January Temperature Forecast Trends Colder In East, Remains Mild In Rockies

J​anuary's temperature forecast has trended colder in the East while remaining mild in the West, according to an updated outlook released Sunday by The Weather Company and Atmospheric G2.

Here's the big picture on January's forecast: For the month as a whole, most of the East is expected to have temperatures colder-than-average, from Florida to Maine and parts of the Great Lakes. M​uch of the West can expect milder-than-average temperatures, with the Four Corners region being the most above average.

Since the map below is an overall snapshot for all 31 days in the month of January, it masks some notable week-to-week temperature swings. Specifically, temperatures in the first half of January will likely be much farther below average compared to what the forecast for the month as a whole shows in the eastern half of the country.

H​ow the month's temperatures might evolve from beginning to end:

• First, December's rather mild ending in most of the central and eastern states will be erased by a cold plunge to start January in those regions. So there is high confidence of a much colder pattern returning as the month begins.
• AG2 forecasters say the cold pattern in the East might reach a peak around mid-month, but how temperatures toward the second half of January evolve is still uncertain.
• "Unlike December, when we were more confident in a warm back half of the month, we are less confident in that occurring in January, given the peak of the cold likely won’t crest until mid-month" said Todd Crawford, Vice President of Meteorology at Atmospheric G2.
• S​o rather than a big, widespread warmup in the East to end the month like we saw in December, the weather pattern might only allow for a gradual waning of the cold. If the chilly pattern is even more stubborn to ease, then the outcome for the full month could be colder than what the AG2 forecast shows right now.

This pattern is associated with a southward-plunging jet stream sending cold air from Canada into the eastern states, as depicted in the graphic above. It's the same pattern that was in place much of December and led to several cold outbreaks in the East during the first half of the month.

T​he other southward jet stream plunge in this type of pattern is in the northern Pacific.

Sandwiched in between is the opposite impact over the West, where the jet stream riding to the north of that region brings milder-than-average temperatures.

Chris Dolce has been a senior meteorologist with weather.com for over 10 years after beginning his career with The Weather Channel in the early 2000s.