Weather Blog: December 2021 outlook

Weather Blog

A look at the December 2021 temperature and precipitation outlooks for NW Arkansas and the River Valley.

December is finally here and that means the holidays are in full swing. Gift shopping, family gatherings, and of course, all those holiday treats and feasts! Will we be celebrating the holiday season in shorts and t-shirts or bundled up with multiple layers? Ultimately, only time will tell, but we can offer an overall overview of the expected weather pattern for the final month of the year.

Temperature Outlook

It appears Old Man Winter isn’t ready to bring on the chill quiet yet across the Lower 48 States. At least, not in full force. We will still have cold days throughout the month, but the overall pattern favors warmer than average temperatures for December for most. This is especially true in the southern U.S. where the darker shades of red are.

Northwest Arkansas and the River Valley are heavily favored to see above-average temperatures overall this month. There is a slightly higher risk for warmer than average temperatures in the River Valley compared to Northwest Arkansas according to the Climate Prediction Center (CPC) outlook.

Precipitation Outlook

The precipitation outlook across the Lower 48 is similar to a typical La Nina winter pattern with favoritism towards below-normal precipitation in the southern U.S. and above-average precipitation in the Northwest and Great Lakes region.

Northwest Arkansas and the River Valley region are in the “neutral zone” for precipitation this month. This means the overall pattern does not favor above-average precipitation or below-average for the month. Another way to think of it is we have equal chances to see above-average precipitation this month as we do for below-average precipitation.

December Preview

Northwest Arkansas

The first month of Meteorological Winter continues to decrease our average temperatures, but not drastically. Our average daily high will go from 54°F to 47°F between now and New Years Day. Average daily overnight temperatures will remain below freezing for the entire month at Drake Field in Fayetteville, AR.

Our sunrises continue to get later this month, nearing 7:30 A.M. by the start of the new year. However, our sunset times reach their earliest of the year at the beginning of the month so we actually gain some daylight towards the end of the day. Unfortunately, we still lose 7 minutes of sunlight overall this month since the Winter Solstice is not until Tuesday, December 21.

In terms of precipitation, Drake Field receives 3.07″ of liquid precipitation on average during the month of December. According to the National Oceanic & Atmospheric Administration’s records, Fayetteville receives 1.1″ of snow in December on average.

River Valley

The average daily high in Fort Smith will also decrease throughout the month, going from 57°F to 51° by New Year’s Eve. Our average overnight temperatures will drop below freezing this month too.

Similar to Northwest Arkansas, our sunrise times will continue to get later this month while our sunsets start happening later in the day. Overall, we will still lose 8 minutes of daylight this month before we begin to see net gains for sunlight next month.

Fort Smith Regional Airport receives an average rainfall of 3.48″ in December according to the latest climate normals. The data shows December is also when Fort Smith receives its first measurable snowfall with 0.6″ of snow being the monthly average.

1981-2010 Climate Normals vs. 1991-2020 Climate Normals

Every 10 years, the National Weather Service updates the statistics used to calculate climate normals for a location. Generally, this happens on years that end with a 1 (example: 2001, 2011, 2021, etc).

Why every 10 years? Updating the numbers every year could lead to skewed data, especially if the site is only a few years old. By doing updates every 10 years, it ensures the value is more representative of the site’s actual climate instead of being potentially altered drastically by a single historical event.

Take last February’s record-breaking cold for example. If we altered the data based on last February’s cold air outbreak alone, we would introduce a cold bias into the statistics. However, by including 9 more years of data in the update, we mitigate the effect of a single historic cold event on the averages and get a better idea of what a typical February actually brings to the region.

So what’s changed with the most recent update for December? Let’s find out!

Northwest Arkansas

The new climate normals being used for December 2021 incorporate data from 1991-2020 while December 2020’s values used data from 1981-2010. You can see the comparisons above with 1981-2010 numbers on the left and 1991-2020 values on the right.

The average daily high temperatures at Drake Field in December have increased slightly in the recent update. Our range went from 52°F at the beginning of December to 54°F in the most recent update. The average high temperature at the end of the month has also increased by a degree.

Our nighttime temperatures have gotten slightly warmer according to the 1991-2020 climate record update. December’s new average low temperature at the beginning of the month is 31°F and 26°F at the end of the month.

The average amount of rainfall Drake Field receives in December has decreased by 0.17″, going from 3.24″ to 3.07″ with the new update. In terms of snowfall, our monthly average for Drake Field has decreased from 1.5″ (1981-2010) to 1.1″ (1991-2020).

River Valley

Fort Smith Regional Airport also saw some changes in their climate normals with the new update.

Our average daily high temperature increased slightly too in December, going from 56° to 57° at the beginning of the month. With the normal climate normal update, Fort Smith does not drop below 50°F for their average daily maximum temperature. The new average daily high on December 31st is 51°F.

Average overnight temperatures changed slightly. The 1981-2010 climate normals have Fort Smith’s average overnight temperature dropping into the 20s by December 31st. The newly updated climate normals from 1991-2020 keep Fort Smith’s average daily low in the 30s for the entire month.

This is interesting! Unlike Northwest Arkansas, Fort Smith’s monthly precipitation average for December has increased by 0.19″. The previous normal precipitation amount was 3.29″, the updated value is 3.48″. Our average snowfall for the month decreased slightly though, moving from 0.8″ (1981-2010) to 0.6″ (1991-2020).

Keep in mind, this is an overall look at the pattern for December 2021. The daily/weekly variations in the forecast may not follow the outlooks exactly. Be sure to stay up to date with your Weather Authority team on all the forecast details on-air, online, and on social media!

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