Thursday, May 31, 2018 5 P.M.

Severe wind gusts ripped across the area this afternoon as winds gusted as high as 59 mph at Standiford Field.  Many reports of 50+ mph came in from around the state.  That cluster of strong storms is continuing to create trouble over southeastern KY.

Meanwhile, to our west what was expected to be the “big event” tonight is having a tough time organizing.  No surprise there.  This afternoon’s big cluster of storms has used a huge amount of the potential energy expected to fuel tonight’s storms.  So, no “big event” is likely tonight.  A line/cluster of thunderstorms could develop into our area around 9 P.M. until Midnight. But they won’t be very strong, even if they do reach us.  No additional severe weather is expected tonight  It appears that tonight’s outbreak may stay south of KY.  Lots more energy available over TN.

Thursday, May 31, 2018  Noon

After a largve production of heavy/severe thunderstorms in the central plains overnight, two distinct developments today as that energy moves east.

1).  A pulse of upper energy is moving rapidly eastward and is creating a developing strong cluster of storms over southern Illinois. This system is expected to expand eastward across southern Indiana and extreme northern Kentucky over the next few hours.  Some severe thunderstorms are likely this afternoon.  Primary threat will be brief, strong gusty winds.  Smaller threat will be hail.  If everything develops as expected, the cluster of storms will move through the Louisville area from about 2 P.M. to 3:30 P.M.

2).  The “main event” from the midwestern system is expected to develop later this afternoon and reach our area tonight.  Best time for us looks like 8 P.M. until Midnight.  Again, strong, gusty winds will be primary threat.  This time, however, the storms are expected to be more widespread.

NOTE:  How this afternoon’s storms play out could have a significant say in how tonight’s system develops. I’ll have an update on that later.

Sat. May 26, 2018  12:30 P.M.

Up to an hour of rain and possible thunder late this afternoon appears to be the only weather disruption we’ll see this long weekend.  Memorial Day weekend is often referred to as the “unofficial beginning of summer.”  This year, however, it’ll be more like the middle of summer, especially tomorrow and Monday.

This afternoon, I expect a narrow line of showers/thunder to form over southern Indiana by around 2 P.M.  They will drift slowly southeastward through the Louisville metro between about 4 P.M. and 5:30 P.M.  It should not be a solid line, so not everyone will see rain.  Even those who receive rain won’t get much, probably less than a quarter inch.

The rest of the weekend will be hot, humid and dry.  Only a scant chance for a thunderstorm tomorrow and Monday.  Highs both days will be near 90 degrees.  (heat index: low 90’s)

Tuesday, March 20, 2018

On my previous post I gave two reasons why I wasn’t expecting to see much snow tonight.  The second reason has been my downfall to getting this forecast correct.  The weak secondary upper has formed, BUT it formed too far east to disrupt the flow of wrap around moisture westward into Ohio Valley.  The result?  More snow than I expected.

As of 8 P.M. we already have two inches on the ground.  The snow should become very light over the next hour or two, then continue overnight.  Louisville area should have 2″ – 4″ by morning.  Deeper snows north and northeast of the city.  Lower totals south of the metro area.

Sunday, March 11, 2018  4 P.M.

Majority of snow stays south of Louisville

As expected (at least by readers here), Friday’s weak Alberta Clipper failed to generate much snow around the metro area.  Today a strong Clipper is approaching our region and will pass through tonight.  This time, however, the storm has its eyes focused on central and southern Kentucky.  You guessed it…little, if any snow for the Louisville area.  Another missed opportunity in a winter highlighted by misses.

Once again, temperatures will play a big role in tonight’s weather.  Surface temperatures locally will stay above freezing during the precipitation event, so no problems are expected with area roads.  They will stay wet, even if we do get a small amount of snow.  In fact, most major roads will be dry before the morning rush hour.

But, let’s talk about central/southern KY

Starting about 20-30 miles south of I-64 on down to the Tennessee border, SNOW will be the primary factor.  Sloppy, wet snow (probably beginning as rain) appears likely for about 4-6 hours tonight.  Time frame should be roughly Midnight until 6 AM EDT.  Most of the southern two-thirds of KY should receive from 2″ to 4″ of snow – mostly on the grassy areas.  Some spots could get as much as 4-7″ of snow.  That would be enough for the heavy wet snow to break some tree limbs and/or power lines.

Louisville area summary

Light rain will move in during the evening.  Rain will mix with, or change to, snow around Midnight.  Precipitation should diminish by about 3-4 AM.  Snow accumulations, if any, should be less than one-half inch – on grassy areas only.  No traffic problems are anticipated.

Friday, March 9, 2012 6 P.M.

Rain and (mostly) white rain overnight

A weak Alberta Clipper system will work its way through the lower Ohio Valley tonight. First, we’ll see rain developing this evening.  Then, as a little colder air arrives, the rain will mix with snow.  We’ll also probably see all  snow for an hour or so.  The lower atmospheric temperatures will be the key as is often the case.

The models can’t agree on much.  But, two items are shared by all of them.  First, temperatures near the surface will stay several degrees or more above freezing during the precipitation event.  Second, the highest likelihood for accumulating snow will stay mostly north of I-65 AND, especially, east of Louisville.  Primary time for snow in the metro area will be from 1 A.M to 4 A.M.

