Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/01/16


AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
1139 AM PDT SUN MAY 1 2016 .SYNOPSIS... A departing low pressure system will bring the slight chance of showers and thunderstorms today across the mountains, foothills, and antelope valley. A high pressure system will briefly build into the region through Tuesday, supporting a gradual warming trend. A slow moving low pressure system will likely bring a cool down to the area with showers also possible Thursday through the weekend. && .SHORT TERM...(TDY-TUE) Satellite imagery showing partly to mostly cloudy skies across the Los Angeles basin this morning...otherwise mostly clear skies across the district. Latest ACARS sounding and pilot reports showing marine layer depth between 2000 and 2500 feet across LA county this morning. Look for another mild day across the region, with most inland areas climbing into the 70s. Main upper level low pressure is spinning across Arizona this morning, but a secondary weak upper level trough and associated vorticity energy is forming on the back side of the low pressure system across central and southern California. This feature will likely generate some weak cyclonic flow over the forecast area today. Some residual moisture across the region today, with precipitable water values of around .7-.8 inches. With ample early May sunshine and still some cold air aloft (500 mb temperatures as low as -18 degrees celsius across interior sections), there will likely be enough instability and moisture to generate some showers over the mountains this afternoon. With lifted index values ranging between -2 and -4, and CAPE values between 300-500 J/kg, the convective parameters do indicate a slight chance for thunderstorms this afternoon across the mountains. With the upper level wind flow from the northwest and mid level flow from the north-northeast, could see some storms drift off the mountains into the adjacent foothill portions of the valleys, as well as the Santa Clarita and Antelope Valleys. If any thunderstorms do develop today, they could be slow moving, capable of producing a brief heavy downpour, gusty winds, and small hail. *** From previous discussion *** Another night and another mdl fcst of an eddy and a significant marine layer stratus deck. Again this is not a high confidence fcst and could easily see less clouds. The upper low will be much further east and the only convection will be limited some afternoon cu over the mtns driven only by afternoon heating. By Tuesday a large upper low begins to approach the west coast. The increase in cyclonic turning associated with this low will help the overnight marine layer stratus deck to form and move into the vlys. Otherwise skies will be partly cloudy and max temps will be several degrees above normal. .LONG TERM...(WED-SAT) A cooling trend should begin by Wednesday with an upper-level trough approaching from the northwest. Models are in good synoptic agreement that a cutoff low will develop over the area Thursday night through Friday, then slowly drift east on Saturday. There will be a chance for hit and miss showers in most places late Wednesday night through Saturday. At this time, it looks like late Thursday through Friday would be the best chance for any showers. Thunderstorms are not in the forecast at the moment, but they may need to be added at a later time, as 500 mb temps are as low as -25 deg C when the center of the upper low moves overhead. && .AVIATION...01/1800Z AT 1737Z at KLAX, the marine layer depth was 3300 feet. The top of the inversion was around 3900 feet with a temperature of 13 degrees C. a newly reinvigorated eddy was causing some ceiling issues in southern la county. klax remains on the north edge of the cloud shield. the clouds over coastal la county are expected to slowly push to the east this afternoon as the sea breeze clears the skies for a time. elsewhere...skies will be mostly clear this afternoon except in the mountains and deserts where a stray thunderstorm is possible during the afternoon. tonight...there is moderate confidence in the development of marine clouds across the coastal and valley sections for later this evening and overnight. there is less confidence for the central coast. KLAX and kbur...moderate confidence in the 18z taf. mvfr conditions are expected for the overnight hours extending into monday morning. && .MARINE...01/900 AM... Winds have diminished across the coastal waters. There is rather high confidence that conds will remain below SCA levels across the entire waters through at least Tue. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement in effect until 9 PM PDT this evening For zones 34-35-40-41-87. (See LAXCFWLOX). PZ...NONE. && $$ PUBLIC...Gomberg AVIATION...Sweet MARINE...Sweet SYNOPSIS...Munroe weather.gov/losangeles
AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
