Saturday, December 5, 2015

December turns warm, and will stay that way for a while

Spectacular weather for the first weekend in December, which is always a busy one! The Memphis Marathon couldn't really have asked for finer conditions (remember the ice storm a couple years ago?) with chilly temps early that warmed quickly and light wind. Christmas Parades abound today as highs reach the lower 60s with sunny skies. Normal highs are in the mid 50s with lows in the mid 30s this time of year.

Current metro temperatures from
Above average temperatures will continue for the foreseeable future as upper level ridging dominates the region (with a few quick passes of transient upper level disturbances) and high pressure at the surface resides over the eastern U.S. We'll likely get used to afternoon temperatures in the 60°+ range over the next week! The first upper level "imperfection," and its weak surface cold front pass, by tomorrow, bringing cloud cover and maybe a few sprinkles, but a very small chance of measurable rainfall. Despite the cloud cover, temperatures should still reach 60°.

Upper level (500mb, or 18,000') loop showing an approaching trough and disturbance (red to purple colors) moving across the south-central U.S. through noon tomorrow. Graphic courtesy Rapid Refresh model.
By Monday, the passing trough is replaced by another ridge of high pressure as the sun returns and temperatures climb into the upper 50s. Tuesday and Wednesday features more of the same with slightly warmer weather. Highs return to 60° or a bit higher each day.

By 6am Tuesday, high pressure covers most of the central and eastern U.S. leading to tranquil weather and above average temperatures for the Mid-South. With the high to our east, wind becomes southerly on Tuesday. Graphic courtesy NOAA.
As we head into the latter half of the week and next weekend, strong southerly flow (marked by moderate south wind and moisture feeding into the region from the Gulf of Mexico) establishes itself over the southern U.S. This pattern means a couple things: more clouds and periodic rain chances, but also even warmer temperatures.

Towards the end of the week, strong southerly wind pushes temperatures up but also means periodic rain chances. The GFS model depicts this pattern well for Friday night. Graphic courtesy Pivotal Weather.
Medium range models are having a tough time so far with timing of low pressure systems and cold fronts, thus also rain chances. We're carrying a low end rain chance (20%) Thursday with 30-40% chances on Friday and Saturday. By Saturday night or Sunday, a large-scale surface and upper-level system will push through, bringing a round of showers and maybe a few thunderstorms and dropping temperatures from the mid (to perhaps upper) 60s back down into the 50s to start the third week of December. We'll have to re-address the timing of said systems as we get closer to the mid-week timeframe. Until then, enjoy the relative warmth! (For those keeping score, our MWN Winter Outlook predicted above normal temperatures for much of December. So far we look to be right on track.)

The Climate Prediction Center temperature outlook for the third week in December shows a 60-70% chance of continued above normal temperatures for the metro. In fact, most of the nation east of the Rockies could experience above normal temperatures, on average, from December 13-19.
Erik Proseus
MWN Meteorologist

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