Severe Thunderstorm Warning 10, NWS San Diego, CA

Area Forecast Discussion
National Weather Service San Diego CA
215 PM PDT Tue Sep 3 2019

.SYNOPSIS...
High pressure over the southwest will bring hot, humid weather this
week with scattered afternoon showers and thunderstorms over the
mountains and deserts. The weather will turn cooler and less humid
this weekend as a trough of low pressure moves inland over the West
Coast.

&&

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

Cumulus development today was an hour later than on Monday, with the
first storms forming over the San Bernardino Mountains at 11:30 AM.
Baldwin Lake picked up 0.28" of rain through 1 PM. Weak winds aloft
are preventing these pulse storms from lasting too long, with the
rain shaft cutting off the storm updraft. Brief moderate rain is
likely with these cells through early evening as they drift slowly
north-northwest. Some storms may move into the high desert.

The hot and humid airmass that's been in place since the start of
the Labor Day weekend will be in place through Thursday. Wednesday
will probably be the hottest day this week when the 850 mb temps and
2-meter temperatures reach their peak. Easterly midlevel winds will
be stronger tomorrow too, and there may be some additional warming
from downslope flow into the Inland Valleys. Heat Risk impacts on
Wednesday will be greatest in the Inland Empire where high
temperatures will be 100-106, or about 10-12 degrees above average.
A Heat Advisory was issued for the Inland Empire Wednesday. Thursday
will also be another hot and humid day.

Ocean water temperatures at the coast today ranged from 71 at
Huntington Beach to 77.5 at Scripps Pier. This is a contributing
factor to the high humidity in the coastal zones.

Easterly flow around the base of a 595 dm high over the Four Corners
will continue to stream warm, humid air into the area through
Thursday. Precipitable water values of 1.20" to 1.40" in the
mountains combined with afternoon heating and surface convergence
with the afternoon sea breeze will trigger afternoon thunderstorms
over the mountains and deserts through Thursday. The stronger
easterly winds Wednesday may send some storms into the far eastern
valleys.

A pattern change will bring cooler, drier weather to Southern
California this weekend. A trough moving inland across northern
California Friday will deepen and dig south down the West Coast
Saturday and Sunday. Stronger onshore flow will spread cooling
inland, and the marine layer clouds will return to the coastal zones
and western valleys.

&&

.AVIATION...
032020Z...Coast...Mostly clear with SCT clouds around 20,000 ft
through this evening. Low clouds and fog will redevelop tonight
along the immediate coast, with bases around 400-500 ft MSL. Low
confidence in impacts at coastal TAF sites overnight. Any low clouds
that form will clear by 16Z Wednesday.

Valleys/Mountains/Deserts...Scattered showers and thunderstorms
continuing through 01Z, mainly over the mountains and the High
Desert. Storms that develop will have cloud bases around 9000 ft MSL
with tops up to 40,000 feet. Gusty outflow winds and heavy rain are
likely in these storms.

&&

.MARINE...
Patchy dense fog is possible over the waters tonight into Wednesday
morning. Areas of visibility 1 mile or less possible. Otherwise, no
hazardous marine weather is expected through Friday.

&&

.SKYWARN...
Skywarn was activated for San Bernardino and Riverside Counties
today for afternoon thunderstorms.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory from 11 AM to 8 PM PDT Wednesday for San
     Bernardino and Riverside County Valleys-The Inland Empire.

PZ...NONE.

&&

PUBLIC...Moede
AVIATION/MARINE...Connolly

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN DIEGO CA
949 AM PDT TUE SEP 3 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0130 AM     HEAVY RAIN       1 NW PALM SPRINGS       33.83N 116.51W
09/02/2019  M0.98 INCH       RIVERSIDE          CA   ASOS

            PALM SPRINGS AIRPORT ASOS RECORDED 0.98 INCH
            OF RAIN BETWEEN 1:30 AM AND 5 AM ON 9/2. THE
            HEAVIEST RAIN WAS BETWEEN 2 AM AND 3 AM.

&&

SC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN DIEGO CA
219 PM PDT TUE SEP 3 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0500 AM     HEAVY RAIN       1 NNW PALM SPRINGS      33.83N 116.51W
09/02/2019  M0.98 INCH       RIVERSIDE          CA   ASOS

            0.98 INCHES OF RAIN 2 AM TO 5 AM. 0.70
            INCHES BETWEEN 2 AM AND 3 AM PDT.

&&

AOT

Special Weather Statement
National Weather Service San Diego CA
257 PM PDT Tue Sep 3 2019

CAZ058-062-032245-
San Diego County Mountains CA-San Diego County Deserts CA-
257 PM PDT Tue Sep 3 2019

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN SAN DIEGO COUNTY
UNTIL 345 PM PDT...

At 256 PM PDT, Doppler radar was tracking a strong thunderstorm near
Hwy S2 Between Canebrake And Imperial County Line, or near Mount
Laguna, moving southeast at 5 mph. Additional thunderstorms were
intensifying near Live Oak Springs and Boulevard.

Pea size hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Southeastern Mount Laguna, I-8 Between Boulevard And Imperial County
Line, I-8 Between Pine Valley And Boulevard, Boulevard, La Posta
Indian Reservation, Live Oak Springs, Manzanita Indian Reservation
and Campo Indian Reservation.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3283 11649 3292 11642 3269 11619 3262 11632
TIME...MOT...LOC 2156Z 330DEG 6KT 3281 11639

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