Warm Weekend, Cold Month?

Posted on: 4:45 pm, March 7, 2013, by , updated on: 06:55pm, March 7, 2013

March has been a very cold month so far compared to the averages:

  • Huntsville is running 10.5º F below the 1981-2010 climatological average for the first six days of the month.
  • Muscle Shoals is 9.0º F below the 1981-2010 climatological average as well.

See the actual averages and records for Huntsville and Muscle Shoals.

So where do we go from here? Well, there is at least a little, short-lived warming trend on the way for tomorrow and the weekend! Temperatures finally go back above average and start feeling more like Spring underneath a mostly sunny sky on Friday, Saturday and Sunday:

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A round of rain and storms is likely by Monday morning of next week. Expect rainfall in the inch to two inches range between 12 AM Monday and Monday afternoon. That system’s severe weather potential is fairly low for most of the South because there won’t be a lot of warm and humid air to fuel powerful thunderstorms. Some storms could still be strong with some small hail and gusty winds, but the over-all threat is low when it comes to destructive thunderstorms and tornadoes.

Cooler air follows that next rain-maker, but it will not be quite as cold as this current cold snap has been. Temperatures back off to near or slightly below the average on Tuesday and Wednesday.

More of this below-average temperature trend is likely through the rest of March for two reasons: a persistent trough in the East brings cool air south and “average” increases about a third of one degree every day in the month of March. That means air that was near average temperature on March 1st is about five degrees below average by March 15th.

That means that although we expect temperatures to be “anomalously” cold (unusually cold), the cold will be relative to an increasing average. Average increases significantly in March and April as the sun gets higher in the sky and arctic intrusions are less and less common.

Here is the CFS (Climate Forecast System) output for the next two weeks. It’s indicating surface temperature “anomaly” (difference from average):

Screen Shot 2013-03-07 at 4.29.21 PM

Remember, the anomaly is looking colder due to the persistent cool pattern in the east keeping us from warming up as much as we usually would. That does not mean it’s going to be brutally cold for the rest of March, but it does indicate that there is at least some potential for more frosts and freezes over the next two weeks.

This is the ensemble forecast specifically for Huntsville, and it shows the chance of temperatures dropping below 35º F (frost/freeze territory) through March 23rd. To the right, the NAO (North Atlantic Oscillation) is still forecast to be in negative territory which suggests the persistent cooler-than-normal and drier-than-normal weather pattern will continue through at least the next 10-14 days.

Screen Shot 2013-03-07 at 4.34.11 PM

Beyond that, the pattern should start to relax a little and give us some warmer weather in early April. Here’s the CFS surface temperature anomaly for the last week of March and first week of April:

Screen Shot 2013-03-07 at 4.38.16 PM

Long-range forecast take-aways:

  • Spring flowers and garden vegetation that is prone to frost damage should either be planted in a place where you can protect it from frost for a while, or you should just delay planting for about 2-3 weeks.
  • Chances are good that we will see at least 5 to 10 more nights of freezing weather through early April in the Tennessee Valley.
  • The average last freeze in Huntsville is April 3rd; that means they can come early and late, but most of the time it’s not safe to plant until at least the first week of April. Some communities like Valley Head, Russellville, and Winchester (the usual cold spots) have an average freeze date of April 11th – over a week later.

-Jason
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