Friday, April 5, 2013

Significant Severe Weather, Tornado Event(s) Still Expected Next Week...

All of the ingredients continue to come together in suggesting that one or more days of significant severe weather are likely during the period Monday through Wednesday of next week.

As I mentioned in a post yesterday, the European model and the U.S. based GFS model were in disagreement with respect to the timing of the surface front that will focus severe weather development.  In the last 24 hours, the GFS has slowed the progress of the front considerably (as we suspected it would yesterday) and is now in very close agreement with the European model as to the timing.  I point this out because, unfortunately, it results in an even higher level of confidence as far as the forecast of this major event.

The images below show the severe weather threat areas as forecast for Monday, Tuesday and Wednesday of next week, respectively.

On Monday, the primary threat will exist along and ahead of a surface dryline extending from the western High Plains of Kansas, western Oklahoma and Eastern portions of the panhandle region of Texas/Oklahoma:

Coverage is expected to be scattered on Monday afternoon and evening, with very large hail, damaging winds and a few tornadoes possible, primarily within the area shaded in green on the image above.

At this time it appears that all ingredients are coming together for a widespread and significant severe weather episode on Tuesday afternoon and evening.  The primary threat area is shown in green and reddish-orange on the image below:

Present indications suggest that conditions will be favorable for large hail, damaging winds and tornadoes, some of which could be strong and/or long tracked on Tuesday afternoon and evening.  The highest threat of significant severe weather is indicated within the reddish-orange shaded areas on the above image and includes the cities of Dallas, Oklahoma City, Tulsa, Joplin, Fayetteville and Ft. Smith.

By Wednesday, the primary threat will have shifted East/Southeastward into the middle and lower Mississippi Valley region, as indicated on the image below:

Once again, large hail, damaging winds and tornadoes will all be possible with severe storms in the indicated areas on Wednesday.  The primary tornado threat will exist within the reddish-orange shaded areas, which includes the cities of Shreveport, Baton Rouge, Little Rock, Memphis and Jackson.

There is some question as to how unstable the atmosphere will be able to become on Wednesday due to forecast widespread precipitation.  This may limit the extent of the "significant" tornado risk as compared to Tuesday, but we still cannot rule out the possibility of a strong tornado on Wednesday.  This threat should become more clear as we approach the event, so please watch for further updates.

Speaking of widespread precipitation, as we pointed out in a post a week or so ago, it appears that fairly widespread, locally heavy rainfall will also occur in association with this system.  The image below shows the European model total rainfall forecast valid through 7pm CDT next Thursday:

As you can see, rainfall amounts in excess of 2-3 inches are forecast on a fairly widespread basis (scale in inches at the right of the image) from the central and southern Plains into the Midwest and middle through lower Mississippi Valley region.  While this is good news for drought stricken areas in Kansas and Oklahoma, it will cause flooding problems in the Mississippi Valley region.

This is a potentially dangerous weather situation that is shaping up for the period Monday through Wednesday of next week, and particularly on Tuesday. Please pay attention to the weather if you live in the indicated areas.  Take some time now to review severe weather safety and preparedness tips, and plan where your best sheltering option will be at home, work or school.  Some of the severe weather threat will also take place at night, so make sure that you have a way to receive severe weather warnings during the overnight hours.

We'll continue to monitor this situation with additional updates forthcoming as details become more clear...

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