Slight Warm-up Today but Week Stays Chilly

| December 26, 2017 @ 7:23 am

Some cirrus clouds still seen in the morning satellite image over the northern third of Alabama, but they are fairly thin, so I’m expecting to see a mostly sunny day. The sunshine should help us get out of the deep freeze with highs today around the 50-degree mark. That should feel pretty nice after a high of only 39 degrees at the Birmingham Shuttlesworth International Airport yesterday. Even at 50 degrees, that’s still 4 degrees below our 30-year seasonal averages for December 26th.

When it comes to the computer guidance, we’re still dealing with model madness as the two major global models remain at odds. The upper air pattern is still stuck in the broad trough across nearly all of the US. And it looks like this cold pattern will not be changing significantly for the next 10 to 11 days. An overrunning pattern is forecast to develop later today and advance eastward. There is still some slight differences on just how far north the precipitation will push, but the GFS and EMCWF are much closer on this run. The ECMWF is a tad further north than the GFS – see the graphic below – and we could see the precipitation begin as a mix of rain, sleet, and freezing rain between about 3 am and 9 am. The current diagnosis suggests this will be short lived and very light without any significant impacts for travel, but with the early morning temperatures Wednesday sitting around the freezing mark, we’ll need to be carefully watching the developments then. The GFS suggests the precipitation will be further south without any wintery mix at all.

Thursday and Friday both models depict the upper air pattern sticking with the broad trough, so we are not going to get very warm with the afternoon highs in the 40s and morning lows in the upper 20s to lower 30s. Both models depict a continuation of the overrunning situation, but both are showing the precipitation over South Alabama and the Gulf Coast area. Friday a strong trough moving through the Great Lakes will sharpen the trough aloft just a bit resulting in pushing the overrunning area further south and east.

For the weekend into New Years Day the forecast is downright challenging since the two global models are in no way agreeing. This means the confidence in the forecast from 5 to 8 days out is low. Actually I would suggest confidence is very, very low when you consider that one model shows precipitation and the other model shows complete dryness. The actual real solution is probably a mix since we often see the two models grow closer to each other with time. In the meantime, everyone wants a forecast for what is likely to be a complicated situation.

The broad upper trough is still in place on Saturday, so the forecast looks to remain cold but dry with highs around the 50-degree mark. Sunday another big change is forecast by the GFS with a strong trough moving southward across the western Great Lakes with the short wave over Baja California ejecting eastward. The GFS is quite bullish on precipitation across the Lower Mississippi River Valley while the ECMWF is completely dry for the Southeast US with precipitation across the Gulf of Mexico. So which do you pick? To add additional trouble to the forecast, the GFS is suggesting a broad band of freezing precipitation across the northern third of Alabama roughly along and north of the I-20 corridor. I think the safest bet for the forecast is to do what the National Weather Service forecast has done, and put in a chance of rain or light sleet or snow. This is on the edge of voodoo, so we’re pretty sure models will have a better handle was we get closer to the event. If the GFS is correct, the timing for the precipitation would be from late Sunday afternoon through early Monday morning.

That trough coming across the Great Lakes on Sunday is forecast to dig into the Ohio River Valley promising still colder weather to start 2018. The good news is that the GFS pushes the dry air well south, too, so while the 1st and 2nd of January will be cold, there should not be any concern for winter weather. By the way, this is depicted as brutally cold air with the GFS MOS guidance printing out 14 degrees for the low on Monday and 8 for the low on Tuesday. I think both numbers qualify for the adjective of brutal!! And Monday the GFS is forecasting a high of only 23 degrees. BRRRRRRRRRRR!!

Looking out into voodoo country, the message we’ve been getting remains the same – an active and generally cold pattern. There is another upper trough coming across the Lower Mississippi River Valley around the 4th of January. But that is followed by a deep trough digging into New Mexico which would pump up the ridge over the eastern half of the country and return us to some warmer weather. That trough ejects across the Southeast US around the 8th providing a pattern that would bring the cold trough back to the eastern US.

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I anticipate having the next Weather Xtreme Video posted here by 7 am or so on Wednesday. Remember, while James is on vacation, we maintain a one-a-day schedule. Be sure to catch Charles Daniel on ABC 3340 at 4, 5, 6, and 10 pm today with the latest weather forecasts. Have a great day. Don’t get too silly over the remarkable warm up today. Godspeed.

-Brian-

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Brian Peters is one of the television meteorologists at ABC3340 in Birmingham and a retired NWS Warning Coordination Meteorologist. He handles the weekend Weather Xtreme Videos and forecast discussion and is the Webmaster for the popular WeatherBrains podcast.

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