Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1137 AM PST Wed Nov 24 2021

SYNOPSIS...24/829 AM.

Offshore flow will bring mostly clear skies to the area through next Tuesday.  Another surge of gusty northeast winds will develop today, with damaging winds possible in some areas tonight and Thursday.  Gusty northeast winds should then continue Thursday night into Friday.  High temperatures will remain a few degrees above normal for the coast and valleys through Thursday.  An extended duration of very dry and warm weather can be expected at least through the holiday weekend.

SHORT TERM (TDY-FRI)...24/825 AM.

Sunny skies covered the forecast area this morning and this will continue thru the day.  Offshore gradients to the N and E were increasing this morning, and as of 8 AM the LAX-DAG gradient was around -2.3 mb and the LAX-BFL gradient was -4.4 mb.  The NAM
forecasts the LAX-DAG gradient to decrease thru the afternoon to around -3.8 mb by 00Z.  Gusty NE winds have already developed this morning especially in the foothills and mtns, and these stronger winds will descend to much of the VTU/L.A.  County vlys this morning thru the afternoon.  Wind Advisories are already in effect for the L.A./VTU County mtns, Santa Monica Mtns, Santa Clarita Vly, VTU County vlys and San Fernando Vly.  The gusty winds should reach the VTU County coast late this morning and a Wind Advisory is in effect there starting at 10 AM.  Temps across the region today are expected to be several degrees warmer than normal for the coast and vlys, and a few degrees below normal in the deserts.  The coast and vlys should reach the low to mid 70s this afternoon.

An upper level trof over the region this morning will slide off to the S thru this afternoon as upper level ridging starts to build along and off the CA coast with an increasing N flow aloft.  The upper level ridging will build into CA tonight and Thu, with H5 heights over SW CA increasing to 583-585 dam by Thu afternoon.

A strong 1041 mb surface high is expected to build along the Utah/NV border tonight into early Thu according the the latest NAM.  Offshore gradients to the N and E are fcst to peak at an impressive -9.4 mb LAX-DAG and -4.1 mb LAX-BFL at 12Z Thu.  There will also be good cold air advection and upper level support for strong and gusty NE winds to affect much of VTU/L.A.  Counties tonight and Thanksgiving Day.  950 mb winds are forecast by the NAM to peak around 60 kt Thu morning, and also to 60 kt at 850 mb in the L.A. County mtns late tonight into early Thu.  Surface wind gusts of 30 to 50 mph will be widespread, with damaging gusts up to 60 mph or more possible in the foothills and mtns.

Wind Advisories will continue for the L.A./VTU County mtns, Santa Clarita Vly, San Fernando Vly, VTU County vlys and VTU County coast, while Advisories will start tonight for the San Gabriel Vly, L.A. County coast from Malibu to the Hollywood Hills and Santa Catalina Island. In addition, a High Wind Watch remains in effect tonight and thu for the L.A./VTU County mtns including the Santa monica Mtns and the Santa Clarita Vly.  Needless to say, critical fire weather conditions are expected with the gusty winds and widespread single- digit humidities.  Please see the Fire Weather Discussion below for further details.

Mostly clear skies will prevail across the region thru Thanksgiving Day.  Even with the offshore flow, temps will not warm up significantly for the coast and vlys with highs in the 70s to around 80 on Thanksgiving Day.  Inland vlys and deserts will be cool and generally in the lower 70s Thu except remaining in the 60s for the Antelope Vly.  Low temperatures will turn quite cold tonight, especially in wind-sheltered areas.  Frosts and freezes will also be possible for the interior vlys and deserts, with even a hard freeze possible in the Antelope Vly.

The upper level ridging will persist over swrn CA Thu night and Fri, altho H5 heights should lower to around 582 dam on Fri.  Pressure gradients will remain significantly offshore Thu night into Fri morning (e.g. NAM fcst LAX-DAG -5.9 mb at 12Z Fri).  This will keep gusty offshore flow over the region during the period, strongest Thu night into Fri morning over wind-prone areas of VTU/L.A. Counties.  Some areas may have Advisory level gusts as well. Skies will remain mostly clear over the area thru Fri. It will turn several degrees warmer as well, with the warmest coast and vlys expected to reach the upper 70s to mid 80s, while temps in the Antelope Vly should reach the lower 70s.

A continued very dry airmass over the region will result in another cold night for Thu night across wind-sheltered areas.  Hard freeze conditions are likely in the Antelope Vly, with widespread frost and freezing conditions for the interior vlys possible.