Updated 845am CDT Thursday / 10 October 2013
…. Humidity Levels Increase ….
…. Priming the Atmosphere for a Beneficial Extended Rainfall Event ….
…. Low Pressure/Cold Front Becomes the Factor for the Weekend into Next Week ….
On this Thursday morning…. a high pressure area is over the northeastern USA. A trough.. or line.. of low pressure extends south southwestward from a surface low over eastern Colorado across eastern New Mexico. A cold front extends southwestward from the Dakotas into eastern Colorado then westward into Utah and Nevada. As a result of this surface weather pattern, surface winds are south southeasterly across our area.
In the upper levels of the atmosphere… a deepening eastward moving area of upper level low pressure trough extends southward over the western third of the USA with an intense upper low pressure disturbance at the base of the trough over southern Nevada. An upper level high is over northwestern Gulf of Mexico. As a result, the upper level winds over south central Texas and the Austin metro area about 18,000 feet above the ground are southwesterly 12 to 22 mph.
The surface high pressure area.. over the eastern USA.. in combination with deepening low pressure over the western USA continues to allow for our south southeasterly surface winds and the return of low level moisture to our area. As a result, a partly cloudy sky and some late night and early morning low cloudiness is expected for the latter part of the week into the weekend.
As the southerly winds continue, we are truly “priming” the atmosphere for what I think will be an extended beneficial rainfall event for the Saturday through Tuesday time period. The air mass overhead will become more unstable as the upper level low.. over the western USA.. and the associated surface low pressure area and cold front will move into Texas by late Friday night into Saturday. Latest guidance continues to suggest that the front will wash out overhead Saturday night into Sunday and Monday as a another stronger upper level low and front moves out of the Rockies by Tuesday and Tuesday night. As the upper air disturbance moves by to our north, this second cold front will move through our area on Wednesday (delayed a little since yesterday) with dryer and cooler temperatures moving into the area mid week.
In this interim period.. Saturday through Tuesday.. as the air mass grows more moist and unstable, we’ll see increased cloud cover and rain chances. As time passes, this continues to appear as an extended beneficial rainfall event in the offing with upwards of 1 to 4 inches of rainfall possible before the stronger cold front moves through next Wednesday. I’ll continue to watch this for you.
Regarding my forecast, my local forecast confidence: Very high forecast confidence through Friday.. then medium to high confidence for the weekend into the middle part of next week as it regards the progress and timing of upper air low pressure and fronts over the southern plains and any associated rain chances.
Have a good Thursday…
Meteorologist Troy Kimmel
Contact me:
tkimmel@austin.utexas.edu
http://www.facebook.com/troykimmel