Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
940 PM PDT Tuesday Sep 16 2014
moist flow will continue Wednesday and bring another chance of
thunderstorms. Some minor cooling will occur as the high aloft
weakens. A return to onshore flow will bring more significant
cooling Thursday as a trough develops over the West Coast. This
trough will bring partly cloudy conditions Friday into the weekend
with temperatures mostly near or a little above seasonal normals.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Thunderstorms with strong...damaging winds developed along inland
valley convergence boundaries this afternoon. Downed trees and power
lines were reported in several communities including Mission
Valley...El Cajon and tierrasanta in San Diego County...and Lake
Elsinore in Riverside County. The inverted-v profile on the 00z
Miramar sounding is a classic example of strong downburst wind
potential with midlevel moisture above drier air below 6000 feet.
The heat of the day provided plenty of fuel as valley temperatures
exceeded 100 degrees. Uc Riverside had a high of 111...Chino was
109...and Riverside Airport reached 108.
Easterly winds aloft were strong enough to overpower the afternoon
sea breeze and the T-storms propagated west toward the coastal
zones. In Orange County...strong thunderstorm winds impacted the
Santa Ana Mountains...San Clemente and Laguna nigel. In San Diego
County a line of storms brought strong winds from del Mar to North
Island. At 5 PM...Lindbergh Field had a wind gust of 45 miles per hour...and
Montgomery Field recorded a wind gust of 56 miles per hour. A funnel cloud was
reported just north of Big Bear Lake in the San Bernardino
Heavy rain brought flash flooding to the inland Empire where
Wildomar recorded 1.89" of rain. A rainfall summary and a record
temperature report in headlined on our homepage.
Tonight...precipitable water remains above 2 inches in deserts this
evening...and there is concern that high Theta-E air will interact
with an outflow boundary racing westward across the eastern deserts.
At 9 PM...this boundary was approaching the Salton Sea. It will
continue moving west toward the socal mountains with a chance for
nocturnal T-storms in the mountains and deserts tonight.
Wednesday...although Odile was downgraded to a tropical storm and
will continue track towards Southeast Arizona through Wednesday...moisture
will remain plentiful in socal so tomorrow will be another active
thunderstorm day. The main difference is that the boundaries will
set up a little farther east so the chances for T-storms in the
coastal zones will be a lot lower. The boundary will set up over the
eastern valleys or mountain foothills. Widespread T-storms will develop
over the mountains and deserts where precipitable water will still
be from 1.5-2.0 inches...and convective available potential energy will once again be over 1000
j/kg. Greatest threat tomorrow will be flash flooding since the
airmass with be a little more saturated through the column. Strong
thunderstorm downdraft winds will be more isolated.
As for the heat...Wednesday will be another very warm and humid day
and will flirt with heat advisory levels...but it will not be quite
at hot as it was today. On Wednesday night and Thursday a longwave
trough digging down the West Coast will bring greater cooling and
lower humidities from increasing onshore flow that will push the
subtropical moisture east.
The models stall this closed upper low over Southern California this
weekend and there may be a slt chance for shra/tstorms...but the
moisture and instability look marginal at this time. Early next week
a broad ridge of high pressure will build from the west bringing a
warming trend with temperatures at or above average.
170300z...scattered clouds at or above 5000 feet mean sea level with unrestricted visible through
Wednesday morning. Between 18z Wednesday and 03z Thursday...sct-bkn clouds
layered from 6000 feet to 35000 feet with thunderstorms and showers over
the mountains...deserts and inland valleys. Kont...kpsp and ktrm may
be impacted with reduced visible...and gusty and erratic winds vicinity
800 PM...no hazardous marine weather expected through Sunday.
at 8 PM...the San Clemente basin buoy continued to show a southwest
swell of 4 feet at 19 seconds...and the nearshore buoys showed a
south-southwest swell of 3 feet at 20 seconds. This swell will
continue to produce widespread strong rip currents and elevated surf
through Thursday. Surf of 4 to 6 feet with locally higher sets on
exposed southwest facing beaches is expected. The south-southwest
swell will slowly lower Friday into the weekend...diminishing the
surf and rip current threat.
Skywarn activation may be requested Wednesday.
California...beach hazards statement through Thursday evening for the
beaches in the Orange County coastal areas...San Diego
County coastal areas.