Updated 130pm CDT Friday / 17 August 2012
… Increased Cloud Cover and Rain Chances for the Weekend ….
… Rainfall Amounts Around 1 Inch Possible ….
… With Increased Cloud Cover, Temperatures Down a Few Degrees ….
On this Friday… a weak cold front extends from southern Illinois and southern Missouri southwestward into western Arkansas.. southeastern Oklahoma and across the Red River into north Texas and then southwestward into southwest Texas and southern New Mexico. A surface trough.. or a line.. of low pressure extends southward from the front over southwest Texas into northern Mexico. Surface high pressure continues north of the Texas cold front over Nebraska. Other areas of surface high pressure are over the eastern Gulf of Mexico as well the four corners region. As a result of this surface pattern, a southerly surface wind is prevailing across our area.
In the upper levels of the atmosphere, the upper high pressure ridge, acting like a lid on the atmosphere, has weakened and decreased in size a bit and is located over the southwestern USA with a deepening trough.. or line.. of upper level low pressure extends southward from the Great Lakes states southward over the eastern half of the USA. As a result of the upper air wind flow, the upper level winds are light northwesterly over our area.
As we head into your weekend, the effect of the stable upper level high pressure area (or “lid” on the atmosphere), to our northwest, is weakening locally as low level moisture increases and, as a result, our atmosphere is getting more unstable.
As the weak cold front settles further south, we’ll have all three atmospheric ingredients (moisture, instability and lift) come together overhead for scattered rain showers and thunderstorms for our weekend. I’m continuing to increase the cloud cover a bit along with increasing my rain chances slightly for Saturday, Sunday and into Monday. The latest NWS rainfall forecast guidance continues to suggest an average of one inch of beneficial rain could fall.. in a general sense.. across our area between tonight through early next week.
A more stable weather pattern will evolve again once we get into next week with decreased clouds and rain chances.
For Austin and south central Texas… tonight will see isolated to widely scattered rain showers and thunderstorms with an otherwise partly cloudy sky with lows in the 70s. Southerly wind. For tomorrow, variable clouds with scattered rain showers and thunderstorms with highs in the 90s with a southerly wind.
Have a good Friday night and Saturday…
Meteorologist Troy Kimmel