January Thaw to Peak This Weekend…Then a Return to Reality
While temperatures have basically been on the mild side of normal, look for temperatures to peak this weekend through the 30s and ultimately, into the 40s in many areas. Our milder pattern since mid January has many of the characteristics of the January Thaw as defined by the ‘Glossary of Weather and Climate”;
“A spell of mild weather, popularly supposed to recur each year in late January in New England and other parts of the northeastern United States. Statistical tests show a high probability that it is a real singularity.”
A high probability that it is a real singularity means that the January Thaw occurs more often than chance would indicate. And, though no actual departure above normal is listed, it is generally accepted that it is several degrees and lasts awhile. Since January 13th, temperatures across Southeast Lower Michigan have averaged 5-7 degrees above normal, basically erasing the cold below normal departures experienced the first half of the month.
Taking a look at the graph below, we see a plot of various temperature traces for Detroit over the first half of the year using data taken at Detroit Metro Airport 1958 through 2004. Note the legend on the side of the graph is the temperature. Displayed are several traces representing a range of temperature plots. The temperature plot include; the high temperatures median, mean, standard deviations, highest max temps, 90th percentile, 67th percentile, 33rd percentile, 10th percentile and lowest max temps for the period. Note the boxed area in mid to late January does indeed show a subtle pop in temperatures.
Now for the reality part
A strong cold front is expected to surge across Southeast Lower Michigan late in the weekend attended by rain and wind, then followed by more realistic January-type weather for the close of the month. Latest indications are the last week of the month should erase any positive gain we achieve on the departure for the month from the January Thaw. Well, the warmer temperatures will be nice while they last this weekend.