Good Friday morning! 

It looks like it will be a rainy end to the month of July & it looks like we will have a rainy beginning for the 1st of August tomorrow.

An update, the Flash Flood Watch that was supposed to expire this morning has been extended until tomorrow (Saturday) morning until 8 AM EDT.

Something I would like to talk about this morning, is the explanation of the chance of precipitation. It can be confusing and misunderstood by many so I just want to give you some clarification.

So for example, when you look at our forecast for today, it shows that we have a 40% chance of showers (mainly later on this afternoon) for most of our local area. So some may think, well it is going to rain 40% of the time this afternoon, which is a common thought. Here's what it actually means:

**To summarize, the Probability of Precipitation is simply a statistical probability of 0.01" inch or more of precipitation at a given area in the given forecast area in the time period specified. Using the 40% probability of rain as an example, it does not mean (1) that 40% of the area will be covered by precipitation at given time in the given forecast area or (2) that you will be seeing precipitation 40% of the time in the given forecast area for the given forecast time period.

**Let's look at an example of what the probability does mean. Above I mentioned today's forecast shows a 40% chance of rain for our local area, that means there is a 40% chance of rain at any point in the area from 1:00 PM EDT on into the latter part of the afternoon and into the evening.

**This point probability of precipitation is predetermined and arrived at by the forecaster by multiplying two factors:

               Forecaster certainty that precipitation will form or move into the area

                                                                X                                                                                                                            Areal coverage of precipitation that is expected

                     (and then moving the decimal point two places to the left)

**Using this, here are two examples giving the same statistical result:

         (1) If the forecaster was 80% certain that rain would develop but only expected to cover 50% of the forecast area, then the forecast would read "a 40% chance of rain" for any given location.

         (2) If the forecaster expected a widespread area of precipitation with 100% coverage to approach, but they were only 40% certain that it would reach the forecast area, this would, also, result in a "40% chance of rain" at any given location in the forecast area.

I know this blog was rather lengthy and definitely more informative than my previous ones, but hopefully you have a better understanding of how "chance of precipitation / probability of precipiation" is calculated and what it means.

I'll post another update later on this afternoon with a look at the forecase to kick off the month of August! hope you enjoyed this one & I will catch you back later!

-Crystal

email: crystal@shorelinestations.com

Source for info.: NWS