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Winter Storm Warning: Now that the computer models are able to sample the entire storm system, the precipitation estimates are able to be given with a little more accuracy. This is a primary example of why you don't give snow or ice totals a week in advance, they will always change. Once you get 48 hours out from the event, then we can better estimate the amounts. That said, here goes...
The 4 panel graphic below is a great snapshot in time Christmas Day. The first 3 panels is the model radar reflectivity with the 32 degree line in blue overlaid. Rain that falls east and south of this boundary is just that, rain. The rain that falls along and near this boundary is ice Farther back behind in the colder air it falls as snow(where it turns to a blob of solid red/blue). The last panel is the snow total estimate from the model. According to the scale on the right that reads 20" of snow over OKC. Do I buy that? No. Here's why...
After midnight Monday very light precipitation will start to fall in the form of freezing rain across 2/3 of the state. The SE will remain liquid for now. The freezing rain will get heavier during the early morning hours over C OK up to Tulsa. Right now the freezing rain may not change over to snow until around 10 or 11am in this area. That means at least a good 6-9 hours of freezing rain. Even light freezing rain adds up. So my original forecast from day 1 of half an inch of ice with the potential of more over C OK still looks like a good call. Every model run prior to today was only giving a quarter of an inch of ice before changing over to snow. Quite a difference a day makes. As the freezing line marches south so goes with it the freezing rain across SE OK and N TX. Snow will continue to take over across C/NE OK by noon and for the rest of the afternoon. The storm intensifies across the state as it moves through. The track is still in question believe it or not. This model example I have here has the most northern track right across the I-40 corridor. Other models have the track either across the Red River or N TX. Like I said before, there's a big difference 100 miles can make. If the track does verify farther south, then the higher snow totals seen in this map shifts south a bit and DFW will see an inch or 2 of snow as a result. If it stays north, DFW just gets a dusting of snow. Speaking of snow, the discussion above about ice is why I don't trust the snow totals and the fact that this particular model gets carried away with thunder snow from extreme lift the internal dynamics it creates. Divide by 2 roughly. So does that mean we could see 8-12" of snow over C OK on top of the half inch or so of ice? Yes. Hence a major winter storm.
Now, back to N TX, we will not know the exact position of the freezing rain line until late Monday. Arctic air always plants farther south than the models suggest and they are still holding onto the I-44 corridor as the morning starting position. I have a feeling it will be closer to a line from McAlester to Denton, to Abilene. If so, watch out for morning ice along that boundary as most of the heavier precip for the DFW region will fall before/around daybreak. After that wave moves through, the cold air deepens anyway by noon so whatever falls after that will be a light wintry mix. Just enough to cause slick roads.
One change the models did make that's worth noting. After the storm moves through OK it takes a more northward track through N Arkansas and S MO rather than due east, so the bigger snows have shifted north.
One last note. As the storm system deepens, expect 50 mph winds to develop on the back side creating blizzard like conditions for C and E OK Tuesday afternoon/night. There will also be some power outages due to the ice and wind. With temps staying in the teens on Wednesday and not getting above freezing until next week, this stuff is going to stick around awhile. Not to mention another storm system on Friday that should produce another round of a wintry mix. 'Tis the season! ~Merry Christmas!