Previsão do tempo, weather forecast: CIMSS Satellite Blog

NOAA-18 AVHRR Infrared Window (10.8 µm) image, with surface air temperatures and corresponding station identifications [click to enlarge]

A NOAA-18 AVHRR Infrared Window (10.8 µm) image (above) showed the signature of cold air (violet shades) settling into river valleys and other low-elevation terrain areas across the cloud-free interior of Alaska at 1916 UTC (10:16 am local time) on 18 January 2017. Note that there was a layer of clouds (warmer cyan colors) over much of the North Slope of Alaska; these clouds were acting to limit strong surface radiational cooling, with resulting temperatures only as cold as the -20s F. This AVHRR image was about 1 hour before the low temperature at Fairbanks International Airport (PAFA) dropped to -51ºF (-46ºC) — the first low of -50ºF or colder at that location since 31 December 1999 (-53ºF). While these were certainly cold temperatures, in general they were several degrees warmer than the daily record lows for 18 January:

It’s cold over parts of Alaska, but it’s not approaching record low levels. Many of these records were set in 1947. #akwx @Climatologist49 http://pic.twitter.com/ssWq0ZhV09

— Rick Thoman (@AlaskaWx) January 19, 2017

NOAA-18 AVHRR Infrared Window (10.8 µm) image centered on Bettles (PABT), with surface air temperatures and corresponding station identifications [click to enlarge]

Closer views centered on Bettles (above) and on Tanana (below) further highlighted the influence of terrain on the pattern of surface infrared brightness temperatures.

NOAA-18 AVHRR Infrared Window (10.8 µm) image centered on Tanana (PATA), with surface air temperatures and corresponding station identifications [click to enlarge]

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NOAA-19 AVHRR Infrared Window (10.8 µm) image, with surface air temperatures and corresponding station identifications [click to enlarge]

The cold continued across much of Alaska on 19 January, as seen on a NOAA-19 AVHRR Infrared Window (10.8 µm) image at 1519 UTC or 4:19 am local time (above). However with a lack of cloud cover over the central portion of the North Slope, surface air temperatures were much colder (in the -40s F) compared to what was seen there on the previous day.

NOAA-19 AVHRR Infrared Window (10.8 µm) image centered on Bettles (PABT), with surface air temperatures and corresponding station identifications [click to enlarge]

As was shown on the previous day, closer views centered on Bettles (above) and on Tanana (below) further highlighted the influence of terrain on the pattern of surface infrared brightness temperatures. On this day the minimum temperature at Tanana was -59ºF.

NOAA-19 AVHRR Infrared Window (10.8 µm) images centered on Tanana (PATA), with surface air temperatures and corresponding station identifications [click to enlarge]

Time series plots of surface weather conditions at Fairbanks, Tanana and Bettles during the 18-19 January period are shown below. Note that the surface visibility was periodically restricted 1 statute mile or less, due to ice fog, at all 3 locations.