A temperature drop and gusty winds are headed for Chicago and the Midwest.
Greenland Blocking Pattern
A “Greenland Blocking Pattern” is taking shape, a signal of cool weather for Chicago and the Midwest.
The pattern is to take shape shifting upper steering winds in from the Northwest and bringing cooler air in from Canada as this week proceeds.
The evolving pattern, which features the development of an expansive dome of warmer than normal air aloft from Greenland northwestward to the North Pole sets up a “wavy” or “amplified” jet stream pattern across North America which acts to cool a huge swath of the central U.S.
It’s a development which shifts upper steering winds from northwest Canada southward to the Lower 48 bringing a cascade of cool air-bearing weather systems into Chicago and the Midwest.
And the fact it is a blocking pattern, it’s likely to be a feature which lingers.
What Chicago can expect: Cooler weather and gusty winds
The change is not only to drop temps here in Chicago, it also signals a week of frequently windy weather is ahead as a series of gusty autumn weather systems sweeps across the area.
The coming two days alone are likely to see 40 mph daytime wind gusts taking hold Tuesday and Wednesday, strong winds which ease at night but surge to peak strength during the day.
The temp pullbacks they bring with them are, among other impacts, are to produce a long string of days with highs limited to the 50s. This includes the back half of this coming week and well into next week. It is the longest string of days limited to the 50s we’ve seen here in the Chicago area since late February and early March, nearly 7.5 months ago.
An initial average of the temps recorded here in the Windy City from last Tuesday through today compared to the predicted temps from tomorrow (Tuesday, Oct 13) through next Monday suggests a temp pullback averaging more than 11-degrees. That’s a significant change!
I’ve posted a snowfall map which totals potential snow expected to fall in the coming 7 days. Not to worry. The snow isn’t to fall here in Chicago, but snows will fall and in stick, in some cases for the first time this season, to Chicago’s North and West.
The maps which appear below lay out the predicted upper air pattern–not only for North America–but for the entire Northern Hemisphere. So you are to clearly see the huge pool of “warmer than normal air aloft” predicted to drive the development of Greenland Blocking as the week proceeds and as we move into next week.
By producing “northward buckling” of the jet over Greenland, an offsetting southward buckle or “trough” forms over North America which will drive a series of cool air masses into the Midwest and Chicago.