Friday, Feb.24, 2017 Noon

A strong storm forming between St. Louis and Chicago will intensify rapidly during the day as it moves quickly northeast into Michigan.  North and west of the storm track heavy snow is likely.  However, the “warm sector” south and east of the storm will remain dry most of the day as we wait for a supply of moisture to arrive from the south.  Once the moisture gets north,  the strong dynamics of the parent storm should have no problem producing some severe thunderstorms.  Primary threat will be strong winds.  Hail is a slight risk while tornado chance is pretty close to zero.

This system is similar to the last time severe weather was widely advertised, but failed to show up.  The problem is with the moisture.  The dynamics with the system are tremendous, but the thermodynamics are quite weak.  So, once again, the various models are relatively low on the “probability” of storm formation, but the so-called “conditional probability” for severe storms is high.  What that means in normal people-speak is that the overall chance for a thunderstorm hitting you is small (about 30%).  But IF a thunderstorm forms, there is a high chance it’ll reach severe levels (about 50%).    So, if you multiply the two numbers you get a roughly 15% chance for severe winds within 25 miles of your home tonight. Obviously, the chance at any single point (your home)  is much lower.

The models agree well on timing.  The arrival of the cold front trailing the surface storm and sufficient moisture to generate thunderstorms should be about the same time.  Best timing for Louisville looks like between 8 and 10 P.M.  While some storms should form west of Louisville earlier, this system shouldn’t get well organized until it gets east of I-65.  Areas east of Louisville have a greater chance for wind damage than we do.  Best chance looks like 9 P.M. until Midnight for areas east of I-65.

Caution

As always, you’ll be hearing a lot of hype about storm potential this afternoon/evening.  What you’ll be hearing will be “the worst case scenario.”  Luckily, nature rarely reaches our hyped up expectations.

Friday, January 27, 2017  4 P.M.

A weak upper air disturbance this morning brought us some flurries and a second one will bring us some more flurries for the evening rush hour.  With temperatures safely above the 32-degree mark, no problems are expected.

Cold weather should remain through the weekend with additional weak disturbances bringing additional periods of flurries.  Finally, a much stronger upper air system will cross the area Sunday afternoon and evening.  This is expected to upgrade the flurries to  a period of light snow and/or snow showers.  This morning the GFS and NAM were far apart on their portrayals of what the result will look like, but now the NAM upping its game toward the GFS solution.  But, don’t get too excited – even the “stronger” GFS still keeps snow expectations below one inch.

The current outlook for Sunday calls for some light snow/snow showers between (roughly) 3 P.M. and 8 P.M.  This should not have much of an effect on surface roadways, but bridges/overpasses/etc. could get some slick spots.  Snow accumulation should be light – anywhere from a dusting up to an inch.  For Louisville, about a half inch seems likely.

Bummer

My post earlier this week has already proven me right and wrong.  My long time conviction that long range prediction is  a fool’s game has been proven yet again.  But, my insistence to try it anyway is where I went wrong (probably).  My idea that the cold air arriving this weekend would hold through next week will not happen – unseasonably mild weather will return for next week.  Further, I said that some really cold weather should arrive around Super Bowl time – that part will probably hold, although it’s not looking quite as cold.  The worst part of my “outlook” was that the below normal trend should continue through most of February.  Sadly, that appears to no longer the case.

Moral of the story:  I should follow my own advice!

Saturday, August 13, 2016  11:45 P.M.

What a miserable week of forecasting we’ve been victimized by all week and the worst is still happening.  Thursday and Friday the forecasts, aided by the ever-willing media hype made it sound like we were due for ark-building rains.  Only one thing was wrong – the models had already backed off of the extreme rain forecast by THURSDAY.  By Friday, the models had backed off the threat of heavy rain even more.  It was obvious that heavy, flooding rains were out of the picture for today and Sunday.  So, the NWS did the “obvious” thing – issued a Flash Flood Watch for Louisville area and southern Indiana.

