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Updated December Outlook – Cold East, Warm and Dry West

1 Dec 2017, 2:23 pm

NOAA’s Climate Prediction Center (CPC) updated their forecast for December on Thursday. There are significant changes to both the temperature and precipitation outlooks, which were originally issued in the middle of November. Most of the eastern half of the nation is expected to see colder than average temperatures, with above normal readings in the West. A drier than normal month is in the December forecast for most of the West and parts of the central and southern Plains. Above average precipitation is not expected.

The previous forecast issued a few weeks ago had the South warmer than normal, with the northwest colder than average. It also had the Southeast dry and northern tier of the nation wetter than average.

The CPC notes that the changes are due to a signficant Jet Stream pattern change that is expected in the next week or two, shifting colder temperatures across the East with an upper level trough. The West is expected to see the Jet Stream lift northward with a high pressure ridge developing. Computer models are in very good agreement of the pattern shift occurring.

The typical influences associated with La Nina were also factored into the forecast.  The onset of La Nina (which was announced earlier in November month). La Nina (translated from Spanish as “little girl”) is a natural ocean-atmospheric phenomenon marked by cooler-than-average sea surface temperatures in the central Pacific Ocean near the equator, the opposite of El Nino (“little boy”).

For WeatherNation: Meteorologist Mace Michaels

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