>March 20 Severe Weather Event Forecast Discussion

>This is a forecast discussion concerning a potential for severe weather going into today.
FORECAST DISCUSSION
The RUC model, a very short range model, is indicating the potential for a severe weather event today.
The Best Lifted Index, featured below, is an indicator of instability in the atmosphere. Image from 12z RUC 12 hours out.

The way BLI (Best Lifted Index) is classified is the following:
Values above 0: Very to marginally stable.
Values 0 to -2: Somewhat unstable, storms unlikely.
Values -2 to -6: Unstable, Storms likely, some severe with lift in the atmosphere.
Values below -6: Extremely unstable, severe storms with lift.

Looking at the image above, some hints I can point out are a potential squall line along the instability line. Another hint is that the strongest storms could exist in the northern areas of this squall line, where there is more BLI.
This squall line, should it develop, would move VERY slowly according to the RUC. That would not be good for people in flooding zones. However, it reduces the chances of tornadoes due to how slow it may be going. At the same time, the squall line is expected to be weakening.

Next up, we have the same RUC run’s depiction of Lapse Rates. The time frame is the same time frame as with the image above.
Lapse Rates are indicators of instability. They show the temperature change with height.
Values less than 5.5 to 6 degrees are considered very stable, while values near 9.5 degrees are considered absolutely unstable.
Taking that information and plugging it in to the forecast shows values of 7.5-8 degrees abundant across the right board, with values reaching 6.5-7.5 degrees on the left image.
Based on that, we can make a prediction that at least moderate instability will exist throughout the predicted area of the squall line.

So this is a potential severe weather situation. Keep in mind these are only predictions. It may develop, it may not. The Weather Centre is only just beginning to shift into severe weather phase.

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