Rancho Santa Margarita, CA 92679 Weather

Synopsis

Widely scattered light showers will continue for the coastal basin through tonight, lingering at the coast through early Saturday. More widespread light rain will return Saturday evening with short periods of moderate to heavy rain late Saturday night into Sunday morning. Showers are expected to decrease on Sunday afternoon and end by Monday morning. Dry and warmer for Monday and Tuesday with high temperatures warming to around average on Tuesday.

Discussion

FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE: SAN DIEGO: WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES:

: UPDATED AVIATION DISCUSSION:

Last night, light rain moved through the coastal basin, tapering off early this morning. Overnight accumulations generally totaled less than 0.15" with up to 0.5" in foothill and mountain locations.

Expect mostly cloudy skies across the region for the rest of the day, with a few light, widely scattered showers and a few peeks of sunshine. Showers taper off everywhere overnight except for coastal areas, which could continue to see light showers through Saturday morning.

Saturday will remain overcast across the region, though uncertainty remains regarding the onset of widespread precipitation.

Current high-resolution guidance generally delays widespread rainfall until late Saturday night, potentially near or after midnight. However, the 00z Sunday GFS soundings off the coast depict an already saturated mid and upper level atmosphere with a classic mid-level warm frontal inversion. This suggests showers could develop as early as late Saturday afternoon, with more widespread rainfall spreading across the coastal basin by Halloween evening. Meanwhile, confidence still remain high that precipitation across the Coachella Valley and lower deserts will hold off until the overnight hours of Saturday into Sunday.

Precipitation Saturday night will start off light and steady, with embedded pockets of moderate to locally heavy rain during the early hours of Sunday. Later Sunday morning, widespread rainfall is expected to transition to scattered showers across the coastal basin, with precipitation ending in the deserts. Showers become increasingly isolated through Sunday afternoon, except along the San Diego County foothills and mountains, where more persistent activity will continue. Most precipitation should come to an end by Sunday night with mostly sunny skies returning region-wide by Monday.

The first few hours of precipitation will feature mainly consistent light rain region-wide with perhaps a few pockets of moderate, locally heavy rain in the very early hours of Sunday. Sunday morning, widespread rain scatters out to showers for the coastal basin (no more desert rain), becoming widely scattered by the afternoon except along the San Diego county foothills and mountains. Most rainfall will be wrapped up by Sunday night with mostly sunny skies expected region-wide by Monday.

As the storm is tracking to intersect over Northern Baja California, the higher precipitation totals will be focused over San Diego County (0.4-0.7"), notably near the US/Mexico Border. Elsewhere, totals are more likely to range between 0.25-0.50" (including deserts) with locally higher totals in the mountains.

As the storm clear the region, low temperatures will drop Monday/Tuesday morning to the upper-40s inland and down into the low 30s and 20s in elevated mountain valleys.

Next week, a series of weak, fast-moving ridges and troughs will keep temperatures fluctuation slightly - highs will range from the low to mid-70s daily in the coastal basin and mid-70s to low-80s in the Coachella Valley (and other low desert valleys).

Aviation

310000Z: Multiple cloud layers across the coastal basin with the lowest layer around 3000 ft and the highest layer above 10000 ft MSL. Coverage of BKN low clouds based near 3500-6000 ft MSL increases after 03z Sat, particularly for coastal areas. ISO-SCT -SHRA this evening and Saturday morning for the coastal basin with highest coverage in Orange County. Where -SHRA develops, cigs will likely fall to around 2500-3500 ft. Cigs look unlikely to fall below 2000 ft overnight into Sat AM. -SHRA tapers off Sat AM, with more widespread SHRA Sat evening.

Desert Mountain Slopes/Deserts: High clouds with bases AOA 10,000 ft MSL will continue into Saturday. Southwest to west winds with peak gusts 30-45 kt, decreasing around 09z Sat. SHRA/-RA beginning Saturday evening.

Marine

Westerly winds increase Saturday afternoon into Sunday, but strongest wind gusts will likely stay below 21 kts. There is a 5% chance of isolated thunderstorms Sunday morning.

Beaches

An increasing southwesterly swell (3 ft at 15 seconds from 200 degrees) will bring marginally elevated surf through the weekend and into Monday. Surf up to 6 feet is possible Sunday/Monday. While high tides will continue to wane into the weekend, tides will remain just above 6 feet which could still lead to minor tidal overflow during high tides if breaking waves approach 5-6 feet.

Watches, warnings and advisories

CA: None. PZ: None.