Severe Thunderstorm Threat From the Central Plains to the Northeast; Extreme HeatRisk for the East Coast

Strong to severe thunderstorms are possible from the central Plains to the Northeast through this evening. Widespread damaging winds are the primary threat but hail and a tornado or two is also possible. Extremely dangerous heat continues across the Eastern U.S. Warm overnight low temperatures will provide little to no relief. Read More >

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Summary

A major winter storm impacted northern Arizona over the Thanksgiving holiday, bringing very heavy wet snow, and causing significant travel disruptions, road closures and power outages. The system initially had high snow levels above 8,000 feet, with rain falling in most areas. Colder air along and behind a very strong cold front brought widespread moderate to heavy snowfall (3-4"/hr snowfall rates) above 5,000 feet beginning early Friday morning and continuing into early Saturday. The combination of heavy, wet snow and strong winds caused multiple power outages, most notably in Tusayan and the Grand Canyon. Over 30 inches of snow was reported near Hwy 180 at Hart Prairie (at the base of the San Francisco Peaks). Travel conditions improved over the weekend as roads reopened and temperatures gradually warmed.

Timeline

Radar Loop from November 28, 2019 11:00 PM and November 29, 2019 at 5:00 AM MST

Radar images show the main frontal bands of rain and snow began to impact central and northern Arizona during the night of the 28th into the morning of the 29th.

Radar Loop from November 29, 2019 between 11:00 AM and 5:00 PM MST

Radar images during the daytime on Friday the 29th showing the shift from widespread bands of frontal precipitation to snow showers.

GOES-17 True Color Satellite Imagery After The Storm

GOES-17 Visible Satellite Imagery. Image was captured around noon MST on Saturday, November 30, 2019 and shows the expansive snowpack across northern Arizona.

Observed Storm Total Snow from Thursday night to Saturday morning. Access all local storm reports throughout Arizona for this storm.

Afternoon of November 28th:
- Isolated to scattered rain and high elevation snow showers spread across Coconino, northern Gila and Yavapai counties. Coverage expanded through the afternoon.
- Snow levels were around 7,500 ft MSL.
Evening and Overnight of November 28th:
- Rain became more widespread and stratiform in coverage as high elevation snow showers continued.
- Warmer than expected surface temperatures kept snow levels around 7,500 ft MSL.
- Travel became impossible in areas as the rain turned to heavy snow.
Early Morning of November 29th:
- Rain converted to snow as snow levels dropped from west to east beginning in the early morning hours.
- Snow increased in intensity across Coconino and Yavapai counties.
- Road and travel conditions decreased rapidly in strong southerly winds, high snowfall rates and blowing snow.
Mid-Morning of November 29th:
- Snowfall rates began to decrease across Coconino and Yavapai counties.
- The main band of snow spread east into Navajo and Apache counties.
- Difficult to impossible travel conditions continued.
â€‹Afternoon of November 29th:
- The main band of snow exited Arizona.
- Widespread snow showers continued across central and northern Arizona, mainly above 4,000 ft MSL.
- Difficult to impossible travel conditions continued.
Evening of November 29th:
- Moderate to heavy snow showers linger generally along and south of the Mogollon Rim.
- Difficult to impossible travel conditions continued.
Overnight of November 29th:
- Moderate to heavy snow showers gradually diminish across central and northern Arizona.
Morning of November 30th:
- The last snow was recorded at NWS Flagstaff and Flagstaff Pulliam Airport, with 17.0 and 16.8 inches (respectively) of snow having fallen during this storm. Click here for access to storm reports throughout Arizona from the storm.
- Travel and road conditions begin to gradually increase throughout Saturday, but icy roads persisted into Sunday.

