4 Things to Know About This Week's Weather Pattern Change

Linda Lam
Published: May 21,2017
Another big change in the weather is ahead this week, and it could last through the remainder of May.
After a taste of summer, cooler and less humid conditions have returned to the East. The central U.S. will also see cooler temperatures, as well as a lower risk of severe weather in the week ahead.
(MORE: Tornado Central)
Meanwhile, the West will heat up and experience a stretch of dry conditions.

A change in the jet stream is bringing another pattern flip across the U.S.

The reason for this switch is another change in the jet stream. As the upper-level pattern slides eastward, the result will be a trough – or southward dip in the jet stream – developing over the East, while the West will see a northward bulge of the jet stream – or upper-level ridge. This overall setup is generally not conducive to widespread severe thunderstorms.
Here are four things to watch for with the upcoming weather pattern flip.

1. End of Record Heat in the East

A southerly flow brought record-high temperatures to portions of the East last week. For those not quite ready for summer, there is good news: cooler temperatures are expected across the East this week.
A cold front moved through the Northeast on Saturday and brought temperatures closer to average for this time of year. By Monday, temperatures will be near average through the Midwest, Northeast and South.

Forecast Highs

Instead of highs in the 90s, temperatures will generally top out in the 60s and 70s, with 50s in parts of the Great Lakes region into New England early to mid-week. Closer to the Gulf Coast, highs will reach the 80s.
Low temperatures will also be near average this week. Temperatures will drop into the 40s in parts of the Midwest, with 30s in the Upper Peninsula of Michigan. Lows in the 50s are expected along the East Coast and into portions of the South.

2. Warmer Temperatures Will Develop in the West

While the East cools down, the West will heat up.
The heat kicked into high gear along the West Coast and into portions of the Great Basin on Sunday. Several locations saw highs well into the 90s, and a few places even reached 100 degrees, including Yuma, Arizona, Blythe, California, Palm Springs, California, and Needles, California.
The core of the warmer-than-average temperatures will be in the Pacific Northwest through early this week, where highs will be up to 30 degrees above average.

Forecast Highs Compared To Average

Early this week, highs may reach 80 degrees in Seattle, with 90 degrees possible in Portland, Oregon. In the Desert Southwest, temperatures will soar into the triple digits.
A few record highs are even possible.
(MAPS: 10-Day Forecast)
This will also bring a prolonged stretch of dry weather to the region. Seattle is expected to have its longest dry spell since September. Parts of the Rockies will see a few rain and snow showers at times, but we are not expecting anything like what we saw last week with Winter Storm Valerie.

3. Lower Risk of Severe Thunderstorms

The setup of the jet stream in the week ahead will bring a more northwesterly flow into the central and eastern U.S., which can hinder widespread severe thunderstorm development.
This is good news for areas of the Plains and Midwest, which were impacted by severe thunderstorms, including tornadoes, last week.

This Week's Forecast

Thunderstorms are expected in parts of the Plains Monday, but an outbreak of severe storms is not anticipated. A few strong to severe thunderstorms will push eastward into portions of the South Tuesday and Wednesday, but nothing resembling last week's siege.
Most of the Plains will enjoy a break from the stormy conditions in the middle of the week. Temperatures will also be cooler than average for much of this week in the central U.S.

4. Wet Outlook For East, Midwest

An active weather pattern is shaping up for much of the eastern U.S. through early this week.
A low-pressure system will push into the East through Monday, bringing rain and thunderstorms to the Midwest, Northeast and South. A few severe thunderstorms are possible, and locally heavy rain will also be a concern.

Midweek Forecast

The next round of rain and storms will then slowly move into the Midwest and East midweek.
(MORE: Heavy Rain, Thunderstorms May Lead to Flooding in Parts of the South)
Showers may persist late in the week in parts of the Great Lakes and Northeast. The next disturbance will then slide through the upper Midwest and into the East late week.
For much of the Northeast, this upcoming cool and showery period will be reminiscent of the pattern in early May and may last through the end of the month.
(MAPS: Weekly Planner)
Rainfall totals of 1 to 3 inches will be common through this week for areas east of the Mississippi River, with up to 5 inches in portions of the South. Some of these areas already have saturated ground from heavy rainfall this spring, so flooding could become a concern.

MORE: Mid-May Severe Weather Outbreak in the Plains, Midwest