News & Columns > VickiW > Red Flag Warning Allowed To Expire (Update 3)

Red Flag Warning Allowed To Expire (Update 3)

National Weather Service in San Diego

By VickiW
Sunday, November 16, 2008

Update 3 - Sunday, November 16, 4 p.m.

Although there is still an elevated potential for wildfire through Monday, the Red Flag Warning has been allowed to expire as of 4 p.m. today.

Very low relative humidities, locally gusty east winds, and temperatures ranging from 85 to 95 will exist on Monday. Afternoon humidities will fall below 10 percent for several, but will not meet the 10-hour requirement to expand the Red Flag Warning.

Winds will remain light in most areas; however, gusty east winds from 15 to 25 mph will continue through and below the mountain passes and canyons.

Update 2 - Saturday, November 15, 11 a.m.

The Red Flag Warning has been extended until 4 p.m. Sunday for the region.

A strong high pressure center over northeast Utah today will shift southeast and slowly weaken tonight through Sunday. This will continue to drive moderate Santa Ana winds across southern California today though the mid and upper level support is weakening.

Sustained winds by this afternoon should be in the 15 to 30 miles per hour (mph) range, with gusts up to 50 mph. Similar strength winds are expected overnight and Sunday morning, though the direction of the mid-level winds will be more easterly. This will make winds strongest through and east and west aligned canyons and passes.

Relative humidity will continue to be extremely low for the next 24 to 72 hours and overnight recovery will be very poor.

See Fire Watch.

Update - Friday, November 14, 3:30 p.m.

The Red Flag Warning has been expanded and now includes the coastal slopes below 5000 feet of the San Bernardino National Forest; the mountains of southwestern San Bernardino County and western Riverside County; the Inland Empire; all of the Cleveland National Forest; and the San Diego County mountains and inland valleys. The warning is in effect until Saturday afternoon for relative humidity below 15 percent with northeast winds 25 to 45 miles per hour (mph), with gusts 55 to 65 mph possible.

Moderate Santa Ana winds are still forecast through Saturday with the strongest offshore pressure gradients occurring this evening through Saturday morning. Sustained winds between 25 and 45 mph, with gusts 55 to 65 mph will occur in the wind prone areas through Saturday morning while relative humidity is at or below 15 percent.

Saturday afternoon the relative humidity will drop below 10 percent in these areas but the winds will be diminishing.

By Saturday evening through Sunday morning, winds are forecast to be half as strong, with infrequent gusts to 35 mph, but little to no overnight recovery of humidity is likely and relative humidity will again fall below 10 percent on Sunday.

Very dry air and very warm daytime temperatures will continue into Wednesday, possibly Thursday for the coastal slopes, with poor overnight recovery of humidity. Daytime temperatures will remain in the upper 80s to lower 90s while relative humidity will range between 5 and 15 percent.

Original - Thursday, November 13, 3:07 p.m.

The National Weather Service has issued a Red Flag Warning in effect from 8 a.m. Friday to 4 p.m. Saturday. The areas affected include the Inland Empire and the Santa Ana Mountains and foothills. Moderate Santa Ana winds are forecast for Friday and Saturday; humidities are expected to be below 15 percent; and daytime temperatures are predicted to be almost 20 degrees above normal.

Northeast winds will increase Friday morning through Saturday morning. Sustained winds between 20 to 40 miles per hour (mph), with gusts between 45 and 60 mph, are possible during this period primarily in and below canyons and passes. The wind will diminish Saturday afternoon to northeast 15 to 30 mph with gusts to 40 mph.

Relative humidity will range from a minimum of 7 percent to a maximum of 30 percent from mid morning Friday through Saturday afternoon, but some areas may experience relative humidity below 15 percent for the entire time.

Since little to no wetting rains fell over the region this past weekend and daytime temperatures are forecast to be in the 80s to low 90s Friday and Saturday, the dead-fuel-moisture levels are expected to be extremely low.

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