On the heels of one of the warmest Novembers on record in parts of the eastern U.S., the weather pattern is primed to flip to a colder and stormier one to start December.

Computer models are consistently advertising the potential for a pair of storm systems next week that could produce heavy precipitation and some of the chilliest air of the season in their wake.

The first storm, which could be particularly intense, is projected to take an inland track early next week, from the Gulf of Mexico toward the eastern Great Lakes. Such a track would draw up enough warm air for mostly rain along the East Coast. But interior locations in the Ohio Valley and eastern Great Lakes could see their first significant snow.

There’s some chance for a second storm to develop slightly to the east of the first one around Dec. 3 or 4, opening up the possibility for wintry precipitation closer to the East Coast.

The first storm: Early next week

An upper-level disturbance ejecting from the Desert Southwest will help spark the development of a storm system near the Louisiana Gulf Coast late in the weekend.

Computer models agree that it will tap substantial moisture from the Gulf of Mexico and produce heavy rainfall in the South and Southeast from Sunday into Monday.

The plot thickens Monday when this gulf storm turns north and merges with jet stream energy diving south from the Upper Midwest. The storm may intensify and draw in very cold air on its western side, while funneling heavy rain northward to the east.

The European (ECMWF) weather model forecasts a powerhouse storm, possibly meeting the criteria for a bomb cyclone because of its rate of intensification (a pressure drop of 24 millibars in 24 hours), over eastern Ohio and Western Pennsylvania by Monday afternoon.

Near and east of the storm center, including much of the Mid-Atlantic and Northeast, heavy rain is projected. To the west, heavy snow is shown in western Ohio, eastern Indiana, Michigan and eastern Kentucky. A storm this powerful would also be a big wind generator, creating the possibility of blowing snow and power outages.

The model suggests that the storm could linger over the Ohio Valley and Great Lakes into Wednesday or Thursday next week, resulting in a prolonged period of windblown snowfall.

The Canadian and American models also whip up a storm that tracks slightly to the east of the European model and that is less intense.

The specifics of how strong this storm will be and the location, timing and intensity of rain, snow and wind will come into better focus over the next several days.

In the wake of this storm, models predict lower-than-average temperatures in parts of the East, but not frigid Arctic air.

A second storm?

Between Dec. 3 and 4, some models are showing the potential for a second storm to develop in the South, near the Gulf Coast, and again tracking north.

With cold air better established in the eastern United States by this time, this storm would probably track to the east of the first one if it materializes. A track closer to the coast would open up the possibility of frozen precipitation closer to the East Coast; however, cold air may still only be sufficient for snow in interior areas and especially the Appalachians.

As this potential storm system is more than a week away, uncertainty about its track and strength are very high, and some models have backed off earlier predictions for its development.

Pattern shift sets stage for stormy stretch

This sudden change to a stormy, wintry pattern is the result of a shift in the jet stream. For much of November, the jet — which helps divide cold and warm air masses — has either dipped in the northwest U.S. or remained rather flat across the northern U.S., keeping chilly air bottled up in Canada.

Next week, the jet is set to bulge north over western North America and then plunge south in the eastern U.S., facilitating this taste of winter.

The change in the jet stream pattern is indicated by an abrupt spike in what’s known as the Pacific-North American pattern.

When this pattern is strongly positive, it signifies a strong rise in the jet stream over the West and is typically associated with cold, wintry weather in the East. Meanwhile, in the West, continued dry weather and unusually mild temperatures are predicted, which will only worsen drought conditions.