December 2013 Weekly & Monthly Forecast

This forecast will give depictions of the conditions for each week in December by text, and then graphics for the monthly averages.

Weekly Forecasts

December 1-7: It appears possible that there will be another outbreak of Arctic air from Canada into the United States. Both American and European ensemble guidance systems confirm this idea, thus it is anticipated that this timeframe will be quite cold. It appears that the precipitation anomalies would be most enhanced over the Plains, Midwest and Ohio Valley with a favorable Pacific pattern, though the East Coast will also need to monitor this timeframe as ridging pops up near Greenland to provide a base for a possible negative North Atlantic Oscillation.

Plains: Very Cold, Possible Above Average Precipitation.
Midwest: Very Cold, Possible Above Average Precipitation.
Ohio Valley: Cold, Possible Above Average Precipitation.
Northeast: Very Cold, Average Precipitation.
Mid-Atlantic: Cold, Average Precipitation.
Southeast: Cool, Average Precipitation.
South Plains: Cool, Possible Below Average Precipitation.
Southwest: Warm, Possible Below Average Precipitation.
Northwest: Average Temperatures, Possible Above Average Precipitation.

December 7-14: The cold pattern should continue, but slowly wind down towards the end of this week. Watch out for a winter storm during this timeframe, which may affect the Midwest or East Coast based on the early week teleconnection patterns. Expect warm weather in the West to continue, but possibly edge eastward as the colder weather does begin that winding down trend.

Plains: Cold, Possible Above Average Precipitation.
Midwest: Cold, Possible Above Average Precipitation.
Ohio Valley: Cold, Possible Above Average Precipitation.
Northeast: Cool, Average Precipitation.
Mid-Atlantic: Cool, Average Precipitation.
Southeast: Average Temperatures, Average Precipitation.
South Plains: Average Temperatures, Possible Below Average Precipitation.
Southwest: Warm, Possible Below Average Precipitation.
Northwest: Average Temperatures, Possible Above Average Precipitation.

December 14-21: The cold pattern that kicked off December should have receded by now, and may very well give way to a warmer than normal pattern. If not warm weather, expect an altered precipitation anomaly pattern, which may shift away from the Midwest and Ohio Valley to the Plains once again.

Plains: Warm, Possible Above Average Precipitation.
Midwest: Warm, Possible Below Average Precipitation.
Ohio Valley: Average Temperatures, Average Precipitation.
Northeast: Average Temperatures Average Precipitation.
Mid-Atlantic: Average Temperatures, Possible Below Average Precipitation.
Southeast: Average Temperatures, Possible Below Average Precipitation.
South Plains: Warm, Possible Below Average Precipitation.
Southwest: Cool, Average Precipitation.
Northwest: Average Temperatures, Average Precipitation.

December 21-31: The remaining week and 3 days of December are rather murky, as it is not known just how long this potential warm pattern will last. Depending on upcoming stratospheric developments, this timeframe may or may not see an active weather pattern. There are no significant signals of either active or non-active weather for this period, so the forecast for this timeframe will follow that of the previous week, but is highly uncertain.

Plains: Warm, Possible Above Average Precipitation.
Midwest: Warm, Possible Below Average Precipitation.
Ohio Valley: Average Temperatures, Average Precipitation.
Northeast: Average Temperatures Average Precipitation.
Mid-Atlantic: Average Temperatures, Possible Below Average Precipitation.
Southeast: Average Temperatures, Possible Below Average Precipitation.
South Plains: Warm, Possible Below Average Precipitation.
Southwest: Cool, Average Precipitation.
Northwest: Average Temperatures, Average Precipitation.

Monthly Averages

Temperatures for the month of December will most likely be determined by the first week or two of the month, with significant cold weather anomalies across much of the nation. Temperatures ought to vary from frigid conditions in the Plains, where the Arctic air will originate from, to cold weather in the Midwest and cool conditions in the Northeast. Average conditions may prevail over the Southwest before slightly above average temperatures show themselves along the West Coast.

Precipitation anomalies are set up in accordance with the first few weeks of the month, with a wide, rather uncertain swath of above normal precipitation stationed over the Plains, Midwest and Great Lakes. The Great Lakes will be inundated with lake effect snows as a result of the cold outbreak at the beginning of the month, with another one possibly following close behind. Other areas of the nation are too uncertain to delineate, but we will most likely see precipitation anomalies outlined in the first days of the month.

Andrew