Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
132 PM PDT Thursday Jul 2 2015
isolated thunderstorms possible today across portions of the
mountains and deserts. Drier Friday with smaller precipitation
chances across the region. Dry on Independence day...then slight
chance of thunderstorms Sunday afternoon over portions of the
mountains and deserts with a small increase in monsoonal moisture.
Westerly flow aloft early next week will create dry and seasonal
weather. Night/morning low clouds will develop over the coast and
valleys through the period.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
The 02/1200 UTC GFS and European model (ecmwf) are in relatively good agreement
through the long-term.
At 1 PM PDT...water vapor satellite imagery displayed a broad
upper-level high stretching from northern California to western New
Mexico...and an upper-level low around 550 miles SW of San Diego.
Visible satellite showed cumulus build-ups over the
mountains...and low-level clouds over portions of the coastal
Diurnal heating...combined with a moist atmosphere...will
continue the possibility of isolated showers and thunderstorms
over portions of the mountains and deserts through this afternoon.
The main threats with storms will be lightning...gusty winds...and
isolated flash flooding. Negative vorticity advection is likely
inhibiting convection so far this afternoon. However...an isolated
thunderstorm or two will still be possible...mainly over the San
Bernardino County mountains
The aforementioned upper-level high will sag south
Friday...transitioning middle and upper-level flow from southeast to
more southerly. This will help cut off the monsoonal moisture over
the area...and limit afternoon thunderstorm activity on Friday to
the San Bernardino County mountain peaks.
The high will transition further south over the
weekend...continuing the development of night/morning low clouds
over the coast and valleys and dry weather on Saturday. A slight
intrusion of monsoonal moisture to the mountains and deserts on
Sunday will create the possibility of isolated afternoon
thunderstorms. Then conditions will dry out in the middle and upper-
levels as the cut-off upper-level low moves closer to the region
to our north...shifts middle-level flow to the southwest...and
maintains onshore flow with near seasonal weather and high
temperatures into early next week.
022024z...coast/valleys...through 03/0600 UTC...unrestricted visible and
few-scattered clouds at or above 10000 feet mean sea level. 03/0600-1500 UTC...stratus
gradually developing 10-20 sm inland...with bases 700-1000 feet
mean sea level...tops around 1500 feet mean sea level and areas of visible 3-5 sm. Chance that
visible could drop to 1-2 sm during the 03/1300-1500 UTC time-period for
the coastal taf sites...but confidence is low. Local visible at or below 1 sm
likely for locations 5-20 miles inland...particularly higher
terrain. Confidence in stratus occurrence is moderate-to-
high...except there is low confidence in stratus/fog making it into
kont. Clearing of stratus/fog during the 03/1500-1900 UTC time-
Mtns/deserts...slight chance of showers and thunderstorms through
03/0100 UTC...mainly over the mountains and high deserts. Thunderstorm
bases will be near 8000 feet mean sea level with cumulonimbus tops to 40000-45000 feet mean sea level.
Any storms that form may produce moderate-strong up/downdrafts...frequent
lightning...and reduced visible to 3sm or less in rain. Otherwise...few-
scattered clouds at or above 10000 feet mean sea level with unrestricted visible prevailing through
124 PM...no hazardous weather is expected through Tuesday.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.