Warm and dry weather should stay with us through the rest of the week, and likely will last well into next week as well. High temperatures near 70 degrees will settle into the valley through the weekend, and mostly sunny skies Thursday will give way to occasional cloudiness through Saturday, but no precipitation is expected, and Easter Sunday itself should bring blue skies.

Yesterday, I told you how to map surface highs and lows. When mapping upper-air features, you use some of the same techniques, but you are actually measuring something different. Instead of measuring the actual pressure at certain elevations, you measure the height to whatever pressure level you are interested in. For instance, if you are looking at trying to find the highs and lows at the 500 millibar level, you send up weather balloons at various places around the globe. If one of them reaches that pressure at an altitude of 5300 meters… then that spot could be considered to be in an upper level low compared to another place that needs 5800 meters to reach the same pressure.

In order to map the highs and the lows, it works just like making that topographic map. Lines of equal heights are drawn through the data points, with the peaks (or ridges) being the highs, and the valleys (or troughs) being the lows. It’s a very important map for weather prediction.