Two areas of high pressure modeled by the American GFS at the start of next week on Monday, May 25. (WeatherBell)

Following a damp, dank week for many in the East and a month of soaking rains in the Midwest, a pattern change is finally set to bring summer’s warmth to much of the Lower 48.

Warming temperatures and limited storminess are expected. But there could be a few areas that don’t tap into Mother Nature’s sunnier disposition, with models hinting at some meteorological mischief in the South.

Preliminary indications suggest temperatures from five degrees above average to as much as 15 will settle in across the West, while the Central Plains, Midwest and Northeast could start the week warm, as well. Memorial Day is looking superb for millions.

But there are signs that a couple spots in the country may not be so lucky, as the same pattern bringing pleasant weather to most may also feature a few pockets of chillier or stormier weather. And signs point to the return of more stormy weather after next week.

The setup

Integral to the forecast is the jet stream, finally set to relax after a series of wild meanderings that left it contorted as it snaked across the country this week. The jet stream, or a river of swiftly moving air in the upper atmosphere, forms along the boundary of chillier air to the north and warmer air to the south.

When the jet stream is wavy, long-distance displacements of air masses can bring unusual warmth or cold to normally more moderate regions. But when the jet stream is draped west to east across the country, storm systems are less vigorous with a more gradual temperature contrast south to north. That looks to the case heading forward.

High pressure dominates much of the nation

The American GFS model simulates temperature anomalies in the coming two weeks, indicating likely warmth over much of the country save for the southern Great Plains and Texas. (WeatherBell)

Twin high pressure systems will anchor themselves over opposite ends of the country, a ridge of warmth building in the west late Sunday as another becomes established in the east. By Monday, the two will merge over the north-central United States, bringing a coast-to-coast arc of warmth.

The core of high pressure looks to hover near or over the Great Lakes and Upper Midwest regions toward the early or mid portions of next week, bringing several days of summerlike warmth. Wednesday, Thursday, and potentially Friday should be the warmest in the Northeast and New England.

Thereafter, warmth is favored to continue over much of the central United States, probably leading into the start of June. The National Weather Service Climate Prediction Center is already calling for a moderate to high likelihood of anomalous warmth across much of the country during the last week and a half of May, with an emphasis on either coast.

The American GFS model simulates a rather tranquil west to east jet stream much of next week; this computer-generated map illustrates trends around Tuesday, May 26. Note the clockwise winds of warm, high pressure south of the jet stream. (WeatherBell)

In the Desert Southwest, temperatures may skyrocket — approaching or exceeding the century mark by the end of next week.

“Localized parts of the Desert Southwest may experience maximum temperatures exceeding triple digits,” wrote the Climate Prediction Center.

Where rain and cool temperatures may reign

A comparison between the American GFS model and the Canadian model for Thursday, May 28. Note that, while confidence exists in warmth in the Northeast and West, the main source of uncertainty stems from a low pressure system near the Gulf. (WeatherBell/Matthew Cappucci)

Not everybody will be peaches and cream in the weather department, however. Signs point to a weak zone of low pressure stretching from West Texas to the northwest Gulf of Mexico for the first half of next week, likely to bring clouds, cooler temperatures, and increased rainfall to the Lone Star State.

That could also enhance rainfall up and down the Interstate 35 corridor as far north as Oklahoma and Kansas, with a risk of afternoon showers and thunderstorms this weekend and into early next week.

“Moisture inflow could interact with a series of frontal boundaries traversing the Plains and Mississippi Valley through early next week, leading to the potential for heavy rain and thunderstorms in those regions,” wrote the Climate Prediction Center.

The Climate Prediction Center's temperature outlook from May 26 to June 1. (NOAA/CPC)

There is a growing chance that this system could evolve into a “cutoff low.” That’s a high-altitude low pressure system, characterize by counterclockwise-rotating winds and cooler temperatures, that divorces from the larger reservoir of cold to the north. If this is the case, it would likely meander somewhere near the Gulf Coast, bringing inclement weather somewhere between East Texas and the lower Mississippi Valley.

It’s important to note that, at time ranges this great, details remain highly uncertain.

A tricky forecast in the Northeast

The Northeast will find itself under the western periphery of an offshore high pressure system toward the start of next week. That could induce a northeasterly, onshore component to surface winds, cooling the immediate coastline back some 10 to 15 degrees below its surroundings. This is especially true in New England.

Places like Boston; Portsmouth, N.H.; Portland and Bangor in Maine; Cape Cod, Mass.; and other shoreside New England cities could experience these effects. There’s a chance that, if an onshore “backdoor cold front” manages to surge farther south and west, parts of the coastal Mid-Atlantic could be wedged in beneath a shallow layer of cooler air as well for part of next week.

Pattern breaks down into June

By the end of next week, it’s likely that this pattern — namely, the west-to-east upper-level flow keeping large-scale storminess at bay — will begin to break down as the jet stream contorts into several dips and crests. That will introduce more variability, and potential storminess, to the forecast leading into June.