Identify Weather Threats Snow

Snow

Biggest takeaway:
Most winter storms create transportation issues and slip & fall issues. The biggest storms with heavy snow, strong winds, and whiteout conditions that occur 0-2 times per decade (on average) are a different kind of threat where lives are more directly threatened.

Warning/Trigger for Plan:
NWS Winter Storm Warning (moderate/major) – or – NWS Winter Weather Advisory (minor).

Advance Notice/Time to Activate & Accomplish Your Planned Response:
* Snowfalls >12" often have 3-6 days of advance notice that the threat is there (while details remain to be refined with time). That allows time to plan and lessen the impact on the region. Average lead time for NWS Winter Storm Warnings (for the expectation of at least 5" snow) is approaching 24 hours - with >90% accuracy.
* Minor storms often have less advance notice. Sometimes it is cut to several hours, sometimes less. Winter Weather Advisories average about 12 hours of advance notice.

Frequency:
* Major snowstorms or blizzards are uncommon in our area, but happen 0-2 times/decade on average.
* Minor snows are much more frequent and happen every winter. Although how often per winter depends on your exact location and elevation.

How Accurate Warnings?
If there is a significant winter storm, it nearly always (>90% chance) has a warning out in advance. False Alarms are down to about 1 in 3 – many of those "false alarms" have snow, just not enough to reach our warning requirements.

From a transportation perspective, minor storms are often a bigger threat due to the typically increased uncertainty in the forecast. This is particularly true when road temperatures are below freezing with full traffic on the roads. With that combination, even a fraction of an inch of snow can cause roads to ice over, multiple accidents to occur, and gridlock for multiple hours - trapping people in their vehicles for an extended time.
True blizzards are uncommon in our area, but happen 0-2 times/decade. These need to have a different type of plan since the level of threat to life is much higher, including:
- Outdoor travel and activity should be refrained from.
- Anyone travelling in a blizzard could easily get lost in a whiteout, and run into hypothermia danger.
- Cars can disappear off the road and occupants encounter a similar hypothermia threat.
- Cars and people can get trapped in deep snow.
- For those indoors, be ready for an extended power outage, with subfreezing temperatures.
- Be prepared with food, drinks, money, and medicines to be trapped in your home for a few days.

Safety References:
- Winter Storms...The Deceptive Killers