Biggest part of damaging weather will stay south of Louisville

Wed., April 13, 2022  4:30 P.M.

The atmosphere  is set to produce a significant severe weather outbreak over the next 6 hours, or so.  Wind fields are very strong (more so than usual).  The moisture/heat component is high enough locally, but remains much more conducive to severe weather several hundred miles south of here.  The Storm Prediction Center is highlighting the northern half of Alabama, western half of Tennessee and the southwestern corner of Kentucky as the area of highest risk of the “big three” severe storm events – hail, high winds and tornadoes.  Tornado Watches cover most of that area at this time.

While locally, we’re not in nature’s “bulls eye” but we are still under some risk, especially for strong wind gusts.  A squall line/cold front will quickly cross the area this evening.  Our highest threat for severe storms here will be between 8 P.M. and 10 P.M.  Thunderstorms should produce strong to severe winds and heavy downpours.  An isolated “spin-up”  tornado or two will be possible, especially south of Louisville.  Note:  Spin-ups tornadoes sometimes occur in the area of “kinks” along the line of thunderstorms.  They usually last only a few minutes and fall on the low end of the tornado family – F0 and F1.

Even though 8 to 10 P.M. will be our highest threat time, additional thunderstorms/heavy rain will not leave the area until around Midnight.  Some minor flash flooding could occur

Friday, March 11, 2022  Noon

In reference to yesterday’s blog, as expected the NAM still seems to have the better solution.  The GFS and other models now pretty much agree with the NAM.  On the large scale picture the result should be overall less snowfall for eastern KY and the Appalachian region than previously expected.

For Louisville area, my latest idea is this.  Rain/snow arrives in Louisville area around 6-7 P.M.  Snow becomes dominate from 8 P.M. until Midnight.  Only flurries after that.  Temperatures remain around 32 degrees during the snow so major roadways will only see minor accumulations due to above freezing surface temperatures.  Snow accumulations  on grassy areas should be up to one inch in metro area with higher accumulations south/east of Louisville.  Highest accumulations (2″ – 4″) along central I-75 and east.

Mostly sunny tomorrow with high around 30, but back to near 50 by Sunday.

Thursday, March 10, 2022  6 P.M.

All week the models have been predicting a seasonably cold air mass to reach our area late tomorrow.  They were expecting a quick drop in temperatures from the 50’s during the afternoon, then dropping to near 30 by Midnight.  Meanwhile, the cold air would be able to squeeze some snow out of our relatively dry air.  Snow forecasts averaged about an inch.  Cold air would stick around Saturday with a strong warming beginning Sunday.

Then, this morning’s models started to upgrade the situation(s).  I use the plural because this morning the GFS and NAM models had two distinctly different solutions on how this situation will play out.  The primary headline is that they both end with the same large scale solution – a large spring snowstorm dropping 4″-6″ over southern  and eastern KY tomorrow night then sweep along the Appalachians with 5″-8″ of snow Saturday.

Without getting into too much explanation, while getting to the big picture the GFS paints a snowier picture for us near the Ohio River.  The GFS puts about an inch of snow for far southern Indiana.  About 40 miles either side of the river it predicts about 1″-2″ of snow.  Sliding south and east of Louisville you quickly get to 3″, then 4″+.

The NAM, on the other hand, keeps the band of heavier snows farther south of the Ohio River.  It predicts about 1″ for Louisville (lower north of the river, more south of the city).

As I’ve mentioned before, normally the GFS is a little better than the NAM.  In this case, however, I like the NAM’s solution – about an inch of snow tomorrow night from about 8 P.M. until 1 A.M.

We’ll give it another look tomorrow.

4:15 P.M. Thursday, Feb. 17, 2022

Better news!

Some big changes from earlier.  Wind gusts will be much weaker than previously expected.  Louisville area and Southern Indiana wind gusts will most likely stay in the 30-38 mph range.  No longer a serious damage threat here.

However, wind gusts up to 40-45 mph will still be likely until about 8 P.M. over southern and eastern KY.

Another change…the prospect for severe thunderstorms over southern KY has dropped to a very low level.

For the Louisville area, periods of heavy rain will move through the area for the next hour or two.  Rain will end over the area between 6 and 7 P.M.  Then cold weather moves in overnight.

