Late autumnlike chill to be followed by uptick in temperatures

The typical up-and-down temperature roller coaster of fall has already been on display this month. The coldest air of the season last week was followed by a warmup this past weekend. However, AccuWeather forecasters say that even colder air is on the way this week.

The recent warmup allowed fall foliage enthusiasts to have ideal weather for leaf-peeping on Saturday. Unfortunately, rain moved in on Sunday and knocked some of the leaves off of the trees.

That rain was associated with a cold front. In the wake of the front, gusty winds will knock more leaves from the trees in locations that are at or past peak color.

The biggest change will be in the temperature department. While the calendar may say it is the middle of October, the cold air on the way will be about a month ahead of schedule.

"This setup is something that we see in late autumn, so it is an early taste of it," said AccuWeather Senior Meteorologist Tyler Roys.

With the cold air pouring over the relatively warmer Great Lakes, another aspect of late fall or early winter will occur.

"Lake-effect showers are expected downwind of the Great Lakes," noted Roys.

Since it is still October, most showers will occur as rain. In the higher terrain and away from the immediate influence of the lakes, at least some snowflakes can mix in with the rain. This will especially be the case during the overnight and early-morning hours when temperatures are typically at their lowest values.

"Some of the these showers could fall as a mixture of rain and snow across the interior locations of far northern Pennsylvania and southern tier of New York, though snow accumulation is not expected on any paved surfaces," explained Roys.

With the cold airmass and brisk wind, AccuWeather RealFeel® Temperatures will be significantly lower than the thermometer. For some, it will seem like winter has already arrived.

The cold air will continue to push farther to the south and east on Tuesday. Places like Philadelphia, which were forecast to soar into the 80s F on Sunday afternoon, will fail to reach 60 by Tuesday. A similar scenario is forecast to unfold in Washington, D.C. In both cities, residents and visitors alike will need to trade shorts and t-shirts for sweatshirts quickly.

"For many, this might be the time when people scramble to make sure they have enough heating fuel and turn on their furnaces for the time this season," said Roys.

Lake-effect precipitation beginning on Monday will continue right through Tuesday and likely Wednesday. Unlike on Monday, much of the precipitation Monday night, Tuesday and Wednesday will be restricted to places closer to the lakes. Similar to Monday, mainly rain is expected, but a mix of rain and snow will form in the higher elevations and away from the lakeshores.

The most widespread chill is likely to be on Wednesday. By then, even people in the Southeast will experience temperatures below the historical average. During the morning hours, residents as far south as Charlotte, North Carolina, and Atlanta may be reaching for their pumpkin spice latte as AccuWeather RealFeel® Temperatures fall into the 30s.

By Wednesday night, an area of high pressure will center over West Virginia. As that high approaches, the sky will clear and winds will become much lighter. The combination of the lack of wind and a clear sky will set up ideal conditions for radiational cooling. This phenomenon occurs at night when any heat built up during the day radiates back into space. With the plummeting temperatures, frost will be a concern as far south as northern Alabama, northern Georgia and western South Carolina Wednesday night.

"This will end the growing season in some locations," cautioned Roys.

For those not ready for sustained chill, good news is on the horizon. On Thursday, warmer air will begin to arrive in the western Great Lakes. From Friday through at least the weekend, the jet stream moving northward and warmer flow around high pressure will allow temperatures in the Ohio and Tennessee valleys, New England, the mid-Atlantic and Southeast to be above the historical average. In addition, little to no rain is expected.

While no record highs are anticipated, there are some indications that temperatures above the historical average may last well into next week.