937 AM PDT SUN MAY 1 2016 .SYNOPSIS... A departing low pressure system will bring the slight chance of showers and thunderstorms today across the mountains, foothills, and antelope valley. A high pressure system will briefly build into the region through Tuesday, supporting a gradual warming trend. A slow moving low pressure system will likely bring a cool down to the area with showers also possible Thursday through the weekend. && .SHORT TERM...(TDY-TUE) Satellite imagery showing partly to mostly cloudy skies across the Los Angeles basin this morning...otherwise mostly clear skies across the district. Latest ACARS sounding and pilot reports showing marine layer depth between 2000 and 2500 feet across LA county this morning. Look for another mild day across the region, with most inland areas climbing into the 70s. Main upper level low pressure is spinning across Arizona this morning, but a secondary weak upper level trough and associated vorticity energy is forming on the back side of the low pressure system across central and southern California. This feature will likely generate some weak cyclonic flow over the forecast area today. Some residual moisture across the region today, with precipitable water values of around .7-.8 inches. With ample early May sunshine and still some cold air aloft (500 mb temperatures as low as -18 degrees celsius across interior sections), there will likely be enough instability and moisture to generate some showers over the mountains this afternoon. With lifted index values ranging between -2 and -4, and CAPE values between 300-500 J/kg, the convective parameters do indicate a slight chance for thunderstorms this afternoon across the mountains. With the upper level wind flow from the northwest and mid level flow from the north-northeast, could see some storms drift off the mountains into the adjacent foothill portions of the valleys, as well as the Santa Clarita and Antelope Valleys. If any thunderstorms do develop today, they could be slow moving, capable of producing a brief heavy downpour, gusty winds, and small hail. *** From previous discussion *** Another night and another mdl fcst of an eddy and a significant marine layer stratus deck. Again this is not a high confidence fcst and could easily see less clouds. The upper low will be much further east and the only convection will be limited some afternoon cu over the mtns driven only by afternoon heating. By Tuesday a large upper low begins to approach the west coast. The increase in cyclonic turning associated with this low will help the overnight marine layer stratus deck to form and move into the vlys. Otherwise skies will be partly cloudy and max temps will be several degrees above normal. .LONG TERM...(WED-SAT) A cooling trend should begin by Wednesday with an upper-level trough approaching from the northwest. Models are in good synoptic agreement that a cutoff low will develop over the area Thursday night through Friday, then slowly drift east on Saturday. There will be a chance for hit and miss showers in most places late Wednesday night through Saturday. At this time, it looks like late Thursday through Friday would be the best chance for any showers. Thunderstorms are not in the forecast at the moment, but they may need to be added at a later time, as 500 mb temps are as low as -25 deg C when the center of the upper low moves overhead. && .AVIATION...01/1145Z AT 1100Z at KLAX, the marine inversion was around 1800 feet. The top of the inversion was around 2500 feet with a temperature of 15 degrees C. Just some patchy low clouds across coastal sections of L.A. County early this morning, with MVFR conditions. Expect clouds to fill in a bit more by daybreak, and they could push into the L.A. County valleys, and into coastal sections of Vtu County. There could be some showers and even a thunderstorms in the mountains L.A...Vtu and Sba Counties and the Antelope Valley in the afternoon and evening. More widespread MVFR cigs expected tonight/Mon morning across all coastal and many valley locations. KLAX...Moderate confidence in the 12z TAF. There is a 20 to 30 percent chance that conds will remain VFR this morning. There is a 20 percent chance that MVFR cigs this evening will arrive as early as 04Z. KBUR...Low confidence in the 12z TAF. There is a 40 percent chance of MVFR cigs between 13Z and 17z. There is a 20 to 30 percent chance that MVFR cigs will arrive as early as 08z tonight. && .MARINE...01/900 AM... Winds have diminished across the coastal waters. There is rather high confidence that conds will remain below SCA levels across the entire waters through at least Tue. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement in effect until 9 PM PDT this evening For zones 34-35-40-41-87. (See LAXCFWLOX). PZ...NONE. && $$ PUBLIC...Gomberg AVIATION...DB MARINE...Sweet SYNOPSIS...Munroe weather.gov/losangeles