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Area forecast discussion 
National Weather Service San Diego California
445 am PDT sun Jul 13 2014

Synopsis...
increasing monsoonal moisture will bring a chance of thunderstorms
to the mountains and upper deserts this afternoon and early evening
with the possibility of strong gusty winds. For tonight and
Monday...an upper level disturbance from the southeast and greater
monsoonal moisture will bring a slight chance of showers and
thunderstorms late tonight through Monday morning with greater
chances of thunderstorms with locally heavy rainfall Monday
afternoon and early evening for the mountains...deserts...and
inland valleys. Thunderstorm chances will decrease for Tuesday
afternoon with dry weather expected for Wednesday through Saturday.

&&

Discussion...for extreme southwestern California including
Orange...San Diego...western Riverside and southwestern San
Bernardino counties...

Short term (today through tuesday)...
monsoonal moisture is continuing to steadily increase across the
lower deserts with GPS integrated precipitable water sensors showing
precipitable water values increasing during the past 24 hours from
0.6 inch to nearly 1.4 inches. The NAM shows values fluctuating near
this value into early this evening...with a more substantial influx
of monsoonal moisture from the southeast late tonight into Monday
pushing precipitable water values to around 2 inches. The NAM
appears to have the best handle on the diurnal convection for the
next three days. The available moisture today will mainly be middle
level with the lower levels still dry with soundings having an
inverted v profile. Thunderstorms near the mountains and upper
deserts this afternoon and early evening may initially have strong
gusty winds and somewhat limited rainfall. That rainfall potential
may increase somewhat later in the afternoon if moisture increases
somewhat.

For late tonight into Monday morning...an inverted trough from the
southeast will bring a surge of lower level moisture in addition to
middle and high level moisture. This will also bring a slight chance of
showers and thunderstorms late tonight into Monday morning. Movement
of any thunderstorms is expected to be fast enough to limit heavy
rainfall. The NAM and European model (ecmwf) both show higher level moisture
decreasing from the east Monday afternoon and evening. This would
increase the potential for enough heating in the mountains and
deserts for greater thunderstorm development during the afternoon
and early evening. Precipitable water values will be quite high and
higher resolution models keep convergence boundaries in the
mountains nearly stationary towards the coastal side of the
mountains. If that heating does occur to support greater
thunderstorm development...the potential for flash flooding would
be quite high for the mountains and portions of the upper
deserts...but the flash flood potential index is kept at moderate
for now given the uncertainty with the surface heating. There are
sufficient surface boundaries in the inland Empire to support
thunderstorm development with sufficient heating. But such surface
heating is even less certain there.

For Tuesday...lower level drying is already underway...but enough
residual moisture may remain to support a chance of thunderstorms in
the afternoon...mainly for the San Bernardino County mountain and
desert areas...in line with the NAM.

Night and morning coastal low clouds and fog will become patchier
through Tuesday.

High temperatures will be a little warmer today for most
areas...then cooler with the increasing moisture and cloud cover on
Monday.

&&

Long term (wednesday through saturday)...
drying that began Tuesday should continue Wednesday through Friday
with no thunderstorms expected. Monsoonal moisture may begin to
return from the southeast next weekend late Saturday into Sunday.
With drying aloft...greater coverage of night and morning low clouds
and fog is expected for Wednesday through Friday with coverage
extending inland to the western valleys with coverage becoming a
little patchier again during next weekend. Temperatures will be near
to slightly below average.

&&

Aviation...
130945...coasts/valleys...patchy stratus with bases 1000-1400 feet mean sea level
and tops to 1800 feet mean sea level will slowly fill in along the coast and
spread into the western valleys by sunrise. Stratus clearing 15-17z.
Expect stratus to be patchy again tonight...with periods of ceilings
1000-1500 feet mean sea level between 14/06-17z. Low confidence in timing of
onset at coastal airports. Otherwise...sct-bkn clouds at or above fl200
through this afternoon...becoming broken-overcast at or above fl150 tonight.

Mountains/deserts...slight chance of thunderstorms mainly over the
mountains this afternoon with bases around 10000 feet and tops up to
35000 feet. Otherwise...unrestricted visible with scattered-broken clouds at or above
fl200 through this afternoon...becoming broken-overcast at or above fl150 tonight.

&&

Marine...
300 am...no hazardous marine weather conditions expected through
Thursday.

&&

Beaches...
high tides are expected to be near to slightly above 7 feet for the
open coastline again this evening...which could result in local
minor tidal overflow of low-lying beach areas. A beach hazards
statement continues through late this evening...see laxcfwsgx.

&&

Fire weather...
increasing monsoonal moisture will bring a chance of thunderstorms
to the mountains and upper deserts this afternoon and evening.
Initially...thunderstorms could have strong gusty winds and a few
dry lightning strikes. However...as the monsoonal moisture continues
to increase...there will be greater potential for wetting rains
later in the afternoon. For tonight and Monday...an upper level
disturbance from the southeast and greater monsoonal moisture will
bring a slight chance of showers and thunderstorms late tonight
through Monday morning with greater chances of thunderstorms with
wetting rains Monday afternoon and early evening for the
mountains...deserts...and inland valleys. Thunderstorm chances will
decrease for Tuesday afternoon with dry weather expected for
Wednesday through Saturday.

&&

Sgx watches/warnings/advisories...
California...beach hazards statement through this evening for the beaches in
the Orange County coastal areas...San Diego County coastal
areas.

Pz...none.

&&

$$

Public/fire weather...17
aviation/marine...sunset

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