A genuine early-season heat wave was in full swing 24 years ago. It began Earth Day weekend in 1990 when the temperature soared to 79 degrees at the National Weather Service (NWS) near Negaunee. The warm temperatures then continued through the next week peaking on April 25 when the high hit 89 degrees. In Iron Mountain, it hit 89 on the 24th and 90 degrees on April 25, 1990.
The pattern that spawned the April heat wave was a familiar one; an upper-level ridge built over the central U.S. on April 22 and kept on building as it slowly drifted eastward (Image 1 above). By April 25, it crested just to the east of the U.P. putting us in the hot air coming up ahead of a trough over the southwestern U.S (Image 2).
The seven days from April 22-28 had a mean temperature of 68.1 degrees, an eye-popping 26.1 degrees above average for late April. This would be considered a warm spell if it occurred in July!
Chilly weather the first half of the month offset the heat somewhat. Still, April 1990 ended 4.9 degrees above the long-term average.
April 2014 is keeping with the theme that began at the beginning of winter. The month is now running about four degrees below average and the forecast pattern ahead does not hold out hope for much warmth. A new storm now giving snow to the mountains of southern California will move eastward into the Plains. Initially it will be impeded in its forward progress by a developing block in eastern North America. However with time, it is forecast to lift into the Great Lakes (Image 3). Once the system moves in, itâ??s likely to stick around for a while and that means chilly rainy weather with a chance of some snow mixing in at times.