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May 27, 2011

A Remarkable Chance From Spring To Summer On The Extended... Why?

The extended is dominated by unbelievably hot conditions for this time of the year. In fact, records are in danger Sunday and in particular on Memorial Day. I am forecasting a record high right now! The real question is what in the world is going on????


Forecast Discussion


For all of us weather geeks, and I am one, the interesting part of the forecast is hidden in the details. The eastern part of the US has been under the influence of a big upper level low. That is the actual low that is causing the much cooler temperatures today is about to be replaced with it's utter opposite... a massive dome of high pressure. Take a look at the mid level jetstream setup as of late yesterday first, then we will look at the change for the weekend.


GFS Winds 6 Miles Above The Ground Yesterday

Notice that big low pressure dominated our area forcing the winds to come out of Canada and into our area.




GFS Winds 6 Miles Above The Ground Sunday

Notice the low has been replaced with a massive high pressure anchored over Tennessee.




A couple important features to remember... low pressure areas promote clouds and cooler conditions, but in contrast high pressure areas are locations where the air is sinking. Sinking air heats and it opposes the clouds in the atmosphere. You have seen those cotton puff clouds in the summer seem to look like they are rising, well when a very strong high pressure or ridge is in place it will over come any rising motion and rid our area of clouds. It is interesting to see that with the temperatures just 1 mile off the ground and how that warming is occurring.


GFS Temperatures 1 Mile Above The Ground Yesterday

Notice the chilly greens over our area that are keeping us cool today.




GFS Temperatures 1 Mile Above The Ground Sunday

Notice the unbelievable difference. The greens have been replaced with incredibly warm brick red colors. Those temperatures are a full 25 degrees warmer!




We can see this ridge of high pressure that will be building in is going to warm conditions significantly for the holiday weekend and give us a lot more sunshine on Sunday and Monday in particular. We will look at specific numbers for the weekend after the 4 pm newscast. :)




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