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 will be heating 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).

Changes, however, are in the wind, and they will continue into 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 will bring 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 will go from the 70s and 80s this past weekend, to the 50s and 60s, with a few locations in the Midwest even staying in the 40s, this weekend.

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 40s for parts of the South, especially on Sunday morning. Record low temperatures are even possible, including Daytona Beach, Florida (58), Pensacola, Florida (49) and Huntsville, Alabama (37).
As temperatures cool down in the East, the warmth will make a comeback along the West coast, with highs 15-20 degrees warmer by this weekend. Los Angeles will go from highs in the 70s to highs in the 90s or triple digits in some inland locations. The forecast for hot weather, very low humidity and offshore winds has prompted red flag warnings for parts of California, including the Los Angeles area.
Heat advisories have also been issued for southern California, as well as the San Francisco area.

In addition to the changes in temperature, many locations will go from wet to dry and vice versa.
The West will see dry conditions return, as a cold front has pushed eastward. Rain and thunderstorms will linger in the Northeast on Saturday.
Over the weekend, we can't rule out a few wet snowflakes mixing in with a cold, wind-driven light rain from Minnesota and Iowa into Illinois 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 through at least early Sunday from Upper Michigan to central and Upstate New York. Quite a calling card for fall, eh?

So fall conditions will likely return to the Midwest and Northeast this weekend, while summer won't let go of the West coast yet. Fall is definitely a season of change and this will be apparent to many as we head through early October.