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Where is winter?!! Colder air arrives after the start of 2017

Finishing off the year with a record-breaking Christmas, many people are asking “Where is winter?” Well, it may be right around the corner! A blast of arctic air is expected to filter in the Valley next Wednesday afternoon through next Saturday morning. Daytime highs will struggle to climb out of the 30s Friday and Saturday afternoons, and overnight lows will drop back into the upper teens to 20s.

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A note of caution about any “snow” forecasts on weather apps and on social media: Forecast models are notoriously inconsistent between model runs beyond the first 5-days of a given forecast, and many apps are running off of model out put statistics. Our Live Alert 19 app is hand edited multiple times a day, every day, allowing WHNT News 19 meteorologists to tailor the forecast for the Valley based off of our analysis of the data for the region.

Consider the two images below, which depict the futurecast for 18Z (12pm CT) Thursday, January 5. The image at the top was rendered based off of Friday, December 30 morning data. The bottom was rendered based off December 30 evening data. Notice how the images are not similar, illustrating the variability in the run-to-run output of the same model for the same forecast date and time.

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GFS model data for Thursday afternoon, January 5, 2017 as ran at 12Z Friday, December 30. Note the grey shading, which indicates the possibility for light precipitation in the Tennessee Valley. The green over Texas-Louisiana-Arkansas suggests rain in that region.

GFS model data for Thursday afternoon, January 5, 2017 as ran on Friday, December 30, 2016. Note the absence of snow, even though some apps show a 50% chance for snow.

GFS model data for Thursday afternoon, January 5, 2017 as ran at 00Z Saturday, December 31. Note the absence of precipitation in this model run, let alone the chance for snow, as indicated in some mobile weather apps.

What this means is that the models and apps may not pick up on the correct timing or atmospheric nuances necessary for a wintry weather several days out, resulting in a bust. Treat any forecast beyond the 5-day mark with a critical eye, and expect the forecast to vary leading up to that date.

In the event that wintry weather affects the Tennessee Valley, we will be sure to update you with all of the information that you need to know on-air, on-line and with our Live Alert 19 app.