Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 09/06/16


AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
831 PM PDT MON SEP 5 2016 .SYNOPSIS... Temperatures will warm to near normal by Wednesday as a trough of low pressure exits the region and onshore flow weakens. Temperatures will fall below normal for the end of the week through the weekend as onshore flow increases again. Night through morning low clouds and fog will continue to affect some coastal and valley areas. && .UPDATE... Overall, a quiet evening across the district. Overnight, the only issue will be the development of the marine layer stratus. For areas north of Point Conception, sounding data indicate marine inversion based around 1400 feet. With weak onshore gradients prevailing through the night, stratus/fog should develop along the Central Coast with the best coverage across the west coast of Santa Barbara county. For areas south of Point Conception, the stratus forecast is much more tricky and confidence in what exactly will happen is low. Onshore flow is currently weaker than last evening and the latest AMDAR soundings across the LAX basin indicate several weak inversions in the lower atmosphere. So, stratus/fog should develop, but amount of areal coverage will be questionable. Current forecast has stratus/fog pushing into the coastal valleys and up to the south coast of Santa Barbara county. Will keep with this forecast thinking for the evening update, but would not be surprised to see the stratus coverage be noticeably less than current forecast. Otherwise, no issues with winds or temperature forecasts tonight and Tuesday. No significant changes are planned for the forecast at this time. && .SHORT TERM...(MON-THU) Trough slowly exiting the area to the east tonight and early Tuesday with rising heights behind it through Wednesday. The warmer air mass combined with weaker onshore flow will lead to a shallower marine lyr, earlier clearing, and warmer daytime highs. Interior areas will see the biggest jumps next couple days with Antelope Valley and interior SLO valleys breaking into the 90s as early as tomorrow and the coastal valleys by Wednesday. Gradients trend about a millibar offshore each of the next couple days, but by Wednesday afternoon a good onshore trend develops as the ridge weakens. Still, most areas will see their warmest day of the week on Wednesday. Coastal temp forecasts were trimmed back a couple degrees because of that afternoon onshore trend and most of the model guidance and local historical studies favoring slightly less warmup near the coast. Heights don`t change too much Thursday, but strong onshore trends will bring cooling to most areas except the very far interior. Moisture from Newton expected to remain well east of our area and not expected to have any role in our local weather. .LONG TERM...(FRI-MON) After the cooling Thu very little change is expected through the weekend. Both the GFS and ECMWF show a little vort max spinning up off the coast of northern Baja Thursday, unrelated to Newton, and moving north into the coastal waters off San Diego late Friday into early Saturday. So far models show absolutely zero moisture associated with this feature so right now there is no concern for any convective development. But something to keep an eye on. Otherwise, looks like a very quiet weather weekend in southern California with temps within 5 degrees of normal in most areas and just typical night/morning low clouds and fog for coastal areas. On Monday a trough moving into the Pac NW will lower heights further and cool daytime highs a few degrees area-wide. Still not seeing any threat for monsoon convection the next 10 days at least, maintaining our basically absent monsoon season so far. && .AVIATION...05/2305Z... At 2300Z, the marine inversion at KLAX was based near 2500 feet. The top of the inversion was 5200 feet with a temperature of 16 degrees Celsius. Overall, low confidence in 00Z TAF package. Current sounding data indicates marine inversion is very weak which leads to very limited confidence in the extent of stratus development tonight, especially south of Point Conception. Will continue with previous thinking of MVFR/IFR ceilings developing overnight at all coastal and valley TAF sites except for KSBP and KPRB. However, confidence in timing of stratus arrival, let alone confidence in stratus development, is low. KLAX...overall, low confidence in 00Z TAF. High confidence in VFR conditions prevailing through this evening. However confidences wanes considerably tonight as there is a 50% chance that MVFR ceilings will not develop at all. If MVFR ceilings do develop, confidence in timing is also low. KBUR...overall, low confidence in 00Z TAF. High confidence in VFR conditions through this evening. Overnight, there is a 50% chance that MVFR ceiling restrictions may not develop. If ceiling restrictions do develop, confidence in flight category and timing is low. && .MARINE...05/830 PM... For the Outer Waters, high confidence in current forecast. Northwest winds will remain at Small Craft Advisory levels through tonight for all three zones (670/673/676) and into Tuesday night for 670/673. By Wednesday and continuing through the end of the week, winds and seas are expected to remain below Small Craft Advisory levels. For the Inner Waters, high confidence in current forecast. For the week, winds and seas are expected to remain below Small Craft Advisory levels. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...Small Craft Advisory in effect until 3 AM PDT Wednesday For zones 670-673. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Tuesday For zone 676. (See LAXMWWLOX). && $$ PUBLIC...MW/RAT AVIATION...RAT MARINE...RAT SYNOPSIS...Bartling weather.gov/losangeles