Friday, 28 June 2013

Erratic jet stream brings extremes and warnings to U.S.

Major Heat Wave in the Making for West US
Temperatures will be at full throttle later this week over the interior West, reaching dangerous levels, challenging records and elevating the wildfire threat.



27 June, 2013

While many folks over the interior West are accustomed to and expect hot weather during the summer the developing pattern will take the heat to the extreme. In some cities record highs for any date throughout the year could be equaled or breached.

The weather this week will favor an expanding area of sunshine and building heat over the West. As temperatures soar to record-challenging levels, dry fuel and the potential for spotty dry thunderstorms will push the wildfire threat to new areas and raise the risk in other locations.

Building heat, drought and the risk of wildfires could result in a fireworks ban in some communities as Independence Day activities increase.

The pattern bringing clouds, showers and cool air to the Northwest will gradually erode, dissolve and disappear.

Once the pattern sets up, the heat wave will last through next week in many areas. Grassy and wooded areas that are green now may become dry fuel for fires as the atmosphere heats up.





Cities that will experience record-challenging heat on a daily basis during the pattern into next week include Las Vegas, Phoenix, Salt Lake City, Denver, Boise, Idaho, Rawlins, Wyo., Medford, Ore., and Fresno, Calif.





Cities that could set new annual extreme temperature marks include Flagstaff, Ariz., Las Vegas and Reno, Nev. In Flagstaff, Ariz., the all-time record high is 97 set on July 5, 1973. In Las Vegas, the all-time record high is 117 degrees set on July 19, 2005 and July 24, 1942. At Reno, the all-time high is 108 degrees set most recently on July 5, 2007. Death Valley, Calif. could reach their hottest June temperature on record of 128 degrees set June 30, 1994

According to Western Weather Expert Ken Clark, "People driving through desert areas during the pattern should make sure their vehicle can make the journey and that they carry extra water in case their vehicle breaks down."



With time, the heat can expand to part of the Pacific coast by way of a slight offshore flow. However, the worst of the heat will hold up just inland. The pattern will make the beaches a hot spot to avoid the heat.


The system producing the heat and sunshine will allow widely separated, pop-up thunderstorms with time. Most of the storms will form and die over the mountains, but there will be a few exceptions.

A few locations can receive a downpour. However, many of the storms will bring little or no rainfall. This phenomena, commonly called "dry lightning," can spark new wildfires.


While the natural spark for wildfires cannot be avoided, people are urged to be very careful when using outdoor power equipment and open flames. Never park a vehicle that has been running for any length of time over dry grass and brush as the hot exhaust can start a fire.


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