National Weather Service Weather Forecast Office

The weather pattern for the month of September was such that allowed the upper midwest to remain very dry.  One key factor in the dry spell was the upper level low pressure system that was pinched off from the upper level flow, and remained nearly stationary for several days.  While it did pass over northern Minnesota, the upper low stalled out over northern Illinois, before remaining there for several days.  Many locations in Minnesota saw well below an inch of rainfall for all of September, and the Minneapolis/St. Paul International Airport recorded its driest September on record, and the second driest September in Twin Cities history (in 1882, 0.27" of precipitation was recorded in the month of September at the old Twin Cities Official Weather Observation Site, which at that time was Fort Snelling).  The upper low mentioned above did retrograde slightly back to the west before finally starting its journey east.  While Minneapolis only received 0.36" of rainfall in September, Eau Claire recorded 1.67" of rainfall.  The nearly stationary low was able to produce some rainfall in Wisconsin, but not much in Minnesota.  Not only did it not produce precipitation in Minnesota, it helped block the weather pattern and prevent other systems from producing rainfall across the North Star State.

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
258 AM CDT SAT OCT 1 2011

...PUBLIC INFORMATION STATEMENT...

DRIEST SEPTEMBER ON RECORD SET AT MINNEAPOLIS/ST PAUL
INTERNATIONAL AIRPORT

A NEW RECORD LOW PRECIPITATION TOTAL FOR THE MONTH OF SEPTEMBER
WAS SET WITH JUST 0.36 INCHES OF PRECIPITATION RECORDED THIS
SEPTEMBER. THE PREVIOUS RECORD DRIEST SEPTEMBER OCCURRED IN 1940
WITH 0.41 INCHES RECORDED THAT SEPTEMBER.

...BELOW IS AN UPDATED LISTING OF THE FIVE DRIEST SEPTEMBERS RECORDED
AT MSP...

YEAR       PRECIPITATION TOTAL (INCHES)
---------------------------------------
2011                      0.36
1940                      0.41
1952                      0.42
2009                      0.46
1969                      0.49


...BELOW IS A LISTING OF OTHER LOCATIONS THAT ALSO SAW VERY LOW
PRECIPITATION TOTALS IN SEPTEMBER 2011...

LOCATION   PRECIPITATION TOTAL (INCHES)
---------------------------------------
REDWOOD FALLS             0.13
CHANHASSEN (NWS OFFICE)   0.26
FLYING CLOUD AIRPORT      0.28
MANKATO                   0.32
ST. PAUL                  0.47
CRYSTAL                   0.48
RED WING                  0.58
ST. CLOUD                 0.74
ALEXANDRIA                0.87

$$

SPD

As shown in the graphic below, the drought conditions across Minnesota continue to expand.

For more information on the drought conditions, see the Drought Monitor.