Impacts

Power was reported to have been lost in the Munds Park region of Coconino County.
Power was lost to portions of northwestern Coconino County along Old Route 66.
Power and heat were lost to most of Grand Canyon Village and a State of Emergency was declared for this area.
Emergency shelters in Grand Canyon Village were established and opened to take in anyone impacted by the storm.
Roads, highways and interstates were shutdown due to the winter weather conditions both during and after the storm.
- SR-89A was closed between Sedona and the I-17 junction due to snow, rockslides and downed trees.
- Desert View Drive (SR-64) between Grand Canyon Village and Desert View was preemptively closed.
- I-40 was preemptively closed between Kingman and Winslow, AZ.
- Northbound I-17 was preemptively closed between the SR-179 exit to Sedona and Flagstaff.
- SR-260 was closed between Camp Verde and Heber.
- SR-87 was closed between Payson and Winslow.
- SR-67 was preemptively closed on the Kaibab Plateau.
- US-191 was closed from Morenci to Alpine.
- US-60 was closed between Globe and Show Low.
- SR-89 was closed between Drake and Ash Fork.
Petrified Forest National Park experienced a full closure on November 29th.
Grand Canyon National Park experienced either partial and full closures on November 29th and 30th.
There was a flash flood within the bounds of the Havasupai Reservation from rainfall runoff late Thursday night.
- Flash flood took place in Supai Creek near the village of Supai, Arizona.
- Resulted in people camping to have their belongings washed away and be displaced from their campsites.
Travel was difficult to impossible across much of the region from early in the morning on November 29th into the morning of November 30th.
- Icy and snow covered roadways persisted into the afternoon of November 30th.

Pictures

16-19 inches of snow fell across the Flagstaff area early Friday morning through early Saturday. Photo Credit: The Republic

Prescott saw several inches of snow leading to hazardous travel conditions. Photo Credit: The Republic

Heavy snowfall and low visibility on Interstate 40 between Kingman and Seligman Friday morning. Photo Credit: ADOT

Whiteout conditions were seen Friday on SR-264 near Window Rock. Photo Credit: ADOT

Gusty winds accompanied this storm leading to wind blown snow sticking on the trees around the higher elevations of northern Arizona. Photo Credit: The Republic

Flagstaff residents woke up to a winter wonderland on Friday November 29th, 2019. Snow showers continued through the day leading to several inches of additional accumulation. Photo Credit: The Republic

Heavy snow falling early Friday morning on Milton Rd in Flagstaff. Photo Credit: ADOT

Snow covered Milton Rd in Flagstaff mid-morning Friday. Photo Credit: ADOT

SR-260 was closed between Camp Verde and Heber during the storm due to very hazardous travel conditions. Photo Credit: ADOT

Snow-packed roadways were seen across much of the higher terrain of northern Arizona. Here is a look at conditions on SR-64 in Williams on Friday afternoon

Heavy snow fell across the south rim of the Grand Canyon and brought up to two feet in some areas. Photo Credt: GCNP

Interstate 40 was closed through a large portion of northern Arizona during the storm. Photo Credit: ADOT

Meteorology

Three primary ingredients are needed for heavy snow: cold air, moisture, and lift. A plume of subtropical moisture moved northeastward into Arizona from the night of November 27th, 2019 into the afternoon of November 28th, 2019. This warm and very moist airmass led to widespread precipitation across northern Arizona. The source region of the moisture initially resulted in high snow levels above 7,500 feet through Thanksgiving night. Snow levels dropped rapidly early Friday morning along and behind a very strong cold front and upper level low pressure system, which generally moved to the east. This system provided additional strong lift and moisture into the region, resulting in widespread moderate to heavy snowfall through much of Friday. The system exited the region early Saturday, with temperatures struggling to reach freezing Saturday afternoon along the Mogollon Rim.

Progression of the air masses that created the heavy rain and snowfall from Thursday during the day into Friday night.

Points of Contact

For more information on impacts and general inquiries about this event, please reference the contacts below:

National Weather Service:
- Brian Klimowski, Meteorologist-in-Charge at (928) 556-9161 ext. 222 or brian.klimowski@noaa.gov
- Tony Merriman, Warning Coordination Meteorologist at (928) 556-9161 ext. 223 or tony.merriman@noaa.gov
Arizona Department of Transportation: at info@azdot.gov

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Severe Thunderstorm Threat From the Central Plains to the Northeast; Extreme HeatRisk for the East Coast

Heavy Snowfall November 2019