Update on Texas Heavy Rainfall, Severe Weather Event for Tuesday and Wednesday...

All of the ingredients necessary for a widespread heavy rain event are coming together in central and eastern Texas late this afternoon, including the Austin-San Antonio corridor region along I-35.

Above is the latest surface weather map, with the green shaded areas showing rich moisture building up in the Gulf of Mexico.  Surface winds (as noted by the purple lines) are shifting to the East/Southeast, which will pull the moisture Westward into the region overnight tonight and into Tuesday.

Later tonight, a "low level jet stream" will form just above the surface across southcentral and southeast Texas, pulling moisture into the region at speeds of around 50 mph, which will further make the atmosphere moist and unstable for the upcoming event.

Meanwhile, in the upper levels of the atmosphere, a strong area of low pressure is currently located just South of Yuma, AZ, over extreme northwestern Mexico:

Strong jet stream winds are already spreading East ahead of the system across the Lone star state, as indicated by the yellow arrows on the water vapor satellite image above.

The system is forecast to swing toward the Southeast tonight and move across Texas Tuesday and Wednesday, resulting in widespread shower and thunderstorm development.

Both locally heavy rainfall and severe thunderstorms are likely in association with this system.  Computer forecast model guidance is suggesting a total of 2-4 inches of rain will be common along the Austin to San Antonio corridor, with localized amounts up to 6 inches possible, and I agree with that assessment.

Here is how the latest high resolution NAM computer forecast model is forecasting the precipitation situation to shape up over the next 24-48 hours, and I agree with the overall trends that are depicted by this model.  First, accumulated rainfall from 6am to 6pm CST on Tuesday:

...through 6am CST Wednesday:

...and through 6pm CST Wednesday:

As you can see, the model is depicting a maximum rainfall swath of 5-6 inches along and East of I-35 between Austin and Dallas.  Widespread 3-5 inch rainfall amounts are indicated surrounding that bullseye.

The heavy rain may cause flash flooding in the urban areas of Austin and San Antonio, particularly tomorrow night and Wednesday morning.

In addition to the threat of heavy rainfall and flash flooding, severe thunderstorms will be a distinct possibility across mainly southcentral, southeastern and east-central Texas, including the Austin/San Antonio corridor, the Corpus Christi area and the Houston Metro area.

Below are the latest severe weather outlooks for Tuesday into Tuesday night (first) and Wednesday (second), from the Storm Prediction Center (SPC) in Norman, OK:

Severe weather will primarily take place along and to the South of a surface warm front across Deep South and southcentral Texas on Tuesday afternoon.  This threat will spread Northward into the Austin/San Antonio region on Tuesday night, and then shift East into southeastern Texas (including the Houston area) on Wednesday.

Damaging wind gusts and hail up to 1 inch in diameter will be the primary severe weather threats during both periods of time.  Isolated tornadoes are also possible, including during the overnight hours on Tuesday night in the Austin / San Antonio area.

If you live across the severe weather threat areas for Tuesday and Wednesday, please be alert.  Listen to NOAA Weather Radio, local media or other trusted sources for the latest information, watches and warnings.  If you live in the Austin/San Antonio and adjacent areas, please make sure that you have a way to receive severe weather warnings at night.

Stay tuned for more on this situation tomorrow and Wednesday.  If you don't already follow me on facebook, Google+ or twitter, please do so as I am likely to make more frequent, short posts on those outlets during an ongoing severe weather situation.

For more information from 'The Original Weather Blog', including shorter, more frequent posts during rapidly changing weather events, please be sure to follow me on facebook and twitter:

 

If you are in need of highly customized, site specific weather forecasts and/or storm warnings for your business, school or event, be sure visit my professional webpage at WeatherGuidance.com.

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Update on Widespread Heavy Rain and Localized Severe Weather Event for Texas / Lower MS Valley...

An upper-level low pressure system is swirling about just to the Northwest of Las Vegas, NV at this hour (as shown on the water vapor satellite image above).  This system will dive toward the South/Southeast tonight and Monday, the make a move toward the East across Texas on Tuesday and Wednesday.

Widespread, heavy rainfall can be expected in association with this system, particularly across central and eastern portions of Texas (especially along and to the East of I-35, including the Austin-San Antonio corridor).  Total rainfall amounts for the two day period will average 2-4 inches with locally heavier amounts near 6 inches possible.

