Another Sharp Cold Shot Heading for the Great Lakes and Southeast Lower Michigan /Updated 9/29/

The projected pattern development this fall settled on in the my Autumn Outlook has come to fruition this first month of the fall. While September has had its very nice weather and long periods of mild to warm weather, those warm temperature departures have been cut down due to impressive cold shots with another due to arrive at the close of the month. A strong cold core upper low pressure and attending polar cold front will push south into the Lakes region late week.
Cold, blustery fall conditions will prevail early Friday into Saturday with cold but calmer weather for Sunday. Look for a nice warm-up during the first week of October. Check out this warm-up on the surface map loop from HPC and temperature/precipitation plots. To keep up to date on this changing weather scenario with local forecasts, see:  NWS DTX. 

Records (low max's and lows) for the weekend cold period are below, most seem safe but it's very interesting to note the cold of 1974 comes back to haunt us again this weekend. The cold snap we saw mid-month was also similar to the cold snap that occurred in 1974 on Sep 22nd & 23rd (albeit in was a colder in 1974). In addition, the earliest snowflakes ever observed at DTW in Detroit were observed by yours truly (and others on station) back on October 1st, 1974 (all three stations had record lows on the 2nd).

RECORD LOW MAXIMUMS

OCT 1ST
DETROIT......46F 1920,1899,1886
FLINT........52F 2003,1985,1974,1924
SAGINAW......49F 1974,1899

RECORD MINIMUMS

OCT 2ND
DETROIT......29F 1974
FLINT........27F 1974
SAGINAW......30F 2003,1974

As we get ready to close the month, overall temperature averages as of the 26th are hovering around normal give or take a degree. By the end of September, Southeast Lower Michigan should close the month within a degree or so of normal.

We started the month with sweltering highs peaking into the mid to upper 90s during the month's open /1st-3rd/, only to be shot down by a sharp cold front and subsequent lows cratering into the mid 40s to mid 50s just a couple days later /5-7th/! A second even more potent cold air mass (originating in the Arctic and Northwest Canada) plowed into Southeast Lower Michigan mid month after the region had just recovered well into the 80s /9-12th/.  This second cold snap caused temperatures to dive down well into the 30s away from the immediate Detroit heat island and lake shores. This mid month cold snap led to record of near record cold at the surface and aloft across the Great Lakes in some areas when compared to surface and upper air data. Some patchy frost was observed in rural areas along with a record low tied at Flint on the 15th /38/ and just missed by a couple degrees on the 16th (35/33)! 

Mild to warm weather has returned to the region as the summer and autumn continue to fight for reign, while producing RAIN (at least in the  far south). Detroit Metro Airport is again closing in a top 10 record wet month with 5.80" as of 26th. This coming after a wet summer across portions of the region, while others were barely normal.

"By the end of the summer, the three climate stations saw normal to above normal with the entire region seeing around normal, though time-dispensed very unevenly, to locally above normal in the heaviest storm areas. Detroit with 7.66" in July saw its second wettest July on record (second only to 1878 with 8.76")."

This established rainfall pattern of the summer was expected to carry over into at least, early fall in the Outlook. While Detroit has seen a very wet September, further north across Flint and Saginaw (as of the 26th) are decidedly below normal for September. The uneven rainfall pattern continues with the Detroit Metro area south continuing to receive the most (and not unlike the Summer of 2010).