Category Archives: forecast

Beautiful evening

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.

Another close call

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.

Sloppy night ahead

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.

Narrow line of heavy snow approaching

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.

Snow system still fading

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.

A little snow for MLK Day

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.

Wintry Mix tomorrow

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!

Late week snow still on track

Wed. Jan 10, 2018  5 P.M.

Heavy snow likely near Louisville

Today’s latest from the GFS products department…

Forecast for 12 hours ending at 7 A.M. Saturday.

Unfortunately for local snow fans, this is probably a little too optimistic for Louisville.

Yesterday there was a very wide range of computer solutions for the storm late this week.  Confidence is higher now as two changes have occurred in the past 24 hours.  First, the various models have converged in their solutions.  Second, the very unusual (and snowy) solution by the operational GFS has faded into a much more realistic-looking forecast today.

In general, my current expectation goes like this:  strengthening low pressure will develop over the northwest Gulf of Mexico and move northeastward tomorrow.  It will accelerate quickly along the spine of the Appalachians tomorrow night.  That storm track will be very important.  A little farther west than expected and we’ll see almost all rain with just a little snow at the end.  If the track moves a little east of current thought, we could be in for a heavy snow (5″-10″).

The highest probability, though, would be for the storm to follow the current projected path OR to the left (west) of the current prediction.  As usual, the NAM is a little more rambunctious with this system.  It almost always is more energetic than the GFS 48 hours in advance, but the GFS is almost always better in the end.

So, here’s what I expect – rain showers become likely by afternoon tomorrow. Rain continues tomorrow night and Friday morning.  Temperatures turn colder by Friday afternoon and the rain changes to snow by mid-to-late afternoon.  Temperatures will drop rapidly as the rain transitions to snow.  A “flash freeze” of roads will be possible.  Snow diminishes after midnight.  Total snow accumulation for the Louisville area:  1″ – 3″  Less snow will fall east of Louisville.  For instance, Lexington should see little more than flurries.

Note:  Very heavy snows are expected west and north of Louisville.  A swath of snow should fall over western TN, western KY, southwest and central IN.  Paducah, Evansville, and Indy could get as much as 6″-12″ Friday afternoon and night.

Potential storms update

Sat. Nov.18, 2017  3:10 P.M.

Severe Thunderstorm WATCH expanded  WHY?

The Storm Prediction Center has seen fit to expand the Tstorm Watch to cover most of Kentucky.  At least for northern half of KY and southern half of IN, watch seems pretty useless.  As mentioned earlier, the part of the storm line approaching our region has lost any severe weather characteristics.

So, risk of severe thunderstorms for Louisville area is extremely low.  Southern KY has a very slight risk.

Nasty weather late this afternoon

Saturday, Nov. 18, 2017  2 P.M.

Cold Front approaching rapidly

A strong cold front is pushing rapidly (about 50 mph) southeastward across the lower Ohio Valley. Currently, is is stretched from about Indy southwest to near Paducah.  That pushes the front through the Louisville area between about 4:00 and 5:00 this afternoon.  The front has become active with a narrow line the showers/thunderstorms along it.

The Storm Prediction Center has issued a Severe Thunderstorm Watch for all of southwestern Indiana WEST of I-65 and most of KY west of Louisville.  Louisville is not in the Watch.  Nevertheless, the front is already beyond it’s severe weather.  A couple of severe winds reports came from southern Illinois as the system developed (often the case in marginal situations), but over the past hour or so the energy has become more evenly distributed along the cold front.  Thus, the threat for severe weather in Louisville area is very low.  Strong winds, yes; severe winds, probably not.

What to expect:  Winds will be quite gusty as the front approaches.  Wind gusts of 35 to 45 mph will be likely.  The cold front will bring a narrow line of showers and thunderstorms through the local area between about 4:00 and 5:00 P.M.  During that time we may see gusts reach 50 mph.

Temperatures will remain in the mid 60’s before the rain.  An hour later they should be in the lower 50’s.  After the rain departs, strong winds will continue for a few more hours.  This time they will be from the northwest around 30-40 mph.

NOTE:  Yesterday I was hoping the cold front would arrive around 3:30 so that the UL-Syracuse game start would be delayed, but played straight through after that.  Now, it looks as though the game should start but still be in the first quarter when the thunder hits. Then a delay of 60 minutes to 90 minutes before resumption..