Weather History as a Predictor of Ice Conditions
Ice is constantly changing: getting thicker or thinner. Holes are forming or freezing up. Pressure ridges are forming and evolving. One of the best predictors of what to expect on ice you are planning to go out on is the weather history, particularly over past week or so. Even a few hours above freezing can significantly change the ice conditions. For most of us, our memory for weather specifics from a week ago is not great. It is easy to overlook a brief, intense warm spell.
I have been using the weather underground.com . They have an extensive database of weather history. When you get to the main page, pick a city that best represents the ice you are interested in. On the page for that city there are sections for:
- Weather at a Glance
- Travel & Activities
- Weather Stations
About halfway down in the 'Nearby' section there is a History & Almanac subsection (a quick way to get there from the top of the 'city' page is to press the 'Page Down' key three times).
Click 'View' and on the resultant page click 'Weekly' and then use the 'Previous Week' tab as needed. The date shown for a week is the Sunday at the beginning of that week.
On the lower part of that page there are graphs and a table. The graph in this example starts on Sunday January 24, 2010.
The graphs are an easy way to get a quick understanding of the history. The tables show the amount of precipitation and what form it fell in. Look for any above freezing weather. Note how much wind there is when it is above freezing. Temperatures above 45 degrees with some wind are likely to make major changes in the ice. If the ice is relatively new, see if you can identify when it caught. How many freezing degree day have there been since the lake caught?...since the last significant thaw? ...etc? If it is in the Spring, how strong has the sun been? Anytime: how much snow fell? Was it windy enough to blow it into drifts? Have an understanding of the recent weather history will let you develop a significantly better understanding of ice behavior.
You can do pretty much the same thing in the 'Weather Stations' section. You may find one of the local stations that is much closer to the ice you are considering going out on. These stations are, for the most part, are not as well situated as a professional station for wind and some other measurements. They often have much shorter historical records.