Monthly Archives: March 2018

Beautiful evening

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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

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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

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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

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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

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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.