East Santa Barbara Channel from Pt. Conception to Pt. Mugu CA including Santa Cruz Island Marine Forecast
FORECAST FOR PZZ650 CURRENTLY UNAVAILABLE
| 251 AM PDT Thu Sep 23 2021 |
Synopsis for the southern California coast and Santa Barbara Channel including the Channel Islands National Marine Sanctuary and National Park - PZZ600
at 09Z, or 2 AM PDT, a 1028 MB high was located about 400 NM W of Portland, OR. A 1008 MB thermal low was located in western Arizona. Little change in this pattern is expected through Fri.
| Area Forecast Discussion|
National Weather Service Los Angeles/Oxnard CA
334am PDT Thu September 23 2021
A cooling trend will continue today as onshore flow strengthens ahead of an area of low pressure over the Great Basin. This trough will back into the region through the weekend and a cooling trend will likely linger. Some clouds and shower activity possible each day. Another area of low pressure will bring the possibility of unsettled weather and gusty winds for the northern areas midweek next week.
Short Term - Today through Saturday
The latest satellite imagery show an upper-level trough over the southern Idaho this morning and extending into the Great Basin. This trough of low pressure will cutoff from the flow late today and dig southwest into the region through Saturday. Model solutions are still varying quite a bit in the exact position of the trough as it arrives along the southern California or Baja California coastline. Any changes by several hundred miles in either direction north or south could be the difference between cooler or warmer weather, and showery or drier weather. Ensemble members still lean towards cooler weather through the weekend with most solutions keeping the area dry. Shower activity cannot be ruled out for the southern and eastern areas of California, but much will depend where the trough settles.
NAM-WRF solutions continue to be the most favorable for cooler and showery weather based upon the position, but these solutions are trending drier and seem to the outlier. GFS and ECMWF (European Centre for Medium-Range Weather Forecasts) solutions are starting to converge on the movement of the trough over southeast California, skirting San Diego County, and settling just off the Baja California coast over the weekend. Given the uncertainty, sky coverage and temperatures were nudged to the latest model guidance. A persistent marine layer will likely remain in place across the coastal areas, possibly struggling to clear away from the land mass each afternoon. Onshore flow seems likely to persist for the period, but ECMWF gradients do indicate a period of offshore flow developing in the latest run on Saturday. Slight chance Probability of Precipitation was introduced for the southern and eastern portions of the area, mainly for the mountains as some ingredients are still present for the possibilty of rain or showers.
Long Term - Sunday through Wednesday
After Sunday, the operational model solutions diverge more as ECMWF solutions are more progressive with the cutoff trough's movement. GFS solutions are tending to be slower with the trough movement. Given the history of cutoff troughs in the region, the GFS solution could end up playing out. Ensemble members both of the ECMWF and GFS solutions seem to favor cooling extending for early next week, but there is some variance of the ensemble members toward the warm side. For now, the forecast keeps consistent with a cooling trend for early next week.
By midweek, a majority of the ensemble members of the GFS, ECMWF, and CMC are indicating the possibility of another trough bring light rain or showers to the region. Ensemble indicate light rainfall occurring between Tuesday and Wednesday. Run-to-run consistency is lacking in the operation model runs, but confidence is moderate in a very deep marine layer (around 3000 or 4000 feet deep) developing during this time period. Precipitation could end up being night through morning drizzle and/or showers along the coastal slopes of the mountains, but there are some members which lean toward amounts between a tenth and a half inch. Higher confidence exists for a continued cool weather pattern with gusty winds over the northern areas as a frontal boundary fall apart just north of the area. Almost all ensemble members indicate the possibility of advisory level wind gusts possible along the Central Coast and extending into southern Santa Barbara County Wednesday into Thursday. This will need to be monitored over the next several days as the model performance issues should improve between Friday and Saturday.
Moderate to high confidence that Small Craft Advisory (SCA) level winds across the southern two outer waters zones (PZZ673/676) will decrease below SCA (Small Craft Advisory) levels by mid morning. Otherwise and elsewhere, expect winds and seas to remain below SCA (Small Craft Advisory) level through Monday. However, short-period, choppy, wind-driven seas will continue across the waters today. With the shallow marine layer, there will likely be patchy dense fog with visibility one nautical mile or less across the coastal waters at times thru Fri night.
NOAA Los Angeles/Oxnard CA Office: Watches - Warnings - Advisories
CA...NONE. PZ...Small Craft Advisory in effect until 9am PDT this morning for zones 673-676.
Hazard Potential Outlook (Saturday - Wednesday)
Showers are possible mainly over the mountains through the weekend. Another period of possible showers could develop between Tuesday and Wednesday. Gusty northwest winds are possible along the Central Coast and across southern Santa Barbara County with gales across the coastal waters between Wednesday and Thursday.