Following widespread 1 to 2 inches of rain on Christmas Eve, dense fog developed in parts of the Greater Phoenix Area in the morning of Christmas Day, particularly in the southwest and far southeast parts of the metro. No reports of ground traffic being impacted were found.
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The episode as NWS PSR wrote it up.
Following widespread 1 to 2 inches of rain on Christmas Eve, dense fog developed in parts of the Greater Phoenix Area in the morning of Christmas Day, particularly in the southwest and far southeast parts of the metro. No reports of ground traffic being impacted were found. The fog was considered significant seeing as it is a once, maybe twice, a year occurrence in the Phoenix area.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Phoenix, AZ wrote its last area forecast discussion before the first event at Dec 25, 4:45 AM MST, 45 minutes earlier.
Area Forecast Discussion National Weather Service Phoenix AZ 445 AM MST Sat Dec 25 2021 .UPDATE...12z AVIATION DISCUSSION... && .SYNOPSIS... Several fast moving weather disturbances will progress through the region next week resulting in a persistent unsettled weather pattern. Mostly cloudy days and occasional chances of light rain will be far more common than has been experienced so far this cool season. Temperatures will remain below seasonal normals through the entire week. A more energetic and wetter weather system may enter the picture next weekend. && .DISCUSSION... A stagnant hemispheric flow pattern will persist through next week with pronounced high amplitude ridging anchored over the central Pacific while a complex omega block dominates eastern Canada. This pattern results in longwave troughing becoming the main feature stuck over western North America with embedded fast moving shortwaves rotating through the larger cyclonic circulation. The prevalence of anomalously strong zonal jet energy downstream through the Rockies/plains should keep these shortwaves dampened and progressive limiting both the forcing magnitude and residence time within the forecast area. However, a seasonally moist environment has become established over the region and shows no signs of dislodging as model forecasts indicate total column PWATs 0.50-0.75 inches and sfc-H8 mixing ratios aoa 5 g/kg being maintained in lower elevations of south-central AZ throughout the week. While a subtle H7 shortwave and weak warm advection scheme were invigorating pockets of very light rain this morning, the more notable wave currently near 40N 135W will rapidly sweep into the western Conus in response to an impressive 175kt jet core developing over the Great Basin. However, the forecast area will remain in the anti-cyclonic side of this jet core with forecast BUFR soundings suggesting rather marked H7-H5 warming occurring as a result. Modest H8-H7 frontogentical forcing acting on a moist layer should be sufficient to support a few showers, though the capping aloft and limited ascent through a greater depth will likely hinder better rainfall potential. HREF membership is not particularly bullish on shower chances, and conceptually this looks like a scattered shower/very low QPF event with the best chances focused over higher terrain. Operational and ensemble guidance show at least one (and possibly a pair) of similar shortwaves descending and amplifying along the West Coast before sweeping across the SW Conus Monday night and Tuesday. Synoptic forcing associated with this configuration appears better than the predecessor Sunday with slightly better moisture profiles (although not near the magnitude of the moisture inclusion from this past system Friday). Not surprisingly, the preponderance of guidance indicates the best chances/amounts in orographic upslope regions of central AZ with parameters tapering off into the lower desert regions of SW AZ. One potential greater impact lies with the potentially for snow at higher elevations as NBM median snow levels values drop near/below pass level with minor accumulations. However, close investigation of forecast soundings indicate maintenance of the midtropospheric inversion while significantly limiting saturation within the -12C to -18C dendritic growth layer result in very low confidence of any snow impacts. During the latter half of next week, ensemble spread with respect to individual shortwaves naturally grows though the overall general troughing pattern persists. Given the uncertainty, NBM POPs are essentially evenly spread across the entire multi-day time frame; though realistically, only a brief light shower is the more likely outcome at some point during the Wed-Thurs time frame. Towards the end of next week, the first signs of a possible pattern realignment are revealed in most ensemble output with stronger waves cresting the central Pacific ridging and allowing more prevalent downstream pattern retrogression and amplification nearing the SW Conus. While still a week in advance, there are many facets of the forecast that conceptually match wetter, higher impact events with deep PV anomalies digging west of the Baja and tapping a pool of subtropical moisture in deep southerly flow. && .AVIATION...Updated at 1140Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Much-improved flying conditions when compared to yesterday, but still some things to keep an eye on. Visibilities have thus far remained aoa 5SM for most of the overnight. Localized patchy fog/mist is possible early this morning due to very moist conditions but chance at any one TAF site appears less than 20%, so left out of TAFs except SDL where 6SM/BR has been rather persistent. Model soundings keep some low- level moisture in place today. Expect SCT/BKN cumulus/stratocumulus at times with BKN/OVC deck thickening up top (>FL180) through the afternoon. Rain chances are aob 20% today; left VCSH in for a time at SDL which appeared to have slightly better chance for a passing shower (of light intensity) this morning/early afternoon. Winds should favor SE trajectories, becoming SSW tonight ahead of a disturbance passing through the Desert Southwest. A couple forecast models hint at isolated showers tomorrow morning - but confidence was too low to include in TAFs at this time. Southeast California/Southwest Arizona including KIPL and KBLH: Expect periods of high clouds with perhaps FEW/SCT cumulus developing today. Models indicate increased wind speeds with locally gusty conditions out of the W/SW this evening and tonight ahead of a quick-moving disturbance. Clouds may develop below FL080 toward the tail-end of the TAF period. && .FIRE WEATHER... Monday through Friday: With temperatures hovering below normal through the week, a moist atmosphere with periodic chances of wetting rains will be common. Minimum afternoon humidity levels will struggle to even reach 40% following excellent overnight recovery of 60-100%. Given the numerous weather disturbances passing through the region, occasionally gusty winds may affect some districts though speeds do not appear unusually strong at any point, and should not pose any enhanced fire risk given the underlying wet conditions. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && DISCUSSION...18 AVIATION...Heil FIRE WEATHER...18
The national radar mosaic for the moment the first event began.
2 dense fog. Local standard time, as filed.
Chandler Municipal Airport and Phoenix-Mesa Gateway Airport both reported visibilities down to or below a quarter of a mile from 0547MST to 0950MST. There were also multiple photos and videos from this area showing visibilities down to a few hundred feet.
The Buckeye Municipal Airport reported visibility down to around a quarter of a mile between 0710MST to 0940MST. A report on social media also said visibility was down to around 100 feet in Laveen around 0900MST.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2021Every state in 2021This day in weather historyWarnings in Arizona, December 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 992781, 992782.