Posted at: 01/14/2014 7:31 PM
Updated at: 01/14/2014 8:03 PM
Near Blizzard Conditions Felt Today, Round Two Thursday
Normally, a 1-3" snowfall doesn't cause too much of a fuss. Yes, it will slow down the drive time just a bit but normally it won't cause a major ruckus. Today's 1-3" did. The reason can be attributed to the strong winds that accompanied today's snow into the area.
A compact, but potent Alberta Clipper produced very strong winds this morning with wind gusts topping 50 mph across a few points in north Iowa. And for a brief time, blizzard conditions were met. The picture below comes to us from Trenton T. taken near Bolan, IA in Worth County, around sunrise. This was about the same time as the strongest winds impacted the area.
In the extreme and isolated cases strong winds caused white out conditions where visibility was limited to just a few yards.
The worst was without a doubt seen in northern Iowa, however blowing snow did cause issues across all of the local area. Blowing snow caused minor drifting on several rural routes. Dozens of spin outs and accidents were reported as well.
Conditions are improving as I write this (Tuesday Evening) but it won't last for long. Another Alberta Clipper is on the way for Wednesday night into Thursday. Again, strong winds are forecast. Below is a (very conservative) estimate for sustained winds (in blue) over the 48 hour period encompassing Wednesday and Thursday. Also shown are temperatures in red.
Alberta Clippers are well known for their strong winds and cold air and not so much for heavy snow. The strongest winds are normally found on the trailing side (west) of the area of low pressure. Winds are enhanced due to high pressure being squeezed next to the clipper, also by the cold air that is rushing in, which promotes a sinking action bringing stronger winds aloft down to the surface. Often times with fresh snow, it will result in a blizzard.
In the below image shows a computer model surface forecast for 3pm Thursday afternoon. The blue lines running north to south are isobars, or lines of equal pressure. The tighter those lines are, the stronger the wind will be. Notice how this is on the back side of the area of low pressure centered over the upper peninsula of Michigan. Precipitation for the previous three hours is the color contouring over the local area, less than 0.05" liquid equivalent (IE: Not much snow).
Forecast snow from Wednesday night to Thursday is only anticipated to be trace amounts up to one inch. Again, normally not a huge issue, however with the winds I'm anticipating to be approaching 25-35 mph sustained with gusts closer to 45-50 mph, it could create a blizzard.
A Blizzard Watch is in place for areas to our northwest for Thursday (as of Wednesday evening). This map will likely change a bit from now to Thursday, either expanded or upgraded.
There is criteria for a blizzard, however snow amounts is not one of them. Snow must be present, but the only criteria for a Blizzard are sustained winds must be in excess of 35 mph for three or more hours, plus, visibility must be reduced to under 1/4 of a mile. If the forecast continues to progress as expected, the Blizzard Watch above, will likely be upgraded to a Blizzard Warning.
If you recall, blizzard warnings were not in effect for Tuesday. The main reason was the criteria for wind was borderline. Yes there was some sustained winds close to 35 mph, however it wasn't widespread and they didn't persist for more than a couple of hours.
Thursday may be the better chance to meet the criteria on the flat ridge tops of SE Minnesota and northern Iowa.
So be prepared. It may not be a lot of snow, but that snow will likely have significant impacts, with widespread blowing snow, drifting in the open and restricted visibility. We're tracking the forecast for Wednesday night into Thursday closely and we'll keep you updated.
Storm Tracker 6 Chief Meteorologist