Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
1243 PM PDT Thursday Jul 24 2014
strong high pressure building over the southwest will bring hot
weather inland through Friday...followed by slow cooling and
increasing humidity this weekend. A shallow marine layer will
moderate temperatures near the coast. Monsoon moisture may produce a
few afternoon showers or thunderstorms over the mountains this
weekend. Quite warm again early next week under high pressure aloft.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Hot conditions this afternoon over the mountains have resulted in
some cumulus clouds...otherwise just some high cirrus clouds were
evident inland. Along the coast and over the coastal waters...low
marine clouds persisted locally. Clouds were more prevalent along
the western Baja California coast. At midday...temperatures were running 3 to 6
degrees above values observed yesterday at noon at many mountain and
valley sites. Blended satellite tpw shows over two inches over the
northern Gulf of California at midday. In addition...the precipitable water was slowly
increasing over socal from the southeast.
A heat advisory is in effect for the inland Empire...and the
mountains and lower deserts today and again for Friday. Along the
coast...a sea breeze and shallow marine layer will keep it cooler.
For tomorrow...models are showing an influx of monsoonal moisture
aloft which should increase higher clouds and raise dewpoints at
lower elevations. The added moisture and slight height falls should
result in lower afternoon temperatures...however with the added
humidity...it may be just as uncomfortable inland.
Along the coast...hi res models develop a weak eddy in response
cyclonic flow developing aloft and an advancing weak subtropical
wave from the south. This looks reasonable and should result in a
slight deepening of the marine layer and more extensive coastal
clouds in the morning. Overall...a bit cooler on Friday.
Slight chances of thunderstorms are in the forecast in the mountains
beginning on Friday and continuing through the weekend...mainly due to
the increased moisture. Instability looks marginal.
A strong subtropical high will remain anchored over the southern
rockies...but will flatten a bit...taking on more of an east-west
orientation with the ridge axis remaining from socal...east across
northern Texas...and the lower Mississippi Valley. While backing
upper-level flow will bring in more moisture aloft...the ridge axis
should keep instability in check and is expected to keep
thunderstorm activity to a minimum...until possibly later in the
weekend when the ridge axis becomes more aligned with The Rockies
and a weak easterly wave approaches. However...these nuances in the
flow are weak indicators at this point.
Slightly cooler through the weekend...then warmer again next week as
the persistent subtropical high builds back toward the southwest.
There will be some monsoonal moisture in the vicinity due to
southerly flow aloft...but thunderstorm chances look to remain muted
for any given period due to the uncertainty of tracking the very
weak easterly waves circulating around the high...and the various
model moisture field differences.
Along the coast...a shallow marine layer...mild ocean water temperatures...
and onshore flow should hold daytime temperatures to just a few
degrees above average.
242000z...coast/valleys...patchy stratus will occur this afternoon
along the immediate coast of San Diego County with local broken ceilings
around 800 feet mean sea level. For tonight...stratus will develop within 10-15
Michigan of the coast between 06z-12z...with greatest coverage in San
Diego County. Most ceilings will be 800-1000 feet mean sea level with tops to 1200 feet
mean sea level. Local visible below 3 Michigan will occur in the coastal valleys.
Ksan/kcrq/ksna will have ceilings...though timing is somewhat low
confidence. Most areas will clear by 17z Friday.
Mtns/deserts...unrestricted visible will continue through Friday. Mostly
scattered clouds will occur above 15000 feet mean sea level through Friday...with some
cumulus/towering cumulus with bases 9000 feet mean sea level Friday midday/afternoon with a slight
chance of thunderstorms over the mountains.
at 1 PM PDT...no hazardous marine weather through Monday.
spotter activation will not be needed today.
California...heat advisory through 9 PM PDT Friday for the Coachella
Valley...Riverside County mountains...San Bernardino County
mountains...San Bernardino and Riverside County valleys-the
inland Empire...San Diego County deserts...San Diego County