Western Heavy Rain, Dry Lightning Risk (VIDEO)

Prolonged exposure to the extreme heat could result in potentially deadly heat stroke or dangerous heat exhaustion.

Courtesy: AccuWeather.com

(SACRAMENTO, Calif.) - Forecasters at AccuWeather.com, say they are monitoring two areas of thunderstorms across the West over the next day or two that have potential to create new wildfires over California. Temperatures in the central valley and the high desert today will soar above 110 degrees, with highs in the 80s and 90s spreading east to the western Plains and north into western Canada.

Storms associated with the Southwest monsoon will bring drenching rainfall to portions of New Mexico and Arizona through Thursday. The rainfall will be enhanced by a southeasterly flow off the Gulf of Mexico. Where thunderstorms are persistent and slow-moving, flash flooding can occur.

While some of this moisture will not make it over the Sierra Madre Oriental, there is copious moisture flowing from this direction, as evidenced by the very heavy rainfall in recent days across South Texas and eastern Mexico.

The California Department of Forestry and Fire Protection reports there are 323 active fires, down from a peak of more than 1,700 since lightning sparked the fires nearly three weeks ago.

Erratic winds on Tuesday allowed flames to jump the fire lines in Butte County and in the Sequoia National Forest east of Bakersfield. Five residences and four more outbuildings were destroyed in the Sequoia National Forest.

Associated Press reports in Butte County, thousands of residents of Paradise were ordered to evacuate after fire destroyed 40 homes in the neighboring town of Concow.

Evacuation orders also remained in place foras many as 1,000 residents of Concow and Yankee Hill, about 85 miles north of Sacramento.

Over 13,000 residences and nearly 300 commercial buildings are threatened by the fires. More than 18,000 California firefighters are on the fire lines, assisted by fire crews from other states and members of the California National Guard.

AP reports officials are taking no chances that firefighters could be struck by heat-related illnesses. Crews are taking breaks in air-conditioned trailers before returning to the fight against the blazes.

Red Flag Warnings are up across the Southwest. The excessive heat, combined with low humidity and local breezes, could lead to explosive fire growth. Extreme caution should be used when dealing with any flammable materials that could spark a new fire.

Dry thunderstorms erupting over the Sierra this afternoon could ignite new wildfires. The Southwest Regional News story reports thunderstorms today will produce drenching downpours over New Mexico and West Texas. However, the monsoonal flow will not reach much of the Desert Southwest or the West Coast.

Daily temperature records will fall again today. Record high temperatures set on Tuesday include:
* Red Bluff, Calif.: 111° (old record 109° in 1952)
* Sacramento, Calif.: 108° (old record 104° in 1997)
* Modesto, Calif.: 107° (old record 102° in 2006)
* Napa, Calif.: 103° (old record 101° in 1985)
* Carson City, Nev.: 97° (tied record in 1985)

Prolonged exposure to the extreme heat could result in potentially deadly heat stroke or dangerous heat exhaustion. The elderly, children, people with health problems and those engaging in excessive physical activity outdoors are especially vulnerable.

People who must remain outdoors for an extended period of time are urged to wear light clothing, drink plenty of non-alcoholic liquids and avoid strenuous activity. Children or pets should never be left in a vehicle, even with the windows open.

Officials are concerned increased use of air conditioners could put a strain on California's power grid. Peak energy demand during this heat wave could approach the record set in July 2006. Associated Press reports that the California Independent System Operator, the agency that monitors the state's power grid, is urging residents to conserve energy.

While no blackouts are expected, ISO officials are concerned about the potential for an unexpected shut down of a power plant. In addition, some transmission lines could be in danger from the hundreds of wildfires burning across California.

Smoke from the fires has added to the health concerns. On Monday, Gov. Arnold Schwarzenegger activated California's excessive heat emergency plan, opening cooling shelters and sending staff and volunteers into communities to advise those most at risk from the heat and smoke.

According to West Coast Expert Meteorologist Paul Yeager, the extreme heat will continue on Thursday.

"In the San Francisco Bay area, temperatures jumped into the lower 100s in parts of the interior East Bay (places like Concord and Livermore) and the North Bay (Santa Rosa and Napa). Farther to the north, it's gotten hot in Portland but not Seattle, and farther to the south, it's remained hot in the valleys to the east of Los Angeles. No major changes will take place for the next couple of days."

The beaches have been the only locations spared the intense heat. Slightly cooler temperatures will return by Friday as the large area of high pressure weakens.

Experts say the combination of hot air and relatively high dew point temperatures will allow a few thunderstorms to erupt over the Sierra Nevada of California this afternoon. Unlike the Southwest thunderstorms, which will bring locally heavy rains, there is simply not enough moisture over California to bring much rainfall. The primary impact of any storms will be lightning that can create new wildfires.

Here is the Accuweather.com SW Regional Weather Report:

Video

Source: AccuWeather.com