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Posts tagged ‘mountains’

Mountain Wave Clouds

This morning as the upper low and storm system exited the region. Strong northwest flow moved in and we got 2 distinct types of mountain wave clouds. Which can be seen from the visible satellite.

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There are some pretty neat things going on here when you take a look at the surface winds at 10m(image left below) and then take a look at the vertical velocities(image right below). You can see in the wake of the mountains we have some lift in the green areas which is indicative of lee mountain rotors.

Surface Winds                                     700mb Vertical Velocities

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If you look closely you see 2 types of cloud formations. One is a mountain wave pattern over Virginia and West Virginia and also visible in the northern mountains of North Carolina near Boone. If you look further south you can see cirrus clouds coming off the mountains of Southern North Carolina the upstate of South Carolina into NE Georgia.

Wave Clouds                                                Cirrus Clouds

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What is going on here is some chaotic vertical motions caused by the departing low pressure system interacting with the mountains. Moisture at high levels & mid-levels along with cold dry surface air make for some cool cloud formations. Here’s a diagram of the process. You can see how the lee side turbulence and rotors cause the wave clouds but also how those rotors can create higher level cirrus clouds downwind of the mountains.

System Mountain Wave - Rotor

Cold wet weekend ahead but some ice for the mountians

This upcoming weekend is going to be one for good books, good movies and good coffee. Cold high pressure to our north will wedge a dry and cold air mass up against the mountains. While this is going on a low pressure system will approach from the west spreading moisture up and over this cold dome of air. The results will be cloudy, cold and wet conditions just about all weekend long. Though for one area up against the Blue Ridge Mountains there could be some wintry weather in the form of ice. The HPC shows the probabilities of ice and the amount of rain/precipitation that will fall

Ice Probabilities

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                  Precipitation Forecast                         NAM Model Precip Type Sunday morning

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This is a look at the NAM model sounding from the Bufkit. Lets hope that this model doesn’t verify because those red bars are hours of freezing rain and over 1.00” of it.

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So here is what I’m thinking if that cold dry air get trapped up against the Blue Ridge and in some of the high mountain valleys. You combine that with the mechanically cooling due to lifting the moist air into the eastern upslope areas of the mountains. It will produce a mix of rain and freezing rain. I don’t expect major issues right now but if the trends stay cold and dry in Ashe and Watauga we could have some ice issues Sunday. Stay Tuned!

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Damaging wind storm heading our way

As we all know there is a massive blizzard in the middle of the country slamming a large section of the heartland. We will stay on the “warm” side of this storm but won’t escape all of it’s impacts entirely. There are extremely strong winds associated with this storm. As the combination of strong jet stream level winds along with the pressure gradient between the storm, a 990mb low, and the arctic high 1055mb, to the west will create damaging winds. High wind warnings will likely be needed in the mountains with wind advisories for the piedmont tonight and tomorrow. These winds and the combination of possible thunderstorms could bring major problems tonight and tomorrow for the Carolinas. These winds will be from the southwest which means a warm wind but still dangerous. Let me show you why.

Here is the NAM model sounding showing the core of highs winds moving in early tomorrow morning. 2am-8am.

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I’ve highlighted this high wind core with the yellow arrows but notice the legend on the left how close to the surface these winds are. Often times with mixing at the surface these winds “mix” down or are transported down to the ground pretty easily. This mixing is what causes the gustiness of the winds.

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Now for the mountains this is a even bigger problem because…well the elevation puts them right into the high winds. This means no mixing is even required for 70-80mph gust to occur at higher elevations.

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With the snowmelt and wet ground many trees will be coming down tonight through the day on Wednesday. Be prepared for power outages and tree falls especially in the mountains.  Plus I bet Grandfather mountain breaks that wind gust record again this week.

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