A cold front moved through Arizona on Saturday, leaving an unseasonably cool Sunday in the 70s, but a warm-up is set to begin today, with a forecast high of 82 degrees for the Valley, 6 degrees below the average. A trough of low pressure is now moving into the Plains and is expected to move across the Arizona/Mexico border on Thursday, leading to the highest rain chances across southern Arizona. However, there is still a significant uncertainty as to the track and timing of this low, with models showing it moving towards the southern edge of the peninsula.