Scientific Forecaster Discussion
fxus66 klox 292104
Area forecast discussion
National Weather Service Los Angeles/Oxnard California
204 PM PDT Sat Apr 29 2017
gusty offshore winds and continued warming west of the mountains
can be expected through today. A transition to onshore flow will
bring cooler conditions to the coast but some locations will warm
across interior areas as high pressure builds overhead through at
least early next week.
Overall, 12z models in good synoptic agreement through the period.
At upper levels, ridge will remain over the eastern Pacific,
maintaining a northwest flow pattern aloft over the district. Near
the surface, flow will become weakly onshore to the east and
remain weakly offshore from the north.
Forecast-wise, excitement levels will be low through the period.
For this afternoon/tonight, offshore gradients will continue to
weaken. So, there will be some locally gusty northeast this
afternoon/tonight, but remain below advisory levels. So, the wind
advisories will be allowed to expire at 200 PM today. With the
continued weak offshore flow, skies should remain mostly clear
tonight and Sunday. As for temperatures on Sunday, weak onshore
flow will return on Sunday, so coastal and coastal valley areas
should be cooler (especially along the beaches) while interior
sections actually warm a few degrees.
For Sunday night and Monday, high resolution models continue to
indicate an eddy spinning up over the bight. If this develops as
forecast, some stratus/fog will be likely across the la coastal
plain and southern coastal waters. So, will keep stratus/fog in
the forecast. Other than this potential stratus, skies should
remain mostly clear across the area Sunday night/Monday. As for
temperatures on Monday, coastal/valley areas of Ventura/la
counties will cool a few more degrees. However, interior sections
will warm a couple of degrees as well as the central coast (due to
a little offshore push Monday morning).
For Monday night/Tuesday, 12z models indicate little change in any
parameters. So, will go with a relative persistent forecast: clear
skies except for some la County coastal stratus and little change
in temperatures from Monday.
Overall, 12z models continue to exhibit good synoptic agreement
through the period. At upper levels, ridge will move across the
district Wednesday/Thursday with a unseasonably potent trough
developing along the West Coast Friday/Saturday. Near the surface,
weak diurnal flow prevails Wednesday/Thursday then onshore flow
reestablishes on Friday/Saturday.
Forecast-wise, Wednesday/thurday look to be rather benign days.
With upper ridge over the area on Wednesday and to the east on
Thursday, skies should remain mostly clear although some
night/morning stratus will be possible across southern areas.
Temperatures will remain above seasonal normals with Wednesday
likely the warmest day with some slight cooling on Thursday. No
wind issues are anticipated Wednesday/Thursday.
For Friday/Saturday, things start to change. Through the
Friday/Saturday time frame, sharp upper trough will approach the
West Coast and develop a closed low off the central coast on
Saturday. With this pattern, onshore flow will be on the increase
which should allow for an increase in night/morning stratus/fog
across the area (especially on Saturday morning). Outside of any
stratus, mid/high level clouds will be on the increase as trough
approaches, but things will remain dry. So with stronger onshore
flow and more cloud cover, temperatures will be exhibiting a
cooling Friday and even more so on Saturday.
At 17z at klax...there was no marine layer or inversion.
High confidence in VFR conditions everywhere through
Sunday...except for a 10 percent chance for LIFR fog at klgb klax
ksmx. More likely Monday morning. Gusty northeast winds will
weaken quickly this afternoon. Klax klgb koxr klgb should see
gusty west winds after 20z.
Klax...high confidence in VFR conditions through Sunday...except
for a 10 percent chance of LIFR fog 12-16z Monday. West winds with
gusts to 25 knots should form by 21z. Northwest winds around 10 knots
are possible 02-09z. No significant east winds expected.
Kbur...high confidence in VFR conditions through Sunday. Low
confidence on winds 18-21z...with north-to-east winds/low level wind shear and
random fluctuations and direction shifts. Moderate confidence in
southeast wind forming 21-23z.
Moderate confidence in low-end (winds to 25 kt) Small Craft
Advisory (sca) conditions for west winds through this evening over
the Santa Barbara Channel and Santa Monica basin. Will then
abruptly shift to westerly this afternoon and remain gusty through
this evening. Otherwise Small Craft Advisory conditions will pick up off the outer
waters tonight, then persist through Tuesday or Wednesday. The
Small Craft Advisory will likely be extended each day.
Due to the gusty winds...choppy seas should be expected in most
areas (including near shore) into next week.
Pz...Small Craft Advisory in effect until midnight PDT tonight for
zones 650-655. (See laxmwwlox).
Small Craft Advisory in effect until 3 am PDT Monday for
zones 670-673-676. (See laxmwwlox).
Hazard potential outlook...(tue-sat)
no significant hazards expected.