Today worked out just the way the models predicted – a few very light showers in the metro area with heavier rain over central Indiana.  However, the Flash Flood Watch was expanded over a larger area Sat. morning…ever though the NWS forecast had reduced the chances for rain by about 20% or so for next 48 hours!

A few showers are possible overnight, but very little, if any, rain is likely for Sunday and heavy rain Monday will stay far to our west.  But, the Flash Flood Watch remains in effect through Monday.  My advice to the NWS is pretty simple:  Stop hyping a dead forecast…it died a long time ago.

Thursday, March 31, 2016

Today is another situation where we have a very fine line between strong thunderstorms and a marginally “severe” storm or two.  Nothing really to worry about as the situation just can’t quite get its act together.

Large trough dropping into the midwest will slowly push eastward tonight and tomorrow.  A strong short wave disturbance is rotating around this trough and aiming for the south.  The northern halves of AL and MS as well as western TN  should see a significant severe storm outbreak this evening and tonight.

Meanwhile, a much weaker short wave is moving over western KY right now and is generating a cluster of showers and thunderstorms as it moves toward us.  Look for this rain to reach Louisville about 4 P.M. and depart before 7 P.M.  Some of the embedded thunderstorms could be strong but should not reach into the “severe” range.  (Although with the trend of recent years for the NWS declaring almost any strong thunderstorm “severe”,  I would not be surprised if a  warning or two is issued.)  Keep in mind that a 58 mph wind (the lower limit of severe storms) will do a lot of damage.  Compared to a 50 mph wind gust (which doesn’t do a lot of damage, a 58 mph wind gust has about 35% MORE FORCE!

Later tonight, a cold front will cross IN into KY.  This front should become very active in the next few hours.  Severe thunderstorms will be possible with this front, especially over western and south central Indiana from about 6 P.M. to 9 P.M. EDT.  The southern end of this area will reach the Louisville between 9 P.M. until midnight.  No severe weather weather is expected with this line.  In fact, there’s a reasonable chance it’ll die out before reaching us.

Wednesday, Feb. 24, 2016

As the major surface low pressure area moved right over the area this morning, we actually got a break from the heavy rain and even saw some sunshine with temperatures in the upper 50’s for an hour or two.  Then, as the low moved northeast, the colder air on it’s backside dropped temperatures in a hurry…and the rain resumed.

But, we’ve seen the worst  of it now.  Winds will start decreasing this evening and the rain, possibly changing to snow, will be diminishing between 7 P.M. and 9 P.M.  After 9 P.M., light rain showers and/or snow flurries will be scattered around the area during the night.  Whether we have  rain or snow  showers doesn’t make any difference.  If it’s snow, it’ll melt on impact so there’ll be no accumulation – so it essentially makes a situation I like to call “white rain.”  It has the same impact as rain.

Temperatures should remain above freezing in the Louisville area, so traffic problems should be no worse than wet roads.

4-5 days ago the models were predicting a major cold air outbreak to hit the eastern half of the country this weekend.  But, nature didn’t seem to get the message – in reality the cold air is pushing east rather than south.  So, now it looks like a cold day tomorrow followed by warming Friday into the weekend.  Not as warm as last weekend, but still very nice for late February.

Note:    I know some forecasts floating around include the possibility of up to an inch of snow (on grassy areas), but that idea seems to me to be a real outlier.

Monday, 2/8/2016

Beautiful snow shower passed by my house this morning…left a nice coating of snow, but now it’s just about all gone.  Additional snow showers are likely with much the same result – melting soon after the shower passes.  Some accumulations on grassy areas, but roads remain wet.

It’ll arrive a little earlier than I thought yesterday (see Super Sunday blog), but the small pocket of upper air energy is still on target to bring us more, perhaps heavier,  snow showers this evening.  It looks as though the best chance for snow accumulations will come between about 6 P.M. – 10 P.M. tonight.  After that, it looks like more of a “flurries” regime than a “snow showers” one overnight.  I still expect road problems tonight and tomorrow morning’s rush hour.

Due to the “hit ‘n’ miss” nature of the snow showers, snow accumulations by tomorrow morning could be quite varied.  I expect that most of the area will receive at least one inch of snow, but areas hit by one or two of the heavier snow showers this evening could easily reach 2″ -3″ (or higher) by morning.

