Next Week's Pattern Change to Bring Big Temperature Drops, Fall-Like Weather to Parts of Central U.S.

 Linda Lam

Published: September 5, 2020

Big temperature changes are ahead in parts of the western and central United States because of a shift in the jet stream.

Temperatures will go from feeling like summer to late fall in a short period – especially in the Rockies and portions of the Plains – by Tuesday.

The big temperature drop is due to the development of a more amplified jet stream and an unseasonably strong cold front. This weekend, the jet stream will generally be located near the Canadian border, but early next week, a southward dip in the jet stream will develop over parts of the Rockies and Plains as a northward bulge emerges near the West Coast.

This more amplified pattern is due, in part, to two typhoons in the Western Pacific that are expected to influence the upper-level pattern and bring this early taste of fall to parts of the U.S.

A change in the jet stream will allow colder temperatures to surge southward into parts of the United States.

Roller Coaster Forecast

A strong area of high pressure will bring record heat to the West this holiday weekend. This hot, dry pattern also increases wildfire concerns.

High temperatures will be 10 to 20 degrees above average for much of the West, which will break record highs across much of the region. Highs in the 90s and 100s will be widespread across the region, and lows will be warmer than average as well.

The heat will even reach the beaches in Southern California, which often provide relief during a brutal heat wave.

This prolonged period of dangerous heat has prompted the National Weather Service to post excessive heat warnings and heat advisories from Arizona to California.

Numerous daily record highs and warm low temperatures are anticipated. Septemeber or even all-time records cannot be ruled out in a few spots such as Palmdale, California, where the September record is 109 degrees.

Possible Record Highs

Temperatures will begin to fall early next week, in some spots, incredibly so.

Cooler conditions will begin to arrive in the northern Rockies and Northern Plains Sunday and Monday. By the middle of next week, above-average temperatures will mostly be confined to the Pacific Northwest as the jet stream surges northward over this area.

By Tuesday, high temperatures 20 to 45 degrees colder than average will extend from the Rockies into the Northern and Central Plains. Below-average temperatures will likely expand into parts of the Mississippi Valley, Southern Plains and Midwest Wednesday and Thursday.

This drop in temperature will lead to big changes in many locations. Parts of Colorado and Wyoming, including Denver and Cheyenne, will see high temperatures fall by more than 50 degrees from Sunday to Tuesday. Some spots may see drops of over 60 degrees.

Forecast Highs

Morning lows will also take a big tumble.

Low temperatures will be 15 to 35 degrees colder than average for the Rockies, Plains and parts of the upper Midwest during the middle of next week.

This means temperatures will drop into the 30s and 40s for much of this region, with 10s and 20s in the higher elevations.

Forecast Morning Lows

A cold front will usher in these changes and also bring precipitation. Temperatures will be below freezing in some areas, particularly the higher elevations of the Rockies, which will allow snow to fall. A few snowflakes will mix in with a chilly rain by Tuesday in the Front Range Urban Corridor, including Denver.

(MORE: Snow Could Fall in the Rockies Next Week)

Elsewhere, showers and thunderstorms – a few of which could be severe – will accompany this front in the Plains and Midwest.

It remains a bit uncertain how far east the cooler conditions will stretch, but milder temperatures will likely reach portions of the East late next week.

In addition, this milder pattern may persist into mid-September in parts of the central U.S., according to NOAA's Climate Prediction Center. Areas toward both coasts will likely continue the warm trend heading into mid-month.

(MORE: September Temperature Outlook)

Temperature Outlook

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.