Like most meteorologists on social media, I have a tendency to be a little share-crazy when there’s a chance for severe weather. I’ll share forecast info, radar captures, photos, and outlook maps. Last week, I was asked what some of the icons on the Storm Prediction Center’s storm outlook maps mean. Here’s a basic overview using the Day 1 Outlook map for last Thursday afternoon below:
Starting with the box in the lower left corner, “Day 1 Categorical Outlook” lets the viewer know which day the map is for. The SPC issues outlooks for days 1-3 and an experimental map that covers days 4-8 all together. Typically, day 1 is the day the map is issued and is valid through the next morning, but it’s always a good idea to check the dates below the title.
In this case, the map was published on Thursday, April 18th and valid through Friday morning. The times are stated in Zulu time, which is an international standard also known as Greenwich Mean Time. 1630Z translated into our time, currently Eastern Daylight Time (EDT), is 12:30pm. So this map was valid for 12:30pm Thursday into 8:00am Friday.
On this map, we see areas shaded in green, yellow, and red with the short-hand “SLGT” and “MDT.” The green area represents the region where showers and thunderstorms are possible, but organized severe weather is not expected. The yellow area denotes a slight risk for severe weather. Red indicates a moderate risk for severe storms, and if there were an area of hot pink on the map, it would show where a high risk for severe weather exists. (See my previous post on what the risk categories mean.)
Occasionally, you might see an area shaded in green that says “SEE TEXT.” Typically it means that while no organized lines of severe storms are expected, it is possible people in that area might see some isolated severe storms pop up. Reading the text below the map on that page will explain in detail, but much of it will be in meteorology terminology.
The SPC Day 1 Outlook Map for Thursday, April 18th, 2013.