Updated  Thursday / 16 February 2012

…. Clouds and Rain Chances Already Underway As Series of Disturbances Pass ….
…. Major Part of Storm System/Cold Front Brings Best Rain Chances Friday Night ….
…. Clouds Break Late Saturday/Sunday; Clouds Pick Up Again by Early Next Week ….

On this Thursday… a cold front extends from the middle Mississippi Valley southward into southern Louisiana and into the northwestern Gulf of Mexico and just south of the lower Rio Grande Valley of Texas. Surface high pressure area is western Kansas. As a result of this surface pressure pattern, a northeasterly wind is blowing across our area.

In the upper levels of the atmosphere… a deep trough.. or line.. of upper air low pressure is located over the southwestern USA with the center of the upper air low over extreme southern California and the northern part of the Baja Peninsula. Within this broad low pressure counterclockwise circulation, disturbances are rotating (like spokes on a bicycle wheel) northeastward through Texas. As a result of this pressure pattern, the upper air winds are strong southwesterly across Texas and our local area.

Clouds and rain chances have increased much more quickly than I thought they would as the first in a series of upper air disturbances moves northeastward across our area.

The main show, however, comes later Friday into Friday night and early Saturday as the main upper air low pressure moves east northeastward overhead. The cold front, that came through the area yesterday and is in the Gulf of Mexico now, will try to return into the area in advance of the upper air storm system but will not make it this far northward. As a result, while we will see rain showers and thunderstorms, this will be a “overrunning” event (the moisture rides up over the surface based cooler air) for us. The heaviest rain and strongest thunderstorms will be to our distant southeast down toward the Texas coast. The passing upper air disturbance will trigger the development of a surface low and cold front well to our southeast in the vicinity of the old frontal boundary over south Texas and the northwestern Gulf of Mexico.

As that surface low moves eastward across the northern Gulf (and away from us), high pressure will build into the area from the north and rain chances will drop and a more stable atmosphere will return by late Saturday through Sunday. As a result, sunshine will increase as we wrap up the weekend.

Clouds will increase again as yet another weather system.. in a progressive (quick moving) series of disturbances.. affects Texas by late Monday and Tuesday. A cold front will swiftly sweep through our area in the wake of the upper air disturbance on Tuesday.

High pressure will settle southeastward into the area with a dry and stable weather pattern for the middle into the latter part of next week.

My forecast confidence through this week is still high to very high (even though I missed our clouds and rain chances today). My confidence for the forecast for next weekend into next week is medium to high (with rain chances/cold frontal passage time being issues).

For Austin and south central Texas… tonight will see a cloudy sky with scattered rain and rain showers.. mainly late. Lows near 50 with a northwesterly wind. For tomorrow, a cloudy sky with scattered rain showers and thunderstorms. Highs around 60 with a northeasterly wind.

Have a good Thursday night and Friday…
Meteorologist Troy Kimmel