Author Archives: wx

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 “iffy” March snow forecast

Tuesday, March 20, 2018  2 P.M.

Another big nor’easter is on track to pound the eastern U.S. from northern West Virginia, north Virginia and northern Maryland northward into New England.  4″ to 8″ of snow will be likely over a large area while some spots could record a foot of snow, or more.

Meanwhile, we’ll be on the back side of this big snow-maker.  The computer forecast models are predicting about a 2″ – 4″ snow in about a 100 mile wide swath from southern Indiana and extreme northern KY  northeastward toward Lake Erie. That swath could reach 6″ or more over east-central IN and northwestern Ohio.  The Louisville National Weather Service’s forecast includes Louisville in that 2″ – 4″ snow area.  But, don’t count on that much snow here.  I have two good reasons for predicting why our Louisville snowfall total should be lower.

First,  the western side of Northern Hemispheric storms is a weaker precipitation-maker than the warmer eastern side.  The northwest side of these systems has to “wrap around” moisture from the active eastern side of the storm. That’s a hard job to pull off. Nevertheless, it does work.  Whatever moisture that does make the wrap around is rather small, but efficient.  As it reaches the northwest quadrant of the storm, it encounters colder air which squeezes out some moisture.  Little, if any, moisture can get far enough around to reach the southwestern quadrant of the storm.  The problem here is that the Louisville area will be in the Southwestern quadrant of the system by Midnight-2 A.M.

Second,  several models are predicting a weak low pressure to form west of the primary storm center.  This development is expected over east KY and West Virginia.  When that happens this evening, it will interfere with the wrap around precipitation mechanism of the parent storm.  So, we have another problem with the potential snowfall here.

With all that to consider, here’s my forecast:  a light rain/snow mix will begin during the afternoon rush hour and quickly  turn over to snow this evening.  Periods of light snow will continue overnight changing to flurries by daybreak.   Temperatures will remain in the 30″s all night, so roads should remain mostly wet with just a few slick spots.

How much snow?

Louisville area: !” to 2″ on grassy areas

South of Louisville: less than 1″

Southern Indiana: 2″ to 4″ north of the Ohio River.  4″+ over south-central counties northeast to the Ohio border.


March 11 evening snow update

Significant changes in past few hours.

Models have been running the precipitation farther north this evening.  It now appears the southern one-quarter of KY will stay snow free.  Heaviest snow band looks to be between a few miles south of I-64 to southern KY.  Basically, Bullitt Co and south.

Also, models are predicting faster movement of the storm (should leave Louisville area by 3 AM.  Faster movement means lower precip. totals for us.

Another change:  Models are now predicting colder temperatures overnight.  That means slightly more accumulation of snow AND possible road problems for Louisville.

So, for Louisville area:  some rain, but mostly snow.  Louisville could see an inch of snow on grassy areas with some slush on roads.  Major roads, however, should have few problems

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.

The little engine that could

Tuesday, January 16, 2018  3 P.M.

The relatively small weather system that moved ever so slowly over southern IN and KY yesterday was amazing to watch.  It just didn’t want to move in spite of the models efforts to move it away last evening.  Watching the snow pattern move across the radar screen last night was like watching the proverbial paint dry.  In spite of the prolonged period of snow, the system still couldn’t generate much snow, but it was an amazing effort.

The last very cold surge (for at least two weeks) of Arctic air has arrived and will dominate our weather for the next two days.  We’re seeing a good example of the power of the sun this afternoon.  The air temperature is only in the mid teens but yet we’re getting a lot of melting on asphalt roads.  Concrete roads don’t absorb as much heat, so they haven’t melted as much snow.

By all large scale features, we should be having temperatures at zero or below tonight.  The coldest part of the cold air mass will be over us tonight,  we have a snow cover, clear skies and light winds.  That normally would produce temperatures in the 0 to -10 range.  However, model and human forecasts are predicting a low range of 5 to 10 degrees. Why?  Lake Effect

We normally think of snow when Lake Effect is mentioned.  Not this time.  This is more subtle.  The model suite is in agreement that low level winds (3,000 to 8,000 feet) will develop a fetch (flow pattern) from Lake Michigan SSE across IN and into the eastern half of KY.  It’s too weak to produce snow, but it should be able to produce mostly cloudy skies after midnight.  The clouds trap what little heat we have so our temperatures stay higher.  (Skies should remain mostly clear 30-40 miles west of Louisville, so sub zero temperatures are likely there.)

The ability of today’s weather forecast models to pick up on such small details as a Lake Effect’s ability to alter our weather (hundreds of miles away)  is really amazing.  We’re light years ahead of the two primitive models I started using more than 50 years ago.



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.

Today’s snow

Monday, Jan. 15, 2018

Not much to worry about this afternoon

A cold front pushing toward us has been producing some nice snow over southwestern IN this morning.  However, current short-term models are forecasting a considerable weakening of the snow field this afternoon as it passes through the I-65 corridor.  Plus, southerly winds have pushed temperatures to around 32 degrees and they should stay there this afternoon.

As a result, my forecast needs a little revision:

Light snow should begin around 1 P.M. and be mostly over by 5 P.M.  Flurries will continue overnight.  This afternoon’s snow will mostly melt on roadways, so this evening’s rush hour will only have a few slick spots.  As always, drivers will find those slick spots and we’ll have some accidents.  Overall, however, things should be pretty good considering holiday traffic will be lighter than usual.

Snow accumulations will be light.  Within a 30 mile radius of Louisville, the Ohio River will be a dividing line.  On the Kentucky side of the river, snow accumulations should run around 1″ on grassy areas (little, if any, on roads as discussed earlier).  South and east of Jefferson County snow totals will diminish to less than an inch.  On the Indiana side of the Ohio River, snow totals will be higher – 1″-2″ in the counties touching the Ohio.  Farther north and west, it’ll probably be more like 2″-3″.
NOTE:  I wasn’t surprised to see snow overnight.  However, the amount of snow really surprised me.  Best I thought nature could do was around .1″, maybe .2″  The half inch sure fooled me.  I’m hoping the prediction described above will be better.


Moisture increasing

Sunday, Jan. 14, 2018  11 P.M.

Evening models have all increased their forecasts for snow Monday.  Still a possible dusting overnight; then afternoon snow Monday should average around 1″ with some isolated spots perhaps as high as 2″.