Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 211037
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
337 AM PDT Fri Jul 21 2017

.SYNOPSIS...
A high pressure ridge will bring seasonally hot weather inland
through the weekend. A surge of monsoonal moisture early next
week could produce a few afternoon thunderstorms over the
mountains Monday and Tuesday.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

High pressure will dominate the weather on this TGIF and
throughout the weekend ahead. The result will be benign weather
conditions. Marine layer stratus is more formidable this morning
and looks to continue in this state throughout the weekend, so
morning and nighttime low clouds will plague the coast to the
inland valleys, but we expect sunshine to the coast each
afternoon.

A few showers occurred yesterday over eastern sections of San
Diego County. However, moisture has since decreased. As such, no
additional convection is expected. Hi-res models keep it dry and
concur.

The ridge will slide east as a large scale trough moves into the
U.S. west coast early next week. Meanwhile, an inverted mid-level
trough will move towards the west across northern Mexico,
eventually rounding the SW periphery of the ridge, getting pulled
northward into Southern California early next week. This could
result in active weather for the area as it brings a marked
increase in moisture, especially at mid levels (PW perhaps to near
2 inches). A low level moist surge looks likely across the lower
deserts, making for a humid time there early next week...and
potentially bringing conditions ripe for a few desert tstorms.

There are some model differences in the placement of the
trough/moisture plume. While some increase in moisture looks to
begin during the day on Sunday, the larger influx of moisture
will occur Sunday night or Monday. Held off on adding tstorms to
the forecast for Sunday. The better chance of showers and
thunderstorms looks to be on Monday-Tuesday over the mountains and
portions of the deserts. However, as was the case recently, it is
possible we could see a few tstorms develop anywhere should
elevated instability becomes high enough. That will be something
to monitor. For now confined tstorm chances to the
mountains/desert regions.

The inverted trough/high moisture will depart the area to the
northeast late Tuesday as the northern stream large scale trough
over northern into central California grabs it, sending it
northeast. This will bring back a drier airmass for the middle to
latter part of next week.

&&

.AVIATION...
210930Z...Coast/Valleys...Low clouds will cover most of the area
from the coast to 20 miles inland this morning. Bases will be 1000-
1500 ft MSL with tops to 1800 ft MSL. Expect local vis 3-5 miles til
16Z where clouds and terrain intersect. Most areas will clear 15Z-
17Z. Low clouds expected to develop again this evening, impacting
coastal TAF sites 06-09Z Sat with SCT-BKN cigs 1000-1500 ft MSL.
Confidence in timing is moderate.

Mountains/Deserts...Local surface gusts over 25-35 knots from the
west are likely late this afternoon/evening on desert mountain
slopes and through San Gorgonio Pass. Otherwise, mostly clear with
unrestricted vis will prevail through tonight except for SCT clouds
with bases AOA 8000 ft MSL this afternoon.

&&

.MARINE...
No hazardous marine weather is expected through Tuesday.

&&

.BEACHES...
High tides will reach near or above 7 feet during the mid-to-late
evenings each day through Sunday. This could result in minor
tidal overflow at low lying beach areas during times of high
tide. A Beach Hazards Statement has been issued.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement from this afternoon through Sunday
     evening for Orange County Coastal Areas-San Diego County
     Coastal Areas.

PZ...NONE.
&&

$$

PUBLIC...Gregoria
AVIATION/MARINE...PG



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