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Here's an example of the air mass motion technique:
You are forecasting for Columbus, Ohio (located in the center of the state). You can look at the Northeastern US surface map and see that the temperature at 17Z is 58 and winds are from the west in the area between 5 and 15 knots. To make your forecast, you need to determine the source region for the air tomorrow.
The first step is to determine whether this wind pattern will persist. A check of the sea level forecasts shows that the pressure gradient is forecasted to become weaker and change its orientation, so the surface wind ought to become northerly tomorrow rather than westerly.
I therefore expect the air parcel which reaches Columbus during the day tomorrow to have traveled east at about 15 knots part of the time and southeast at about 10 knots the rest of the time. I get the following air path:
The current temperature in Chicago is about 45 degrees. Allowing a few degrees because it is not yet the time of day to hit the maximum, my first estimate of the max is 48.
Now I adjust for changing conditions. I know of two: first, Chicago is cloudy today, and I expect Columbus to be clear tomorrow. This will heat up the air mass. I'll bump up my high to 54. Second, the cold air mass is one of the first cold air masses of the season, and is passing over warmer ground. This should heat it up a bit more, so I'll forecast 57.
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