Pattern change to spread milder temperatures to the east

Published in 8 December, 2020

At a Glance

  • A changing jet stream pattern is expected late this week.

  • The Plains will cool off as milder temperatures return to the East.

A weather pattern change later this week will spread milder air toward parts of the South and East.

The week has begun with a southward plunge of the jet stream in the East, which has resulted in temperatures that are below average for early December. Meanwhile, a northward bulge, or ridge, in the jet stream over the West, Plains and Midwest is bringing warmer than average temperatures to many parts of those regions during the first half of the week.

That weather pattern will essentially flip late this week, with a southward plunge of the jet stream forming over the western and central states as the milder ridge migrates toward the eastern states. You can see the general evolution of this pattern change in the animation below.

storm Bringing 1

Here’s an overview of what this will mean this week.

Temperature Changes Incoming

A topsy-turvy temperature pattern is in place early this week where areas as far north as eastern Montana and the Dakotas are milder than the Southeast.

Highs temperatures in the Northern and Central Plains the first half of the week will be 15 to 30 degrees above average for early December. Many locations in the East will have temperatures that are below average to start the week, especially in the Southeast.

For example, Tuesday’s high temperature in Rapid City, South Dakota, could be 5 to 10 degrees warmer than Jacksonville, Florida. The average high on Dec. 8 in Jacksonville, Florida (68 degrees), is typically 31 degrees warmer than Rapid City, South Dakota (37 degrees).

Low temperatures will drop into the 40s deep into South Florida by Wednesday morning.

noreaster forecast 2
Forecast Highs

(The Plains will trend colder as the South and East turn milder.)

The jet stream pattern change will flip the script on this temperature story by Thursday and Friday.

Highs in the 50s or low 60s will return as far north as the Ohio Valley and mid-Atlantic while many parts of the Southeast warm back into the 60s or even low 70s.

Much of the Northern and Central Plains will see highs plunge back into the 30s and 40s late in the week, which is more typical for this time of year.

(MAPS: Track the Daily Temperature Change)

noreaster forecast 3
Forecast Highs This Week

(Atlanta, Baltimore and Charlotte will trend milder. After an early week warmup, Denver and Kansas City will turn colder.)

This pattern change may also generate a storm later this week with snow, rain and wind in the Midwest, South and East. For the latest on this system, check out our latest complete forecast briefing.

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