Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service San Diego California
424 am PDT sun Jun 25 2017
hot weather will continue for inland areas today under high
pressure aloft. For Monday through Wednesday...high pressure will
weaken and onshore flow will strengthen with the marine layer
deepening and cooling spreading inland. Areas of night and
morning coastal low clouds and fog will spread into portions of
the valleys for Tuesday and Wednesday with high temperatures
returning to near average on Wednesday. Minor day to day
temperature changes are then expected into next weekend with the
marine layer becoming a little shallower.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
High pressure aloft centered over southern Arizona and northwest
Mexico will continue the hot weather for inland areas today.
Desert areas will experience high temperatures similar to those of
Saturday while hotter portions of the inland Empire may be a few
degrees warmer than Saturday as the marine inversion is stronger
and a little shallower than 24 hours ago.
Early this morning...satellite imagery shows widespread stratus
over the coastal waters extending into the far western valleys of
San Diego County and spreading northward along the Orange County
coast. The band of mid level moisture that brought isolated
thunderstorms Sunday afternoon to the north slopes of the San
Bernardino northward into the upper deserts has moved to the
north. However...residual mid level moisture may still be
sufficient for some clouds over the mountains this afternoon.
For Monday through Wednesday...high pressure aloft will begin to
weaken and low pressure systems moving inland to the north will
strengthen the onshore flow. Cooling will begin to spread inland
on Monday with high temperatures returning to near average on
Wednesday. Slight deepening of the marine layer is possible on
Monday with greater deepening expected for Tuesday and Wednesday.
This will push night and morning coastal low clouds and fog into
the western valleys early Tuesday morning...and into portions of
the inland valleys by early Wednesday morning with the local
workstation WRF nest of the GFS showing a weak coastal eddy
Wednesday morning. The stronger onshore flow will also bring
stronger and gusty southwest to west winds to the desert slopes of
the mountains into the deserts each late afternoon through late
For Thursday into next weekend...minor day to day temperature
changes are then expected with the marine layer becoming a little
shallower. Mid level moisture could bring a few clouds to the
mountains Friday and Saturday afternoons.
240915z...coast/valleys...stratus with bases 600-900 ft mean sea level
continuing to fill in along the coast this morning and should spread
10-15 sm inland by 14z. Areas of vis 3-5 sm where stratus nears
higher coastal terrain. Stratus clearing 15-18z, though some beaches
may remain broken through the afternoon. Marine layer will be much more
shallow tonight into Monday morning. Low confidence in timing of low
clouds/fog at coastal airports...likely not until after 08z. Bases
will be around 300-500 ft msl, possibly lower. Areas of fog with vis
below 1sm possible along the coast and up to 5-10 miles inland
should any stratus develop.
Mountains/deserts...a few cu may develop over the mountain ridges
during the late morning and afternoon, dissipating by sunset.
Otherwise mostly clear with unrestricted vis through Monday morning.
northwest wind gusts near San Clemente Island may reach 20-25 kt
during the afternoons and evenings Sunday through Tuesday,
potentially resulting in conditions hazardous to small craft.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
California...excessive heat warning until 9 PM PDT Monday for Coachella
Valley-San Diego County deserts-San Gorgonio Pass near
Heat advisory from 10 am this morning to 9 PM PDT this evening
for Riverside County mountains-San Bernardino County
mountains-San Bernardino and Riverside County valleys-the
inland Empire-San Diego County mountains-Santa Ana
Mountains and foothills.
Excessive heat warning until 9 PM PDT this evening for apple and