Monthly Archives: January 2016

Still looks good for snow this week!

Monday afternoon, Jan. 18, 2016

There have been some changes since yesterday (see Sunday’s post) with the models, but nothing big enough to downplay our snow chances yet.

NAM and GFS are now closer together concerning the weak upper air disturbance crossing the midwest and Ohio Valley Tuesday night and Wednesday.  In fact, today’s runs have the NAM now more aggressive than the than the GFS.  Their current forecasts are now in the 2″-4″ for the NAM and 1″-3″ for the GFS.  More on this system tomorrow.

Meanwhile, both models continue to point toward Friday as this week’s MAIN EVENT.  A system developing over the southern Rockies is expected to develop into a large storm over the southcentral U.S. then travel over TN and up the Appalachians Friday.  That’s prime territory for deep snows for us.  It’s too early to predict an exact path, but this morning’s GFS is predicting 6.8″ of snow for Louisville.

Let’s wait and see!!!

Two good shots for snow this week.

Sunday,  Jan. 17, 2016

A few flurries arriving this afternoon along with another shot of Arctic air will set the stage for what could turn out to be a snowy week.  The first good chance will arrive Wednesday while the second seems to be on tap for Friday.  The current GFS model looks pretty impressive, but I’m always forced to use the disclaimer – A lot can change in a few days.  But, it’s always fun to speculate.  So here goes…

A weak to moderate disturbance will drift into the Ohio Valley by Wednesday.  It’ll be overriding the cold air mass arriving today, so surface moisture will be very limited.  Nevertheless, the GFS is trying very hard to generate its own moisture and is showing the potential for 2″-3″ of snow.  The NAM is much weaker with this system, but still shows the potential for an inch (possibly as much as two) of snow.

Friday’s system, at this point, looks to be stronger and have more moisture available.  Thus, the snow-making potential could support 4″ + accumulations.  But, there will be some hurdles to jump over before a deep snow can occur.  What happens Wednesday will go a long way toward determining what’s going to happen Friday.  If Wednesday’s system is as strong as the GFS suggests, it’ll drag in another surge of cold air and help support a larger snow on Friday.  The weaker NAM solution plays toward a rain/snow mix early Friday, then snow later.  Either way, it looks as though Friday’s system will be warmer, so it shouldn’t be as bad on the roads.

Of course, potential doesn’t often equal reality.  But, it looks pretty good at this time.  Check back for updates as the events draw closer.

Observations from this week’s snows

Thursday, Jan.14, 2016

The two snows this week pointed out a couple of interesting items: (1) The time and temperature that snow falls is very important and (2) the difference between “snowfall” and “snow accumulation.”

First, according to airport (SDF) data, the two systems had approximately the same liquid water content, so all things being equal we should have had about the same results.  But, we certainly didn’t.  Sunday’s snow fell during rapidly falling temperatures (from above freezing into the 20’s.  The warmer roads, at first, melted the snow.  As it got colder, the roads froze into icy sheets with a thin layer  of snow on top.  Meanwhile, the snow which fell onto the grassy areas didn’t melt (because of no solar radiation at night) and accumulated up to around an inch locally. If that snow had fallen during the day, the result would have been much like what we saw Tuesday.

Tuesday’s snow arrived around daybreak, so it didn’t have the advantage of night to get a jump on accumulations.  Plus temperatures were above 32 degrees.  That snow continued most of the morning, including a strong snow shower around 11 A.M.  That snow shower, if it had occurred around, say, 6 or 7 A.M., would have created a huge mess on the roads.  But, it happened during the day and the roads just stayed wet.

Now, the snowfall vs. accumulation.  This can be confusing because when we forecast snow, we talk about the expected accumulation – how much will my ruler measure on a flat, NON grassy surface.  However, the National Weather Service reports two measurements- snowfall and snow accumulation.  As we saw this week, the two are NOT the same.

Sunday morning’s snow (at night) was right in line with expectations – the weather service reported .8″ of snowfall and 1″ on the ground.  Accumulations are rounded to the nearest inch, so a measured “on the ground” .5″ to 1.4″ would be reported as 1″, etc.

