Joe’s Wx Blog: Appetizer now…main course later

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3:30 Update…

The snow is winding down and temperatures are only in the upper 20s so we’ve seen some slick areas develop as expected. Conditions should improve somewhat later this afternoon. I saw this image from the NWS in Chicago’s FB page yesterday and I think pretty much everybody is feeling this way, unless your a big groundhog lover.

 

The afternoon data is still pretty well set on a snowstorm for the KC area later Saturday into Sunday AM. Nothing really has changed and again as the stuff below talks about there are still some questions about the surface temperatures at least during the onset of the storm. Model data would suggest a broad swath of 4-10″ of snow possible, and after eliminating perhaps the 1st 1-2″ or so due to melting and/or rain you can get an idea of what the general trends area. The Canadian Model and the GFS are the most bullish with the snowfall accums…approaching 8-12″, while the EURO is less…odds are some sort of compromise will be the best way to go with this from 2+ days out.

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Radar looks pretty impressive on this Thursday AM but there is still a lot of lower level dry air out there and that’s why, as of this writing, the snow has not really reached the ground. We call it virga and there is plenty of it out there this AM. So let’s analyze that statement a little more by using this mornings upper air report from the balloon launch done in Toopeka earlier this AM…

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Click on this image to make it larger…

For the purpose of this discussion when the RED and GREEN lines are very close together, that means the air is saturated…when the lines are farther apart that means the air is drier. The more the lines are apart the drier the air is. Notice the lines spread apart around 780 mbs or about 7-8K feet up. That means that as the snow falls it’s evaporating before it reaches the ground. As the atmosphere saturates and the lines come together farther down through the atmosphere, eventually snowflakes will be reaching the ground.

Another way at looking at this is by looking at the base of the clouds above us by using the various airports around the region since they report the cloud bases. Add on 2 0’s to figure out the base.

ScreenHunter_01 Mar. 21 09.19

So for example the 070 @ KCI means the cloud base is 7000′ up. The 060 means the cloud bases are about 6000′ or so. As the ceilings come down the atmosphere get’s saturated closer tot he ground and eventually at least some of the snow will make to the ground.

So now you need to look at radar…

Again most of that is NOT reaching the ground as of the 9AM hour. There are some flakes reported around Lawrence.

This will gradually change though as the morning and early afternoon moves along and eventually at least some areas from KC westwards will get at least some snow. One thing that is different about today compared to the other day is that the temperatures are colder out there. Readings are in the 20s and when the snow starts may actually drop a couple of degrees. So should the snow fall enough to wet the roads, we’ll need to watch for some refreezing on the bridges and overpasses as well. This should mostly be a daytime event and accumulations for most should be under 2″ if not under 1″ and the gang on the air have a good handle on things with their maps they’ve been showing. Again the main issue may be some refreezing later today.

We should have a bit of a lull tomorrow, and whatever falls whether it be a little snow or some drops will be minor.

Then we’ll focus on the weekend. This is the period of most concern and the potential of an accumulating snow continues to increase. There are no real changes at this point needed. It looks like the worse will be Saturday PM into Sunday AM and while there may be a period of rain at the onset, eventually there should be a changeover to snow. There are still many questions with the storm’s evolution

1) How organized will the storm be as it comes into the area…will it be in pieces or will it be more of a solid storm aloft. More pieces, less focus on the heavier snow potential…more of a solid or organized storm, the better potential for heavier snow bands.

2) How long will the rain last, and potentially cut down on the snow accumulations?

3) What will the temperature be here on the ground? If it’s snowing and 35° then accumulations will be minor for awhile, the longer that goes on the less overall accumulations from the storm. This may be a bigger issue in the long run than what it appears now. With the precip not getting here till SAT PM, we may be melting some of the initial snowfall. Roads may be OK till SAT night.

Conditions should improve by Sunday afternoon in the region. At this point I’m expecting accumulations, but it is far too early to project (with confidence) how much or who will see the most snow. I have a feeling this will NOT be a “close down the city” type snowstorm for the area.

Here is the bottom line…more snow is likely over the weekend, initially maybe it’s rain but then it changes over. How much melting will occur and how organized the storm is, is still a question and that won’t be answered with confidence for another day or so.

Joe

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