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Red Flag Warning Today (Update)

National Weather Service in San Diego

By News Staff Member
Tuesday, September 22, 2009

Update - Tuesday, September 22

The National Weather Service in San Diego has issued a Red Flag warning, which is in effect from 9 a.m. today to 9 p.m. Thursday. The Fire Weather Watch is no longer in effect.

Northeast winds of 15 to 25 mph with gusts reaching 35 mph are expected Tuesday and Wednesday mornings, mainly through and below passes and canyons. Humidity will drop below 10 percent each day, today through Thursday.

Friday through Sunday will remain very warm, but humidities are expected to recover slightly as weak onshore flow returns.

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

A Red Flag Warning means that critical fire weather conditions are expected. A combination of strong winds, low relative humidity and hot weather will create explosive fire growth potential.

Update - Sunday, September 20, 2009

A strong, high pressure will strengthen over the west this week and a weak to moderate offshore flow will develop at the same time. The result will be high temperatures and low humidity, along with locally gusty offshore winds through canyons and passes.

On Tuesday, the winds will be strongest below Cajon Pass and in the Santa Ana Mountains. On Wednesday, the strongest winds will be through the Banning Pass and in the foothills of San Diego County. Winds will be strongest during the mornings Tuesday and Wednesday, then will diminish Wednesday afternoon.

Low humidity will continue through Thursday without winds.

The National Weather Service in San Diego has issued a Fire Weather Watch, which is in effect from Tuesday morning through Thursday evening. Northeast winds of 15 to 25 mph with gusts reaching 35 mph are expected Tuesday and Wednesday mornings mainly through and below passes and canyons. Humidity will drop below 10 percent for most of the day Tuesday through Thursday.

A Fire Weather Watch means that critical fire weather conditions are forecast to occur. Listen for later forecasts and possible Red Flag Warnings.

Original - Saturday, September 19, 2009

A strong, high pressure will build over the western United States early next week and will bring an extended period of hot weather that will last through Friday. Temperatures next week will be 10 to 20 degrees above average with record highs possible in some areas.

High pressure will strengthen over the eastern Pacific this weekend and move inland over Oregon and northern California, remaining nearly stationary through Wednesday. Dry, northeast winds around the high will increase the offshore flow and bring hot, dry weather to southern California. High temperatures at the beaches will mostly be in the 80s. However, just a few miles from the coast, the highs will be in the 90s to near 100. Inland valley and foothill temperatures will range from 95 to 110. Mountain highs will range from near 100 degrees at 3000 feet to around 80 degrees at 6000 feet. In the high deserts, high temperatures will range from 95 to 105, and in the lower deserts, the highs will range from 100 to 110. Tuesday and Wednesday are expected to be the hottest days, followed by marginally cooler days on Thursday and Friday.

The hot, dry conditions and weak offshore flow will elevate the fire danger next week. While the offshore winds are not expected to be very strong, the combination of triple digit heat, single digit humidities and very dry fuels will elevate the fire hazard potential next week.

The high-pressure ridge is forecast to break down for gradual cooling next weekend.

Prevent heat exhaustion and heatstroke by avoiding strenuous activities during the hottest part of the day. Wear light-colored and loose-fitting clothing and drink plenty of water. Never leave people or pets in enclosed automobiles, even for a short time.