January in the West
Unusually cold conditions dominated the West, especially in the interior, this month as strong inversions developed in the Great Basin and other low-lying areas. These inversions resulted from widespread snow cover established in December and intrusion of cold air masses followed by persistent ridges of high pressure at upper levels. These conditions prohibited vertical mixing and horizontal flow, resulting in poor air quality and record low temperatures in affected areas. Precipitation was below normal for much of the region, though with several pockets above average in the Southwest and Montana.
Precipitation in the conterminous West was generally confined to two events this month. The first occurred over the 4th-12th and brought 10.2 in (26 cm) of snow to Salt Lake City, Utah and 24-36 in (60-90 cm) of snow to the northern portion of Utah’s Wasatch Range between the 10th and 12th. Salt Lake City received a total 23.8 in (60 cm) snowfall for the month, 190% of normal and the city’s 13th snowiest January since records began in 1874. The second event began on the 24th in conjunction with a plume of subtropical moisture over the Southwest. On January 26th, a weather balloon sounding at Phoenix, Arizona showed the most moisture present in the atmosphere of any January day since balloon launches began there in 1950. Phoenix recorded its 7th wettest January day in a 118-year record on the 26th at 1.18 in (30 mm). Portions of southeastern California, southeastern Utah, Arizona, and southwest Colorado also received a majority of their January precipitation from this event. Outside that area, dry conditions prevailed. Of note in the southern Great Basin was only trace of snowfall on Mt. Charleston near Las Vegas, Nevada where normal January snowfall is 21.9 in (56 cm). This month ties January 2003 for the least January snowfall at Mt. Charleston. Snow water equivalent in the Sierra Nevada snowpack started the month near 140% of normal and ended the month close to 90% of normal for the date. Despite daily record snowfalls and above normal precipitation in the northern and southern reaches of Montana, statewide precipitation averaged approximately 0.2 in (5 mm) below normal this month. This breaks a trend of above normal precipitation since October that followed a very dry spring and summer.
Frigid air settled into the Great Basin and other interior valleys this month. Salt Lake City, Utah, at an average 19.4 F (-7 C), experienced its coldest month since 1949 and 6th coldest January since records began in 1874. Their normal January temperature is 29.5 F (-1.4 C). There are an average 9.4 days below freezing at Salt Lake City in January, but in this past month 22 days failed to reach the freezing mark. This total remains a few days behind January 1949 where 26 days had sub-freezing highs. Grand Junction, Colorado had not recorded more than 21 sub-0 F (< -17.8 C) lows in a winter until hitting its 22nd of the season at -3 F (-19.4 C) on January 22nd with almost two months of winter remaining. Grand Junction also saw its 4th longest stretch of sub-freezing highs at 22 days from December 19-January 9. Freezes affected California’s citrus January 10-14, prompting farmers to take measures to prevent crop damage. Los Angeles, California hit a minimum 34 F (1.1 C) on the 14th, the coldest temperature recorded there in over 20 years.
January provided relief from persistent drought in the northwestern portion of the Hawaiian Islands. After its driest December on record, Honolulu, Oahu finally saw above normal precipitation this month at 2.42 in (62 mm), 105% of normal. The islands of Kauai and Molokai also fared well this month with above normal precipitation at most locations. Dry conditions continued for Maui and Big Island, especially in leeward areas, which were generally below 50% of normal for the month.
Further north, Alaska was warmer and wetter than normal for the month. Several daily snowfall and precipitation records as well as high temperature records were set throughout the state. Average temperatures in the Interior and Western regions were most notable with anomalies up to 10 F (5.5 C) above normal. Following its coldest January on record in 2012 at nearly 20 F (11.1 C) below normal, Kotzebue, Alaska recorded an average 8.7 F (-12.9 C), 11.5 F (6.4 C) above normal this month and the 8th warmest January in a 63-year record. During a brief but intense cold snap late in the month, Chicken reached -62 F (-52.2 C), Eagle dropped to -57 F (-49.4 F). Fairbanks saw -48 F (-44.4 C) on the 27th for the second time this winter (also Dec 17th), and measured -40 F (-40 C) 14 times during the month. This followed after 0.15” (3.8 mm) of extremely atypical liquid rain fell on the 14th, the most rain in January in 50 years.
Significant Events for January 2013
January 24: Freezing Rain in Great Basin: A rare freezing rain was reported at several Great Basin locations including Salt Lake City, Utah, Elko, Nevada, and Boise, Idaho. A storm system pushed subtropical moisture aloft over the region. Falling rain was super-cooled as it moved through the cold air trapped in the valleys. The droplets froze upon contact with objects on the surface, interrupting travel throughout the region. In Salt Lake City, this was the 9th incidence of freezing rain since 1940.