Tuesday, however, was a much different story.  The “official” snow on the ground at 7 A.M. was 1″.  Then came the snow.  It was daytime and temperatures were above 32.  The snow”fall” total reported by the NWS was 1.8″.  At 1 P.M. the officially reported accumulation on the ground was listed as 0.

Good illustration of the difference between snowfall and snow accumulation – we started with one inch on the ground, then a snowfall of 1.8″.  After it was over, we had less than a half inch of snow on the ground.

NOTE:  Situations like this allow almost everybody to proclaim a “correct” forecast.  Monday night, the NWS and many others forecast an accumulation of 1″-2″.  I wasn’t watching Tuesday evening, but based on past experiences, I’d say that a common comment went something like this…”just like we predicted, we had 1.8″ of snowfall…”  They may proclaim to be “correct”, but they were wrong!  And they are trying to convince you they were right.  So, if you are keeping score – give them two strikes instead of one.

There is a difference between snowfall and snow accumulation. although many times forecasters wish you didn’t know.


NOTE:  I don’t know why, but this post today brought to mind an old story circulating about our old “climate specialist” Al Gore.  As you probably know, back in 2007 or so, Al famously announced to the world that due to global warming,  the Arctic would be ice-free (In summer) and the polar bears would have vanished by 2013 or 2014.  Well, here we are in 2016 and the Arctic still has plenty of ice and polar bears.

The comment:  When Al Gore was born, Earth had 7000 polar bears.  Now there are only 30,000 left.





More Snow?

Monday, Jan. 11, 2013

Another Winter Weather Advisory for the area.  Yesterday turned out different than I expected as temperatures dropped much faster than I was expecting, so there were plenty of road problems in spite of the less than an inch (.8″) that was recorded at the airport.

Tonight’s situation is entirely different…we’ll be on the tail end of what is commonly called an Alberta Clipper that will move through the Great Lakes late tonight and tomorrow.  There’s not usually too much to get excited about south of the clipper’s path, but this time may be a little different – at least the NWS seems to think so.  Me, I’m not so sure, but I do think we’ll get something tomorrow morning.

This evening and early tomorrow morning, we’ll probably see what appears to be lots of snow  on the radar, but don’t be fooled.  High levels will be producing snow, but the lower level air is too dry for it to reach the ground.  The result is called virga (falling precipitation that evaporates before reaching the ground).   It looks good on the radar, but the result is disappointing to snow lovers.

That virga over night will be from a weak upper air disturbance preceding the primary clipper system.  While it shouldn’t produce more than a few flakes of snow, it will serve to increase the low level moisture levels so that the primary system should have more chance to drop some snow.

As mentioned above, the major problems with the clipper will be far to our north, but the cold front trailing the system will come racing across Indiana and Kentucky tomorrow morning.  While the atmosphere is very cold right now, it’s hard to squeeze much moisture into the air.  But, it should be able produce a few hours of snow (probably between 6 and 10 A.M. in the Louisville area (earlier to our west and later to our east).

All the models I’ve seen are generating only small amounts of precipitation (less than .10″ liquid), so that doesn’t hint at much snow.  Also, temperatures are expected to remain in the lower 30’s tonight, so the roads should be able to handle it pretty well.

With the Winter Weather Advisory, the Weather Service (and most of our media sycophants) is predicting 1″-3″ of snow.  The indicators don’t look that strong to me.  It’s possible that a few scattered snow showers could produce a few isolated swaths of 1″-2″ of snow (especially over southern Indiana).  The vast majority of the area should see anywhere from a dusting to up to an inch of snow.


  Sat. Jan 8, 2016  9 P.M.

Quick look at the winter weather advisory for the area.  Seems to be a bit overdone.  Temperatures should remain above freezing during the time of expected snowfall.  Being it is night, there is a chance for some very sloppy accumulations on grassy areas after 4-5 A.M. but no problems with the roads.  Any accumulating snows should end by daybreak.  Cold and windy, possible flurries Sunday with falling temperatures into the 20’s.

Any snow accumulation on grassy areas should be less than one inch.  Road problems are not espected.