31/133 PM.
Cooler but more humid conditions this weekend as tropical moisture moves over the region, with a chance for showers or a thunderstorm. Near normal conditions will follow Monday and Tuesday, with a modest warm up towards the end of next week.
(tdy-Tue), 31/213 PM.
Looks like the increased onshore flow is taking hold this afternoon with temperatures in most areas starting to trend down from yesterday. However, humidities are trending up as remnant moisture from tropical storm Alvin moves into the area from the southeast. No rain or thunderstorms yet as of 2pm in our area but it's been an active day across southern San Diego County.
That moisture is expected to work its way north through the rest of the day and overnight. Forecast soundings in the mountains show some impressive instability later this afternoon with CAPE's around 1500 J/kg in the northern Ventura and Santa Barbara County mountains. Not quite as unstable in the LA Mountains but enough for at least a slight chance of storms through the evening. Steering flow aloft is from the east at around 10mph through this evening then veers to the north later tonight into Sunday as the upper lows moves inland. Could be some brief heavy rain with storms and with the relatively light winds aloft there could be some very isolated flooding.
At lower elevations south of Pt Conception there could also be some scattered showers but rain falling through a deep dry layer below 700mb means a lot that water will evaporate in transit. So most populated areas will just see some sprinkles or light showers at most.
This high PW air mass will continue into Sunday, but will start to shift to the east, confining most of the activity east of Ventura County. Instability parameters are not as favorable Sunday across the area with the exception of the eastern San Gabriels where an isolated storm is still possible through the early evening. Otherwise, most areas will either be dry or just get some sprinkles.
The muggy air tonight will likely keep overnight temperatures warmer than usual so the Sunday lows have been increased above most of the guidance numbers. Highs Sunday will continue the cooling trend with most inland areas 5-10 degrees cooler than today, and possibly more if clouds are thicker than expected. Though the humidity will more than compensate for the decrease in temperatures.
The area will be returning to more typical late Spring conditions Monday and Tuesday as another upper low drops south along the California coast and just offshore of Pt Conception Monday afternoon. Increasing marine layer coverage is expected with temperatures mostly 1-4 degrees below normal and either slow or no clearing near the coast.
(Wed-Sat), 31/215 PM.
Little change expected Wednesday, with typical June Gloom conditions on the coastal side of the ranges, and breezy warm conditions on the desert side. Ensemble projections show a range of outcomes for the back half of next week, ranging from little change to a modest warm up as the flow turns more northwesterly.
31/1731z.
At 0736Z, the marine layer was 1500 feet deep at KLAX. The top of the inversion was around 2800 feet with a temperature of 27 C.
High confidence in TAFs for KPRB, KPMD, and KWJF. There is a less than 10% chance of thunderstorms for KPMD/KWJF after 00Z. There is a 15% chance of IFR conds at KPRB 12Z-17Z.
Moderate confidence in TAFs for KBUR and KVNY. There is a 30% chance for IFR to MVFR conds 10Z-17Z.
Low confidence in remaining TAFs. Slow clearing at coastal sites south of Point Conception today, with a 20% chance for little to no clearing. SCT to BKN IFR to MVFR conds may impact these sites until return of OVC conds tonight. Otherwise, clearing times may be off by 2 hours today. Return of cigs tonight may be off +/- 2 hours and minimum flight cat may be off by one cat, but IFR to MVFR conds as most likely as marine layer depth increases.
KLAX, Low confidence in TAF. SCT to BKN010-018 conds may bounce back and forth through late this afternoon before the return of OVC conds (+/- 2 hours from TAF). There is a 10% chance for OVC003-004 cigs tonight. There is a 20% chance cigs remain OVC010-015 tonight through the remainder of the period. No significant east wind component expected.
KBUR, Moderate confidence in TAF. There is a 30% chance for IFR to MVFR conds 10Z-17Z.
31/205 PM.
For the Outer Waters conditions will remain below Small Craft Advisory (SCA) levels through Sunday morning. There is a 40-50% chance of SCA level wind gusts across the northern Outer Waters, around Point Conception, and south to San Nicolas Island Sunday afternoon into the overnight hours. Additionally, there is a 50% chance for seas to reach 10 feet in the northern Outer Waters late Sunday into Monday afternoon. Thereafter, conditions look to remain below advisory criteria through next week.
For the nearshore waters along the Central Coast, high confidence in conditions remaining below SCA criteria through the week. However, there is a 20-30% chance for SCA level wind gusts Sunday afternoon into late night.
For the Santa Barbara Channel, high confidence in conditions remaining below SCA criteria through next week. However, there is a 20% chance of SCA level wind gusts over the western portion during the afternoon and evening hours on Sunday.
For the Inner Waters off the Los Angeles and Orange County coasts, high confidence in conditions remaining below SCA levels through next week.
An upper level low pressure system off the coast of Baja California will bring a 10-20% chance of thunderstorms through Sunday, especially south of Point Conception. Anything thunderstorm could produce lightning, rain, and gusty, erratic winds.
Ca, Beach Hazards Statement in effect from Sunday morning through Tuesday afternoon for zones 354-362-366. (See LAXCFWLOX). PZ, NONE.
