Monday, March 21, 2011

March 21 Severe Weather Outbreak Forecast Discussion

This is a forecast discussion concerning the severe weather outbreak predicted tomorrow.
FORECAST DISCUSSION

According to basic look-overs on forecasts, a squall line should develop tomorrow and push into the Midwest as it weakens.

BASIC OVERVIEW
Here we have the Storm Prediction Center's outlook for tomorrow. Immediately, based on the way the slight risk area is organized, a squall line will be the method this time for severe weather.
A warm front will lift into Wisconsin and Michigan, dragging in nice, warm air. At the same time, a strong low pressure system with a cold front behind it will be the ignition for this squall line.
Based on latest forecasts, this should not be a terribly intense storm system and the storms will weaken as they move into Illinois.
However, the percentage risk for severe storms is somewhat concerning.
The 15% is the base starting point for a slight risk situation. This morning, where was even a 45% risk area in Iowa. However, as we see above, that area has been cancelled. At the same time, the 30% area has been expanded east.
Based on outlooks, it appears the primary risk of severe weather will be hail. Since hail is created by strong lifting up and down in the clouds, it can be assumed that these storms that do produce hail will be accompanied by strong lifting in the clouds.

In summary, the main risk of severe weather is Iowa into Illinois. The main threat type of severe weather is hail. A squall line is expected to develop.

ADVANCED COMPONENTS OF THIS STORM
Storm Prediction SREF ensembles indicate the Craven/Brooks significant severe weather parameter is still about double the threshold for what is considered the potential for significant severe weather. Image below.
This shows that the strongest part of the squall line should be in Iowa extending through Kansas and Oklahoma. Will keep an eye on this parameter.

Other concerns...
Lapse Rates looking fairly unstable.

Another update may be issued tonight, with another full write-up tomorrow.

No comments: