Great Plains Blizzards
"Blizzard Warning": winds expected to exceed 30 knots (35 mph) and falling or blowing snow will reduce visibility to less than a quarter-mile for at least 3 hours
"Stockmen's Warning": when severe winter weather threatens cattle in major ranching areas
"Traveler's Warnings": when winter conditions make travel difficult or impossible
"Blizzard of 1997": killed nearly $4.7 million worth of livestock, caused $6 million in farm property damage, and cost farmers $21 million for extra feed consumption
The north-south oriented Rocky Mountain Range effectively isolates the lower atmosphere over the Great Plains from the warm air over the Pacific
The "endless" Arctic nights allow air over the Canadian Arctic to cool rapidly, creating the bitterly cold air that plunges south and contributes to blizzards
Developing cyclones to the lee of the Rockies provide the strong winds that drive the arctic air southward, as well as bring up the warmer, moist air from the Gulf of Mexico
Blizzards are most frequent over North & South Dakota, Minnesota, Nebraska, northern Iowa and eastern Colorado, as well as to the north in Alberta, Saskatchewan and Manitoba Provinces of Canada; these geographical areas are just north of the primary storm tracks and just south of the Canadian Arctic
North & South Dakota, and Minnesota average 1-2 blizzards per year
"Blizzard Recipe": cold, wind and snow. Arctic air mass cools to 30 below to 50 below zero F, creating high pressure at the surface (usually in excess of 1030 mb). The leading edge of this air mass is called the arctic front
"Colorado Cyclones:" low pressure develops to the lee of the Rockies; the jet stream flows over the Colorado/New Mexico region, creating divergence at the jet stream level, associated with the curvature change within the wave and/or with jet streaks; air flowing over a mountain range will create a cyclonic circulation on the lee side, just due to the compression of air moving over the mountain tops and expansion down the lee slopes ("Lee Cyclogensis")
Trowel (trough of warm air aloft) provides major source of snowfall
Air traveling from the Mississippi River Valley west to the foothills of the Colorado Rockies will rise from less than 500 feet above MSL, to about 5000 feet above MSL; this "upslope" component would cool air between 16 F and 27 F, depending on whether the air is saturated or unsaturated
Great Plains Blizzards (continued)
1-2 feet of snow typical in a blizzard, in a swath hundreds of miles wide and hundreds of miles long
Due to the low water content of the snow, blowing and drifting snow is an added problem; snow drifts can reach 10-20 feet in a blizzard
"Alberta Clippers:" small, fast-moving storms that usually develop in the arctic air entrenched over Canada and the northern U.S.; typically drop only 2-5" of snow, but due to the bitterly cold air, the snow has an extremely low water content and is easily blown and drifted; most of the snow falls in the northeastern geographical quadrant measured from the storm center.
"Ground Blizzards": occur when extremely cold winds blow across snow covered ground, creating a shallow layer (tens of feet above the surface) of blowing snow and whiteout conditions; usually occur in the wake of a snowstorm; can occur under a clear sky, and be worse than the actual snowstorm.
"Blizzard Safety:" 1) carry a winter storm survival kit that includes blankets, sleeping bags, flashlight (extra batteries), a first aid kit, a knife, high calorie non-perishable food, extra dry clothing, drinking water, a large can with plastic cover for sanitary purposes, a small can for melting snow to make additional drinking water, waterproof matches (or a lighter), and several large candles.
Burning a single candle inside a car can provide light, as well as warming the interior several tens of degrees, reducing the need to run the car engine, further preventing carbon monoxide poisoning from the exhaust.
2) Carry basic winter auto safety items, including a sack of sand, shovel, windshield scraper and snow brush, tool kit, tow rope, booster cables and accident hazard flares.
3) Stay with your vehicle! People seeking help often become disoriented in blinding snow only feet from their vehicle and can get lost, usually becoming a fatal decision.
4) Carry a cell phone to alert authorities and family, and hasten rescue.
About Winter Weather Deaths: 70% occur in automobiles, usually in accidents on icy roads; about 25% are people caught out in the storm; the majority are over 40 years old; people die of heart attacks while shoveling snow; people die of hypothermia from prolonged exposure to cold (50% of those are over 60 years old, 75% are males, 20% occur in the home).