Area Forecast Discussion
Issued by NWS San Diego, CA
FXUS66 KSGX 252029
AREA FORECAST DISCUSSION
National Weather Service San Diego CA
129 PM PDT MON JUL 25 2016
Partly cloudy skies through Tuesday as a wave of humid air moves
through the region. There is a slight chance of showers and
thunderstorms this afternoon mainly in the mountains. High
pressure will bring slightly warmer weather this week with patchy
coastal clouds nights and mornings. For Friday through next
weekend, an influx of monsoonal moisture will bring cooling for
next weekend, and a slight chance of afternoon and early evening
thunderstorms, mainly near the mountains.
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
A wave of unstable air came out of Mexico last night and
generated a line of showers and isolated thunderstorms that
skirted the Mexico border this morning. No rain gauge measured
rainfall, but brief light showers and sprinkles were reported.
Some cumulus clouds were getting started in the San Bernardino
Mountains by midday because of surface based convection as the
sun warms the earth. The shield or blob of clouds over San Diego
and Riverside Counties seems to be inhibiting the surface heating
needed for convection. So the chance of thunderstorms is slight
in all mountains, but most likely in the San Bernardinos.
Meanwhile, patchy low clouds and fog were observed at the coast
even with this wave changing up the regular weather. High
pressure aloft will slowly build this week over the Southwest and
that will continue to feed monsoon moisture skirting our region
mainly just south of the border. Another wave of moisture is shown
by guidance to move through the region Tuesday much like this
morning but with an important difference: the moisture appears
higher up and more stable than the our current blob. That means we
don`t expect rain. Less moisture is expected Wednesday and
Thursday, but maybe enough for you to see a few higher clouds
along with cumulus over the mountains in the afternoons. The
marine layer and some coastal cloud coverage will continue each
night and morning, but rather random and patchy. Temperatures
inland will inch upward over the next few days, but only a few
degrees above seasonal averages. The moisture increases just
enough Friday to warrant small chances of showers and
thunderstorms in our mountains and deserts that afternoon. Over
the weekend the high pressure backs off as a low pressure trough
pushes down from the north. That will bring slightly cooler
weather and more coastal clouds. The monsoon moisture continues
sufficient to warrant a slight chance of showers and thunderstorms
in the mountains each afternoon Saturday through Monday.
252000Z...Coast/Valleys...Variable FEW/SCT low clouds along the
coast and SCT/BKN mid/high clouds through this evening. Low clouds
will redevelop along the coast late this evening, with bases 800-
1300 ft MSL and tops to 1600 ft MSL, and push around 15-25 SM inland
by early Tue morning. Vis of 2-4 SM BR is expected where low clouds
near higher terrain. Stratus will clear towards the coast by mid-Tue
Mtns/Deserts...Isolated TS are possible today over mtn peaks, with
gusty winds, strong up/down drafts, small hail and dangerous
lightning expected where storms develop. Conditions will improve by
this evening. Otherwise FEW-BKN high clouds through the period.
No hazardous marine weather is expected through Friday.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.