Moisture is rapidly feeding into the system, but the majority of the moisture won’t arrive in time for significant snow west of I-65.  Areas from eastern Oldham and Shelby Cos to Georgetown may see 1-2″ of snow on grassy areas with isolated 3″-4″ amounts, but very little on roadways.  In Indiana, eastern Clark and Jefferson Counties may see 1″-3″.

Back home in the Louisville with temperatures up and smaller precipitation amounts expected, we should experience only a few, brief problems on the roads.  Otherwise, snowfall accumulations will be small – less than an inch on grassy areas.  Any minor accumulations on road surfaces will disappear by morning.

Oh yes…”White rain”

White rain is my definition for snow that essentially has the same effect as regular rain.

Monday, Jan. 15, 2018 5 P.M.

After weakening all afternoon, the area of snow around us has developed a narrow line of moderate to heavy snow.  The line should pass through Jefferson County between 6 P.M. and 7 P.M. this evening.  This will cause roads to become snow-covered and icy, especially untreated roads.  This could give the county a quick 1/2″ to 1 1/2″ of new snow.  Flurries after that.

Monday, Jan. 15, 2018  2:30 P.M.

Model and radar trends are still weakening.  Light snow will continue until roughly 7 P.M. but roads will stay wet this afternoon.  Untreated roads will start getting icy after 4-5 P.M.  We will see just a small additional accumulation on grassy areas (less than one inch).  As snow moves southeast this evening continued light accumulations will occur, but still less than an inch.

Meanwhile, southern Indiana has seen light snow most of the afternoon with little accumulation.  The snow will fade by 5-6 P.M. with around 1″-2″ accumulation over the region north and west of the Ohio River.

But, everything will freeze hard again tonight as most of the area will see single-digit temperatures by morning.

Sunday, Jan. 14, 2018  3:30 P.M.

Another Arctic blast coming…will it arrive with some snow?

Another bit of the so-called Polar Vortex is breaking away from the Arctic and will settle down over the western Great Lakes over the next 48 hours.  That keeps any heavy snow threat far to our north.  But, we’ll see two attempts at some light snow during the next 24 hours.

First, a weak warm front is moving east from Arkansas and Missouri and should pass overhead tonight.  It is currently creating some light snow west of the Mississippi.  However, as it comes east it’ll be hitting drier air.  Thus, the snow system will fade.  We may see some flurries or even a dusting of snow from the warm front, but nothing of any consequence is expected.

Second, a better chance for snow will come around midday tomorrow as the Arctic cold front comes quickly across our area .  There should be enough moisture to squeeze out some light snow and snow showers for a couple of hours.  With snow  showers in the mix a few isolated areas could get a quick inch (or so) of snow.  But most of us will probably get less than an inch of snow.  That’s not much, but even a small amount can create road problems.  Luckily there will be enough time to get roads back in shape by rush hour (for those who don’t get the holiday off).

Longer term…

Tomorrow’s shot of cold air will be the last for awhile.  Temperatures should warm significantly by late week with rain becoming our primary precipitation threat, probably Sunday,  In general it looks like the upper air pattern will shift to a  “western U.S. cold- eastern U.S. warm” pattern for at least two weeks.  Our January Thaw is on the way – right on schedule.

Thursday, Jan. 11, 2018  5 P.M.

Slide from rain to snow begins tomorrow morning

A couple of subtle changes in the forecast models point to some changes in how tomorrow’s winter storm will affect us.  First, the timing has accelerated so that the majority of the wintry mix will fall during the daylight hours.  That suggests lower snow/ice accumulations than previously expected.  Second, the storm development has been delayed.  Thus, the storm should not reach full classic cyclone status until tomorrow evening…after most of the snow has ended here.  This implies a shorter duration of the icy precipitation.

As usual the models show small differences between each other.  But, in general, they stand in pretty good agreement.  On the larger scale they have shifted the storm track just a little westward from yesterday.  You might think the general agreement among the models means that tomorrow’s weather is well defined.  Not so!  Freezing rain and sleet are extremely difficult to predict.  That’s because they are created only within VERY narrowly defined parameters.  Rain and snow can occur under a huge range of atmospheric conditions, but not sleet and freezing rain. In the lower 2000 to 3000 feet above the earth, one half of a degree(Celsius) of cooling can convert rain to freezing rain. Another half degree cooler and it can  change to sleet.  Another half degree and snow becomes dominant.  Computer forecast models are very good, but splitting hairs in near-surface temperatures is a little too much to ask.

So, it comes down to us humans to try figure it all out.  This human thinks it’ll work out something like this.  Rain showers this evening will become steady rain after midnight.  Temperatures fall into the 35-38 degree range by 7 A.M. Cold rain for the morning rush hour.  Sleet should begin  by late morning and change over to snow around 1-3 P.M.  Snow should taper off to flurries by 7-8 P.M.

That’s my timeline.  Here’re the results I expect:

Rush hour:  rain and cold                                                                                                                        Roads should get slushy/icy by Noon                                                                                         Afternoon rush hour:  Slick, icy roads, snow falling. Temperatures drop below freezing.       Night: Windy and cold with snow flurries.  Snow should end by midnight.                                  Total Snow/ice accumulation for Louisville area:  1″ – 3″  (Jefferson County and east closer to 1″-2″  while up to 3″ west of Louisville/southern IN)

Note:  I still expect a band of heavy snow from western KY northeast to Evansville, Indy and Ft. Wayne.  This swath of land should see a 4″ – 8″ layer of snow tomorrow.

Well, that’s what I think will happen tomorrow.  Now it’s time to settle back and wait to see what really happens!