LOUISVILLE, Ky. — Another Friday, another cloudy, grey, and wet day (or even snowy for some). Friday rain has been a feature of January. Speaking of which, today is the last day of the first month of the year! Congratulations, you survived it. Now it’s on to February which looks to begin somewhat active.
- Friday precipitation will largely come to an end by the mid-afternoon
- Generally calm weather for the weekend
- Temperatures spike into the 60s to start next week
- Rain and maybe some thunderstorms likely Tuesday and Wednesday
- Another steep drop in temperatures to end the week
Weather setup: An area of light-to-moderate rain and snow was the main feature across Kentuckiana for Friday. For much of the region it was just a nasty cold rain. Cold rains are one of my least favorite types of weather, but I digress. Snow as seen almost exclusively in southern Indiana where up to around 1” fell, but quickly melted because temperatures were near freezing and then rose above freeze with rain falling on top of it.
The rest of Friday will see scattered light rain showers gradually coming to a close by the late afternoon and early evening, but a few areas of sprinkles will likely linger into the night. Expect a mostly cloudy sky Friday night with light winds from the north.
Saturday will be dry, but once again very cloudy. It seems like the theme for January has been rain and clouds every weekend! It’s very frustrating if all you want to do is spend your day off enjoying some sunshine. The good news is despite clouds, Saturday will be largely dry. Temperatures warm into the middle 40s.
Another cloudy Saturday.
The forecast really starts to change Sunday. The weather pattern takes a dramatic shift as a very large ridge will take over much of the contiguous United States starting Sunday and lasting into the start of next week. Remember, a ridge is generally not friendly for active weather. It is favorable for much warmer weather, and this is going to be a spring-like ridge with spring-like temperatures beginning Sunday and lasting through Wednesday. Temperatures will easily reach 20 degrees above normal to start the week.
A big ridge will bring us spring-like temperatures, but a storm is also entering the Pacific Northwest.
Next week’s storm is very impressive to look at in the middle layers of the sky, but will it stay so impressive as it gets closer to us?
But look back to our west. Another storm will be developing and will be our next storm system. It’s a tricky forecast, but models generally agree that we’ll see rain start spreading up the Ohio Valley beginning early Tuesday morning and potentially lasting through Wednesday night. With temperatures forecast for the lower 60s Tuesday and upper 50s Wednesday, a few embedded thunderstorms are not out of the question.
Widespread rain and maybe some thunderstorms are likely Tuesday and Wednesday as the center of the storm passes overhead.
Temperatures Monday and Tuesday will be nearly – or over – 20 degrees above normal in the lower and middle 60s! But notice the sudden change next Friday…
Long term: The 60s will leave as quickly as they came for the latter half of next week when we again see a big shift in our weather. This is again where the forecast gets challenging as a shot of colder air is expected to overtake the Ohio Valley sometime Thursday and result in falling temperatures throughout the day with that slight chance of precipitation remaining. With lows Thursday night below freezing, that would mean snow is possible. How significant might that snow be? Probably not very, but it’s a week away and models will continue to change. Not all of them are certain Kentuckiana will see snow. We’ll have a better idea of what Thursday and Friday will bring after this weekend.
Science! Alright, let’s talk some science. Did you look at radar earlier this morning? If you did, you might have noticed a band of what appeared to be heavy rain falling along the Ohio River at one point. Radar was painting elements in oranges and reds, which normally mean strong rainfall rates…yet only about a quarter of an inch of rain fell in this area. What’s the deal?
This looks like heavy rain doesn’t it? Well, it’s not.
This was an example of “bright banding.” Radar is a phenomenal and critical tool for meteorologists but can sometimes be misleading. Not everything on radar is as it appears. Bright banding is a phenomena where radar reflectivity (the colors you normally see on a radar) is higher than surrounding areas as the radar beam is scanning the area where snow is melting into rain.
Radar works by sending out strong pulses of electromagnetic radiation into the atmosphere and “listens” for whatever bounces back. Think of it like echolocation that bats use to find food. Water is a lot more reflective than ice, so it’s easier for radar to see. As a snowflake starts to melt it develops a thin coat of water over it. The radar detects this and thinks it’s a region of heavier rain or large rain drops, when it’s just melting snow! As the melting flake falls and continues to liquefy, reflectivity values decrease.
An example of bright banding as seen using a tool known as correlation coefficient.
One way we can find a bright band is through a radar tool called correlation coefficient (CC). Basically, CC measures how uniform objects are in size in the atmosphere. It’s a very useful tool for tornadoes to determine if there’s any debris in the air, but it can also help tell us where falling snow is melting. You can generally see this by a bright band on the map where things aren’t quite the same as the area around it. Pretty neat stuff!