Ation and Marine sections for 900 AM,
Marine layer low clouds have filled in quickly tonight over the coastal areas and into the western valleys, much more widespread than they have been the previous few nights. Elsewhere skies are clear. Low clouds should spread into the far southern and western portions of the Inland Empire by sunrise, gradually clearing back to the coast by late morning. A weak upper level low pressure system to the southwest progresses eastward to our south today, with high temperatures around 3-5 degrees above normal.
Weakly cyclonic flow remains in place through the weekend, then another weak trough will move across the area on Monday. This will bring minor cooling through Sunday, with greater cooling on Monday with the trough passage. By Memorial Day, high temperatures in the mountains and valleys will be anywhere from 3-7 degrees below normal, with near normal temperatures along the coast and in the deserts. The marine layer deepens through this period as well, filling in across the coastal basin each night and morning with at least partly cloudy conditions at the coast through the day.
A deeper upper low drops into the Pacific Northwest and somewhere into the Great Basin or Southwest as it closes off Tuesday into Wednesday. Ensembles are still struggling with the track and depth of this low, with around 36% of the ensembles comprised mostly of the GEFS and Canadian showing a far lower amplitude and progressive track, while the remaining 64% having the low lingering somewhere in the vicinity through at least Thursday, potentially into Friday. The lower amplitude/faster track would result in less cooling and deepening of the marine layer, while the deeper/slower low would bring much greater cooling, gusty onshore winds, a deep marine layer, and potentially drizzle or light showers for the mountains westward sometime Tue-Thu. Slightly warmer with less marine layer cloud cover once the low lifts out late in the week.
A weak area of low pressure will linger over the area through Monday, bringing temperatures near to slightly above normal with night and morning clouds and fog for the coastal and western valley areas. A stronger area of low pressure moves by from the north, bringing cooler and breezier weather by the middle of next week. A subtle warming trend with less wind will occur for the latter part of next week.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, updated Aviation and Marine sections for 900 AM,
Marine layer low clouds have filled in quickly tonight over the coastal areas and into the western valleys, much more widespread than they have been the previous few nights. Elsewhere skies are clear. Low clouds should spread into the far southern and western portions of the Inland Empire by sunrise, gradually clearing back to the coast by late morning. A weak upper level low pressure system to the southwest progresses eastward to our south today, with high temperatures around 3-5 degrees above normal.
Weakly cyclonic flow remains in place through the weekend, then another weak trough will move across the area on Monday. This will bring minor cooling through Sunday, with greater cooling on Monday with the trough passage. By Memorial Day, high temperatures in the mountains and valleys will be anywhere from 3-7 degrees below normal, with near normal temperatures along the coast and in the deserts. The marine layer deepens through this period as well, filling in across the coastal basin each night and morning with at least partly cloudy conditions at the coast through the day.
A deeper upper low drops into the Pacific Northwest and somewhere into the Great Basin or Southwest as it closes off Tuesday into Wednesday. Ensembles are still struggling with the track and depth of this low, with around 36% of the ensembles comprised mostly of the GEFS and Canadian showing a far lower amplitude and progressive track, while the remaining 64% having the low lingering somewhere in the vicinity through at least Thursday, potentially into Friday. The lower amplitude/faster track would result in less cooling and deepening of the marine layer, while the deeper/slower low would bring much greater cooling, gusty onshore winds, a deep marine layer, and potentially drizzle or light showers for the mountains westward sometime Tue-Thu. Slightly warmer with less marine layer cloud cover once the low lifts out late in the week.
221700z, Coast/Valleys, Low clouds will scatter out by 18Z. Low clouds will redevelop and move ashore 01-05Z this evening and fill nearly all the coastal basin overnight into Saturday. Bases will likely be around 1800-2200 feet MSL with tops to 2600 feet. Vis reduced 3-5SM in far inland valleys, and 0-3SM in lower foothills. Scatter out Saturday 17-19Z.
Otherwise, mostly clear and VFR conditions through Saturday morning.
No hazardous marine conditions are expected through Wednesday morning.
Ca, None. PZ, None.