Here is how I expect the heavy rainfall threat to pan out for Tuesday:

...and for Wednesday:

As much of this region is currently in a moderate to extreme drought condition, the rainfall will be very welcome, even though some of it may run off quickly during strong to severe thunderstorm activity.

Along with the good will come a threat of the bad, in the form of severe thunderstorm activity.  As I've been pointing out for several days now, this situation looks very similar to the one on January 25, 2012, which produced widespread heavy rainfall, damaging wind gusts and at least 1 tornado along the Austin/San Antonio corridor of I-35.  That trend has not changed as of this update, and strong to severe thunderstorms will indeed threaten the region on Tuesday and Wednesday:

The severe weather and heavy rainfall threat will shift East/Northeastward into portions of the lower Mississippi Valley region on Thursday.

If you live across the heavy rain and severe weather threat areas outlined for Tuesday and Wednesday of this week, please stay alert.  Take the time now to review your severe weather safety and preparedness tips so that you are ready to go if severe weather threatens.

At least some of the threat of severe weather will take place during the nighttime hours.  Make sure that you have a way to receive weather warnings when you are asleep at night, and identify your best sheltering option at home, work or school so that you can move there quickly if threatening weather is observed or a warning is issued.

For more information from 'The Original Weather Blog', including shorter, more frequent posts during rapidly changing weather events, please be sure to follow me on facebook and twitter:

 

If you are in need of highly customized, site specific weather forecasts and/or storm warnings for your business, school or event, be sure visit my professional webpage at WeatherGuidance.com.

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Update on Heavy Rain / Severe Weather Event for Texas and the Lower MS Valley...

I wanted to give a quick update on the storm system that I detailed in a post yesterday, and its potential impact on Texas and at least the lower Mississippi Valley region for the early to middle of next week...



First things first, a significant (and much needed) rain event will take place across the central and eastern two thirds of Texas, southeastern Oklahoma and much of Louisiana and Arkansas.  Most of this rain will fall during the period Tuesday through Wednesday:

As you can see on the cumulative rainfall forecast image above, widespread rainfall amounts of 2-4 inches are expected, with localized amounts of 4-6 inches possible across much of the region.  This rain will be very welcome indeed, as the vast majority of this region continues with a severe to extreme drought situation:

As I mentioned in a post yesterday, the European computer forecast model has been the most consistent thus far in forecasting this storm system, and I believe that it continues to be the most reliable with its depictions through today.  The latest run of that particular model is forecasting 4 inches of rain to fall in Austin, mainly from 12 Noon Tuesday through 12 Noon Wednesday, as shown on the graph below:

While the rain will certainly be welcome across the region, on the negative side of the coin, a threat of severe weather will come along with it as well.

While some of the severe weather details still need to be worked out (mainly with respect to timing), the area shown in red on the image below is likely to have the highest threat of severe weather on Tuesday, which includes the Austin-San Antonio corridor along I-35, "The Valley" in Deep South Texas, the Texas Coastal Bend and the Houston metropolitan area:

I still believe that the situation for Tuesday looks very similar to that of the heavy rainfall and severe weather event that took place across the Austin-San Antonio corridor area during the early morning hours of January 25, 2012.  That particular event produced widespread heavy rainfall (in excess of 6 inches in some locations), damaging wind gusts and at least 1 tornado.

While it is still too early to pinpoint some of the details as to the severe weather threat, if you live across the region shown in red on the map above, please pay attention to the weather on Tuesday and Tuesday night.  Make sure that you a have a way to receive severe weather warnings and identify your best sheltering option in case threatening weather approaches your area.

The threat of severe weather will shift East/Northeast into Louisiana, southern Arkansas and still the Northeast part of the Texas coast (including Houston) as well as east-central Texas for Wednesday.  More details on the Wednesday severe weather threat will be available tomorrow as the situation becomes more clear.

For more information from 'The Original Weather Blog', including shorter, more frequent posts during rapidly changing weather events, please be sure to follow me on facebook and twitter:

 

If you are in need of highly customized, site specific weather forecasts and/or storm warnings for your business, school or event, be sure visit my professional webpage at WeatherGuidance.com.

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