Weather Discussion #0316

2:00 PM CDT | December 17, 2017

The weather around Christmas still remains sketchy, as the weather models continue to show little consistency. There has been a trend toward a more progressive system late next week. This is in contrast to the cut-off low over the Southwest many depicted a couple days ago (see post). It also appears that this first disturbance could be followed by a second piece of energy. How does this fit with the recurring cycle theory? Take a look at this graphic from 6:00 AM November 5th.

There were two distinct pieces of energy well to our north. The first disturbance, as mentioned in the December 14th post above, did not dig southward but progressed eastward. A chilly airmass moved into the state on November 6th, and the second piece of energy moved through the Plains. This resulted in an overrunning event on November 8th. It was a wet day with temperatures chilly but above freezing. With the recurring cycle theory we know when certain features will cycle around again, but we do not nececssarily know how they will behave. If the ridging off the west coast were to amplify as the earlier model runs indicated, it would be possible for the disturbance to become cut off from the main flow this time. The guidance that did this and parked the low to our west showed a crippling winter storm or "Snowpocalypse", as one Dallas-Fort Worth meteorologist referred to it. Since then, most of the guidance has backed off on this scenario and now show a more progressive system. The following graphics are from this morning's GFS (American) and CMC (Canadian) models. They are valid Friday evening and Saturday morning, respectively.

As you can see, they both depict two distinct pieces of energy, just farther south. This fits with the recurring cycle theory being 47.5/48 days apart from the first cycle. The first disturbance could bring moisture to the region late next week; but, it is more likely to be in the form of rain than it appeared on Friday. Of greater interest may be the second piece of energy, in terms of wintry precipitation. We should still see a very cold airmass move into the region around Christmas. Any energy lagging behind would have the potential to lift moisture over this airmass. Once the first disturbance moves into the upper air network on Wednesday, the models will have actual data with which to work. This should lead to more consistency with the weather models, and then we will have a better idea of what to expect on Christmas. I will continue to update as necessary, and I would urge those who will be traveling to keep an eye on your local forecast.

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