Winter Weather Advisories, Watches and Warnings for North Idaho and Northwest Montana
Each year, with more and more people moving into our beautiful part of the country I am asked what are the criteria for the various advisories, watches and warnings for winter weather that are issued for our area. The National Weather Service has established criteria that constitute the issuance of these advisories or warnings. They will be presented very straightforward in this article to make it as easy as possible to see when the various advisories, watches or warnings are issued. Keep in mind that this is not an across the board criteria but specific to our region of the country. Only the National Weather Service can issue advisories, watches or warnings but the qualifications for each are different for different parts of the country depending on their climate so this is specifically for North Idaho and Northwest Montana.
Winter Weather Advisories (Formerly Snow Advisories):
Valley locations (below 3000 feet): Between 3” to 4” in less than 12 hours or greater than 3” and up to 6” in 24 hours.
Mountain locations (above 3000 feet): Advisories not issued.
Winter Storm Watches or Warnings:
Valley locations (below 3000 feet): 6” or more in 12 hours.
Mountain locations (above 3000 feet):
Early/Late Season (between 4/1 to 10/31): Greater than 4” expected in 12 hours or greater than 6” in 24 hours.
All other times: Greater than 8” expected in 12 hours or greater than 12” in 24 hours.
Freezing Rain Advisory:
All areas: Freezing rain event resulting in significant inconvenience and that could lead to life- threatening situations if caution is not exercised
Ice Storm Warning:
All areas: Ice storm producing significant and possibly damaging accumulation of ice (usually ¼ inch or greater)
Blizzard Warning:
All areas: Winds 35 mph and falling and/or blowing snow reducing visibility to < ¼ mile lasting for 2 hours or longer. This is the most extreme weather warning issued for our region and usually is accompanied by heavy falling snow in addition to considerable blowing and drifting of snow and low visibilities.
Wind Chill Advisory:
All areas: Wind chill forecast of minus 35 degrees F or lower with a 10 mph or greater wind speed.
Wind Advisory:
All areas: Sustained winds 30 to 39 mph lasting for one hour or longer and/or wind gusts 45 to 57 mph for any duration which are not associated with thunderstorm activity.
High Wind Watch/Warning:
All areas: Sustained winds 40 mph for at least 1 hour or any gusts 58 mph or more for any duration which are not associated with thunderstorm activity.
This is a summary of the most common advisories, watches or warnings issued for our region from the National Weather Service. I will add that the Missoula NWS often does not follow these criteria and forecasters in that office have been given leeway to make determinations for advisories, watches and warnings as they see things. On this web site, I will mention an advisory, watch or warning if one has been issued by the weather service in my “forecast discussions” section but will not include it in the forecast if the criteria is not likely to be met based on my experience of living here for a long time. With this being North Idaho and Northwest Montana, we are accustomed to winter weather and the hazards that go along with that. Winter Storm Warnings should not be issued for an expected 2 inches of snow in my opinion as we frequently see snowfalls of that amount on a regular basis multiple times throughout the winter months here. I have seen a Winter Storm Warning issued for this and that is not a joke. It was actually embarrassing in my opinion for a warning to be issued for that event. Similarly a snow advisory/winter weather advisory should not be issued for these types of snowfall amounts. Now if you are in say Seattle or Portland or somewhere that typically does not see snowfalls on a regular basis then an advisory would certainly be warranted based on the previously mentioned snowfall amounts. Again I can not issue any advisories, watches or warnings and no private weather forecasting service can, that responsibility solely and entirely rests with the National Weather Service whose mission is to protect lives and property. Hope this helps clear up some of the misconceptions about the various advisories, watches and warnings we can see during the winter months in our region.