© 2019 Terry Swails

SEVERE WEATHER RISK FOR THE REGION TODAY...

May 17, 2017

 

Tuesday was the 4th consecutive day with a high above 80 degrees in Cedar Rapids (and the majority of my area). Wednesday will be the last in this mild stretch of weather before a major change in the pattern ushers in much cooler air.

 

The cold front and associated low pressure that brings the colder conditions will also bring the threat of severe weather to much of my area Wednesday afternoon or evening. The system is already responsible for producing numerous tornadoes Tuesday. Significant damage was reported in Elk City, Oklahoma and Chetek, Wisconsin. At last report 1 person was killed and 25 injured in Chetek where a trailer park was destoyed.

The set-up Wednesday for my region will be complicated by ongoing convection in the morning. It's likely that it will diminishing and end by late morning...noon at the latest. This will give the atmosphere a chance to recover but how much heating is realized will be critical in determining the intensity of late day storms. 

 

The Storm Prediction Center has this region currently under an enhanced risk.

The 3k NAM gets CAPE into the 1200-1800 j/kg range which is plenty unstable. There's also good cross-over from the surface to 500mb that would indicate supercell development. The graphic below shows the areas in red where supercell composites are high at 6:00pm.

That same area is also showing significant tornado potential.

In fact, the 3k shows helicity tracks that would point to long tracked supercells. (The helicity reflective of the rotational ability of the storms). This is an ominous trend if indeed it comes to fruition.

Here's the simulated radar at 7:00pm showing the discrete cells advancing through eastern Iowa.

There are also some healthy soundings showing nicely curved hodographs at peak heating. Hodographs depict the veering of winds from the surface to jet stream level. Here's a simulated sounding for east central Iowa showing a tornado prone environment.

Clearly the 3k NAM has a serious look to it. However, I've seen many times when things look good on paper but fail to live up to the billing in real time. Often it's hard to really get a grip on the magnitude of the situation until a few hours before it happens. However, I think it's worth sounding a cautionary alarm to pay attention to forecasts as the day unfolds if you are in parts of eastern Iowa, Missouri, western Illinois, and SW Wisconsin.  

 

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