From NOAA’s Climate prediction Center:
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT THU AUG 31 2017
30-DAY OUTLOOK DISCUSSION FOR SEPTEMBER 2017
THE BACKGROUND CLIMATE DRIVERS REMAIN UNCHANGED FROM THE 0.5-MONTH LEAD FORECAST. THE MJO HAS RECENTLY EMERGED OVER THE INDIAN OCEAN, BUT ITS FUTURE
EVOLUTION IS UNCERTAIN. THE DEVELOPMENT OF HURRICANE IRMA IN THE ATLANTIC BASIN IS CONSISTENT WITH THE CURRENT MJO EVOLUTION, BUT BEYOND THAT THERE IS LITTLE
TROPICAL VARIABILITY TO HARVEST FOR THE MONTHLY FORECAST AT THIS TIME.
THE UPDATED MONTHLY OUTLOOK MAINLY TAKES INTO ACCOUNT THE LATEST FORECASTS FOR THE NEXT ONE TO TWO WEEKS, WITH SOME MINOR INFLUENCE FROM THE LATEST WEEKS 3-4 GUIDANCE. THE FORECAST RIDGE/TROUGH PATTERN THAT WAS DISCUSSED FOR THE 0.5-MONTH LEAD FORECAST IS FORECAST TO BE ESPECIALLY AMPLIFIED DURING THE FIRST
5-10 DAYS OF THE MONTH, THOUGH SLIGHTLY FARTHER EAST THAN WAS FORECAST A COUPLE OF WEEKS AGO. THIS AMPLIFIED PATTERN DOMINATES THE UPDATED MONTHLY FORECAST,
WITH SOME TENDENCY TOWARD THE LONG-TERM TREND MORE LIKELY LATE IN THE MONTH. THE IMPACT OF THIS ON THE MONTHLY FORECAST IS TO SHIFT AREAS OF PROBABILITIES
EAST, WITH BELOW-NORMAL TEMPERATURES FAVORED OVER MUCH OF THE EAST-CENTRAL CONUS.
The growing season has been anything but normal for farmers in the Corn Belt. They have been plagued with flooding, replanting, drought, not enough heat and other issues. Following the Farm Journal Midwest Crop Tour, many farmers have been praying an early frost won’t come their way.
But it could be knocking on their door much sooner than anticipated.
Between September 6 and 10, northern Illinois, northern Iowa, northern Nebraska, the Dakotas, Minnesota and Wisconsin could possibly see frost.
“There’s a lot of evidence of that,” Clark told host Mike Adams. “We’ve been talking about that since [Aug. 2] in our data analysis.”
Clark said part of the reason for the cold front is because of Hurricane Harvey. He said normally a cold front follows a hurricane, and three things are lining up for areas to see a frost in early September.
- A western U.S. ridge is forming. The heat in the Pacific Northwest causes the ridge to expand, which will dislodge colder air into the Plains.
- A high pressure system near Greenland.
- There’s a typhoon forming in the western Pacific Ocean which could add more of a risk of cold in September.
With these factors aligning, Clark said on the morning of Sept. 7, lows could fall between 34 and 39 degrees—between 15 and 18 degrees colder than normal—that would be a “legitimate threat” of an exceedingly early frost.