High And Dry With A Return Of Jack Frost
April 08, 2012 7:28 PM
In the Northern Plains not only has it been unusually warm the last several months, but also quite dry. In particular, the month of March left us parched in many locations throughout the region. Friday night we had the chance to get some rain, but unfortunately there was just too much dry air to overcome and the showers broke a part as they moved to the east. In the upcoming week temperatures will take a dive becoming closer to average. Rain is also in the forecast once we get into the later half of the week. In the meantime, high pressure will settle over South Dakota, giving us clear skies and light winds.
We had a dry a fall, and not to mention a winter lacking in snowfall...the graphics below show some of the statistics. Precipitation amounts include both rain and melted snow. Over the last several months, March stands out, with many of us a good inch or so below normal.
Portions of northwest Iowa, southwest Minnesota, and eastern South Dakota are still in a severe drought, with Minnehaha County included in a moderate drought.
Speaking of dry air, when you have clear skies and light winds, temperatures really like to drop…this is what meteorologists call radiational cooling. Through the first half of the upcoming week a cold and dry dome of air will sink southward into South Dakota, dropping temperatures closer to where they should be this time of year; highs will be in the lower 50’s and overnight lows will be several degrees below freezing.
High pressure aloft in the upper levels of the atmosphere...high pressure = dry skies
With cold air in place, frost will be possible over the next couple of days. Frost forms when A) temperatures drop below 32 degrees and B) when temperatures reach their dewpoint. Winds will be key throughout the first half of the week, as wind speeds can keep temperatures up at night, but with high pressure in place they should begin to weaken come Tuesday morning.