1530 UPDATE SANTA ANA EVENT

Changes Since Last Briefing:

Confidence has increased for a moderate Santa Ana wind event. This will bring a period of strong gusty winds from the San Bernardino County Mountains through the Inland Empire and Santa Ana Mountains into inland Orange County as well as very low humidity. Best chances of critical fire weather conditions is late morning Saturday through midday Sunday.

Weather Summary

High pressure will build over the Great Basin Saturday and combine with mountain waves from the San Bernardino Mountains and bring strong gusty winds late morning Saturday through midday Sunday. This will be accompanied by very low humidity and dry fuels.  Winds will decrease by Sunday afternoon, but humidity will continue to be low through Monday.

Weather Threats and Impacts:

Strong winds and low humidity will cause critical fire weather conditions.

Forecast Winds:

  • Areas of northeast winds 20 to 30 MPH with local gusts to 50 MPH.  Strongest winds will be through and below passes and canyons.

Confidence: Moderately high.

Forecast Relative Humidity:

Humidity will fall to 7 to 10 percent in many areas, including the valleys and mountain slopes, Saturday with 5 to 10 percent humidity possible Sunday.  Nighttime recovery will be poor.

Confidence: High

Timing:

  • WInds will increase late Saturday morning and continue through mid-afternoon.  Some decrease in winds will occur late Saturday into Saturday evening before increasing again late Saturday night and early Sunday morning.  Winds will decrease midday and afternoon Sunday.  Relative humidity will be low late-morning Saturday through Monday.

Confidence: High

Locations Impacted:

  • San Bernardino County Mountains (especially southwest slopes and near Cajon Pass)
  • Inland Empire
  • Santa Ana Mountains
  • Inland Orange County (mainly near the Santa Ana Mountains)

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