It’ll be very cold tomorrow…temperatures should remain in the 20’s all day with gusty winds and flurries to add to the uncomfortable conditions.

Super Bowl prediction:

I was happily surprised with yesterday’s game.  Didn’t believe the Broncos could pull it off.  Their offense wasn’t going to win any championships, but that incredible defense took care of stopping Cam and co. as well as doing much of the job for the offense!

So,  congrats to the Broncs…Kent Taylor must be happiest man in Louisville today!

Tuesday, 2/2/2016

First, the Wind Advisory…

...WIND ADVISORY IN EFFECT FROM 1 PM THIS AFTERNOON TO 7 AM EST
WEDNESDAY...

.THIS AFTERNOON...CLOUDY WITH SCATTERED SHOWERS AND
THUNDERSTORMS. HIGHS AROUND 70. SOUTHEAST WINDS 10 TO 20 MPH.
GUSTS TO AROUND 40 MPH IN THE AFTERNOON. CHANCE OF PRECIPITATION
40 PERCENT.
.TONIGHT...BREEZY. SHOWERS AND THUNDERSTORMS. SOME THUNDERSTORMS
MAY PRODUCE DAMAGING WINDS. LOWS AROUND 50. SOUTH WINDS 10 TO
25 MPH WITH GUSTS TO AROUND 40 MPH. CHANCE OF PRECIPITATION NEAR
100 PERCENT.

Now, here is the NWS definition for a Wind Advisory…

Wind Advisory

A Wind Advisory is issued when the following conditions are expected for 3 hours or longer.

1) sustained winds of 31 to 39 mph    

AND/OR

2) wind gusts of 46 to 57 mph.

Notice anything unusual?  Yes, the forecast doesn’t came anywhere close to the definition.  And, this is the third time they’ve done this in the past couple of months!

So, let’s put it this way…it’s going to be noticeably windy this afternoon and tonight.  But, Wind Advisory criteria?  Very doubtful.

Severe weather situation

As a massive winter storm moves slowly NE out of Kansas toward the western Great Lakes, a major outbreak of severe storms is expected along the Mississippi Valley late this afternoon into early evening.  The western third of KY and southwestern IN could be hard-hit.  But for the Louisville area the situation is much different.

As is often the case with winter severe storm outbreaks, the dynamics (wind fields, etc) are very strong.  But the thermodynamics (temperatures, moisture, etc) are weak.  Sometimes, the dynamics can overwhelm the weaker thermo and wreak havoc.  That is expected late this afternoon and early evening along and near the Mississippi River.  Severe storms and some strong, long track tornadoes appear possible.

During that time, the thermodynamics will be at their peak.  But, the models never bring any positive thermos into central KY or southern IN.  Any instability dies quickly to our west after 6 P.M.  As the cold front slowly advances eastward, the expected severe storm areas consolidate into the line of gusty winds and very heavy rainfall as it approaches the I-65 corridor.  Biggest threat for our area should be flash flooding.  It’s possible we could see 2″-3″ of rain in a few hours, so watch out for flooding in low-lying areas.  If flooding is going to occur, it should be Midnight or later

As for the timing of the windy, rainy and possibly stormy weather…  For the Louisville area, the primary squally system should pass the area between 10 P.M. and 2 A.M.

Note:

The definition of the severe thunderstorm is Winds reaching 58 mph or higher and/or one inch hail.  I don’t believe either of those items will occur in the Louisville area tonight.  NEVERTHELESS, I do believe a Severe Thunderstorm Warning will be issued locally.  After all, can anybody remember the last time a moderate to strong line the thunderstorms has passed Louisville WITHOUT a warning being issued?  (It’s kind of like that Windy Advisory thing.)

Stuff:

I was happily impressed with the Cardinals win over UNC last night.  Good testament to the character of the team to bounce back from Saturday’s game with UVA.  It also speaks well for a team, such as UVA, that can completely change a game with their exceptional defense.