11/209 AM.
A significant and long lasting heat wave is expected to affect the region starting Thursday and extend well into next week with MODERATE to HIGH heat impacts likely.
(Wed-Sat), 11/840 PM.
***UPDATE***
Skies were mostly clear skies today with minimal marine layer clouds and warm temperatures. Highs trended about 6 to 12 degrees above normal with the warmest valleys reaching the low to mid 80s and cooler 60s at the coasts. No significant marine layer clouds are expected tonight, and offshore winds for San Luis Obispo and Santa Barbara Counties will keep the area clear. Breezy offshore winds will continue into Wednesday, and there could be an argument made for boosting the high temperatures over the Central Coast. Otherwise, highs for Thursday and Friday look on track.
Winds have developed tonight over the Santa Lucia mountains, with gusts just below Wind Advisory levels. Could see a few localized gusts 45 mph, but currently thinking a Wind Advisory will not be needed. Also expecting offshore winds for the San Gabriel mountains, I-5 corridor, Santa Monica and Santa Susana mountains but these winds will be below advisory levels.
***From Previous Discussion***
Overall, 12Z models in good synoptic agreement through the short term period. At upper levels, ridge will build over the area tonight/Thursday then will gradually weaken Friday and Saturday. Near the surface, weak offshore flow will prevail through Friday then onshore flow strengthens on Saturday.
Forecast-wise for the short term, main issue will be temperatures. With high pressure building aloft and the weak offshore flow, there will be no significant marine influence to speak of through Friday. So, temperatures will increase dramatically. At this time, Thursday looks to be the warmest day area-wide. However on Friday, the marine influence will begin to weakly return which will allow for some slight cooling for the coastal plain, but temperatures will remain hot away from the coast. Afternoon temperatures Thursday and Friday will generally be 15-25 degrees above seasonal normals. Additionally, overnight low will remain on the warm side. So, given these conditions, there will be the potential for record heat across the area and HEAT ADVISORIES will remain in effect for all coastal/valley areas from San Luis Obispo county to Los Angeles county. On Saturday, weak to moderate onshore flow returns, which will combined with the weakening upper level high, to bring 5-10 degrees of cooling to the coasts and valleys with little change across interior sections.
Other than temperatures, no significant concerns for the short term. The weak offshore pressure gradients will generate some gusty northeast winds across the area through Friday. However, upper level support is limited, so do not anticipate any widespread advisory-level gusts. As for clouds, varying amounts of high clouds will keep conditions varying from mostly clear to partly cloudy through Saturday. Additionally, there could be some return of marine layer stratus/fog to the coastal plain Saturday morning.
(Sun-Wed), 11/123 PM.
For the extended period, 12Z models continue to exhibit good synoptic agreement. At upper levels, high pressure will build, once again, across the area, peaking in strength by the middle of next week. Near the surface, weak diurnal flow is expected.
Forecast-wise for the extended period, focus will remain on another round of heat. At this time, deterministic models and their respective ensembles, indicate very hot conditions next week (peaking on Tuesday and Wednesday). Once again, high temperatures will be at least 15-25 degrees above normal with warm overnight lows. So, widespread HEAT ADVISORIES are likely along with the potential for record-breaking daily temperatures. Depending on how things develop, monthly temperature records could also be in jeopardy. In addition, the Antelope Valley may break a record next week for the earliest 90 degree day in the calendar year.
Given the unprecedented length and magnitude of this extreme heat wave, heat stress will be increasing each day, especially in areas that aren't used to the heat, like the coastal areas, where people may not have methods to cool off their homes. Try to complete outdoor activities early in the day or in the evening, and don't leave people or pets in cars.
As for chances of any rainfall, both deterministic and ensembles indicate little, if any, precipitation for the area through March 26th.
12/0251z.
At 2249Z, the marine layer depth at KLAX was around 300 feet deep. The top of the marine inversion was around 1900 feet with a temp of 22 deg C.
Moderate to high confidence in the 00Z TAFs with generally VFR conds expected at all airfields thru the fcst period. There is a 30% chance for brief reduced visibilities for coastal sites from 12 to 15Z.
KLAX, Hi confidence in the 00Z TAF with generally VFR conds expected thru the fcst period. Any easterly winds should remain less than 7 knots. There is a 30% chance for north winds of 3 to 6 kt around 15Z.
KBUR, Hi confidence in the 00Z TAF with VFR conds expected thru the fcst period.
11/845 PM.
Moderate to high confidence in the current forecast.
For the outer waters, there is a 60% chance Small Craft Advisory level wind gusts will affect the waters through at least Friday night, although the northern waters (north of Point Sal) may drop below SCA levels during the morning and afternoon hours on Friday. Friday night through Sunday night, there is a 50-60% chance of SCA wind gusts, with the highest chances across the northern waters where local Gale Force gusts will be possible. Seas will be near SCA levels Friday night through Saturday night. Monday and Monday night, there is a good chance conds will drop below SCA levels for all the outer waters.
For the inner water N of Point Sal, conds are expected to be generally below SCA levels through Monday night, except for a 50% chance of SCA wind gusts at times during the afternoon and evening hours Friday and Saturday.
For the inner waters S of Point Conception, conds are expected to remain below SCA levels through Monday night.
Ca, Heat Advisory remains in effect from 10 AM Thursday to 8 PM PDT Friday for zones 88-340>342-346>352-354>358-362-366>375-548. (See LAXNPWLOX). PZ, Small Craft Advisory in effect until 9 AM PDT Thursday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Thursday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Friday for zone 673. (See LAXMWWLOX).
