Arizonans may notice a noticeable difference in weather shortly before the Christmas holiday, when a wetter pattern develops across the Desert Southwest later this week.
According to the National Weather Service in Phoenix, the sustained high pressure that has kept conditions dry will start to shift eastward by midweek. In its place, a powerful low-pressure system is forecast to form off the West Coast, allowing plenty of Pacific moisture to flow inland and improve rain chances in Arizona.
Forecasters predict cloud cover and rain possibilities might increase as early as late Tuesday, with the most extensive effects likely on Wednesday and Christmas Eve. Moisture levels may rise two to three times higher than average during this time, indicating a better chance of measurable rainfall.
The most affected locations are in central and southern Arizona, with potential regional travel consequences, particularly during periods of heavy rain. While widespread flooding is not expected, wet roads may hinder holiday traffic and cause slippery driving conditions.
Snow levels are forecast to stay high, often above 7,500 to 8,000 feet, restricting winter impacts to the highest elevations. This means that if precipitation does occur, most lower desert towns will get rain instead of snow.
The National Weather Service adds that exact rainfall totals and peak rain possibilities remain uncertain. Forecasts can be modified as the system approaches and confidence rises.
Residents planning holiday travel are advised to stay up to date on weather forecasts and allow additional time on the roadways later this week.