Sunday, February 11, 2024 4 P.M.

After bringing lots of rain to the southwestern states last week, all that’s left is a small cutoff upper level disturbance left behind as the major system moved on. The system is now being re-absorbed into the primary jet stream flow as it ejects toward the Tennessee Valley. A small surface low will develop tomorrow over TN and move over southeastern KY tomorrow night. That’s a classic snow situation for us! However, the big questions are exactly where the snow will fall? and will cold air arrive in time?

The models have been ignoring this development for the past few days, but are now paying attention. Unfortunately, they can’t seem to agree on the exact details. One area for agreement is that it’ll be a rain changing to snow situation. That change depends on the arrival of colder air that is expected tomorrow evening.

This morning’s GFS for the area has the rain/snow line along the Ohio River with accumulations of 2″ to 6″ inches of heavy, wet snow over the southern quarter of Indiana by Tuesday morning. Meanwhile, the KY side of the river should see an inch of snow or so – mostly on grassy areas. On the other hand, the NAM places the northern edge of the snow along the river. That puts about the northern third of KY (Including Louisville area) into the area of heaviest snowfall. That could mean about 2″ to 4″ of sloppy, wet snow for us but little snow for Indiana.

Now, however, the afternoon run of the NAM paints another take on the situation. This forecast pushes the whole situation about 60 miles south of it’s earlier solution. That means extreme southern Indiana and the KY counties touching the Ohio River will see rain tomorrow afternoon and evening with little or no snow on the tail end.

The afternoon GFS hasn’t arrived yet. It’ll be interesting!

STUFF: If the 49ers win tonight, they will tie the Pittsburgh Steelers and New England Patriots for the most Super Bowl victories. 6 each.

Sat. July 29, 2023 12:30 P.M.

National Weather Service has an 80% chance for thunderstorms this afternoon. It would be nice to get some rain, but an 80% chance? Where did that come from?

Scan of various models and derived data puts the chances lower than 20%. Even the Storm Prediction Center only goes to 40% chance this afternoon.

The 80% chance forecast looks like a big gamble. Let’s see how it plays out!

Also, for the past few days the longer range outlook for next week has kept our daily highs in the upper 80’s. Most recent model runs put daily highs back into the 90’s. Will our August end up being hotter than July? (Just guessing here, but I’d go with yes.

5:15 P.M.Thursday

Line of storms is falling apart. Strongest cells will be moving through Oldham County for the next 15 minutes.

Thursday, June 29, 2023 4:30 P.M.

A couple of hours ago a massive line of intense thunderstorms was moving ESE from Illinois to Indiana. Severe thunderstorm warnings have been moving in lockstep with the squall line. Two hours later (now), the severe warnings are still being issued. In fact, a warning now covers all of southern Indiana down to the Ohio River.

However, radar indications show considerable weakening along this line. It is still potent, just not as bad as it was. The Storm Prediction Center has placed the western two-thirds (everywhere west of I-75) of KY in a Severe Thunderstorm Watch this evening.

Primary threats are strong winds with a smaller chance for large hail. Storms should move through the metro area between 5:30 and 7 P.M. Expect the usual strong wind gusts of summer thunderstorms with scattered (mostly) minor damage.

As of 5:00 P.M. the line of storms is closing in on the Ohio River. It continues to weaken, but is still moving fast enough to generate gusts to 50mph, or so.

Luckily the super cell has weakened a bit, become less organized and changed directions over the past hour.

Primarily, the cell has turned a little of the original path it was taking. So, now the biggest threat seems to be southern Floyd County and the southwestern half of Jefferson Co. From there it should head into Bullitt and Nelson Counties.

Strong winds and hail are still likely, but any tornado threat has lessened.

5:30 P.M. Sunday, June 25, 2023

We’re in a Tornado Watch and it looks like some damaging weather has got parts of Louisville in its sight. Instability is high, wind shear is strong and, even though the cold front headed our way is not very strong, severe weather chances are high.

A “super cell” thunderstorm has broken away the broken line of storms plagueing southern Indiana this afternoon and headed on a path that brings it through northern Floyd Co., western Clark Co. during the next half hour. Then the storm will cross the Ohio River into northeast Jefferson Co., Oldham Co. and into Shelby Co. between 6 and 7P.M.

Super cells are never to be taken lightly. Brief very strong winds and large hail appear likely with this storm. Even a tornado is possible. Be carefull.

