Pattern Change Will Bring Return of Rain, Snow to California, Warmer Temperatures in Plains and South

Linda Lam
Published: March 19,2017
A pattern change this week will bring a return to conditions that have been more familiar this winter, compared to the weather in early March.
The recent weather pattern has brought warm and dry conditions to the West and cold and wintry conditions to the East. But, thanks to a shift in the jet stream, changes are ahead.
(MORE: 5 Reasons March Weather Is Frustrating)
Wet conditions, along with cooler temperatures, will make another appearance in the West. Meanwhile, temperatures have turned warmer in parts of the Plains and South. The risk of thunderstorms will also begin to return to portions of the central and southern U.S.

A shift in the jet stream is bringing a pattern change.

The changes correspond to a shift in the upper-level pattern. The upper-level ridge of high pressure that has been responsible for the mainly dry and warm conditions in the West has moved east. This is allowing an upper-level trough, or southward dip in the jet stream, to approach the West and bring the storm track farther south toward California.
Below is closer look at what noticeable changes can be expected this week.
(MAPS: Weekly Planner)

Big Changes for the West

Much of the West, with the exception of the Pacific Northwest, has experienced a mainly dry, warm pattern since late February. The stretch of dry weather came to an end Sunday in parts of northern California.
Wet weather will continue throughout this week as multiple storm systems move into the West. The good news is these storms will not be as strong as some of the atmospheric river events that occurred in January and February.

Rain and Snow Forecast

The first of these arrives Monday, continuing into Tuesday and Wednesday.
At least some rain should reach as far south as Southern California by Tuesday, but rainfall totals there will generally be less than an inch. The heaviest rainfall totals will likely be found in northern California and western Oregon, where more than 3 inches of rain is expected in the foothills.
In the higher elevations of the Cascades and Sierra Nevada mountains, snow totals will likely be measured in feet through the upcoming weekend. Snow levels are expected to lower below pass level by Wednesday in the Sierra, with snow falling above 5,000 feet midweek.
(MORE: Where March and April Are the Snowiest Months)
Yet another strong Pacific storm is expected to move into California late in the week.
Another change from last week will be much cooler temperatures, bringing an end to the record-breaking warmth that much of the West has been enjoying.
(MORE: Record Warmth/Cold Dividing the Nation)
Temperatures will be 15 to 25 degrees colder by midweek compared to the highs over the weekend.

This Week's Forecast

Highs will be near to slightly below average for the West Coast, Desert Southwest and Great Basin. Low temperatures will also return closer to average midweek.

Warmer Temperatures and Storms Return to Central, Southern U.S.

The above-average temperatures recently in place over the West have now spread into parts of the Plains where record highs will be threatened into Monday.
Saturday's warmth sent the mercury to 79 degrees in Salt Lake City, which was the second-warmest March reading on record there. Phoenix set a new daily record high of 95 degrees Saturday, and Cheyenne, Wyoming, topped out at a record-breaking 76 degrees.
On Sunday, Kansas City shattered their previous record of 81 degrees by topping out at 87 degrees. This is also their warmest temperature so early in the season. Meanwhile, El Paso, Texas, reached 90 degrees on Sunday, which was the second-earliest 90-degree temperature on record there.
In addition, the earliest 90-degree day on record was recorded Sunday in Topeka, Kansas. That city's high of 90 degrees shattered the 110-year-old daily record by 8 degrees.

Forecast Highs

The warmth will push into the Midwest and across the South on Monday, with some warmer temperatures even reaching parts of the Northeast.
By midweek, the above-average conditions will be concentrated mainly in the South, Rockies and High Plains, as a cold front knocks temperatures down in the Midwest and Northeast.
(MORE: When the Last Freeze of the Season Typically Occurs)
Much of the South will see highs in the 60s and 70s through the week, with 80s toward Texas and Florida. Lows will dip into the 50s for much of the region, with 60s in Texas and toward the Gulf Coast.
Dew points will also increase, making it feel more humid in Texas and portions of the Deep South.
(MAPS: 10-Day Forecast)
The warmer temperatures may help to set the stage for a return of thunderstorms. An area of low pressure will move into the Plains later this week and is expected to strengthen as it pushes east.

Thursday Night's Forecast

By Thursday, moisture and instability may increase, adding to the likelihood of thunderstorm development, with a few severe thunderstorms possible.
This threat for strong, possibly severe thunderstorms may be more expansive in the Mississippi Valley on Friday.
However, given this is several days away, details are uncertain and will change over time.
(MORE: Severe Weather Possible Late Week)
Be sure to check back to weather.com for forecast updates.

Winter Hangs On In the Northeast, Great Lakes

While there will be a brief relenting, yet another cold plunge will frustrate those in the Northeast and Great Lakes by the middle of the week.

This Week's Forecast

Highs will be 10 to 20 degrees colder than average, while lows will be up to 25 degrees below average from the Northeast into the Great Lakes behind a midweek cold front.
The interior Northeast and parts of New England won't see temperatures rise above the freezing mark, and lows will plunge into the single digits and teens mid-to-late week.
(MORE: "Marchuary" Continues in Northeast as New Cold Blast Arrives This Week)
Breezy conditions are also likely midweek, which will make it feel even colder.
These chilly temperatures will also allow the chance for some wintry precipitation at times.
(MAPS: 7-Day Rain/Snow Forecast)

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