Severe Weather Today: 7/12/15

Due to the Severe Weather Threat today, I will not post a NM Weather Forecast.

The Storm Prediction Center (SPC) has issued a Moderate Risk today for parts of the northeastern Great Plains.

Associated with the Moderate Risk is a 5% Tornado Threat Ring.

The threat stems from ample moisture (some of which is from evapotranspiration from growing corn) and the soil moisture ahead of a frontal boundary that is pushing its way east across Minnesota. There is also a shortwave trough approaching from the southwest.

The visible satellite imagery shows that there is cloud cover over much of Minnesota so far this morning.

The infrared satellite imagery shows that some of the cloud cover, particularly in the northeastern part of Minnesota, is thicker and cooler-topped.

The water vapor imagery of the continental United State shows the shortwave trough as a dry area in the western South Dakota.

The 12Z upper air sounding from Minneapolis/St. Paul, MN, shows a lot of fat Convective Available Potential Energy (CAPE). The morning started out with 1133 J/kg surface-based CAPE, and a surface dewpoint of 68 F.

The shear was a little weak, with only 24 kts of deep-layer shear and 8 kts of low-level shear. However, the approaching shortwave trough is expected to increase the shear, perhaps high enough to support rotating storms.

The surface observation map shows that dewpoints have already increased into the low to mid 70s across the Moderate Risk area. I don’t even want to think about how miserable a 75 F dewpoint is, and whether or not my desert-dwelling body could handle that. However, if I am drawing the front in the correct place (almost north to south over the central Dakotas), the surface winds are almost parallel to it.

The surface-based CAPE has already exceeded 6000 J/kg in northwestern Iowa! Throughout the entire Moderate Risk area, CAPE is ramping up quickly.

Shear is also increasing throughout the region. Effective bulk shear exceeds 30 kts near Minneapolis, and climbs to over 40 kts in southwestern Minnesota, southeastern South Dakota, northeastern Nebraska and northwestern Iowa.

Overall, I think there will be plenty of storms today. However, with the surface winds parallel to the frontal boundary, they will likely go into a linear mode quickly. However, the high CAPE and potential for adequate shear may generate a few supercells to begin with. The places to look will be at initiation in northwestern Iowa, southwestern Minnesota, or perhaps even into eastern South Dakota. Another place of interest would be to target south-central Minnesota, and wait for a cell or two to form ahead of the linear system; find an outflow boundary in the rich dewpoints and wait for a storm to spin up along the boundary.

I would probably set up shop in Sioux Falls, SD and wait for storms to fire. I think the action will be east of there, but I think that is a good place to wait for the surface boundary.

Thank you for reading my prediction.

The Severe Weather Outlook is from the Storm Prediction Center website.
The satellite imagery is from the NOAA Satellite and Information Service.
The surface observation and upper level charts are from Unisys Weather.

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About highplainschasing

This blog is about my tales in storm chasing. My name is Seth Price and I am an instrumentation instructor at New Mexico Tech. My amateur radio call sign is N3MRA.
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