A Cool Start to a Mild Labor Day Forecast
by Angela Schilling, Meteorologist
September 04, 2011 10:20 PM
Fall is in the air! Technically Fall doesn’t start until September 23rd, but over the next week or so temperatures will be a few degrees below normal and dewpoints will be quite low. Labor day weekend has proved to be a mild one, but breezy. Our winds will slowly be on the decrease Sunday night into Monday morning, and by tomorrow afternoon, our winds will also start to change direction.
Dry air heats up and cools off much quicker than moist air. A ridge of high pressure is building into the Northern Plains, bringing cool Canadian air along with it. Dense, dry air can act as a blocking mechanism keeping storms to our south. As of Sunday evening an area of high pressure is over South Dakota and an area of low pressure is just to our northeast in Minnesota. The closer the two are together, the stronger the winds. Over the weekend it was quite breezy with northwesterly winds at around 15 to 25 miles per hour, with wind gusts up to 40 on Saturday and 30 on Sunday. As the ridge of high pressure continues to build into the region and the area of low pressure continues to travel east bound the distance between the two decreases, and our winds will begin to calm.
Radiational cooling is the ideal set up to get cool overnight lows. During the day the sun heats the ground, and during the night the ground loses its heat through terrestrial radiation. The lower the dewpoint temperature the drier the air, and the easier it is for heat to escape. Through the summer months of July and August our dewpoints were in the 60’s and 70’s, keeping overnight lows above 60 degrees. However, Monday morning will be quite cool for this time of year with temperatures in the lower 40’s. Interesting to point out our winds will also begin to calm Sunday night and our skies will remain clear. Clouds act like a barrier or a blanket during the nigh time, keeping the heat from escaping.
If you have any outdoor plans for Labor Day at least you can count on a dry forecast with lots of sunshine, it will just be a little bit cool waking up Monday morning…and highs will be in the lower 70’s. Throughout the week temperatures will gradually be on the rise, as our winds become more southerly.