Updated 915am CT – Friday / 20 March 2015
.. Strong Upper Level Low Pressure To Pass Overhead Tonight Through Saturday ..
.. Three Inches or More of Rainfall Possible Today through Saturday Night ..
.. Flash Flood Watch in Effect From 1pm Today Through 7pm Saturday ..
On this Friday morning…. a southeastward moving cold front is moving southeastward through our area this morning. As a result of this surface weather pattern, our local surface winds are becoming northerly as the front moves south.
In the upper levels of the atmosphere.. a strong upper level low pressure disturbance is located over western and northwestern Mexico. As a result, our upper air winds at about 18,500 feet are southwesterly at 45 to 55 mph.
The strong upper level disturbance.. to our distant west.. will be approaching the area by tonight with it moving overhead tomorrow and tomorrow night with abundant atmospheric moisture in place across the area. The approaching upper level storm will combine with the cold front to result in widespread rain and even thunderstorms through Saturday into Saturday night.
Given colder temperatures aloft and the resulting atmospheric instability, there will be some embedded thunderstorms as the system passes. Forecast precipitation amounts.. in both the manual NWS guidance as well as the atmospheric model output.. have increased with upwards of 3 inches or more of rain possible through Saturday and Saturday night. NWS Austin-San Antonio meteorologists are suggesting that some isolated spots may see as much as 6 to 8 inches of rain. They have already revised the Flash Flood Watch to go into effect at 1pm today and continue through 7pm Saturday evening. Make no mistake… where 3 to 8 inches of rain occurs, there will be flooding problems. Local interests throughout south central Texas.. especially with numerous events going on around the area.. are strongly encouraged to monitor the latest information regarding this potential heavy rain/flood event for tomorrow into the upcoming weekend. Over the coming days, it will likely pay to remember the NWS Sloan as it regarding flooding.. “Turn Around, Don’t Drown.”
As the upper level low pressure moves northeastward out of the area and the cold front moves further southeast, we’ll see rain chances decrease by late Saturday night and early Sunday morning. Clouds will break a bit by Sunday afternoon.
A drier and more stable weather pattern.. with a warming trend.. will prevail for the first half of next week.
Another cold front is slated to move southeastward through the area with a slim chance of rain and thunderstorms by daybreak next Thursday.
Regarding my forecast, my local forecast confidence: My forecast confidence is medium to high through the weekend. The main questions will be the precipitation timing and amounts as well as flash flood potential. My forecast confidence rises back to high to very high for the first half of next week with my confidence falling again (reference rain chances) by next Wednesday into Thursday as the next cold front approaches and moves through the area.
Have a good Friday….
Meteorologist Troy Kimmel
Contact me:
tkimmel@austin.utexas.edu
http://www.facebook.com/troykimmel