692 FXUS66 KLOX 192352 AAA AFDLOX Area Forecast Discussion...UPDATED National Weather Service Los Angeles/Oxnard CA 452 PM PDT Tue Oct 19 2021 updated aviation discussion .SYNOPSIS...19/905 AM. Today will be sunny with a noticeable warming trend. Wednesday and Thursday will feature more warming and partly to mostly cloudy skies along with night through morning low clouds across the coastal area. There is a chance of a significant storm in the Sunday to Monday time period. && .SHORT TERM (TDY-FRI)...19/140 PM. Synoptically, there is a 542 dam upper low offshore around the CA-OR and a weak ridge has built in from the south in the wake of yesterday's cold front. A trough associated with the upper low will clip the northern part of our area on Wednesday, bringing a slight chance of showers to northwest SLO County. The ridge builds higher on Thursday and should bring the high temperatures of the week, to near normal levels. Ensembles have an impactful storm system dropping from the Gulf of Alaska and drawing in moisture from the Pacific and impacting the area primarily Sunday and Monday. A weak ridge has moved into the state in the wake of yesterday's trough passage. Heights will rebound to 576 dam. There will be weak offshore flow both from the north and the east in the morning. These offshore gradients will reverse in the afternoon to weak onshore. Skies will be clear since the cool air that spilled into the area yesterday wiped out the marine inversion. The lack of cold air advection will allow the mountains and interior to warm 8 to 12 degrees today. The weak offshore flow and delayed seabreeze will bring 2 to 5 degrees of warming to the coasts and valleys with the exception of the SBA south coast where the lack of northerly offshore flow will keep max temps 2 to 5 degrees cooler. Despite the warming, max temps will still end up 5 to 10 degrees below normal. Onshore flow and weak cyclonic turning will bring marine layer stratus back to the coasts later tonight. On Wednesday a weak front will wash out over Monterey County. There is a small chance that the NW portion of SLO county could see a light shower. The onshore push ahead of the front will keep the low clouds across the beaches through the afternoon. Mid and upper level clouds embedded in the SW flow aloft will create partly to mostly cloudy skies over the southern half of the state. The switch to onshore flow will cool the coast several degrees but slightly higher heights will allow several degrees of warming for the interior. Expecting the marine layer cloud pattern to develop Wednesday night and cover most of the coast with low clouds. The beaches across the Central Coast will again struggle to clear due to better onshore flow slight lift from an approaching trough. Moist SW flow aloft will persist across the state and there will be enough mid level clouds to make the rest of the day partly cloudy (maybe a few instances of mostly cloudy - especially over SLO county). Heights will continue to rise Thursday and will reach 582 dam in the afternoon. These height rises, along with weak offshore flow from the north, will combine to bring 5 to 10 degrees of warming to almost all of the area. This will make Thursday the warmest day of the next 7 with max temps coming in a few degrees either side of their normals. The ensembles agree that the xtnd periods weather will be dominated by a powerful Gulf of Alaska low that will spin off of the WA/OR coast before moving across the west coast on Monday. The first impulse will push into areas north of Pt Conception Friday. This first impulse does not look that significant and rainfall if any will be light and concentrated over SLO county (As always the extreme NW tip of SLO county could see substantial more rainfall than the rest of the area). Skies will be mostly cloudy as the system washes out over it. Max temps will fall 3 to 6 degrees due to falling heights and increased cloud cover. .LONG TERM (SAT-TUE)...19/157 PM. Saturday will likely be dry but will remain mostly cloudy with perhaps a few periods of partly cloudy skies. Heights will continue to fall and max temps will dip another 2 to 5 degrees. Coastal and Valley max temps will almost all be in the 60s and lower 70s, which is 5 to 10 degrees below normal. The main impulse from this upper low will primarily affect our area Sunday and Monday. The upper low will be just to the west of Coos Bay OR by Sunday afternoon. This location will focus a WSW to ENE oriented powerful jet stream over Central and Southern CA. By Monday morning the area will be under the right front quadrant of a 130kt jet streak. Model solutions show this system entraining a substantial amount of moisture into its flow pattern and early PWAT estimates are near 1.7 inches. The exact timing of this event is still a little murky, but should be between a late Sunday to Monday afternoon peak. The most rain will very likely fall over the Central Coast. Preliminary rain estimates for the two day period from WPC call for about 2 inches of rain for the Central Coast and 1 inch for areas South of Pt Conception. As we have seen over the years, a slight positional difference or orientation change with respect to our transverse mountains can have a significant impact on rain amounts. By Tuesday the center of the storm should have moved to our east but we will still be in a trough so continues cloudy skies are likely. && .AVIATION...19/2351Z. At 2330Z, there was no marine layer at KLAX. Moderate to high confidence in the current forecast. There is a moderate (50 percent) chance of MVFR conditions at KSMO, KLAX and KLGB late tonight into Wed morning. Otherwise, VFR conditions are expected at the airfields thru Wed afternoon. KLAX...There is a 50 percent chance of MVFR conditions from about 11Z-17Z. Otherwise, VFR conditions are expected thru the TAF period. KBUR...High confidence in VFR conditions through the TAF period. && .MARINE...19/113 PM. Small Craft Advisory (SCA) level conditions have expired for the southern two outer waters zones. Otherwise, winds and seas are expected to be below SCA levels through Thursday. There is a moderate (30-40 percent) chance of SCA level northwest winds for the waters south of Point Conception, including the southern California bight Wednesday evening. Winds are expected to increase and a large northwest swell is expected to build from Friday through the weekend. There is a moderate (30-40 percent) chance in SCA level winds and hazardous seas greater than 10 feet across the coastal waters, especially Saturday through Monday. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && .HAZARD POTENTIAL OUTLOOK (FRI-TUE). A storm system will affect the region Sunday and Monday, with around two inches of rain in the north of the area, with around one inch of rain in the south. && $$ PUBLIC...Rorke/jld AVIATION...Sirard MARINE...Sweet/Lund SYNOPSIS...jld weather.gov/losangeles