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)

20/1256 AM.

For the extended, 00Z models continue to exhibit good synoptic agreement. At upper levels, high pressure, over Arizona and New Mexico, peaks in strength on Tuesday then gradually weakens Wednesday through Friday. At the surface, moderate to strong onshore pressure gradients will continue with some continued weak northerly offshore gradients.

Forecast-wise, main concern in the extended will be the heat. With H5 heights peaking, Tuesday will be the warmest day of the extended period with coastal areas 3-6 degrees above seasonal normals and valleys/interior sections 5-10 degrees above normal. For Wednesday, H5 heights lower slightly which will allow for a couple degrees of cooling, but some increase in mid-level moisture will make things feel very similar to Tuesday. On Thursday and Friday, the gradual cooling trend will continue. Moderate heat risk will be likely on Tuesday/Wednesday with a slight improvement on Thursday/Friday. Given the influx of visitors to the area and plenty of outdoor activities, will continue with the EXCESSIVE HEAT WATCH for the Los Angeles county valleys and mountains.

Secondary concern for the extended forecast will be the potential for some precipitation on Wednesday. Deterministic models indicate increasing PWATs (150-200% of normal) moving into the area on Wednesday. This matches up well with ensembles indicating high chances of PWATs greater than 1.00 inch. However, most of this moisture looks to be confined to 700 mb and above. So, at this time, there is a 5-15% chance of showers/high based thunderstorms on Wednesday just about anywhere, but with best chances over the higher terrain. This will need to be monitored closely over the coming days.

AVIATION

20/1106Z.

At 1000Z at KLAX, the marine layer was 1400 feet deep. The top of the inversion was near 4700 ft with a temperature of 17 degrees Celsius.

For 12Z TAF package, high confidence in KSBA, KWJF and KPMD.

For KSMX, KPRB, KSBP and KCMA, moderate confidence in 12Z TAFs as timing of flight category changes could be +/- 3 hours of current forecasts.

For KOXR, KSMO, KLAX, KLGB, KBUR and KVNY, low confidence in 12Z TAFs as there is a 50% chance that CIGs develop in the 12Z-18Z time frame.

KLAX...Low confidence in 12Z TAF. There is a 50% chance of MVFR CIGs in the 12Z-18Z time frame. For tonight, low confidence in return of CIG restrictions. No significant easterly wind component is expected.

KBUR...Low confidence in 12Z TAF. There is a 50% chance of MVFR CIGs in the 12Z-17Z time frame. For tonight, there is a 30% chance of MVFR/IFR CIGs after 09Z.

MARINE

20/1256 AM.

For the Outer Waters, high confidence in current forecast. Today through Wednesday, winds and seas are generally expected to remain below Small Craft Advisory (SCA) levels. However, there will be a 10-20% chance of SCA level winds on Sunday and Monday.

For the Inner Waters (both north of Point Sal and south of Point Conception), high confidence in current forecast. Today through Wednesday, winds and seas are generally expected to remain below SCA levels. However, there is a 10-20% chance of SCA level winds across the western half of the Santa Barbara Channel tonight through Sunday night.

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.