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SKYWARN

An even earlier “heads up” on severe weather

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Earlier, in commemoration of Indiana Severe Weather Preparedness Week, I wrote about the important distinctions between watches and warnings. Readers who saw that post will recall that the National Weather Service usually issues weather watches hours before severe weather develops in the watch area.

You can also know about the possibilities of severe weather days in advance, if you know where to look.

In addition to watches, the NWS Storm Prediction Center (SPC) issues convective outlooks. In this case, “convective,” refers to thunderstorm development through atmospheric instability. Convective outlooks include maps that show various risk levels for severe thunderstorms in various parts of the country as far into the future as six days.

For example, on April 27, 2014, a large, violent tornado killed 16 people in Vilonia and Mayflower, Arkansas. Five days earlier, the SPC indicated a risk of severe weather in that area on a convective outlook map (see below).

Day 4-8 convective outlook from April 22, 1014 for Indiana Severe Weather Preparedness Week
“Day 4-8 Convective Outlook” map issued by the Storm Prediction Center on April 22, 2014, five days before a tornado killed 16 people in Arkansas. Note the green area labeled “D6,” which includes the area where the tornado eventually formed and which indicated a 30 percent or higher probability of severe thunderstorms within 25 miles of any point on April 27.

Anyone who wants an advance look at severe weather probabilities can look at SPC convective outlooks on the SPC website. During severe weather season, I review every morning at least the “Day 1 Convective Outlook” (which shows risks for the same day) and the “Day 2 Convective Outlook” (which shows the next day’s risks).

For a more localized outlook, I also view the “Hazardous Weather Outlook” that our local NWS office issues. This text-only product indicates local forecasters’ assessment of the risks of hazardous weather within their coverage area the same day (day one) and for the following week (days two through seven).

So, what can you do with this information? When an outlook indicates a risk of severe weather in a few days, you can:

  • Develop and/or review a plan for what to do if sever weather strikes.
  • Encourage others to develop a plan.
  • Assemble a disaster supply kit and pet kit.
  • Check your NOAA All Hazards radio for fresh batteries and operation.

By knowing about outlooks, watches and warnings when they’re issued, you can keep from being surprised by severe weather.