Change in Upper Air Pattern Mid-May Liable to Bring More Contrasting Temperatures and...

I my blog regarding May's weather outlook I stated; I expected a warmer than normal May and thus far, Southeast Lower Michigan is averaging 8 - 10 degrees above normal thru the 13th. In addition, on 5/2 when I wrote the blog I stated:

"Why there is still the risk of a frost or freeze, none looks likely in the next week to 10 days anyway and there's less than a 30% chance through the month with the above normal temperatures. I'll keep the blog updated if the risk does arise if colder air masses make their way out of Canada".

I stated that because even though I expected a warm May overall, sharply contrasting air masses have been the rule this spring and I expected May to be no exception. After days in the 80s (including record territory), sharply colder air from Canada has aggressively plowed back across the region, driving temperatures down some 30-35 degrees recently! While temperature swings of 30-40 degrees in the month of May happen, it's not as commonplace as its spring month counterparts of March and April across Southeast Lower Michigan.

Our upper air pattern has reverted back to "ridge-trough pattern" of April as opposed to primarily ridge the first two weeks of May. The projected pattern discussed on the 2nd served well the first two weeks of the month (or as stated  "next week to 10 days") with above to much above temperatures. In addition, I stated I would update if the need arises after that period and the need has come....

Remainder of May Outlook
After a cold start and risk of scattered frost across the region overnight into Thursday morning as a rather strong high pressure dominates, look for temperatures to start a moderate climb once again through the 60s and into the 70s and breaking into the 80s over the weekend. In addition, the risk of showers and thunderstorms will be on the increase as the warmer air rudely surges back into the region. With this contrasting pattern in the works the next few week, severe weather potential also rises.

Looking ahead, I expected this oscillating pattern to be more the rule than the exception through  much of the remainder of the month. While temperatures will average above normal for the month, enough cold air will also be able to make it down occasionally to bring the possibility of a frost and/or freeze.

The old adage of planting after Memorial Day (and it comes the earliest possible this year) still seems the best advice - especially in the more frost/freeze prone areas of Southeast Lower Michigan!


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

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