the mts, and for a brief period at lower elevations. This
will result in some ponding of water and urban flooding where
drainage is not sufficient, and debris flows below recent burn
scars. Area rivers and streams will be flowing since the ground is
moist from previous rains, some aquifers have now filled
sufficiently, and channels have been opened up from previous rains.
None of our rivers are expected to reach flood stage, but flow may
be sufficient to close low-water crossings. Also, enough rain and
runoff is forecast to begin flows in the Whitewater Basin including
the Coachella Canal. See LAXESFSGX for details. Low-water crossings
in the Coachella Valley may be impacted by Sunday.

&&

.AVIATION...
021645Z...BKN-OVC layers 7000-10000 ft MSL and FEW-SCT layers 2000-
4000 ft MSL expected through the morning. Widespread RA beginning to
infiltrate from west to east late this morning into afternoon. Cigs
800-1500 ft MSL and 1-4 SM VIS, then rising to 3000-6000 ft MSL late
this evening with -SHRA continuing into Sunday. Coastal mountain
slopes remaining obscured through Sunday morning.

Strong winds will develop late this morning with areas of south
winds 15-25 kt gusts 30-40 kt near the coast and 20-40 kt gusts 50-
65 kt along the ridges and north slopes of the mountains, peaking
this afternoon. Winds will shift to the SW/W and weaken
substantially behind the cold front this evening.

&&

.MARINE...
South-southeast winds will continue to strengthen this morning, with
winds generally 20-30 knots with gusts 30-45 knots during the late
morning and afternoon. A cold front mid-late Saturday afternoon will
switch the winds to westerly, decreasing to 15-25 knots. Large wind
waves will result in choppy seas of 10-12 feet. Winds will be
lighter Sunday, but a combined seas will remain around 9-12 ft due
to a large west swell. A Gale Warning is in effect from 6 AM to 4 PM
PST this afternoon.

Conditions are favorable for isolated waterspouts in the vicinity of
the cold front this afternoon, though the thunderstorm potential is
minimal.

&&

.BEACHES...
A long period west swell of 10-12 ft/14-15 sec from 280 degrees will
arrive Sunday. This will generate surf of 4-7 ft with locally higher
sets in Orange County and 5-8 ft with sets to 10 ft in San Diego
County. A Beach Hazards Statement is in effect today for elevated
surf, followed by a High Surf Advisory on Sunday for the increasing
surf. Strong rip currents are likely throughout the weekend. Swell
and surf will subside through the day Monday.

&&

.SKYWARN...
Skywarn activation is requested all areas this afternoon into this
evening.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory until 6 PM PST this evening for Coachella Valley-
     Orange County Coastal Areas-Orange County Inland Areas-
     Riverside County Mountains-San Bernardino and Riverside
     County Valleys-The Inland Empire-San Diego County Coastal
     Areas-San Diego County Deserts-San Diego County Mountains-
     San Diego County Valleys-San Gorgonio Pass Near Banning-
     Santa Ana Mountains and Foothills.

     High Wind Warning until 6 PM PST this evening for Apple and
     Lucerne Valleys-San Bernardino County Mountains.

     Flash Flood Watch through this evening for Orange County Coastal
     Areas-Orange County Inland Areas-Riverside County Mountains-
     San Bernardino County Mountains-San Bernardino and
     Riverside County Valleys-The Inland Empire-San Gorgonio
     Pass Near Banning-Santa Ana Mountains and Foothills.

     Winter Storm Warning from 4 PM this afternoon to 9 PM PST Sunday
     for San Bernardino County Mountains.

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

     High Surf Advisory from 6 AM Sunday to 11 AM PST Monday for
     Orange County Coastal Areas-San Diego County Coastal Areas.

PZ...Gale Warning until 4 PM PST this afternoon 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.

&&

PUBLIC...Gregoria (Update)/Prev Discussion (10)
AVIATION/MARINE...APR

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>