Cold and Complex – The Forecast

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Very complex forecast to deal with when it comes to Tuesday especially. For today, however, we remain dry with a mix of sun and clouds and highs approaching the 50 degree mark during the afternoon. Changes get underway on Monday, but for the moment, I believe Monday will be a dry day as clouds continue to increase and thicken up.

An upper short wave trough coming out of the Southern Rockies will generate a surface low in the northwestern Gulf of Mexico Monday. That surface low will move along the Gulf coast Tuesday and into the Southwest Atlantic on Wednesday bringing rain to Central Alabama beginning Monday evening and continuing through much of Tuesday. While the surface low is in a nearly ideal position for bringing a winter weather event to the Southeast US, there are a number of concerns.

The first concern is whether it will be cold enough for snow. According to the latest models which seem to be in good agreement, it will not be cold enough. But there is a good deal of concern as to whether or not the models are handling the change in heat flux. There is not doubt that the precipitation will be snow well above the surface where it is very cold. This precipitation will transport cold downward – negative heat flux – and as Dr. Tim has pointed out in his discussion below posted last night, there is concern that the models may not be handling this well. If the models are not handling the negative heat flux appropriately, then the temperature profile in the lower portion of the atmosphere – ground to about 850 millibars – could be much colder than the models suggest. This could result in a rapid change to snow earlier with snow lasting a good deal longer and presenting a significant threat for us.

Another concern I have is the strength of the 850 millibar low. The models are in good agreement that the low at 850 will be fairly strong which means there could be a significant transport of warm air from the northern Gulf into North Alabama. This transport of heat could offset the cooling I mentioned in the paragraph above.

So at this time I am sticking with a mixture of snow and rain from late Tuesday afternoon or early Tuesday evening into early Wednesday morning with the main snow event across portions of Tennessee. Under this scenario, there is not likely to be any significant travel issues for Central Alabama.

But I caution anyone reading this to stay tuned for later developments. It will only require some subtle changes for the event to go more toward rain or more toward snow. If the weather is a concern for you, then it is wise to stay up with the latest changes as the whole weather system unfolds and we can be more certain on what will be happening.

The precipitation, no matter what type, should end early Wednesday. With clouds likely to stick around much of the day, look for snow flurries during the day Wednesday. With the upper long wave trough anchored over the eastern half of the country, we won’t be seeing a significant warm up any time soon. We could be seeing temperatures approaching 50 again by next Saturday with dry weather from Thursday into the weekend.

Peeking further in time – well into voodoo country – the GFS maintains the long wave trough over the eastern half of the country so the cold will continue under this pattern. With a continuation of strong impulses moving through the flow we will be seeing additional threats of winter weather, the timing of which is impossible to nail this far in advance.

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James Spann will be back with the next edition of Weather Xtreme Video bright and early Monday morning. Stay tuned to the Blog for additional information on the overall developing situation. We’re your best source for good, solid weather information. Enjoy the day and Godspeed.

-Brian-

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Category: Alabama's Weather