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2PM Update-Quick Hitting Wintry Precip?

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After a morning of some pretty dense fog, the sun is shining for the time being but there is a line of clouds off to the west of the metro that may have a few sprinkles in it for NE KS, but the activity is weakening as it approaches KC. Here is the latest visible satellite picture showing the cloud cover.

We should enjoy a decent day after this band of clouds moves through the region.

Tomorrow though is sort of interesting as a series of weak waves quickly zip through the area. KR inserted a chance of some precip into the forecast and I’ll keep that going. Here is a look at the map @ about 18K feet.

There is a little dip through the midwest and all those colors that you see across the plains indicate weak vorticity, or the tendency for the air to “spin”. There are many ways of looking at this, is it positive vorticity which would be an increasing tendency for the air to spin or negative vorticity? In our case the next map shows more colors which tells me that the dip is “sharpening” or intensifying. Notice as well additional stronger colors showing up through the Plains. They go hand in hand meaning that the trof (dip) is intensifying. Given enough moisture in the atmosphere you get clouds and the vorticity helps to give you lift, hence precipitation.

So with that said, the models are generating at least some precipitation, more so on the latest NAM. Now the question is how does the atmosphere look from a temperature standpoint as the precip gets going. Right now the lower 5K feet is forecasted to be too warm to support snow, however it is dry, which means that as the precip falls through the warmer and dry bottom 5K it will evaporate and “cool” the atmosphere down. This means the chances of some sort of wintry mix, or a combination of rain/sleet/snow would be increasing as the afternoon goes along. It does appear that temperatures would more than likely be in the 34-39° during the event. this means that the roads should be OK through the day tomorrow. Plus the speed of the system is such that it won’t last long.

Should this thing be even weaker, it would struggle to generate precip this far south. Odds favor less than 1/10″ of moisture at this point.

Remember last Saturday when I got my weather geek on showing the sounding information. Well I want to do it again and show you the forecast sounding for KC. This verification time would be Noon on Friday. Click on that image to make it larger.

The thin blue line on the right that zig zags represents the forecasted temperature of air as you go up into the atmosphere. The dashed zig zag line just to the left of the solid blue line is the dewpoint as you go up. The solid diagonal blue line with 32° on it represents the freezing line. So when the solid blue line is to the right of the diagonal 32° line, it means the air is above freezing. To the left and it means the air is below freezing. So based on this information the forecast @ NOON tomorrow is that the air will be above freezing from the surface up through 5K feet or so. There is no way, IF this is correct, we get snow out of that. Now I want you to notice the spread between the solid blue (temp) and the dashed blue (dewpoint) {where I have the circle}. The farther the spread the drier the air is. Now as that disturbance or series of disturbances generate precip, it will fall through the atmosphere into the drier air below and evaporate. The solid blue line representing the temperature will pull to the left and potentially go to the left of the diagonal blue 32° line. As that progresses farther down towards the surface the rain will eventually mix with and potentially change over to some sort of wintry mixture.

The 3PM forecast sounding off the NAM indeed shows this. The time that whatever would  fall would be so short that the window for precip is probably something like 1-7PM or even narrower than that. Again I haven’t seen anything that concerns me at this point for accums. Should we only be about 35° or so @ Noon tomorrow, here on the ground, that would be a little more concerning. IF that were to happen there could be some minor accums on the grassy surfaces I guess. With this though occurring during the daylight I still think the roads will be just wet here and not white. Closer to IA though is a bit more concerning for some slick areas with perhaps 1″ possible.

Today is the 38th straight day without seeing .50″ of moisture or more. It is also the 20th day since DEC 1st that we’ve seen highs 50°+ @ KCI. In the last 2 years COMBINED we did that 7 times!

The “Winter That Isn’t” continues!

Joe

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