textproduct: Los Angeles

SYNOPSIS

19/802 PM.

Below normal temperatures will continue through the weekend, with a deep marine layer and a few spots of drizzle, as well as gusty winds over the interior. A significant warming trend will start Monday and peak around Wednesday. A push of moisture midweek will bring at least a low chance for rain.

LONG TERM (TUE-FRI)

19/200 PM.

Warming temperatures will continue through the middle of next week as high pressure continues to strengthen and spread further over the area. Hgts will slowly rise over the area, with global models still showing hgts peaking around 593-595 dam late-Tuesday or Wednesday, which is about 8-9 dam higher than normal. Hgts of this value will squish the marine layer down to 1000 ft or less which will greatly reduce the amount of low clouds in the vlys. It will, however, strengthen the marine inversion which will make coastal clearing more difficult. Mdt to stg onshore flow will continue although there will be weaker onshore flow to the north in the morning. These onshore gradients and the strong capping inversion will bring plenty of low clouds to the csts and some lower vlys. The marine layer will moderate the cstl warming and only 1 or 2 degrees of warming is likely each day there. For the vlys and further inland areas, however, the absence of a marine layer and building hgts will allow for 3 to 6 locally 8 degrees of warming each day. By Tuesday triple digit heat is likely in the Antelope Vly while the vlys will warm into the upper 80s and lower 90s.

The warmest days will likely be Wednesday and Thursday. Vly temps will likely end up in the upper 80s to mid 90s. There is even a low chance (5-10%) of eclipsing 100 in the San Fernando and Santa Clarita valleys. These abnormally warm temperatures will lead to pockets of moderate HeatRisk for some inland valleys. With the potential for moderate HeatRisk in parts of the LA Basin, and the consideration of the influx of visitors, an Extreme Heat Watch is in effect for next Tue-Thu. This chc of heat warning will be continuously monitored over the next three days.

In addition to the warming temps with the strong high pressure, models point to a decent push of moisture up from Baja CA midweek, with PWATs climbing up to 150% of normal. This moisture flux will increase chances for rain showers and storms (5-10% chance). An increase in mid and upper level clouds may also help alleviate some of the heat impacts.

AVIATION

20/0532Z.

At 0400Z at KLAX, the marine layer was 1900 feet deep. The top of the inversion was near 4700 ft with a temperature of 18 degrees Celsius.

For 06Z TAF package, high confidence in KWJF and KPMD.

For all other sites, only low to moderate confidence in 06Z TAF. Timing of flight category changes could be +/- 4 hours of current forecasts. Additionally, there is a 40% chance that CIGs do not develop at KPRB, KSMO, KLAX, KLGB, KBUR and KVNY.

KLAX...Low confidence in 06Z TAF. Timing of flight category changes could be +/- 3 hours of current forecasts. There is a 40% chance that CIGs do not develop overnight. No significant easterly wind component is expected.

KBUR...Low confidence in 06Z TAF. Timing of flight category changes could be +/- 3 hours of current forecasts. There is a 40% chance that CIGs do not develop overnight.

MARINE

19/806 PM.

Fairly high confidence in winds and seas staying below Small Craft Advisory (SCA) criteria through early next week, but typically gusty winds of 15 to 20 knots will form each afternoon and evening over portions of the nearshore waters as well as around the Channel Islands. Very localized gusts to 25 may be possible at times in those areas.

LOX WATCHES/WARNINGS/ADVISORIES

CA...Extreme Heat Watch in effect from Tuesday morning through Thursday evening for zones 88-368-372-373-379-380-548. (See LAXNPWLOX). PZ...NONE.