Scientific Forecaster Discussion
fxus66 ksgx 172142
Area forecast discussion
National Weather Service San Diego California
242 PM PDT Tue Sep 17 2019
low pressure over the west will bring cooler weather this week,
with more extensive coastal clouds during nights and mornings.
Gusty winds are expected in parts of the mountains and deserts
each afternoon and evening. The low pressure weakens Friday,
bringing warmer weather and less coastal cloudiness this weekend.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
* cooler through Thursday, then warming this weekend
* elevated fire weather conditions mountain crests to the deserts
* dry weather favored through next week, but watching a tropical
moisture surge early next week
Onshore wind flow will strengthen through Thursday as a closed
upper low off the Pacific northwest opens up and dives
southeastward over the intermountain west. The result will be
cooler temperatures through Thursday as the onshore pressure
gradient increases. Temps this afternoon are running 2-5f degrees
cooler compared to this time yesterday.
The trough will pull away from the region ahead of another trough
poised to dig southeastward this weekend into early next week.
Weak offshore flow will ensue Friday and into the weekend with
GFS and European model (ecmwf) both show a significant (pw near 2 inches) tropical
moisture surge into Arizona ahead of this upper feature during
the early to middle part of next week before the upper trough
moves east. GFS and ec ensembles favor dry weather for our socal
service area, in line with wpc quantitative precipitation forecast next 7 days, showing no rain
over socal. However, it is Worth noting that a few members do show
1"+ of rain into the lower deserts centered around next Tue-Wed.
So this will be something that we will be keeping an eye on over
the next few days...to see the placement of the upper trough and
moisture pull from the south early/mid part of next week.
As that trough pulls away from the region during the latter part
of next week, another period of weak offshore winds could occur
with warm temperatures prevailing.
Looking ahead through month's end, above normal temps are favored
with no strong signal for precipiation.
171930z...coast/valleys...VFR conditions expected for rest of today.
Patchy low clouds with bases 1200-1800 ft mean sea level will redevelop along
the coast after 08z Wed, and gradually extend inland. Intermittent
ceilings will impact coastal taf sites 10z-16z Wed. Only visible
restrictions will occur on elevated coastal terrain obscured by
Mountains/deserts...VFR conditions prevailing through Wednesday.
Near the surface, gusty west winds 20-30 kt primarily over the
mountains and through passes and canyons.
northwest winds will strengthen slightly on Thursday evening, when some
locations over the outer waters near San Clemente Island may see
gusts approaching 20 kt at times. Otherwise, no hazardous boating
conditions are expected through Sunday.
gusty and locally strong onshore winds are expected each afternoon
and evening from this afternoon through Thursday. Top gusts
should reach 35 to 45 mph. These local winds will combine with low
inland humidity to elevate fire weather conditions for favored
pockets along mountain ridges, through mountain passes and into
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.