Updated 915am CT – Tuesday / 21 April 2015
.. A More Unstable Air Mass Developing ..
.. Rain and Thunderstorm Chances Return Mid and Late Week ..
On this Tuesday…. a weakening stationary front extends across the western Gulf of Mexico into Mexico south of Brownsville. Surface high pressure is located north of the front over the northern parishes of Louisiana. As a result of this surface weather pattern, our local surface winds are light easterly.
In the upper levels of the atmosphere.. an strong counterclockwise rotating upper air low pressure area is located over Lake Superior. Another strong upper level low pressure disturbance is off the coast of southern California. As a result, our upper air winds at about 18,500 feet are westerly at 40 to 50 mph.
The drier and cooler air mass.. associated with the surface high over northern Louisiana.. is starting to move east of the area this morning as surface low pressure becomes better developed to our west. By later today into tonight, the front, to our distant southeast, will shift back northward as a warm front.
With the return south southeasterly surface wind later today into tonight and Wednesday, we’ll see low level moisture to begin to return to the area. We’re also seeing a moderate westerly upper level winds are bringing some mid and high level Pacific moisture.. in the form of mid and high clouds.. to our local area.
Another series of weak cold fronts will approach the area from the north by tomorrow through the latter part of the week. Even though I don’t see the fronts making their way this far south through Friday, there will start to be the influence of passing upper air disturbances from the counter clockwise rotating system over the southwestern USA. This resultant increased upward motion in the atmosphere along with a more moist and unstable air mass will bring us increased clouds as well as rain and thunderstorms chances by tomorrow through the latter part of the week.
The latest NWS/Storm Prediction Center guidance suggests the possibility of stronger.. potentially severe.. thunderstorms for parts of Texas (including parts of our local area) for tomorrow through Thursday and Friday. In addition, the latest NWS rainfall forecast guidance now shows the potential of 3/4 to 1 1/4 inch of rain between now and Saturday.
A drier and more stable air mass return Saturday into Sunday with more sunshine expected. Another approaching front along with a passing upper air low pressure disturbance will result in the return of rain and thunderstorm chances to the forecast by Sunday night into Monday.
Have a good Tuesday….
Meteorologist Troy Kimmel
Contact me:
tkimmel@austin.utexas.edu
http://www.facebook.com/troykimmel