The April climate maps for the United States show that the vast majority of the nation was warmer than normal. The Midwest departures for the month ranged from just above normal in northeastern areas to 4 and 5 degrees above normal here in the western areas. (Graphics provided by High Plains Regional Climate Center.) Note that our area was also in close proximity to the driest areas and in the majority of the Midwest which had below normal moisture. The combination of warmth and dryness allowed planting progress in parts of the northwest Cornbelt to proceed at a record pace. It seems that growers were particularly eager to make progress following two consecutive springs which were plagued by problems with cool and wet weather.
Southwest Minnesota ended up with its sixth driest January through April since 1895, with 4-month precipitation totals averaging 2.60″, or 51% of the long-term “normal” amount. The only drier starts to a calendar year were seen in 1959 (when an El Nino event was ending), in 1980…and in three other years between 1926 and 1934. (The chart above was provided by the National Climatic Data Center.)
It’s not very often that we experience dust storms in this part of the Country. March and April do tend to be our windiest months, but with much of the early spring featuring soils which are snow-covered, frozen, or damp from recent snowmelt there is not much opportunity for the wind to rob our fields of topsoil.
Unfortunately, the week between Palm Sunday and Easter Sunday produced
an amazing three days when windblown soil reduced visibility at times in some of the open country of southwest Minnesota. Temperatures in the lower 80s combined with 60 mile per hour wind gusts on April 1st. Some vehicles were blown off of highways northwest of Marshall, Minnesota and other drivers reported briefly enduring visibilities reduced to near zero in blowing dust.
The month of March ended up among the top 10 or 15 driest in the past 120 years across southwest Minnesota, and the fact that it was also consistently warmer than normal kept the little snow which did fall from staying on the ground very long. Soils thawed early in the month as temperatures soared into the 60s on most days during the week of March 9th to 15th, including the first 70 degree temperatures reaching southern Minnesota more than 3 weeks ahead of the normal first occurrence of such warmth.
El Nino conditions increased in strength across the Pacific Ocean during the last weeks of winter, a counter-seasonal sort of progression because El Nino usually weakens with the approach of springtime. Local weather was also not as expected during March, because most years with El Nino have had near to above normal March precipitation over southern Minnesota and northern Iowa. In the past 30 years, I find only three occasions (in 1988, 2003, and 2005) with El Nino present in March when below normal precipitation was prevalent across the area. Each of the three years had much more abundant precipitation (near to above normal) during the month of April.
While the rapid transition from very cold to very warm weather was most welcome during the first half of March, a look at historical temperature patterns shows that such a reversal has not been unique to March of 2015. Just last year, it was even colder at the end of February and the first few days of March. The Minneapolis- Saint Paul airport, for example, did not climb above 20 degrees for the entire 12 day span from Feb. 21st through March 4th in 2014. Then by the 14th of March, most of southern Minnesota had counted 5 days with highs in the 40s or warmer. We also had subzero cold in much of southern MN at the start of March 2011, then starting at mid-month, we had 7 straight days reaching the 40s or low 50s. What’s remarkable about this month is that we have ended up challenging or even surpassing several record highs which were set in March of 2012, which came at the end of a consistently
warm winter. As shown on this map, snow cover was nearly absent across the region at mid-month, which makes this March very similar to mid-March of 2012 for its lack of snow cover. Not only was the ground bare of snow in mid-March, but for most of the northern Plains and northwest Cornbelt, very little snow had fallen from late February into early March. Some parts of southwestern Minnesota had received less than 2 inches of snow in the 30 days from mid-February to mid-March. A look at the percentage of normal precipitation map during that time frame reflects the fact that the entire north-central United States was
in a very dry weather pattern during the late winter. This dryness is not unheard of in late winters when El Nino has been in place, but precipitation has varied considerably in past El Nino winters.
February of 2015 ended up between 6 and 10 degrees colder than normal in southern MN and north IA, depending on how much snow cover various locations had. Generally, the region was 2 to 4 degrees LESS cold in February than in February of 2014! (Map from High Plains Regional Climate Center.)
