In the for what it’s worth department, the record book for today will show a maximum temperature of 70 which is what we had just after midnight.  Then the cold air arrived just after 1AM and the temperature dropped 26 degrees over the next hour and was down to 28 by sunrise.  We did rebound somewhat this afternoon with the sunshine helping to overcome the brisk northerly winds and temperatures made it briefly to 40.  Notice the 24 hour temperature change map from this afternoon which also reflects the shallow nature of this cold air outbreak and the difficulty it has had in moving through the hills of SE OK.

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Not only is the cold air shallow, it is also very dry which means when the precipitation starts later tonight, there will be additional cooling taking place because of the falling moisture evaporating into the drier air.  That is a cooling process and will keep temperatures along the I-44 corridor at or below the freezing mark for later tonight into the day Friday.  Locations further to the N & W of I-44 will stay below freezing until late Saturday or perhaps even Sunday morning and locations further to the S & E will stay above freezing throughout the event.  There continues to be considerable uncertainty regarding the exact placement of where and for how long temperatures will be at or below the freezing mark as the counties along the I-44 corridor continue to be the general demarcation line in that regard.  That is the reason for the various advisories/warnings that have been issued for OK and surrounding states by the good folks at the local NWS offices.

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In general, the I-44 corridor has a freezing rain advisory which means that total amounts of freezing rain are expected to be less than ¼” and most of that will likely be on trees, power lines, communication towers, and perhaps some on bridges and overpasses.  The Ice Storm Warning applies to the counties further N & W where the accumulation of ice will be much more significant and could approach an inch by the time it is all said and done.  By the way, soil temperatures at the 2” level are generally in the 40s as of late this afternoon.

Not only is the position of the surface freezing line critical in determining where the freezing rain will accumulate, but so is the location and depth of the freezing line aloft.  Have used this graphic in the past, but notice again how critical the vertical profile of temperature is in determining the precipitation type.  Keep in mind that although we will have northerly winds and very cold conditions at the surface, just a few thousand or perhaps only a few hundred feet above the surface the winds will be southerly bringing in the warm, humid air that will produce the clouds along with periods of drizzle, showers, rain, and perhaps even some thunder.

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The system that will bring the precipitation is just now moving onshore along the coast of California and is projected to drop SE into NW Mexico and then eject out to the NE from there.  It still has not been well sampled by our observational network which creates additional uncertainty in determining its exact track and intensity as it moves our general direction this weekend.

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Data runs over the last few days have trended to take it further west which is why the temperature forecast for Sunday continues to rise as warmer air at the surface and aloft will be pulled back over us as you can see on our forecast page.  However, the warmer air along with the abundant moisture available at the surface and aloft will also set the stage for a round of heavy storms moving through Green Country Sunday night or into the Monday morning time frame.  Some of those storms will be locally very strong due to the strength of the winds aloft and will also be capable of dropping locally heavy rainfall. 

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There remains the potential for a good soaking rain which will be a real drought breaker for the state.  However, the changes in the track of the upper level storm system has reduced the total amount of expected precipitation.  Even so, 1-2 inch totals should be widespread by the time it all ends on Monday and local amounts may reach 4". 

So, here is how the timing now looks to take place.  A few light showers or drizzle should be developing over S/SE OK early tonight and spreading northward during the overnight hours.  By midnight or shortly thereafter, it should be along the I-44 corridor and continuing to spread northward into the morning hours.  Drizzle, light rain, and showers will continue off and on through Friday, continuing off and on through Friday night, and also through much of the day Saturday and Saturday night.  By Sunday morning, the warmer air should have spread over Green Country and we may have a break in the precipitation and perhaps even a little sunshine that afternoon.  That will be followed by storms moving eastward across the state Sunday night and into the Monday morning time frame.

After that, the rest of next week looks to be generally much warmer than normal along with little or no mention of additional precipitation.

So, stay tuned and check back for updates as this is a very dynamic system and certainly poses the possibility of some significant winter weather issues in the form of freezing rain followed by the possibility of storms and potential flooding.

Dick Faurot