Wednesday, January 29, 2014

Alaska Winter Advisories 2009-2013

A few days ago Rick pointed me to the Iowa State site that contains NWS advisory archives. I have long been interested in the spatial distribution of weather phenomenon and this archive data set practically begs to be mapped. So, here is a map of total winter advisories for all of Alaska between January 1, 2009, and December 31, 2013 – a five year climatology. The types of advisories include: 1) Winter Storm Warnings, 2) Winter Weather Advisories, 3) Blizzard Warnings, 4) Freezing Rain Advisories, 5) Ice Storm Warnings, 6) Wind Chill Advisories, and 7) Wind Chill Warnings. Watches were not included. Any product with "WSW in the header and NEW, EXA, or EXB in the VTEC line was included.

Note: Many of the differences between adjacent zones are due to the specific criteria for those zones. For example, Cordova's zone does not have a Winter Weather Advisory criteria for snow but Yakutat's zone does. I will have a follow up post with maps of the advisory/warning criteria soon.

Total Number of Winter Advisories/Warnings:
Fig 1. Total number of Advisories and Warnings (all types) between 2009 and 2013.

There are a couple of important things to keep in mind. First, there are three NWS forecast offices in Alaska and they each have different advisory/warning thresholds for the zones in their area of responsibilities. Second, particularly with Winter Weather Advisories, sometimes they are the result of snowfall, sometimes they are the result of blowing snow, and sometimes they are a result of the combination of multiple factors. The same is true for Winter Storm Warnings to a lesser degree. In another post, I will display a series of maps showing the advisory criteria. In the meantime, you can find the Alaska Region text document here: .

Maps of Different Advisory/Warning Types:

Fig 2. Total number of Winter Storm Warnings between 2009 and 2013.

Fig 3. Total number of Winter Weather Advisories between 2009 and 2013.

Fig 4. Total number of Wind Chill Advisories/Warnings between 2009 and 2013.

Fig 5. Total number of Blizzard Warnings between 2009 and 2013.

Fig 6. Total number of Freezing Rain Advisories between 2009 and 2013.

 Fig 7. Total number of Ice Storm Warnings between 2009 and 2013.


  1. Brian,

    Very nice indeed.

    Did the blizzard warning map get lost in the mix? Looks like the wind chill map is duplicated.

    One thing that jumps out at me is the low number of winter weather advisories and winter storm warnings in the Lower Kuskokwim Valley zone. Is this region really that sheltered? Do they have climatologically low snowfall there?

    1. The blizzard warning map has been added. Sorry about that.

      There are several differences about the Lower Kuskokwim. 1) more Blizzard Warnings, 2) slightly warmer temperatures, and 3) different forecast office.

    2. Very interesting analyses. Thanks Brian.

    3. Brian,

      Thanks... if I'm not mistaken, the Lower Kuskokwim zone (AKZ152) shows zero blizzard warnings, zero winter storm warnings, and only 10 winter weather advisories in 5 years. I recognize it might be a relatively sheltered region, but I'd be surprised if this reflects the actual snow climatology. I'll see if I can look up some of the station data in the area.

    4. Rick was curious about the Upper Kuskokwim zone (AKZ227). Those two zones were split apart in April 2009. All of the AFC zones have a high Winter Storm Warning threshold so the low number there is not too surprising. Only 1 PAFC zone has more than a handful of Winter Storm Warnings. As for Blizzard Warnings, very few are issued for inland zones so that isn't too surprising either. The number of Winter Weather Advisories seems low though. I looked through the data again and everything is accounted for. Those two seems to be forgotten zones.