12:30 P.M. Thursday, Feb.17,2022

Powerful upper air system – weak surface low pressure.  That pretty well sums up today’s weather pattern.  Those upper winds will translate to the surface this afternoon and evening.  Most of Kentucky will see gusts of 40-50 mph between 3 P.M. and 7 P.M.  The strongest wind gusts will be over southern and eastern KY.  Southern Indiana winds will most likely be in the 35-45 mph range.  Expect to see scattered power outages and downed trees/limbs as well.

Heavy rains will be likely throughout the area this afternoon.  One to two inches possible in some spots (especially north of the Ohio River) in just a few hours.  Flash flood prone areas will likely see some flooding.

The biggest question regarding this system is the possibility of severe thunderstorms.  Sometimes  very strong dynamics will overwhelm weak (or no) instability and do all the work itself.  Most likely, this system will be one of the overachievers.  But, luckily, not for the Louisville area or southern Indiana.

A weak surface low pressure is expected roll up the Ohio River this afternoon/evening.  That provides us protection from severe thunderstorms.  However, along and south of the Western KY Parkway, enough instability will probably develop to allow damaging thunderstorms.  High winds will be the primary threat.

This type of system has a history of strong nighttime tornado outbreaks over the deep south.  Tonight should be no exception.  Most of Mississippi, northern Alabama and western Tennessee have the highest risk.

1 P.M. Thursday, Feb. 3, 2022

For several days I’ve been been looking at model after model after model etc trying to figure out today’s expected icy weather.  Even this morning, five different models are giving different outcomes.  Those results have told me one thing that I didn’t want to know – my expectation for mostly sleet was wrong.  But, it finally brought me the answer.  An old expression from my college days popped into my head – “The last wave on the train is always the strongest”.

I’m not going to explain that now.  Let’s just say the last wave will cross southern and eastern KY this afternoon and evening.  And, it’s a little stronger than the models picked up on earlier.  That changes everything.

In general, the added strength of the wave will slow the progress of the cold air south of the Ohio River and delay the onset of freezing rain entering Kentucky.  The predicted major ice storm won’t get started until most of the moisture is gone.  It’s doubtful that any part of the Commonwealth will get over .25″  of freezing rain.  Most of central and southern KY will see very little.  No big problems with ice.

This last wave will produce periods of moderate rain until about 5 P.M.  Then, as the rain intensity tapers, colder air will arrive.  So we’ll see a few hours of light freezing rain and sleet from about 6- 9 P.M.  After that,  periods of light snow/flurries will continue overnight. Total accumulation of sleet and snow of up to one inch by morning.  Icing of perhaps .1″ to .2″.

Travel conditions should remain generally good through the evening.  As always, the primary concern will be freezing of bridges and overpasses after 6 P.M.

In summary:  the predicted major ice storm will be a dud.

NOTE:  The above discussion refers to Kentucky only.  For Indiana (except for the extreme southern edge), A major winter storm is going on.  From freezing rain and sleet near the river to heavy snows farther north, the Hoosier state travel will be hazardous.

6 P.M. Monday, Jan. 31, 2022

Three days ahead is a very difficult time to figure out what a storm system is going to do.  Never one to shy away from the attempt, however, here’s what the models are telling me today.

1).  Heavy rains are likely Wednesday and Thursday.  2″-3″ are possible.

2).  Another huge mass of cold air is dropping out of Canada and will be dropping only very slowly southward.  Upper upper air winds will be opposing the southward push of cold low level air.  The result will be a very shallow cold air mass reaching us during Thursday.  That is a big indicator for freezing rain and sleet, not snow.

3).  Thursday morning we’ll see rain with slowly falling temperatures during the day.  About 40 deg at morning rush hour sliding to the lower 30’s by evening rush hour.  The southern half of Indiana should be in freezing rain by morning with sleet farther north of the Ohio River.

As temperatures cool  freezing rain could move south of the Ohio during the afternoon.  Freezing rain should be of little consequence for Louisville during the day.

4).  Thursday evening,  precipitation will diminish quickly with a period of sleet/snow.  Accumulation of snow/ice should be less than one inch.

5).  A significant ice storm is likely over southern Indiana (except counties bordering the Ohio River).

6).  Snow will not be a factor locally.  However, the northern half of Indiana should expect 6″ – 12″ of snow Thursday.