Fire weather worsens as heat wave spreads across southern US this week

By Allison Chinchar, CNN meteorologist

An early season heat wave will build across the southern tier of the United States, creating “unstable conditions” for wildfires and forcing some residents to conserve power usage.

“We are expecting above normal temperatures and what that means for fires is generally unstable conditions,” Todd Shoemake, a meteorologist at the National Weather Service (NWS) office in Albuquerque, New Mexico, told CNN. “So if you do start to see fire growth, a lot of times it can become pretty explosive and really rapidly gaining in power and heat.”

A ridge of high pressure will build across the Southwest this weekend, allowing for record-breaking heat to settle in.

High temperatures will soar into the 90s and triple digits, which will pose a threat to those who are outdoors for extended periods of time.

The cities of Albuquerque, Santa Fe and Roswell in New Mexico all have the potential to tie or break record highs this weekend and early next week, making weather conditions at the Calf Canyon/Hermits Peak wildfire even more dire.

The largest fire in New Mexico state history (the Whitewater Baldy fire in 2012) burned 297,845 acres. The Calf Canyon/Hermits Peak fire has currently burned more than 288,000 acres and could surpass the number one fire in the next couple of days, as it is only 36% contained.

Makoto Moore, an incident meteorologist (IMET) at the NWS office in Pueblo, Colorado, is on location at the Calf Canyon/Hermits Peak fire.

IMETs provide on-site weather support and products to teams on the ground, including firefighters, needed to complete their mission.

“I am there primarily for firefighter safety, because I provide a safety weather watch throughout the shift, monitoring radar, satellite and observations to hopefully eliminate any weather-related surprises for all the people working in the field,” Moore explained.

“If thunderstorms develop over or near the fire, I will send out a weather alert for lightning, hail, etc. to the crews via radio. I will also alert for thunderstorm outflow winds that could alter the speed and direction of fire spread.”

One thing which could help firefighters increase containment is the wind forecast, projected to remain relatively light across the region during the next 24 hours.

“A ridge of high pressure over the area this weekend should allow for a general relaxing of the winds, though it will also push high temperatures to near-record levels,” Moore said to CNN.

However, weak winds aren’t always a good thing because it can cause plume-dominated fire activity also known as “plume collapses.”

“Plume collapses occur when the heat generated at the surface by the fire is no longer sufficient to maintain an updraft,” Moore said. “It could be because of the fire running out of fuel, or shading of the solar insolation, or any number of reasons, but the energy at the surface is cut and the column collapses due to its own weight and gravity.”

Insolation is a measure of the solar energy on a specified area in a set period of time.

It is not uncommon with fires and is usually not a significant concern. However, it does become a huge deal if a pyrocumulus cloud forms.

Given enough energy and available moisture, the clouds can turn into a thunderstorm on top of the smoke column and fire.

“This thunderstorm will produce all of the hazards of a normal thunderstorm: lightning, gusty and erratic winds, precipitation, etc., except much or all of the activity is hidden by the smoke column,” Moore said. “Firefighters on the ground may have very little warning before strong gusty winds sweep across an area.”

Meteorologists have signs they can look for in order to forecast such events, including monitoring satellite and radar imagery.

“As for predicting such a thing, we have gotten very good at forecasting wind speeds and if lighter winds are forecast for an intensely active fire, we know that there is a good chance that strong vertically developed smoke columns are a possibility,” Moore said.

Moore pointed out potential column collapses will need to be watched this weekend.

Winds will begin to increase, however, and shift rapidly as a cold front arrives into New Mexico by Monday morning.

“This front will do a couple of things,” the NWS office in Albuquerque cautioned on Saturday. “First it may make it into the Rio Grande Valley for a gap wind event with wind speeds 20-30 mph. Second it will raise dewpoints for central/eastern New Mexico.”

This increase in moisture sounds like it would be a good thing, but in reality it is just enough instability for thunderstorms to develop.

“In the end, given moisture profiles, more than likely there will be a few isolated storms that could produce some lightning and a downburst wind gusts,” the NWS office in Albuquerque said.

The strong winds could rapidly spread any ongoing fires and lightning could spark new fires.

Unfortunately the storms will not necessarily bring heavy rain showers the area desperately needs, not only because of the fires, but also due to the persistent drought.

“The drought level at which the Desert Southwest currently sits, is going to require more than one rainy day, one rainy week, or even one rainy year to improve conditions in a meaningful way,” said Jenn Varian, a meteorologist at the NWS office in Las Vegas.

The increase in cloud cover and higher humidity levels will still allow the firefighters an opportunity to increase containment numbers, but not for long.

“Another longwave trough of low pressure developing over the western third of the country means that the Desert Southwest may be entering another period of hot and dry with strong sustained winds starting Thursday and lasting into the next weekend,” Moore explained.

The heat also drains the firefighters who are wearing layers of thick protective clothing in extreme temperatures.

“Higher temperatures mean higher rates of dehydration and highlights the need for crews to drink more water to stay safe,” Moore said.

Extreme heat resulting in record power demands

More than 200 daily record high temperatures are forecast to be challenged over the next 7 few days from the Southwest all the way to the East Coast by midweek.

In Texas, this prolonged heat wave caused six power generation facilities to trip offline resulting in loss of electricity, according to a statement released Friday by the Electric Reliability Council of Texas (ERCOT). As of Sunday morning five of the six plants were back online.

“We’re asking Texans to conserve power when they can by setting their thermostats to 78 degrees or above and avoiding the usage of large appliances (such as dishwashers, washers and dryers) during peak hours between 3 p.m. and 8 p.m. through the weekend,” ERCOT Interim CEO Brad Jones said in a statement Friday.

Some areas of Texas could break daily high temperatures records every day for at least the next seven days.

Several dozen cities from Arizona to the Carolinas are expected to break high temperature records this weekend.

On Sunday, Roswell in New Mexico and Midland and Odessa in Texas will see high temperatures creep up into the triple digits, remaining there until at least Thursday.

For much of East Texas, Oklahoma, Arkansas, Mississippi and Louisiana, the concern isn’t just the temperatures themselves, but the prolonged period of time in which the heat will stick around.

Even locations known for being hot are hotter than usual. Phoenix and Tucson are forecast to reach 105 degrees on Sunday. Their daily high temperature records are 107 degrees and 104 degrees respectively.

Check the forecast to see how hot it will get where you live

Las Vegas may not be expecting record temperatures, but the accelerated rise in temperatures is concerning.

Last week temperatures in Las Vegas were about 20 degrees below normal. Wednesday topped out at only 69 degrees, compared to the average high temperature of 87 degrees.

“Because of the rapid warm up of about 10 degrees a day, this prevents residents and tourists alike from acclimating to the hot temperatures, and unless they’re paying close attention to the forecast, can catch them off guard when recreating outside this weekend,” Varian said.

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CNN meteorologist Haley Brink contributed to this story.