The first half of February averaged a few degrees cooler than normal across the area. After starting out
with five chilly days, followed by five mild days the pattern turned colder again starting on the 11th of the month. The third week of February is likely to average as much as 15 degrees below normal before temperatures may moderate starting around the 23rd of the month. I’ve often noted the past mild El Nino winters which followed frigid November conditions (1982-83, 1986-87, 1991-92, 1997-98), and that this year followed the pattern in which January tended to have many more days which climbed above freezing compared to the number of days which fell below zero. The February pattern in those winters was also dramatically mild. In fact, only one of those Februaries had even a single low temperature below zero at locations such as Minneapolis, and more than half the days in each one of the four Februaries had highs above the freezing mark. With February of 2015 so clearly taking a colder track, it’s not necessarily time to give up on the mild pattern returning for the end of February and March. We already knew that this El Nino was weaker than in many previous winters, so I’m not surprised that its moderating effects on our winter weather patterns have proven to be a bit more limited. However, with so little snow cover now in place for most of northern Iowa and southern Minnesota, even a small shift to a milder (west to east) upper-level wind pattern could quickly result in the return of well above normal temperatures.
This chart depicts how frequently we’ve seen milder than normal January and February weather during El Nino winters in the past 30+ years (columns with orange headings), even though the month of January has almost always contained a significant cold spell (detailed in columns with white headings).
This past month represented only the second time of the recent El Nino events (the other being in 1998) when we had at least a week of January temperatures averaging ten degrees or more below normal, before a changing pattern resulted in the month ending up warmer than normal. The farthest right column is significant for next month’s forecast because it shows that all but one of these El Nino winters ended up milder than normal during March. Especially after tossing 1988 out of consideration (because it was colder than normal in January) we would have expected February to be mild also. For two months in a row — in both December and January — this winter had months which started cold, and turned out very mild overall. Based on the years in this chart, we would also expect February to follow the same path to end up warmer than normal. That does not appear likely based on the current weather pattern. However, the probability of mild March weather appears high, even if we end up colder than normal during February. There is one recent El Nino winter which was entirely left off the list — and for good reason. The winter of 2009-2010 was consistently very cold and snowy and does not appear to be a good predictor for expectations in the next few months.
In almost every one of the years from the chart above, we saw warmer than normal temperatures during March. 1998 had a chilly March, but El Nino in that year was a lot stronger than it is presently. The only years when the three spring months of March through May combined to average colder than
normal were 1983 and 1995, and those years also rank in the top 5 wettest March through May time frames on record. El Ninos in those two years were also much stronger than what we’ve had recently so they don’t look like good matches to 2015. So tossing out those three strongest El Ninos in the past 30+ years, what is the forecast for March through May?
Of the El Nino years remaining (1987, 1992, 2003, 2005, and 2007), all five were milder than normal during March (2.8 degrees above normal on average). Three of these Marches were wetter than normal, and two were drier than normal — so don’t be surprised if we continue to see more frequent rain or snow. In both April and May, the tendency toward warmth is not as strong — in each month just three of the five years had warmer than normal temperatures. Three of the five years also had above normal spring precipitation across southwest Minnesota. Summarizing the outlook, spring precipitation appears to have a good chance of averaging near to above normal. March is still likely to be a mild month, but April and May temperatures have no more than a 50% to 60% chance of being warmer than normal.
Halfway through the month, January was on track to be among the top 10 or 15 coldest Januaries on record, averaging some 10 degrees below normal across the area. Many locations across southern Minnesota fell below zero on every one of the seven days between January 4th and 10th, and on three of those days, daytime highs struggled to surpass the zero mark. This was impressive cold especially considering that snow depths were no more than two to four inches across most of the region.
