Area Forecast Discussion
Issued by NWS San Diego, CA
FXUS66 KSGX 260437
Area Forecast Discussion
National Weather Service San Diego CA
937 PM PDT Tue Apr 25 2017
At 9 pm PDT, weakening onshore surface pressure gradients were
creating weaker winds compared to yesterday at this time, with
westerly wind gusts of 25-35 mph being reported in portions of the
mountains and deserts. Tightening pressure gradients from an
upper-level trough passing to our north will create westerly wind
gusts of 50-60 mph along portions of the mountains and deserts,
with highest gusts along desert mountain slopes Wednesday night. A
Wind Advisory has been issued for the aforementioned areas from 1
pm Wednesday through 3 am Thursday. A few areas of patchy fog may
develop tonight over portions of the coast and coastal valleys.
Otherwise, the previous forecast remains on track.
A trough moving by to the north will create windy conditions in
the mountains and deserts Wednesday afternoon through Wednesday
night. A warming trend will develop Wednesday through Friday. On
Friday and Saturday a trough moving across the Great Basin will
bring minor cooling along with gusty north winds in the mountains
and deserts. Warmer with lighter winds Sunday and Monday with high
pressure building aloft.
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
Subsidence behind an upper level wave in fast northwest flow
aloft combined with increasing gradient winds will result in gusty
winds in the mountains and deserts Wednesday. Winds will start to
increase around Noon Wednesday and remain strong through the
evening before dropping off around 3 AM. Sustained westerly winds
of 20 to 30 mph will gust to 50-60 mph, with highest gap winds in
the wind prone passes like the San Gorgonio Pass.
Model cross-sections show the potential for weak to moderate
mountain waves with an inversion near 7000 feet. Strongest winds on
the eastern slopes will be 60 mph, but it doesn`t look like these
strong winds will make it to the desert floor. Expect winds of 20-30
mph with gusts to 45-50 mph in the San Diego Deserts and parts of
the Coachella Valley Wednesday in the late afternoon and evening.
Our weather this week will be dominated by northwest flow between
low pressure over the Great Basin and a large upper ridge over the
eastern Pacific. Circulations around these two features are apparent
in the IR loop, with low clouds and cyclonic over the Great Basin,
and cirrus in anticyclonic flow over the northern Pacific. Cirrus
clouds will drift across SoCal in the fairly stagnant pattern this
Wednesday and Thursday will be warmer than today as the Great Basin
low lifts east and heights increase. On Thursday night the flow
aloft turns northerly as an inside slider moves south across the
Great Basin and into AZ. A period of blustery north winds will
filter through the Cajon Pass and into the northern Coachella
valley. The northerly flow will bring a few degrees of cooling
Friday and Saturday.
On Sunday and Monday, the high pressure aloft off the California
coast will exert more of an influence on our weather, bring max
temperatures that will be 5 to 10 degrees above average.
260350Z...Coast/Valleys...FEW-SCT clouds 1500-3500 ft MSL and SCT-
BKN clouds layers AOA 15000 ft MSL through Wednesday evening.
Mountains/Deserts...SCT-BKN cloud layers AOA 15000 ft MSL and
unrestricted vis through Wednesday evening.
Northwest winds gusting to around 20 kt and combined seas near 10 ft
will gradually lower overnight.
Northwest winds and seas will increase again Thursday afternoon
through Friday, with a return of Small Craft Advisory conditions
likely. Winds and seas will lower again over the weekend.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
CA...Wind Advisory from 1 PM Wednesday to 3 AM PDT Thursday for Apple
and Lucerne Valleys-Coachella Valley-Riverside County
Mountains-San Bernardino County Mountains-San Diego County
Deserts-San Diego County Mountains-San Gorgonio Pass Near