Sunday, November 11, 2012

Severe Weather Threat Southern Plains / MS Valley Today...

Above is the latest visible satellite image with an overlay of radar data.  A broad area of showers and embedded thunderstorms continues along and immediately behind a strong cold front (blue line) across eastern Oklahoma and Kansas into western Missouri this morning.  This area of precipitation has produced widespread 1-2 inch rains overnight and this morning, but is not producing severe weather.

The cold front, which stretches back into southwest Texas, will continue moving toward the East and Southeast today.  Warm, moist air is flowing Northward from the Gulf of Mexico ahead of the front (as represented by the yellow arrows), and will set the stage for strong to severe thunderstorm development across the region later this afternoon and into this evening.

Below is the latest severe weather outlook for later today and tonight from the Storm Prediction Center (SPC) in Norman, OK:

While strong to severe thunderstorms are possible anywhere within the brown shaded area on the image, the highest chance of severe storms will take place within the yellow and red shaded area.  This includes the cities of Dallas, Tyler, Texarkana, Shreveport, Little Rock and Ft. Smith.

Strong to severe thunderstorms are expected to develop along the cold front by mid to late afternoon, and progress Eastward during the evening hours.  Large hail and damaging wind gusts will be the primary threats, although a few isolated tornadoes also cannot be ruled out, especially within the brown shaded area on the image below:

The greater Dallas area will be on the Western edge of the greatest chance of strong to severe storms.  If storms are not able to develop along the front before it passes through Dallas by mid-afternoon, then this threat will not be realized.  A greater threat is expected as the front moves further to the East of I-35 toward the ArkLaTex region, as indicated by the red shaded area 2 images above.

Further South along I-35, a "conditional" risk of strong to severe thunderstorms will exist along the front as far South as about the Austin metro area.  I say that the risk is conditional in this region because in order for it to be realized, thunderstorms must first be able to develop.  While the atmosphere will be plenty unstable to support thunderstorm development in this region, it will be more difficult for them to form because of a strong capping inversion that is present overhead.

Any thunderstorms that are able to break through the cap and form in the Austin-San Antonio corridor could become severe with hail and wind gusts to near severe limits the greatest threat, along with lightning strikes.  The most likely time for this to occur appears to be during the hours of 3pm to 6pm today.

Beneficial rains will fall ahead of the front across the Mississippi Valley region into tonight, with widespread 1-3 inch rainfall totals likely:

If you live in the severe weather threat areas for today, remain alert, especially this afternoon and evening.  Listen to NOAA Weather Radio, local media or another trusted source for the latest information and possible warnings.  Be sure to identify the best sheltering location wherever you'll be (especially if you are in an unfamiliar location), that way you can move there quickly if threatening weather is observed or a warning is issued.

Please also note, especially with the earlier sunset now in Standard Time, much of the severe weather threat will take place after dark, especially over the ArkLaTex region and into the lower Mississippi Valley.  This can be especially dangerous, so please pay attention to the weather if you live or have travel plans in these areas.

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