Updated 800am CT – Friday / 19 September 2014
…. Unsettled with Abundant Moisture and Passing Upper Air Low Pressure Disturbances ….
…. Rain Chances Decrease by Tonight into the Weekend ….
On this Friday morning…. a surface low pressure trough extends south southwestward from western Kansas into far west Texas and eastern New Mexico. As a result of this surface weather pattern, our local surface winds are southeasterly.
In the upper levels of the atmosphere… a broad trough.. or line.. of upper level low pressure is moving eastward through the eastern third of the USA with another trough of low pressure moving ashore onto the west coast. The upper air reflection of Pacific tropical cyclone Odile.. with abundant high and mid level Pacific moisture.. is located over west Texas. Weakened upper level high pressure.. acting like a lid on the atmosphere.. as been shoved southward into northeastern Mexico and deep south Texas. 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 west northwesterly at 20 to 25 mph.
After more overnight rain in the northwestern part of the Austin metro area.. with rainfall amounts of up to 3 to 4 inches.. things have once again become a bit more quiet.
At the same time, however, abundant low level moisture continues, along with an unstable air mass, continues over the area. As the upper air disturbances.. from the west.. traverse the area and creates atmospheric lift, we’ll continue to scattered rain showers and thunderstorms through the day today with rain chances decreasing by tonight. The latest computer and NWS manual guidance suggests that we could see another inch of rain with isolated heavier amounts before rain chances decrease. Where heavier rainfall occurs in areas that were flooded over the last 48 hours, we could see rapid development of urban and small stream flooding. In addition, with cloud cover and precipitation chances today, afternoon high temperatures remaining slightly below seasonal averages.
By later tonight into the weekend, the upper level high pressure ridge (the “lid” on the atmosphere) will strengthen a bit with rain chances decreasing a bit and clouds thinning out a bit.
The earlier expected cold front.. that was due Monday.. is not that much of a factor so it looks fairly quiet once we get into the weekend into next week.
Regarding my forecast, my local forecast confidence: My forecast confidence over the next seven days is high to very high.
Have a good Friday….
Meteorologist Troy Kimmel
Contact me:
tkimmel@austin.utexas.edu
http://www.facebook.com/troykimmel