Then the weather pattern shifted, with mild westerly winds aloft replacing the northerly flow experienced earlier in the month, so that temperatures ended the month averaging between 2 and 5 degrees warmer than normal across most of southern Minnesota and northern Iowa. The staying
power of the mild air during the second half of the month was notable. Though we did not set record highs, the nighttime lows were consistently 20 to 25 degrees warmer than normal under frequent cloud cover and with increasingly snow-free ground. To our west over the High Plains the magnitude of the warmth was most noteworthy. Among many, many daily record highs in the Great Plains region during the last week of January, Topeka, KS reached 78 degrees on January 28th — one of more than half a dozen locations in the central Plains to set all-time January records last week. I heard that was the warmest temperature to be recorded at Topeka between November 20th and February 14th — in any winter — and more typical of warmth seen in that area in early May.
Through the first 30 days of the month, January was also much drier than normal across most of the Midwest, with many areas west of the Mississippi River receiving less than 50% of normal precipitation. Parts of central Minnesota, and most of southwest Iowa and adjoining areas of Kansas, Missouri, and Nebraska were even drier — with less than 25% of normal precipitation — though these latter areas did receive substantial snow and mixed precipitation on the last day of January which allowed some places in the western Corn Belt to end the month with near to slightly above normal precipitation.
At sunrise on the last day of January, 70% of the Nation had bare ground with no snow cover — the third greatest percentage in the past 12 years and surpassed only by 2012 (77% snow-free) and 2006 (78% snow-free).
Though December began and ended with subzero temperatures, the 3+ weeks in between featured consistently mild weather, which allowed temperatures to average from three to six degrees above normal across most of southwest Minnesota and northwest Iowa. This mildness of December has been very typical during the past 30+ years following chilly November conditions when El Nino has been in place.
Not only was the month of December mild in our area, but snowfall was less than normal and in many areas bare ground was visible until snow fell during the last week of the month. While precipitation was below normal from the Twin Cities into northeast Iowa and eastward into southern Wisconsin, it was wetter than normal in much of southwest Minnesota and northwest Iowa, and especially so in adjoining areas of South Dakota and Nebraska. Those two states reported their 25th and 15th wettest Decembers on record respectively. In those areas to the west a bit more of the precipitation also fell as snow. Southwest Minnesota reported its 29th wettest December on record, while south-central Minnesota averaged right at normal for the month.
This chart shows a time series of December temperatures over Southwest Minnesota for the past 120 years. Not only does it show December of 2014 (most recent in the series) coming in well above normal (and 23rd warmest of all the years depicted) it also shows the sharp contrast with the previous December which was 16th coldest on record. On a broader scale, December of 2014 was the second warmest on record for the contiguous United States, with states along the West Coast, in New England, and even Texas reporting this past December among their top ten warmest. In the November edition of the Newsletter, I noted the influence of early November’s Pacific Typhoon Nuri in drawing down a period of very cold air, but anticipated that the effects of El Nino would probably turn the pattern mild for December.
Temperatures were remarkably warm during the second weekend of December, and readings for the first half of the month averaged as much as 6 degrees above normal not far to the south and west of Jackson. With little to no snow cover in much of south-central and southeast Minnesota into northern Iowa, our early week chill will give way to a gradual warmup which will bring temperatures back above normal for the four days ending Monday the 22nd. A Monday night weather system may spread some accumulating snow across the region and then usher in some chillier temperatures for the rest of Christmas week. Even colder temperatures and better snow chances are possible during the final week of 2014.
After one of the coldest Novembers in nearly twenty years, the last in a series of Arctic air intrusions will ease its grip on the area during the first few days of December. Though November overall was uniformly between 6 and 10 degrees colder than normal over most of the Midwest (as shown on this map), temperatures to the south and east of our area were not as far below normal during the final week of the month, largely due to some very mild temperatures which advanced across all but far northwestern areas of the region on Saturday the 29th. (Map provided by High Plains Regional Climate Center)
This December temperature outlook (released by the Climate Prediction Center on Sunday, November 30th) reflects an imminent shift in the upper-level winds that will allow air masses of Pacific origin to become dominant during at least the next 10 to 14 days.
This forecast (depicted on the map to left) from the CPC is dramatically warmer than their December forecast released on November 20th. In that earlier forecast, near normal December temperatures were forecast across much of Minnesota and Iowa. There are some signals that (following mild weather early in the month) colder weather could return for the last 10 to 15 days of December, but other forecast tools are inconclusive.