Dense Fog in Arizona, February 1, 2015

A wet Pacific low pressure system moved across the central Arizona deserts on January 31st and then exited to the east. Ample lingering surface moisture combined with light wind and clearing skies to allow for widespread dense fog across the greater Phoenix area during the morning hours on February 1st. Many locations, including a number of local airports, reported dense fog with visibility at or below one quarter mile for several hours or more during the morning. At 0355MST, both the KIWA and the Buckeye airports reported visibility at one quarter mile in dense fog. At 0522MST, visibility at Phoenix Sky Harbor Airport lowered to one quarter mile, and stayed there for several hours, severely disrupting air traffic and forcing a number of delays and diversions. This was a major problem due to the fact that February 1st was Super Bowl Sunday and as a result air travel into the airport on the morning before the game was at near record levels. Additionally, the dense fog created very hazardous driving conditions for motorists arriving at or leaving the various airports around the greater Phoenix area. The dense fog persisted into the late morning; at about 1000MST a trained spotter 3 miles northwest of Goodyear estimated visibility below one quarter mile in dense fog and at 1016MST a trained spotter 2 miles northwest of the Arizona State Fairgrounds estimated visibility down to one fifth of a mile.

A wet Pacific weather system moved across south central Arizona on January 31st, generating widespread showers, and then it exited to the east. Ample lingering low level moisture combined with clearing skies and light wind allowed areas of dense fog to form across southern Gila County during the morning hours on February 1st. According to Gila County law enforcement, visibility was estimated at one quarter of a mile in the town of Globe at 0405MST. The dense fog and near zero visibility created very hazardous driving conditions, especially for motorists traveling along highways 60 and 188. A Dense Fog Advisory was issued for southern Gila County at 0413MST and it remained in effect through noon. Fortunately, no injuries or accidents were reported due to the dense fog.

A wet Pacific weather system produced significant rain across the central deserts on January 31st and then exited to the east. Ample lingering low level moisture combined with clearing skies and light winds to produce areas of dense fog across much of northwest Pinal county during the morning hours on February 1st. According to the official weather station at Casa Grande Airport, visibility dropped to one quarter mile at 0435MST as a result of the dense fog. As late as 1023MST a trained spotter 4 miles east of Sun Lakes estimated visibility below one half mile in dense fog. The dense fog created very hazardous driving conditions and a Dense Fog Advisory was in effect for the central deserts through 1200MST.

A wet Pacific weather system spread considerable showers across the central deserts on January 31st and then exited to the east. Ample lingering low level moisture combined with clearing skies to allow for areas of dense fog across southwest Maricopa county during the morning hours on February 1st. According to a trained weather spotter 2 miles southwest of Gila Bend, visibility was estimated to have fallen well below one quarter mile at 1015MST. Visibility gradually improved during the late morning hours. At 0340MST a Dense Fog Advisory was issued for southwest Maricopa County and the advisory remained in effect through noon. The dense fog created very hazardous driving conditions especially in the area around Gila Bend; fortunately no injuries or accidents were reported as a result of the dense fog.