Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
912 PM PDT Friday Jul 29 2016
an increase in monsoonal moisture over the next few days will
lead to a better chance of afternoon and early evening heavy
showers and thunderstorms over the mountains and deserts through
Tuesday while conditions remain fair west of the mountains.
During the middle to latter part of next week, drier air is
forecast to move in as a West Coast trough develops. This will
lead to decreasing chances of mountain and desert thunderstorms
then. Patchy night and morning marine layer low clouds and fog
will continue to be possible over the coast and western valleys.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
A few thunderstorms developed over the mountains today, but they
were kept in check with no significant impacts. The Max rainfall
recorded was 0.20 inches at Baldwin Lake. 28 lightning strikes
occurred across the mountains and high deserts.
Very active convection is occurring across Arizona including the
greater Phoenix Metro. Thunderstorm outflows continue to lead to
tstorm development further and further west. A large convective
complex is also going over Mexico just south of Arizona. We will have
to see if perhaps eventually some of this outflow or an mesoscale convective vortex comes
from this activity. However, the high res models continue to only
show isolated convection in our mountains and deserts each of the
next few days.
Models show monsoonal moisture increasing from the east to
southeast direction through next Tuesday, with precipitable water
reaching 1.4 inches Saturday, 1.7 inches Sunday and Monday, and
1.8 inches Tuesday. This moisture, in addition to instability
produced by daytime heating, will result in chances for afternoon
and early evening heavy showers and thunderstorms over the
mountains and deserts through at least Tuesday. Storm motion looks
light on Saturday and Sunday, which would increase the flash flood
threat, especially on Sunday when more low level moisture moves
in. The storm motion increases slightly from the east on Monday
and Tuesday, which could result in thunderstorms developing over
the coastal slopes. However, with a 700-300 mb wind of only 10 kt,
it will likely be light enough to continue to the higher flash
Although moisture starts to decrease Wednesday into Thursday,
wouldn't be surprised if there was still enough moisture and
instability to create isolated afternoon/early evening showers
and thunderstorms over the mountains on those days. Meanwhile,
onshore flow will continue to result in patchy night and morning
stratus/fog over the coast and western valleys.
30400z...coast and valleys...patchy stratus will develop within 10-
15 miles of the coast through 14z Saturday, with greatest coverage
expected over South Dakota County. Cloud bases will be between 800 and 1400 feet
mean sea level with tops at or below 1500 feet mean sea level. Local vis restrictions of 1-3 sm will
occur where stratus intersects higher coastal terrain. Clearing to
the coast is expected by 16z Saturday with light sea breezes
Mountains and deserts...scattered thunderstorms will develop
between 18z Saturday and 02z Sunday. Storms may produce strong
uddfs and llws, lightning and small hail. Otherwise, unrestricted vis
and sky clear-scattered at or above 10000 feet mean sea level will prevail through Saturday.
no hazardous marine weather is expected through Tuesday.
with increasing monsoonal moisture and instability, afternoon
and early evening thunderstorms are likely to develop over the
mountains and portions of the deserts through at least Tuesday.
The thunderstorms may initially produce dry lightning strikes
today and Saturday, and then becoming mainly wet strikes by
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.