Updated 800am CT – Monday / 08 September 2014
…. Rain Chances Today and Tonight as Weak Front Washes out Just to our South ….
…. Stronger Cold Front with Rain Chances Late Week ….
On this Monday morning…. a weakening stationary front extends west southwestward from Georgia through southern Alabama.. Mississippi and Louisiana into Texas just south of the Austin area. High pressure.. behind the front.. is centered over Illinois southwestward into western Arkansas and eastern Oklahoma. As a result of this surface weather pattern, our local surface winds are light and variable.
In the upper levels of the atmosphere… an upper air low pressure disturbance moving through the westerly wind flow over the Great Lakes states. Another disturbance is moving ashore onto the northwest California coast. Upper level high pressure.. acting like a lid on the atmosphere.. covers the southern USA from Georgia westward across Texas and into New Mexico. As a result of this pattern, the upper level winds over south central Texas and the Austin metro area, about 18,000 feet above the ground, are variable generally less than 15 mph.
The weak cold front that moved to just south of the Austin area late Saturday night into early Sunday morning, with the scattered rain showers and thunderstorms, is now washing out returning northward as a weak warm front. As a result of this along with daytime heating, abundant low level moisture and limited atmospheric instability, we’ll see widely scattered rain shower and thunderstorm activity today into tonight. The latest short range guidance suggests the greatest chance of rain today into tonight may be over the hill country to the west of the IH35 corridor. Deadly cloud-to-ground lightning along with gusty winds will accompany any thunderstorms that do develop.
By tomorrow through Wednesday and Wednesday night, the upper level high pressure area above us will strengthen a little resulting in increased atmospheric stability with clouds decreasing a bit and rain chances dropping from the forecast. Afternoon high temperatures will warm a bit as well.
By Thursday into Thursday night, an upper air low pressure disturbance will move from the Rockies into the plains and the Mississippi Valley. As it does so, it sets the stage for the strongest surface cold front of the upcoming fall season to move quickly south southeastward through our area and off the Texas coast into far south Texas by Friday evening. Scattered rain showers and thunderstorms will occur ahead of.. along and just behind the front as it moves through our area. Drier and slightly cooler high pressure.. behind the front.. will settle into Texas for Friday and the weekend and into Monday.
Regarding my forecast, my local forecast confidence: My forecast confidence is high through tonight (reference any precipitation timing and amounts)… then very high tomorrow through early Thursday. By Thursday midday into Thursday night and early Friday, my confidence goes back to high (concerned with exact rain chances and timing). By Friday night through the weekend and into Monday, my forecast confidence is very high again.
Have a good Monday….
Meteorologist Troy Kimmel
Contact me:
tkimmel@austin.utexas.edu
http://www.facebook.com/troykimmel