October Chill Targets the East, Summer Returns in the West

Just in time for the first weekend in October, a plunge of chilly air is driving south and providing a crisp taste of fall in the Midwest and East. Meanwhile, the West coast has heated back up.

This past Sunday, Caribou, Maine basked in 84-degree warmth, the hottest temperature on record so late in the season, there. Daily record highs were also set Sunday in at least a dozen other northern cities, including Newark (87), Providence (86), Sault Ste. Marie (80) and Duluth (81). 

(MORE: Record Heat)

Changes, however, are in the wind, and they will continue through the weekend. An upper-atmospheric trough is carving southward into the East and Midwest, while a corresponding upper-atmospheric ridge builds into the West (previously, we had had a ridge in the East and a trough in the West).

Already, the heat is building along the West Coast. San Francisco had the hottest day of the year Friday when thermometers hit 95 degrees at the airport, setting a new daily record high temperature. Further south, thermometers reached the triple digits in Santa Maria, California and set a record high of 100 degrees on Friday.

This pattern change has brought temperatures that are 20-30 degrees colder for some locations in the northern Plains. Temperatures will also be cooler in parts of the Midwest and Northeast, where highs are going from the 70s and 80s last weekend to the 50s and 60s, with a few locations in the Midwest even staying in the 40s, this weekend.

(FORECAST: Minneapolis | Chicago | New York)

With this fresh plunge of cold air, expect some frost and even freeze conditions from parts of the Tennessee Valley and into the Appalachian Mountains Sunday morning.

Cooler temperatures will reach as far south as the Gulf Coast and Florida, where some locations will see highs only in the 70s this weekend. Low temperatures will even drop into the 30s and 40s for much of the Southeast Sunday morning. Record low temperatures are even possible, including Daytona Beach, Florida (58), Pensacola, Florida (49) and Huntsville, Alabama (37).

(FORECAST: Tampa | Atlanta)

As temperatures cool down in the East, the warmth has made a comeback along the West Coast. Los Angeles saw highs in the 90s all the way to the beaches Friday and Saturday. Highs in the San Francisco Bay area also surged into the 90s to near 100, with downtown San Francisco recording its hottest day of 2014 Friday (92 degrees).

Heat advisories will remain in effect for one more day Sunday across interior portions of Southern California, including the Inland Empire.

(FORECAST: San Diego | Lake Tahoe | Portland)

In addition to the changes in temperature, we've seen a shift in precipitation patterns.

The West has seen dry conditions return as the cold front has pushed eastward. Rain and thunderstorms have steadily marched east, but the last of the rain with the front itself should move out of Maine Sunday afternoon.

We've already seen a few wet snowflakes mixing in with a cold, wind-driven light rain from Minnesota into Illinois, Indiana, and Michigan. 

In fact, there should be bands of lake-enhanced rain, and yes, perhaps some wet flakes in the hills away from the lakes, overnight Saturday night through at least early Sunday from Upper Michigan to central and Upstate New York. Quite a calling card for fall, eh?

(FORECAST: Fargo | Duluth | Marquette)

Fall is definitely a season of change and this will be apparent to many as we head through early October.

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