05/1251 AM.
Onshore flow will continue to bring low clouds to the coasts and coastal valleys each night through morning. Onshore flow will start to weaken Monday and cause decreasing clouds in the valleys and gradually warming temperatures. Expect a return to above normal temperatures early this week.
(tdy-Tue), 05/950 AM.
***UPDATE***
With increasing confidence in potentially dangerous heat returning to the local area over the middle of the week, went ahead and issued a heat advisory for all but some of the coastal locations and coastal valleys starting late Tuesday morning and continuing into Thursday evening. While temperatures may be borderline across parts of the advisory area on Tuesday, temperatures will peak out Wednesday and Thursday afternoons, and additional areas may eventually need to be added to the current heat advisory. Other than a few tweaks in max T's through Wednesday to reflect the latest model data, no additional changes were made to the previous forecast at this time.
***From Previous Discussion***
The high clouds streaming over the area disrupted the marine layer early this morning, resulting in fewer coastal low clouds across the coasts and coastal valleys. These high clouds should diminish throughout the day. The combination of the decreasing high clouds and increase in onshore flow will lead to night through morning Marine Layer clouds reestablishing tonight into Monday morning. However, lingering mid-level moisture this evening and tonight may cause the marine layer to be patchy across the coasts and valleys. Starting Monday night, higher confidence in a return of night through morning clouds each day through the week, however combined with high pressure building aloft, the clouds will lessen in extent each night
As for temperatures, expecting a slight cool-down today due to slightly lower heights aloft than on Saturday and the aforementioned increasing onshore flow. This will be followed by warming Monday and especially Tuesday through Thursday with strong high pressure building aloft and weakening onshore flow. Highs in the 80s to mid 90s are expected away from the coast today, rising into the mid 80s to low 90s, with the warmest valleys reaching a few degrees on either side of 100 degrees starting Tuesday. Some heat advisories may be needed by Tuesday, and will be likely for Wednesday and Thursday.
Through Monday, onshore winds gusting up to 35 mph are expected for the Antelope Valley and Foothills, along with Sundowner winds each evening tonight through Wednesday, with peak gusts up to 40 mph.
(Wed-Sat), 05/232 AM.
Above normal temperatures and dry weather are anticipated through the extended period as high pressure continues to strengthen aloft. Make sure to drink plenty of hydrating fluids, check on those sensitive to heat and/or without air conditioner, and never leave anyone in a car without air-conditioning as lethal temperatures can be reached inside a car within a matter of minutes.
At this point, the upper level ridge looks to be centered across southern California over the Wednesday/Thursday time period, when afternoon temperatures should peak. The ridge is then expected to shift north and east by the end of the week and over next weekend, providing some minor relief to end the week. That said, temperatures are still expected to remain near or above normal through next weekend, and likely beyond - with CPC outlooks continuing to favor above normal temperatures through at least week 2.
Given the anticipated warm up, there will be at least a minor to moderate heat risk each day. As mentioned in the short- term discussion, heat advisories will eventually become necessary Tuesday-Thursday, mainly across inland areas including the San Fernando and Santa Clarita valleys.
05/1724z.
At 1640Z at KLAX, the marine layer was 1100 ft deep. The top of the inversion was 2100 ft deep with a temperature of 20 C.
High confidence in VFR TAFs for desert airfields (KWJF & KPMD).
Low to moderate confidence in remaining TAFs. Timing of flight cat may be off +/- 3 hours and CIG heights +/- 300 ft. Confidence in CIG forecast for KOXR, KCMA, KSMO, KLAX, & KLGB is lowest due to disorganized marine layer stratus. There is a 30% chance that CIGs do not arrive/form or remain brief late tonight into tomorrow morning.
KLAX, Moderate confidence in TAF. High confidence in VFR conds through 06/06Z. Low confidence from 06/06Z-18Z due to likely disorganized stratus, with a 30% chance that CIGs do not arrive or brief at times. No significant easterly wind component expected.
KBUR, Moderate confidence in VFR TAF. No wind issues expected.
05/830 AM.
High confidence in winds and seas remaining below Small Craft Advisory (SCA) levels across all waters through this morning. SCA level NW winds are expected to pick up later this afternoon and are expected to persist through at least Thursday across the Outer Waters. There is a 20-30% chance of GALE Force winds Tuesday afternoon through Thursday. Winds will likely be strongest near Point Conception, Channel Islands, and the far northern outer waters. Seas will gradually increase reaching advisory levels mid- week and will subside below Friday into the weekend.
SCA level NW-W winds will reach into the inner waters along the Central Coast and the Santa Barbara Channel starting Monday afternoon through Wednesday or Thursday. Most likely and strongest during the afternoon and evening hours. Local gusts could reach 21 kts during the late afternoon-evening hours near Point Dume and across the San Pedro Channel through Tuesday or Wednesday.
Ca, Heat Advisory in effect from 10 AM Tuesday to 8 PM PDT Thursday for zones 38-88-343>345-353-372-373-375>380-548. (See LAXNPWLOX). PZ, Small Craft Advisory in effect from 5 PM Monday to 5 AM PDT Tuesday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect from 5 PM this afternoon to 5 AM PDT Tuesday for zones 673-676. (See LAXMWWLOX).
