Warmer air will build from California to Washington on Monday and Tuesday raising temperatures to near-record levels.
The jet stream will shift northward into southwestern Canada for much of next week. This will allow dry and milder air to build across the Western states.
The jet stream is a narrow zone of strong winds in the upper levels of the atmosphere that separates the warmer air to the south and the colder air to the north.
A strong area of high pressure over the Intermountain West will stay put for much of the week and lead to mostly sunny skies. This will also cause any Pacific storms to track northward across Canada and not into the West Coast states.
"A strong ridge of high pressure will develop across the western United States and bring warmer weather from California to Washington early this week," AccuWeather Meteorologist Brett Rossio said.
The strong high over the Intermountain West will also lead to a Santa Ana wind pattern across Southern California.
The warmest air will concentrate on Washington, Oregon and California with highs 5 to 15 degrees above average. Temperatures will be more typical of spring than the middle of winter. Temperatures will be near normal across the Intermountain West due to the current snowpack.
On Monday, temperatures will challenge records from Portland and Medford, Oregon, to Sacramento, San Jose and Los Angeles, California.
"Highs across Southern California will easily reach the 80s with a Santa Ana-driven wind contributing to this unseasonably warm weather," Rossio said.
Highs in Los Angeles could rise into the 80s for four or five straight days. The last time downtown Los Angeles reached the 80s prior to this week was on Dec. 8.
This stretch of mild weather will also lead to rapid snowmelt across the mountains. Anyone heading to the mountains for skiing early next week should exercise caution as the mild conditions could lead to avalanches.
Those heading home after Super Bowl 50 on Monday will not have to worry about any weather-related travel delays.
Tuesday will remain warm as records will be challenged from Seattle to Los Angeles for the second straight day.
"With this ridge of high pressure extending far into British Columbia, temperatures could challenge records in Seattle and even Vancouver on Tuesday," Rossio said.
During the second half of the week, the high over the Intermountain West will weaken, causing highs to fall short of record levels in most places during Wednesday into Friday, but still run above normal. This will also cause storms from the Pacific to return to the West Coast.
Showers could return to the Pacific Northwest as early as Thursday. Any additional rainstorms are not expected to reach California for the foreseeable future.