The late night trend of a dramatic increase in ice accumulation near the I-44 corridor began with the Canadian model, followed by the European a few hours later. To add insult to injury, the short term and hi-res models coming in this morning are all now in agreement. This increases the ice totals to the lower end of half an inch and the upper end of 1 inch (hopefully –  one goes much higher).

That’s the bad news. So what’s the good news? Well, amounts up until this evening are paltry which should allow the roadways to be mostly driveable. Just be extremely careful and slow down. One patch of ice is all it takes to set off a chain reaction and that can happen at any moment. The other good news is that this heavy round of ice will move in primarily between midnight tonight through late morning Saturday when most of us are home. Finally, although it’s heavier ice accumulations, the temperatures will start to thaw after lunch so the amount of time encased in ice will be extremely short all things considered.

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So what caused the change? Models picked up on an upper trough axis swinging around the west side of the 500 mb high down into the Gulf as indicated on the map. That energy provides vertical motion. We can see that played out in the 700mb level. Notice the white circle from 6am today and then what happens by noon. An explosion of deep moisture (colors) and lift (dashed contours). That’s what kicks off the heavy freezing rain tonight as it moves into the state.

Upper level disturbance rotating NNE.

Upper level disturbance rotating NNE.

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700mb map showoing the region to focus on. Not much action at 6am.

700mb map showing the region to focus on. Not much action at 6am.

Same region at noon today. Notice the dramatic change.

Same region at noon today. Notice the dramatic change.

So how much ice will we see? As always just an educated guessing game. But here’s the latest from 3 of the models between now through noon on Saturday. The consensus is between 0.5-1″. Don’t pay too much attention to exact placement of the higher amounts, just get the general idea/area.

totp_t5sfc_f30 zr_acc.us_c zr_acc.us_state_ok

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