Severe Thunderstorms Possible Today

The Storm Prediction Center in Norman, OK has placed portions of the Riverton County Warning Area in a "Slight Risk" for severe thunderstorms Today.

Categorical Risk of a Severe Thunderstorm Probablility of a Tornado within 25 Miles of a point

Click here for the latest outlook from the Storm Prediction Center


Why did SPC choose to highlight this area?

 Let's take a look at the forecast models...

The main ingredients necessary for severe thunderstorms are:

1. Moisture. The image below is an image of forecast surface dewpoint.

The best moisture (blue and purple) will reside east of the divide this afternoon.

2. Instability.  The image below represents the forecast CAPE.

Most of the state is unstable east of the divide, but the best instability is represented by the turquoise and green shades in Natrona and Johnson counties and points east.

 3. Lift. There will be two sources of lift today. There will be a cold front diving south that will arrive in Natrona and Johnson Counties during peak heating as well as an upper level jet diving through. The upper jet creates divergence aloft, which, in turn creates a vacuum of sorts near the surface (encouraging lift). The front will provide a more narrow focus for thunderstorm development.

The image to the left shows the 250 MB Jet stream in yellow. The blue shades represent the wind speed with the higher speeds colored turquoise. The maximum speeds will be over north central Wyoming this afternoon and will shift slightly south and east by the evening.


 The Image to the left depicts the forecast position of the cold front late this afternoon. The colored image represents low level moisture (orange means dry, gray to green means wet). The green wind barbs represent the boundary layer winds; note the wind shift associated with the front and the low level convergence zone north of Casper.


4. Wind Shear or Spin. The image below represents forecast Helicity (image) with wind shear vectors overlaid (arrows).

The long arrows indicate areas with greater wind shear (greater chance for severe storms). The red and orange shaded areas represent areas where there are higher helicity values (or more spin, meaning more severe thunderstorms).

The better ingredients will come together later this afternoon and into the evening for most locations east of the divide...with the greatest risk for severe thunderstorms over eastern portions of the CWA.


These storms could exacerbate ongoing flooding. Some of the rivers we are watching are:

Among others... Take a look at the latest Hydrologic Outlook for more. And, keep an eye on our homepage for the lastest watches and warnings.

You can also visit our local AHPS page for a quick look at the status of the rivers near you.

This looks like an active weather day. Keep an eye on our homepage for the latest; including watches, warnings, and advisories; and be sure to "like" us on Facebook to see the latest reports from other fans of NWS Riverton!

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