351 FXUS66 KLOX 191235 AFDLOX Area Forecast Discussion...UPDATED National Weather Service Los Angeles/Oxnard CA 535 AM PDT Sun Mar 19 2023 .SYNOPSIS...19/310 AM. A weak storm system will bring a chance of rain to the area today. Monday will be cloudy and cool. A strong storm will likely bring heavier rain, very strong winds and mountain snow to the area late Monday night through Wednesday. && .SHORT TERM (TDY-TUE)...19/308 AM. Today will be a cloudy and cool day with a slight chance to a chance of light rain. All of this from a weak front that is quite some distance from its parent low which is west of OR. .01 to .02 of an inch of rain has fallen over portions of the Central Coast. High Rez Ensemble mdls show the rain struggling to move past Pt Conception until afternoon or evening. Today's rain will only be a slight nuisance under a quarter inch across the Central Coast and under a tenth of inch south of Pt Conception. Cooler for sure with temperatures falling between 8 to 12 degrees from ydy. Gusty southwest winds are expected over interior areas this afternoon. Advisory level gusts are possible across the western foothills of the Antelope Valley. Monday will be the calm before the storm. It will be a cloudy day with plenty of mid level clouds embedded in the fast moving west flow overhead. All mdls have backed off on the rain chcs and it will be dry a dry day. Continued cool with max temps similar to today's or 8 to 12 degrees blo normal. Yet another strong winter storm will approach from the E Pac Mon night then move into the region on Tue. Mdls have been increasing the strength of this system with almost every run and now it looks like it will pack a serious punch. A 531 dam upper low will spin to the west of the bay area early Tuesday. The upper low will slowly move to the ESE through the period. It will bring three waves of rain to the area the first will be light to mdt prefrontal rain which will start later Monday night and last through Tuesday morning, the next and heaviest will occur with the vigorous cold front which will sweep through the area Tuesday afternoon and evening, thirdly a post-frontal slug of moisture will move through the area Tuesday night and early Wednesday morning. As the core of the cold low moves closer to the area 500 mb temps fall to near -25 C. This will destabilize the atmosphere to bring a slight chc of TSTMs to the Central Coast and the mtns. As the storm draws nearer will have to think about the possibilty of TSTMs in and around the front itself. Rainfall rates are expected to peak on Tue and should be reach 0.50 inch per hour at times with local rates up to 0.75 inch per hour likely and even higher rates possible under any TSTM. The rainfall forecast for this system Mon night through Tuesday night calls for 1.50 to 2.50 inches for the coast and vlys except near 3 inches for the SBA County S coast, and 2 to 4 inches for most of the mtns. If the storm continues to intensify the numbers for the south facing slopes of the transverse ranges may need to be increased. A flood watch will likely be issued for this system later today or early Monday. Unlike last weeks atmospheric river storm...this storm will pack strong and gusty southerly winds. High wind watches have been posted for the entire forecast area Tuesday and Tuesday evening for the possibility of 60 mph gusts. There will likely be the need for a Winter Storm Warning in the mtns for the combination of heavy snow and strong winds, as well as possible Wind Advisories for some of the coast and vlys. With additional significant rainfall, there may also be the eventual need for a Flood Watch for this storm. Snow levels with this system will be very tricky as the strong south flow will likely dramatically rise the snow levels across the coastal slopes while the cold air assoc with the upper low will bring much lower levels to the interior. Not quite in the high rez window to tease out the fine details of this scenario. Snow amounts through Tuesday night are expected to be 1 to 2 feet above 6000 feet with lesser amounts below. Peak snowfall will be at the highest elevations, generally above 7000 ft, with local accumulations of 3 to 5 feet not out of the question. The Grapevine may recieve accumulating snow later Tuesday night. While the mtns are now under a High Wind Watch for the possibility of 70 to 80 mph gusts future shifts may combine the danger of the strong winds with the heavy snow into a Winter Storm Watch or Warning. .LONG TERM (WED-SAT)...19/328 AM. The storm will exit the region on Wednesday. There will be plenty of wrap around moisture coming into the area and this along with the weak PVA assoc with the low and instability from the very col air aloft will keep the area in a showery regime through the period. Another .25 to .75 inches of rain is possible but since it will be so showery the rainfall totals will not be very homogeneous. Snow levels will be about 3500 to 4500 ft and there will likely be another few inches of accumulating snow on I-5 over the Grapevine as well, with travel delays possible. It will be a cold day with max temps mostly in the mid 50s across the csts/vlys or 15 to 20 degrees blo normal. The EC and GFS deterministic and ensembles differ on the movement of a couple of weak weather systems Fri and Sat. The GFS is the wetter solution for the fcst area, while the EC is much drier. The current forecast favors the drier EC solution. Max temps will warm some but will remain below normal. && .AVIATION...19/1232Z. At 1219Z at KLAX, there was no marine layer nor inversion. Moderate-high confidence in TAFs. KPRB, KSMX, and KSBP have a 30% chance of IFR conds after 18Z. There is a 30% chance that conds remain VFR through the period for sites with MVFR conds. KLAX...Moderate-high confidence in the TAF. There is a 30% chance that conds remain VFR through the period. High confidence that any east wind component will be under 6 kt. KBUR...Moderate-high confidence in TAF. There is a 30% chance that conds remain VFR through the period. && .MARINE...19/250 AM. Moderate to high confidence in the current forecast. Gusty southeast winds are likely to increase to Small Craft Advisory (SCA) levels this morning for most of the waters north of Point Mugu. There is a 30% chance of Gale Force winds this morning for the waters north of Point Conception. Winds should decrease below SCA levels by this evening. Then, winds and seas are mainly expected to remain below Small Craft Advisory (SCA) levels through Monday afternoon. On Tuesday, SCA level S to SW winds are expected to develop across all the waters, with a 40% chance of Gale Force winds Tuesday morning and Wednesday. Seas will be delayed a few hours and will develop to SCA levels late Tuesday afternoon into evening. During the day on Wednesday, the SCA level winds will shift NW to W and persist through at least Thurday, and they will subside from the nearshore waters first. Seas will remain SCA level through at least late Thursday, however Friday night winds and seas may again rise to SCA levels. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...High Wind Watch in effect from Tuesday morning through Tuesday evening for zones 38-87-88-340>358-362-366>383-548>550. (See LAXNPWLOX). PZ...Small Craft Advisory in effect until 7 PM PDT this evening for zones 645-650-670-673. (See LAXMWWLOX). && $$ PUBLIC...Rorke AVIATION...Lund MARINE...Phillips/Lund SYNOPSIS...30 weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox