Critical Fire Weather Conditions starting Thursday
updated: Sep 29, 2013, 6:56 PM
Source: Santa Barbara County Office of Emergency Management
Dry and Warm Offshore Wind Event Possible Thursday Evening Through Saturday
Large Fire Growth Potential - the combination of very low relative humidity and gusty offshore winds may bring a significant threat of critical fire weather to southern California Thursday evening through Saturday. Extremely dry fuel conditions already in place would allow for rapid fire growth potential if winds and dry air develop as projected late in the week. The air mass will warm considerably as air is forced down the mountain slopes toward the beaches on Friday and Saturday, adding to the fire growth potential in Ventura and Los Angeles Counties.
Winds will begin to turn increasingly onshore on Sunday, resulting in slightly cooler temperatures and higher humidities. However, there may continue to be several hours of critical fire weather conditions during this transitional period on Sunday.
A large low pressure system will move across the Pacific Northwest on Wednesday and into the central Rockies by Thursday. This "inside slider" will likely bring increasing offshore winds to southern California late Thursday through Saturday. North winds (Sundowner winds) will first develop across the Santa Ynez Mountains of Santa Barbara County Thursday afternoon into Thursday night. Then, northeast winds (Santa Ana winds) will develop across the Ventura and Los Angeles County by early Friday morning, continuing into Saturday. Very dry air is likely to accompany the onset of the gusty winds with many areas experiencing relative humidity less than 10 percent on Friday and Saturday. In addition, temperatures on these days will rise above normal from the foothills to the beaches of Ventura and Los Angeles Counties. At this time, winds are expected to weaken and turn back onshore on Sunday, which would also lead to slightly cooler temperatures and slowly increasing humidity.
TIMING AND FORECAST CONFIDENCE
Although this event is 4-5 days from today, there has been a trend of consistent computer model data to give us moderate confidence of the potential impacts and timing. The details on the overall strength and duration of the winds on Friday and Saturday are less certain at this time. However, this event looks drier and windier than what occurred last week.
Please stay alert to additional emails and/or NWS Los Angeles forecasts this week as this system approaches and as more detailed information becomes available.
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