Looking out to the Long Range

Posted on: 9:07 pm, November 13, 2012, by

It’s November. The weather is supposed to be cool, warm, stormy and dry because it’s a month of transition. We lose 45 minutes of daylight between November 1st and November 30th, and the average high temperature drops from a warm 69º F to a cool 58º F in Huntsville in the same time frame.

The changing seasons and stronger temperature contrasts usually conjure up some rough weather this time of year, but so far, we are skating by with quiet, dry, and unseasonably cool conditions!

This strangely quiet pattern looks like it will continue through at least Thanksgiving. There are no signs of severe weather, widespread heavy rain, wintry weather, or really any “excessive” cold or unusual warmth. In other words, it’s looking rather…normal.

Here’s the NAEFS temperature anomaly (difference compared to normal) through next November 27th (Tuesday after Thanksgiving):

The Tennessee Valley is in a region between unusually cold and unusually warm weather; that typically tells a story of quiet, “average” weather for us. Keep in mind that “average” is really not the norm for us. In fact, for the weather to be near a 30-year average in this part of the country in November is rare; we would normally see flips and flops in weather patterns leading to very warm days followed by some very cold days.

Since we expect to stay near or slightly cooler than average, there is not much reason to suspect any significant severe weather threats over the next 10-14 days. It takes air much warmer than this to bring active storms.

This is a look at ensemble data just for the Huntsville area; while it is point-specific, it is a good indicator of the entire Tennessee Valley area. The first graph shows the probability of a temperature exceeding 60º F in Huntsville on any given day through November 29th:

The following graph shows the probability of temperature exceeding 65ºF in Huntsville through November 29th:

In dealing with probabilities like this, you look for trends…not necessarily a true “chance” of something happening. Based on this information, the going Seven Day Forecast on WHNT.com looks to be right on target with below-average temperatures slowly rising to near-average by the middle of next week.

There is no suggestion here that we will see a big warm-up, but there is good reason to believe there will be at least a few warm days (highs 65-70º) just after Thanksgiving. It’s those warmer days that we have to be wary of; again, there’s no evidence supporting a “severe weather threat,” but in looking at long-range ideas, we gather what we can from the limited information available.

Even longer-range, there are signs of some cold weather in December. The CFS (Climate Forecast System) has been pointing toward a cold December for a while now.

Once we’re out this far, it’s serious guess work. There are no small details available for December other than colder than normal and a little drier than normal. What does that mean?

The average high for the month of December is 53º F in Huntsville; the average low is 34º F. That makes the “average daily temperature” 43º F. If we are to have a “colder than normal” December, we would likely see a lot of days with temperatures running about 5 to 10 degrees below average.

That same CFS model is indicating a daily average for the entire month of December right around 35º F for the Tennessee Valley, so just with some simple math that would give us a lot of days with highs in the 40s and lows in the 20s.

Will it Snow? We don’t know right now. December’s weather pattern looks like it has some potential, but just like the Mississippi State football team, “potential” got over 30 points hung on them in three consecutive blow-outs (thanks Bama, A&M, and LSU). Potential ain’t all it’s cracked up to be. (What, me bitter? Noooooooo….)

I’ll say this much: if there is a legitimate chance of snow, we’ll do our best to let you know as early as we can. There may be things that show up in the model guidance that we never talk about; that’s because we only talk about what we are expecting. We try to stay away from what I call “wish-casting” where we all forecast what we want to see instead of the real weather in front of us!

It promises to be a roller coaster ride of a Winter season; we’ll keep you posted!

-Jason
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