JACKSONVILLE, Fla. - There are a few things that make a weekend enjoyable and weather is one of them. This weekend will rate a 10 on the Gaughan Gauge and for good reason; great temperatures and sunshine will make for a real autumn feel.
A cold front will usher in dry air Friday and break our humidity. Look for blue skies and no clouds. Clouds need moisture to form and model forecasts can predict the height of clouds based on levels of humidity in the atmosphere.
The picture above shows a cross-section of the atmosphere during the next 10 days. It can be used to predict areas in the sky where clouds would develop. The GFS model plot shows higher relative humidity in green and dry air is brown. The days in the week are at the bottom of the graph and the Y axis is higher in the sky.
The absence of clouds over the weekend is represented by the brown dry air extending from over 30 thousand feet to the surface between the two vertical black lines. By Tuesday High clouds, like cirrus, stream in shown by the green between the 400-200 mark. Those numbers represent atmospheric pressure in millibars.
Wednesday the wind off the Atlantic increases low level moisture increasing shallow clouds. Because the brown dry air sits over the low clouds the clouds will not grow vertically. This is why it stays dry all next week.
Sinking air next week under high pressure ensures rain stays suppressed with only the possibility of a brief isolated shower St. Johns county south by the end of next week.