Point Piedras Blancas to Santa Cruz Island CA between 60 and 150 NM Offshore Forecast
|Tonight...Nw Winds 15 To 25 Kt. Seas 8 To 11 Ft.|
|Wed...Nw Winds 15 To 25 Kt, Diminishing To 10 To 15 Kt. Seas 8 To 11 Ft.|
|Wed Night...Nw Winds 10 To 15 Kt. Seas 6 To 9 Ft.|
|Thu...Nw Winds 10 To 15 Kt, Diminishing To 5 To 10 Kt. Seas 5 To 7 Ft.|
|Thu Night...N To Nw Winds 10 To 15 Kt. Seas 5 To 6 Ft.|
|Fri...N Winds 15 To 20 Kt, Becoming Nw. Seas 5 To 6 Ft.|
|Fri Night...Nw Winds 15 To 20 Kt. Seas 6 To 7 Ft.|
|Sat...Nw Winds 15 To 20 Kt. Seas 6 To 7 Ft.|
|Sat Night...N To Nw Winds 20 To 25 Kt. Seas 7 To 9 Ft.|
|Sun...N To Nw Winds 10 To 20 Kt. Seas 7 To 9 Ft.|
|Sun Night...Nw Winds 10 To 20 Kt. Seas 6 To 7 Ft.|
| Area Forecast Discussion|
...UPDATED National Weather Service Los Angeles/Oxnard CA
1158pm PDT Tuesday April 13 2021
A deep marine layer will generate widespread low clouds and fog across the coast, valleys and coastal mountain slopes through at least Wednesday with minimal afternoon clearing and below normal temperatures. Late night through morning drizzle or very light rain is possible across Los Angeles and Ventura Counties during this period. A warming trend is expected Thursday and into the weekend with highs in the 80s likely Sunday and Monday.
.SHORT TERM (TUE-FRI)...13/910 PM.
The marine inversion early this evening was near 2800 ft deep at VBG and near 5000 ft deep at LAX. Extensive low clouds covered VTU/L.A. Counties from the coast to coastal slopes this evening. There were also widespread low clouds along the Central Coast into parts of the Santa Ynez Vly. The low clouds will expand over SLO/SBA Counties overnight, but the S SBA County coast may remain mostly clear until late tonight. With the deep marine layer, cyclonic flow aloft and good onshore low, there should be enough lift for some drizzle or even light rain to develop overnight over VTU/L.A. Counties from the coast to coastal slopes. Isolated measurable precipitation will be possible as well especially in the foothills.
Pressure gradients to the E and N were quite strong this evening. At 03Z, the gradient from LAX-DAG was still +10.3 mb (after an impressive hi of +11.6 mb at 23Z) and for LAX-BFL the gradient was +5.4 mb. These pressure gradients helped to support gusty NW-SW winds this evening along the Central Coast, SBA County S coast, the L.A. County mtns and Antelope Vly. Winds were largely sub- Advisory, but there were still localized gusts to 50 mph in the foothills of the Antelope Vly. These winds should diminish some overnight.
***From Previous Discussion***
Overall, 12Z models in good synoptic agreement through the short term period. At upper levels, low will move into northern Nevada tonight and Wednesday then will meander to the east on Thursday and Friday. Near the surface, moderate to strong onshore flow will persist through Wednesday then will weaken Thursday and Friday.
Through Wednesday, a May Gray/June Gloom type of pattern will continue. Currently, marine inversion is ranging 3000-4000 feet in depth and will likely increase in depth a little bit tonight and Wednesday. With moderate to strong onshore flow, clearing today west of the mountains will be limited with clouds pushing through the coastal slopes tonight/Wednesday morning. For Wednesday afternoon, will anticipate a little bit better clearing as onshore gradients decrease a bit. Other than the marine layer clouds, skies will remain mostly clear through Wednesday. As for winds, current LAX-DAG gradient is around 9.0 MB and should increase somewhat later this afternoon. So, gusty, advisory-level winds, are likely across the Antelope Valley and through the Highway 14 Corridor through this evening. So, will keep WIND ADVISORY in effect for the Antelope Valley/LA Mountains through this evening. On Wednesday afternoon, gradients could be strong enough to produce another round of advisory-level winds in these same areas and this situation will need to be monitored by future shifts. As for temperatures, the deep marine influence and onshore flow will keep the area well below normal through Wednesday.
For Thursday and Friday, the onshore gradients will decrease in strength as H5 heigheights and thicknesses slowly increase. So, will expect a gradually more shallow marine inversion with less inland penetration through the period. As for temperatures, this pattern will allow for warmer temperatures both Thursday and Friday with most areas away from the coast climbing into the 70s by Friday. As for winds, onshore winds should not be any significant issue as the onshore gradients decrease. However, models do indicate a bit of northerly offshore gradients both Thursday and Friday evenings. So, some locally gusty northerly winds are likely, especially through the Santa Ynez Range in southern SBA county.
.LONG TERM (SAT-TUE)...13/149 PM.
Overall, 12Z models continue to exhibit good synoptic agreement through the long term period. At upper levels, trough slowly swings south over the Great Basin while a ridge gradually builds over our area. Near the surface, weak offshore flow will develop Saturday/Sunday before gradually shifting to weak onshore flow Monday/Tuesday.
With this pattern, main forecast focus will be on the offshore flow and temperatures. Weak onshore flow will prevail on Saturday with no wind issues anticipated. By late Saturday night and Sunday, weak offshore flow develops. Both the GFS and ECWMF indicate LAX-DAG gradient around -4.0 MB Sunday morning along with about 20-30 knot wind support aloft. So, weak Santa Ana winds are expected on Sunday with a 30-40% chance of advisory-level winds across Ventura and LA counties. By Sunday night and Monday, the offshore flow will be weaker and more localized with weak onshore winds expected on Tuesday.
As for temperatures, the combination of the offshore flow and building upper level ridge will bring a warming trend to the area through Monday. In fact, most coastal and valley areas will have high temperatures in the mid 70s to upper 80s on Sunday and Monday. Ensembles indicate a very low chance (10-15%) of temperatures above 90 degrees on Sunday and Monday. So, do not anticipate any widespread record-breaking heat for the area, but temperatures will be well above normal Sunday and Monday. On Tuesday, the return of onshore flow will bring a cooling trend to the area.
As for clouds, the marine layer stratus will be greatly limited on Saturday morning, before being obliterated on Sunday and Monday. However, by Tuesday morning, the stratus may make a return to the coastal plain. Otherwise, skies will remain mostly clear through the period.
Overall, moderate to high confidence in forecast. Small Craft Advisory (SCA) level winds will continue through late tonight across the outer waters and over the western portions of the Santa Barbara Channel.
High confidence that winds and seas will remain below SCA (Small Craft Advisory) level for all coastal waters from Wednesday through Thursday afternoon. There is a 40% chance of widespread SCA (Small Craft Advisory) level winds Thursday afternoon or evening, mainly from Point Conception to San Nicolas Island. There is better confidence in widespread SCA (Small Craft Advisory) level winds by Friday across the typical areas from the Central Coast to San Nicolas Island lasting through at least the weekend.
.LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...Small Craft Advisory in effect until 3am PDT Wednesday for zones 650-670-673-676. (See LAXMWWLOX).
.HAZARD POTENTIAL OUTLOOK (FRI-TUE).
No significant hazards expected.