Sunday, June 11, 2023 5:30 P.M.

The Kentucky part of our area is under a Severe Thunderstorm Watch until 11 P.M. Should it be?

The original Watch issued by the Storm Prediction Center did not include the Louisville area. The original watch’s northern boundary covered pretty much of the southern half of the commonwealth. It’s pretty marginal, but a couple of isolated severe storms could hit southern KY this evening, especially near the Tennessee border.

Meanwhile, the Louisville office decided to include numerous counties in northern KY to the original Watch. Bad decision. Radar trends and model forecast trends continue show no threat of severe storms within at least 50 to 75 miles of the Ohio River. The local office invented a risk that doesn’t exist.

3:45 P.M. Wed. April 5, 2023

It appears the Storm Prediction Center is catching on to the reality of the current system over the central U.S. For 6- 8 hours they had Tornado Watches covering a vast area from Louisiana to Michigan. As of this time the number of tornadoes reported has been 0. There have been about 50 severe storm reports scattered throughout that area.

The most recent Watches covering the situation have been downgraded to Severe Thunderstorm and even that may be stretching it a bit. As mentioned earlier today, the thunderstorm line is moving into a less favorable environment, so I wouldn’t expect much, if any, severe weather this evening. Computer models continue to weaken the system for the next few hours.

Between 4 and 5 p.m. a weakening line of showers will spread northeast along the Ohio River near Louisville. Most of this activity will be over southern Indiana, but parts of northern Jefferson County could get some rain as well.

The main line of storms should push across the metro area between 5 and 6 p.m. Heavy downpours are likely as well as strong gusty winds. An isolated severe storm warning is possible, but not likely.

Wed, April 5, 2023 Noon

Severe Storms Center is paying a lot of attention to today’s situation. At Noon, they have Tornado Watches in a solid line from Louisiana to Michigan. Right now, conditions are ripe hundreds of miles to our west.

But, this is a dying weather system spawning the current storms. As weather patterns ease during the afternoon, strong/severe storms should have a harder time forming. As the cold front slowly moves eastward this afternoon/evening, it will be losing it’s supporting wind field and instability.

As a result, severe storms should become more isolated along the front as the threat diminishes. The primary line of thunderstorms is expected to move through Louisville metro between 5 and 7 P.M.

5 P.M. Monday, Jan. 30, 2023

General situation shows a large cold air mass over the midwest slowly dropping southward. Temperatures today have been slowly falling and will continue tonight as temperatures drop into the upper 20’s by morning. Meanwhile, a small upper level disturbance in the jet stream flow will move rapidly ENE over the area tonight. It’s not much of a system, but it does have enough moisture to bring us some icy weather tonight.

That’s where the forecast trouble starts. The lower atmosphere (up to 5,000 feet) is definitely cold enough to support an inch or two of snow overnight along the Ohio River. But, it’s not that simple.

There’s a pocket of slightly above freezing air roughly between 5,000 and 10,000 feet above us. That will be slowly cooling overnight but should still stay slightly above 32 degrees. That’s the fly in the ointment.

The primary consequence will be that some of the snow falling through this warm layer will melt, then refreeze into sleet before hitting the ground. That sets up a very subtle balancing act between snow and sleet for our overnight entertainment.

In general, the whole atmospheric column will be slowly cooling, so snow becomes the most likely result as time goes on. The onset is trickier. Everything depends upon just how thick that warmer air is and how much cooling it will get from evaporation of precipitation aloft.

The models are consistant on two things. First, the amount of moisture falling will be small. Probably between .1″ and .2″ of water. That would be a 1″-2″ snowfall but only about a quarter-inch of sleet. Second, the location of the maximum precipitation will be about roughly 30 miles north and south of the Ohio River.

After putting all those variables into a big pot and letting them simmer, here’s what I think will happen tonight. Precipitation should begin around 8 P.M. in Louisville. At first, it’ll be mostly sleet with a little snow mixed in. As the night goes on, the mix will gradually change to mostly snow with a little sleet mixed in. Any significant snow/sleet will end by 3-4 A.M. The Louisville area should end up with a snow/sleet total of up to one inch.

North of Louisville snow totals could get up to 1″-2″. South of Louisville will see a snow/sleet accumulation up to one-half inch.

By morning rush hour, treated roads should be in fairly good shape with icy spots. Meanwhile, non-treated roads should be mostly snow/ice covered.