Truth Strikes: Debunking Biggest Weather Myths

Sign up for the Morning Brief email newsletter to get weekday updates from The Weather Channel and our meteorologists.

A​ chilly, wet pattern this week isn't what many are looking for and one of the drivers of the weather is the negative phase of the North Atlantic Oscillation, or NAO.

T​he upper-level pattern this week features a southward dip in the jet stream over the central and eastern United States with a ridge of high pressure over eastern Canada and an upper-level low over the northern Atlantic Ocean.

Weather in your inbox

Forecast Location

Sign Up

By signing up you agree to the Terms & Privacy Policy. Unsubscribe at any time.

T​his is a blocking pattern, sometimes referred to as an omega block due to its shape resembling the Greek letter omega. When this omega block is in place, weather patterns can get stuck, meaning an area can experience the same weather for days.

T​he upper-level pattern in place this week also indicates that the North Atlantic Oscillation (NAO) is in the negative phase. A negative NAO occurs when high pressure is in place over the North Atlantic and low pressure is located over the central North Atlantic, eastern U.S. and western Europe.

W​hen the NAO is negative, it often correlates with colder-than-average temperatures and an increase in storminess in the eastern half of the U.S., especially in the winter.

A​ negative NAO has been in place for much of the second half of April and is expected to last into early May. This particular negative NAO episode has also been notably strong for this time of year.​

W​hat Does It Mean For This Week's Weather?

T​emperature Outlook

The dip in the jet stream over the central and eastern U.S. will allow chilly conditions to surge southward through the end of April and likely into early May.

H​ighs will be near average or cooler for most areas east of the Rockies this week. Highs in the 50s and 60s will be widespread, while highs will only top out in the 30s and 40s near the Canadian border.

Low temperatures will also be below average in this pattern. As a result, mornings will be on the chilly side with lows dropping into the 30s and 40s, with 50s in the South.

(​MAPS: 10-Day Forecast)

P​recipitation Outlook

The position of the jet stream will also allow m​ultiple disturbances to track through parts of the Plains and across the South this week, resulting in rounds of rain and thunderstorms.

I​n addition, a broad upper-level low will keep some clouds and showers in the forecast for parts of the Great Lakes and Northeast into midweek.

A​nother system will arrive in the Northern Plains during the second half of the week, which will bring more unsettled weather as it tracks eastward.

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.