Rain Chances Increasing
Today will still be a warm, mostly dry day for the Tennessee Valley. We do have more clouds in the sky than we’ve had lately, but temperatures are still forecast to top out around 87º in Huntsville; highs will range from around 83º in parts of Middle Tennessee and Northeast Alabama to near 88º around Florence and Russellville this afternoon. The chance of rain is tiny: only about 10% through early evening.
A cold front moving into The Valley on Friday will set off a good covering of light rain showers. Some spots could wind up with as much as a quarter of an inch of rain through Friday evening, but most communities will not see much more than a tenth of an inch. Our chance of rain stands at about 50% throughout the day on Friday. The intensity of the rain is expected to be very light:
So there’s a 50% chance of rain, but a 95% chance of at least a tenth of an inch? That doesn’t add up unless you start to break the day into parts. What this graph shows us is the probability of a particular amount of precipitation; not the chance that precipitation will occur. We use a lot of different products to arrive at a confidence level in a rain forecast. Some of the newest technology (these graphs) take ensemble data and boil it down to a probability of a particular event.
It is useful because it goes far beyond the standard percentage chance of rain. It gives us a better way to report to you the chance of getting a “significant” amount of rain. The odds of getting over 0.25″ are much lower for Huntsville: only 62%. These graphs give us confidence that for those of us that get rain, it will likely only add up to about 1/10 to 1/4 inch.
Unfortunately, the news does not get much better through next week if you are looking for a good, soaking rain. This is the Hydrometeorological Prediction Center’s morning 5-day precipitation outlook. Note the donut hole (minimum) of precipitation over the Tennessee Valley through Tuesday of next week:
This area may very well miss significant rain to the north and south over the next week; rain along the approaching cool front will be lessening as it crosses the Valley; a storm system to our southwest will likely bring heavy rain to our south on Saturday, Sunday and Monday of next week. So, while some rain is possible at times over the next several days, there is no time when rain is what we would call “likely.”