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Gusty Winds and Low Humidity Prompt Red Flag Warning

Advisories Issued

By News Staff Member
Thursday, August 6, 2009

National Weather Service Advisory

Update 9:15 a.m.

Much drier air and strong southwest to west winds will affect the desert valleys and desert slopes of the San Bernardino Mountains after the inversion breaks this morning. Wind gusts will increase this afternoon through early evening. Gusts to 55 mph are likely through and below canyons and passes. Surface winds over the desert valleys should diminish after 8 p.m. when the nighttime inversions being to form.

The National Weather Service in San Diego has issued a Red Flag Warning, in effect until 9 p.m. this evening, for the mountains and desert valleys of San Bernardino County. This warning has been issued due to relative humidity below 15 percent and winds gusting over 5 miles per hour (mph).

After 11 a.m. today, the relative humidity will drop to 8 and 15 percent over the north and east slopes of the San Bernardino Mountains and the High Desert Valleys of San Bernardino County. Southwest winds will increase, with gusts above 35 mph. Winds will likely become stronger during the afternoon through early evening hours, with gusts above 50 mph.

After 8 p.m. this evening, winds will begin to diminish and relative humidity will increase.

Over the mountains, the winds will likely continue to gust over 35 mph after 8 p.m., but cooling temperatures should raise the relative humidity above 15 percent.

The National Weather Service has issued a Red Flag Warning. (Photo by NWS and ROTW.)

Areas included in this Red Flag Warning include the Mountain Top and Front Country Ranger Districts of the San Bernardino National Forest, Victor Valley, Apple Valley, Lucerne Valley, Yucca Valley and Morongo Valley. The coastal slopes of the San Bernardino County Mountains are not included in this Red Flag Warning.

A Red Flag Warning means that critical fire weather conditions are occurring now, or will be shortly. A combination of strong winds, low relative humidity and warm temperatures will create explosive fire growth potential.

Original

An unseasonably strong low-pressure system moving inland through northern California will bring strong, gusty winds to the mountains and deserts this afternoon and evening.

The National Weather Service in San Diego has issued a Wind Advisory, in effect from noon until 9 p.m. Thursday, for the San Bernardino County Mountain areas as well as Apple and Lucerne Valleys.

Areas of southwest winds will increase to 20 to 30 miles per hour (mph) this afternoon and evening near ridge tops, on north and east slopes and adjacent desert areas. Gusts may reach 50 mph.

Winds will diminish over night.

These winds will make driving difficult, especially motorists with high-profile vehicles. Watch for broken tree limbs and downed power lines. In the deserts, areas of blowing dust and sand could reduce visibility to near zero.