Area Forecast Discussion
Issued by NWS San Diego, CA
FXUS66 KSGX 272035
AREA FORECAST DISCUSSION
National Weather Service San Diego CA
135 PM PDT SAT AUG 27 2016
High pressure to the southwest will bring a warming trend into early
next week. As the marine layer thins, low clouds and fog will pull
back toward the coast through Tuesday. For the middle and latter
part of next week...a trough of low pressure will redevelop along
the West Coast, bringing a cooling trend and slow deepening of the
marine layer. Even cooler weather is possible for the Labor Day
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
The marine clouds cleared most areas by 1 PM PDT, but may linger
along some coastal areas well into the afternoon. Cumulus clouds
were evident over the mts as well, otherwise skies were sunny.
Surface pressure gradients were a bit weaker onshore than yesterday,
but a few stations in the mts were still reporting peak wind gusts
of 25-30 MPH.
Expect the marine clouds to move back inland this evening, but
should be less extensive than last night with the marine layer
expected to lower considerably. Easterly flow from convection farther
to the east of the forecast area has advected some higher sfc/
boundary layer dewpoints into the mts. The added moisture and clouds
over the mts could result in an isolated shower, but should not be
sufficient for widespread shower activity.
The weak upper-level trough over the region today will slide east
through Monday as high pressure off the coast builds NE across
SoCal. This will result in a dramatic drop in the marine layer depth
Sun into Tue. It will also drive max temps back to average far
inland on Sun, then above average Mon/Tue most areas.
The warm weather will be short-lived as another long wave trough
develops along the West Coast by the middle of next week. This will
keep our late summer temperatures below average, with the model
trends indicating a cool Labor Day weekend shaping up as the marine
layer and the upper-level trough deepen. Even though both the 12Z
GFS/ECMWF model solutions show troughing along the West Coast, the
ECMWF is digging the trough more aggressively off the Coast. This is
the outlier, so it will be discounted for now, but if it verifies,
the weather could be warmer than currently forecast over the Holiday
The chance for any significant monsoonal moisture reaching SW CA
looks very small during the next week, but may have a short window
open from around the middle through the end of next week.
272015Z...Coast/Valleys...Patchy BKN stratus near the immediate
coast with bases 2500-3000 ft MSL will continue this afternoon.
Stratus will spread through coastal areas 02Z-06Z and up to 30 miles
inland by 12Z Sun. KONT could have a CIG for 2-3 hours after 12Z.
Bases will be lower, mostly 1400-1800 ft MSL with tops to 2200 ft
MSL. Areas of vis 2-4 mi will occur in the valleys 09Z-16Z Sun. Most
areas will clear early Sun, mostly 15Z-17Z. Forecast confidence is
moderately high, especially with the lowering of cloud bases/tops.
Mountains/Deserts...Sct cumulus with isolated TCU will occur over
the deserts of San Bernardino County and most mountain areas through
02Z this evening, with bases mostly at/above 9000 ft MSL. Isolated
cumulus will be possible Sunday afternoon. Otherwise, mostly clear
skies with unrestricted vis will prevail through Sunday.
No hazardous marine weather is expected through Thursday.
Skywarn activation will not be needed today.