The Colder Winds of Autumn to Arrive Next Week!

Many people have remarked how warm or balmy the temperatures have been thus far during first half of autumn. Certainly, it's been one of the warmer falls on record thus far, however look for a fairly radical change in temperatures evolving next week. Temperatures thus far (first half of fall) have averaged in the lower to mid 60s across Southeast Lower Michigan; some 5 - 7 degrees above normal for the first half. Ironically; the past few falls /2015, 2016/  have been balmy enough in their entirety to place in the top 5 warmest falls on record across Southeast Lower Michigan. Temperatures for those entire falls averaged generally in the mid 50s /55-57/, above the lower 50s average. My temperature outlook for this fall was generally above normal temperature but with notable sharp swings in both the warmth or the cold and; we are about to see that other-side of the that prognostication next week.

Overnight
First off: the wave colder air that arrived over the weekend with the ample rainfall will bottom-out in the low temperatures overnight. If you are concerned about widespread frost or freezing temperatures - don't be - as temperatures will remain several degrees above freezing. Overnight low temperatures will fall into the upper 30s to lower 40s in the urban heat island areas and areas near lakes therefore; the foliage should be safe.

After; the remainder of the week looks great with warmer temperatures once again to spread back into Southeast Lower Michigan along with predominant dry conditions. This will allow outdoor work and moving outdoor plants, indoors where necessary into at least through the weekend.

Further Ahead
Latest model indications have been leaning toward colder solutions from mid next week into the last weekend of October; just before Halloween and into Halloween at this time.

Looking at the broader indices picture; a positive EPO will become negative as forces in pumping up the ridging of the west coast of Canada and the US - while a negative NAO evolves and slides into place over eastern Canada in partial response.

Checking more into the "core" of the cold with the Arctic Oscillation shows us a definitive change to a negative phase into next week.

Closer to home looking at the winds aloft features for the change next week with a far glance toward Halloween. Note the cold air will come in waves; basically by mid next week, then again the last weekend of October then another around Halloween. Please remember these maps are one models /GFS/ interpretation of the atmospheric evolution of the colder weather. We only look at this to note the trend of pattern change and to a lesser extent; the amplitude and timing.

Any notable changes to the pattern projections and more particulars to the outlook; look for updates.

Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian