November Pattern Change Returns Warmth to East and Mountain Snow, Cold to West

Jon Erdman
Published: October 28,2015

As the calendar turns to November, a significant change in the weather pattern over the U.S. will lead to a pronounced split between winter cold and snow in the West and warmth more reminiscent of early fall in the East.
The polar jet stream will take a sharp southward nosedive in the West while simultaneously bulging northward into eastern Canada.

Weather Pattern the First Week of November

Let's break down the two distinct weather regimes that will be in place as November kicks off.

Midwest, South, East: September in November

Northeast/Midwest Warmth Ahead

South Warmth Ahead

While a sharp cold front is delivering a chillier reality check to parts of the Midwest and Great Lakes right now, November's chilly, raw brand name couldn't be further from the truth in the week ahead.
With high pressure shifting off the Eastern Seaboard, and generally lower pressure in the western U.S., a belt of warm air will flow northward from the southern Plains into the Upper Midwest, Great Lakes, Ohio Valley, and eventually into the Northeast in November's first week.
For some, this warm spell will feel more like a typical late September air mass than an early November one.
The warm-up begins this weekend in the northern Plains, then spreads east into the week ahead. Some of these areas may see the warmth last into November's first full weekend.
Here are some forecast "high"-lights by region:

• Midwest: 60s return to the northern Plains, Upper Midwest, southern Great Lakes this weekend into early in the week ahead. 70s possible from the central Plains to the southern Great Lakes, Ohio Valley, possibly for multiple days.
• South: 70s in most areas with the exception of the Gulf Coast, Florida, central and south Texas where 80s will dominate.
• Northeast: 60s in most areas except a few 50s in northern New England and some 70s in the mid-Atlantic states.

(FORECASTS: Chicago | New York | Dallas)
Unfortunately, we do have to rain a little on this warm parade. The November kickoff warm spell won't always be accompanied by ample sunshine.
One weather system will spread rain through the Southeast and Mid-Atlantic states early in the week ahead.
Then, as a more vigorous weather system lifts into the Plains from the Desert Southwest, rain should become more widespread in the Plains and Midwest late in the week.
(MAPS: 10-day high/low national forecasts)

West: Early-Season Ski Fever

Snowfall Outlook Through Next Saturday

West Forecast Highs Next Week

Perhaps the biggest change as the calendar flips to November will take place in the West.
The first nine months of 2015 were the hottest January-through-September period on record in California, Nevada, Oregon and Washington. Of the other Western states in the Lower 48, only New Mexico hasn't chalked up at least a top three warmest first nine months of the year. It was their sixth warmest January-September.
That was largely due to a dominant jet stream pattern featuring a pronounced northward detour of the jet stream into western Canada, keeping the West warm, relatively dry and lacking mountain snowpack last winter.
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As November begins, this pattern will be flipped.
The jet stream will plunge into the West, ushering in colder air. Like spokes in a wheel, upper-level disturbances rotating through that jet stream dip will lift moist air and wring out valley rain and mountain snow much of the week ahead.
If you're already itching to hit the slopes to carve your first powder of the season, the forecast of significant snow in the Rockies and Wasatch in the week ahead ought to get your pulse racing, or drive you crazy if your favorite resort won't open yet.
Mountain snowpack is also of critical importance for water supply in the West, particularly in California. Some snow is expected in the Sierra, Siskiyous, Cascades, and possibly the Tehachapis and San Gabriels of Southern California in the week ahead.
Some rain is expected, as well, in northern California, but given the orientation of the jet-stream, it is not expected to be heavy.
Then, there's the cooldown.
Enjoy the 70s or low 80s in L.A. and Las Vegas while they last. They'll be replaced by highs in the 60s in the week ahead.
Highs may struggle to get out of the 40s even in lower elevations of the northern Great Basin and the Pacific Northwest, including Salt Lake City, Boise and Seattle.
(MAPS: 10-day high/low national forecasts)
There are some indications the general warm East, cold West pattern may linger into November's second week.
(MORE: Winter Outlook | Strong El Niño To Last Into Spring | When You Typically See Your First Snow )

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