Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 07/23/20

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 156 PM PDT Wed Jul 22 2020

.SYNOPSIS...22/148 PM.

Cooler temperatures and more extensive night through morning low
clouds and fog are expected through Friday with some gusty
afternoon winds across interior sections. For the weekend and
early next week, a gradual warming trend is expected.

&&

.SHORT TERM (TDY-SAT)...22/148 PM.

Overall, 12Z models in good synoptic agreement through the short
term period. At upper levels, weak low will move across Central
California tonight/Thursday with a broad trough developing over
the state Friday/Saturday. Near the surface, moderate onshore
gradients will continue.

Forecast-wise, no major changes to previous forecast thinking as
a rather benign pattern will continue across the area. Current
AMDAR data indicates marine running about 2000 feet deep. With
continued onshore flow and slightly lower H5 heights tonight, will
expect inversion to deepen a bit further with stratus/fog pushing
into the Santa Clarita Valley late tonight. On Thursday, stratus
should dissipate nicely as inversion in not overly strong. For
Thursday night through Saturday, H5 heights will slightly
increase. So, marine inversion should become a bit more shallow,
but still plenty deep enough for night/morning stratus/fog in the
coastal valleys (but not as far as the Santa Clarita Valley).
Other than the stratus/fog, skies should remain mostly clear
through the period.

As for temperatures, Thursday will experience some slight warming
across interior sections, but near persistence conditions across
the coasts and coastal valleys. For Friday and Saturday, there
will continue to be some slight warming in many areas with
increasing thicknesses and lessening marine influence.

As for winds, the continue onshore gradients will generate gusty
southwesterly winds across interior sections each afternoon and
evening. However, speeds are expected to remain below advisory
levels.

.LONG TERM (SUN-WED)...22/148 PM.

Overall, 12Z models continue to exhibit decent synoptic agreement
through the long term period. At upper levels, weak low, located
near the Central CA coast on Sunday, will wobble to the north as a
ridge builds over our area and the Desert Southwest early next
week. Near the surface, onshore flow will continue although it
will weaken slightly from day-to-day.

Forecast-wise, the above synoptic pattern will lead to a continued
benign weather pattern. With rising H5 heights and gradually
weakening onshore gradients, the marine inversion will become more
shallow with less inland coverage each night/morning. By early
next week, there may be some slow clearing along the beaches as
the inversion strengthens (due to subsidence). Otherwise, skies
are expected to remain mostly clear through early next week.

As for temperatures, will anticipate a warming trend for all areas
due to less marine influence and increasing thicknesses and H5
heights.

&&

.AVIATION...22/1751Z.

At 1650Z at KLAX, the marine layer was 2200 feet deep. The top of
the inversion was near 3600 ft with a temp of 20C.

Low to moderate confidence in coastal and valley TAFs and high
confidence in desert TAFs. Confidence is dropping in whether
coastal sites will clear or not. KSBA, KOXR and KLAX may not clear
until late this afternoon, if at all. The valley sites have
cleared and desert TAFs will be dealing with the usual gusty
afternoon winds. After brief partial clearing late this afternoon,
the marine clouds will push back in early this evening to most
coastal sites and envelop the valley sites by late this evening.
Conditions will range from MVFR in south coastal sites to
IFR/patchy LIFR conditions in central coast and valley sites.

KLAX...Low confidence in the 18z TAF. There is a 20-30 percent
chance that the ceilings will not clear this afternoon. No wind
issues

KBUR...Moderate confidence in the 18z TAF. There is a 20% chance
of an earlier arrival in the marine clouds.

&&

.MARINE...22/115 PM.

Moderate confidence in the current forecast. Local gusts to 25 kt
are posible for a brief time this evening, otherwise winds should
remain below Small Craft Advisory (SCA) speeds today through
Thursday.

On Thursday evening, there is a 60% chance of SCA level winds
developing over the far northern outer waters along the Central
Coast. Good confidence in SCA conditions lasting through Friday,
then focused from Point Conception to San Nicolas Island on
Saturday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK (SAT-WED).

No significant hazards expected.

&&

$$

PUBLIC...Thompson
AVIATION...Sweet/Stewart
MARINE...Sweet
SYNOPSIS...RAT

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