ACCUWEATHER GLOBAL WEATHER CENTER — AccuWeather meteorologists say that a change in the weather pattern is forecast to bring an end to the abnormally dry conditions, starting with this next storm.

Fall started off dry for many in the West, but as the wet season nears, a change in the weather is set to bring rain, mountain snow and cooler conditions.

It's been a rather dry start to autumn across the western U.S. since mid-September. The dry conditions have spread from Seattle, which has received only 2.76 inches of rainfall or about 56% of normal, to Sacramento, California, where only 0.28 of an inch has fallen in the same time, a mere 31% of average.

All of Washington and over 99% of Oregon are experiencing at least 'abnormally dry' conditions according to the United States Drought Monitor's latest update.

Rain is likely in many of the mountain passes until colder air arrives, but any hikers or campers should still be prepared for wet and cold conditions.

"After the initial wave of moisture, the incoming storm will open the door for a lot of colder air to flow into the region, allowing many places to have their lowest temperatures so far this season," said AccuWeather Meteorologist Haley Taylor.

Taylor further explained that temperatures are likely to be 5 to 10 degrees below normal on Tuesday and Wednesday, and major cities like Seattle and Portland may struggle to reach the upper 40s.

Falling snow levels are expected through Wednesday across the western U.S., which will cause rain to change to snow in some of the mountainous terrain.

Snow is likely at and even slightly below pass level in Washington, making for tricky travel for motorists in those areas. Snow will be most widespread as colder air arrives Tuesday night.

Farther south, a period of heavy snow is likely to fall in the northern Sierra Nevada from late Tuesday afternoon to Tuesday night, AccuWeather Senior Meteorologist Dave Houk said.

"It is likely to snow hard for several hours by Tuesday evening at Donner Pass, along Interstate 80 in California," Houk explained. "Motorists should expect delays as roads are likely to become slippery and snow-covered for a time."

Snow will continue to spread southward over the Sierra Nevada and linger farther north over the mountain chain into Wednesday.

"If the storm ends up diving far enough south, higher elevations in Southern California may turn cold enough to see their first flurries Wednesday night," Taylor explained.

Whether precipitation falls as rain or snow, the influx of moisture will help to improve the stubborn drought across the region.

Courtney Travis is an AccuWeather senior meteorologist.