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.

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.

Monday, July 13, 2015 (3 P.M.)

Line of thunderstorms moving through Jefferson County and areas to the east have proven to be nothing more than typical old-fashioned summer afternoon “Toad stranglers”.  Once again, the brief heavy downpours may aggravate recent flash flood problems, but the rainfall has been much less than similar events recently.  Severe weather threat is pretty much over for Louisville area, for now.

On the bigger picture, the expected westward expansion and intensification process of the thunderstorm line over us looks as though it is finally underway.  If it continues, look for severe winds to hit many areas of southcentral and southeastern KY later this afternoon before reaching Tennessee by evening.  Currently, the strongest thunderstorms are concentrated along the I-75 corridor.

Later this afternoon, another cluster of severe thunderstorms is expected to break out over northern IL and IN.  This system should drop southeastward this evening and reach the Ohio River area by midnight or later.  This afternoon’s thunderstorm has taken a large amount of energy out of our atmosphere, so if this system moves as expected, any thunderstorms we get should be less of a threat than the current line – except for the heavy rain/flooding threat.

Monday, July 13, 2:15 P.M.

Just finished a nice post describing current situation, but it was lost in internet-land.  So, a brief capsule.

Storms entering Louisville area have failed to develop as expected (so far).  Quick line of thunderstorms will drop southward through Louisville are between 2:30 and 4:00 P.M.  Heavy rain and strong gusty winds are likely.  A few isolated severe wind gusts are possible, especially east of Louisville (Oldham and Shelby Counties).  Little threat of damaging weather west of I-65.

Monday 1:30 P.M. May 11

A Tornado Watch for areas north of the Ohio River (and a small area of Kentucky near Cincinnati) has been recently issued.  But, a quick look at the radar clearly shows any threat to the Louisville has already moved east of the Louisville.

Models are in good agreement that a process known as “bridging” is occurring over the lower Ohio Valley.  That definitely is a downer for severe storms locally AND could very well mean no rain at all from this system.  That’s another big downer since it looks like we won’t get another serious rain chance until early next week.

Meanwhile, back to bridging – sometimes when a storm system moves northwest of us (the big weekend storm-maker is finally leaving the southern plains) it shifts most of the energy northward toward the Great Lakes while leaving a lot of the major moisture over the south. Then, mid-level winds become westerly and drive a wedge of drier air between the northern energy and the southern moisture.  That’s exactly what’s happening today.

Yes, there is a threat from severe (maybe tornadic) storms with the northern system, but not over southern Indiana.  Best chance of severe storms lies north of Indianapolis.  Meanwhile the southern part of the system now is energy-shy but should still produce thunderstorms later today from Tennessee southward.

So, where does that leave us?  Pretty much in no-man’s land.  Bridging is occurring over southern Indiana and most of Kentucky.  There’s still a chance we’ll see showers or a thunderstorm between 5 and 8 P.M., but the probability has dropped to the 20%-30% range.

Oh well, at least it’ll be cooler tomorrow.

4:45 P.M. Tuesday (April 7)

Line of strong thunderstorms moving toward Louisville has been the source of numerous Severe Thunderstorm and Tornado Warnings over the past hour or two.  So far, upper circulation has been noted but no reports of any actual tornadoes.

Radar indications are showing the small line shifting southward while the northern edge is becoming more obscured due to heavy rain.  If this trend continues (it should), the greatest threat to the Louisville area will be just south of the city – northern Hardin, Meade and Bullitt Counties should see strong winds and heavy rains.  A small (weak ) tornado is not out of the question.

Meanwhile, the northern half of the line approaching the Louisville area will lose it’s severe weather threat, but still bring heavy downpours and gusty winds.  All activity should pass east and south of Louisville by 6 P.M.

Note:  4:55 P.M. 

Quick radar update shows line acting as described  above.  Primary severe threat will pass south of Louisville.  Northern area seems to be weakening quickly,  Thus, severe threat for Jefferson Co and Clark and Floyd Cos. will be very low.  Meanwhile, northern Hardin and Bullitt Co. will be hardest hit, maybe with severe winds, but tornado chances are very low.