SBD UPDATE FOR SANTA ANA EVENT 10/5/17

Weather Summary

 

A very dry air mass will warm on Friday and Saturday as weak Santa Ana conditions develop. Onshore flow

returns Saturday night and Sunday morning with areas of coastal clouds and fog. Another Santa Ana wind

develops Monday morning and continues to Wednesday morning. This will bring stronger winds to the canyons,

passes and Inland Empire but not as hot. A return to very warm temperatures for Wednesday. Sea breezes

will be very weak on the coast due to offshore flow, except for moderate onshore flow Sunday and Sunday

evening.

 

Weather Threats and Impacts:

 

Very warm temperatures Friday and Saturday. Extremely low humidity and gusty Santa Ana winds across mountains

and foothills. Elevated fire weather danger. Stronger Santa Ana wind and low humidity Monday and Tuesday, not

as hot but becoming very warm by Wednesday.

  • Fire weather impacts possible

 

Forecast Winds:

 

  • Offshore flow northeast winds developing Friday morning. Gusts 20-30 mph portions of Inland Empire and in mountain passes and canyons, and foothills. Local gusts to 45 mph. Onshore winds Saturday night through Sunday evening.
  • Offshore flow northeast winds developing Monday morning and continuing through Wednesday morning. Gusts 25-35 mph for Inland Empire, foothills, mountain passes and canyons. Local gusts over 55 mph.

 

Confidence: High

 

Forecast Relative Humidity:

  • Extreme low humidity Friday and Saturday. Very low humidity Monday to Wednesday. Good recovery and higher humidity Sunday and Sunday night. Nighttime humidity recovery on the immediate coast each night.

Confidence:  High

 

Timing:

 

  • Event 1: Friday and Saturday for heat and weak Santa Ana wind
  • Event 2: Monday to Wednesday morning for stronger Santa Ana wind.

 

Confidence: High

 

Locations Impacted:  Highway 91 corridor and pass, I-15 and I-215 Cajon Pass, I-10 San Gorgonio Pass, I-8 pass

 

All areas for heat and low humidity, mountain passes and canyons for wind.

 

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