10 January 2011
I thought I’d share with you some of the images viewers sent in of the heavy snow event over North Alabama. In Huntsville, this is the third heaviest snowfall on record. Number one is the 17 inches that fell on New Year’s Eve in 1963. January 1988 brought 9.6″ and the total last night was 8.9″ at the Huntsville Airport.
This event comes just 3 weeks after a very rare white Christmas over the region! Two heavy snows like this in one winter are almost unheard of here. It’s now the 3rd snowiest winter on record for North Alabama. Atlanta has been virtually shut down by snow and ice with hundreds of flights cancelled at Hartsfield Airport.
Most snow events in the South have a ratio of liquid water to snow of less than 10 to 1. This one seems to have been more like 11 to 1. The ratio is affected by temperatures aloft.
Here is another shot of the snow. The highest totals seem to be near Florence in NW Alabama where 11 inches fell.
Wes Junker, a legendary forecaster for NOAA, at the Hydrometeorological Prediction Center (HPC) has some good info on the snow to liquid ratio. This gives you an idea of how difficult forecasting snowfall can be:
Forecasting snow to liquid ratio
Warm ground and boundary layer temperatures can keep snow-water ratios down
a warm layer that approaches zero oC also will usually keep the ratios low.
Storms having clouds with a large amounts of supercooled droplets will not have as high a ratio as storms in which most crystal growth is by deposition.
Soundings that are almost isothermal with a large portion of the sounding near zero oC will usually have a ratio of 8 or 10 to 1.
High winds will keep snow ratios down because snowflakes will fracture and lose their lacy structure
Deep cold air promotes higher ratios but if the temperatures are too cold the crystal type may not be conducive to high ratios. .
Storm tracks often provide keys to forecasting the snow to water ratio
tracks near oceans have more liquid water in clouds which usually produces lower snow-liquid ratios
My initial forecast was for 4-9 inches. I revised it up to 7-13 inches during the event.
5 to11 inches was reported in most areas.
Cool time-lapse video of the snowfall in Madison Al. (Just west of Huntsville):