Very Cold for Christmas Weekend

Snow should be on the light side

Dec.19, 2022  4:30 P.M.

When I started forecasting weather for the Louisville area in 1969, I had one major point of emphasis about weather forecasting:  Don’t ever believe a weather forecast for more than 3 days ahead.  Weather forecasting has improved significantly since then, so,maybe, that could be extended by a day or two.  But the point is, we do not have perfect forecast models.  Nor can we measure weather parameters – humidity, temperature, winds, etc – precisely.  And, to make matters worse, when we measure our weather data, it’s at random spots on the Earth.  Forecast models are set to run on a precise computer grid.  The data is seldom measured at the grid points, so sophisticated smoothing systems have  been created to fit the data to the grid.

Thus, before forecast models even begin computing, we have three significant areas of known error sources within the system.  I am amazed at how well the longer range forecast models perform…most of the time.  But as good as the modern models are, they are not perfect!

So why do professional forecasters continue to believe them?   Why so much hype 7 to 10 days before an event is due to happen?

I can’t answer those questions, even after 50 years of trying.

This week

We are currently in one of those major “hype” situations.  The major outbreak of arctic air set to arrive Thursday night has been predicted to arrive “in 7-10 days” since before Thanksgiving.  So after many misfires it’s actually going to happen.  Since last week, the models have been predicting some pretty dire weather for much of the nation east of the Rockies.  The local outlook was for 4″-6″ of snow, very strong winds and a possible flash freeze in addition to frigid temperatures.  Keep in mind, this forecast was for at least 7 days ahead,

No matter!  The hype machine jumped into full gear.  By the weekend all the talk centered around a massive pre-Christmas storm of legendary proportions right here in Louisville.  But, as should be expected, the forecast models slowly made “adjustments” to the forecast.  Those incremental changes have greatly altered the forecast and possible consequences for us.  Even the most extravagent hypists should have it figured out by now.

This being Monday and the actual event is likely Thursday night, I expect more changes to occur during the days ahead.  Nevertheless, here’s what I’m currently expecting later this week:

Slowing warming temperatures tomorrow through Thursday midday.  Rain should move in Thursday afternoon and change over to snow Thursday evening.  Snow will last 2-3 hours with accumulations around 1″ – 2″.  Very windy, with temperatures dropping into the single digits by Friday morning.  Friday remains cloudy, windy and cold with snow showers and flurries.  Additional accumulation up to an inch.  Temperatures will reach only the lower teens.

Note: the possibility of a Flash freeze Thursday is much lower now than earlier thought.

Severe storm chance very low this evening

Possible severe storms stay north of Louisville

Wed. June 8, 2022 5 P.M.

Storm Prediction Center did a good job of narrowing in on the severe storm threat area over southcentral and southeast Indiana.  However, they pushed their Tornado Watch box too far south.  Or did they?  More on that later,

Back to the current weather, the primary factors for severe storms have already moved east of I-65, so damaging weather threat is generally over for the Louisville area.  However, a weak wind shift line/cold front is trying to form over southern Indiana.  That will give us about a 30% chance for a thunderstorm around 7-8 P.M. tonight.  Then a little cooler, but much drier day tomorrow.

Tornado Watch?

As mentioned above the Storm Prediction Center pinpointed the severe threat today very well.  In fact the boundaries for the Watch they issued did not include extreme southern Indiana or  metro Louisville.  Their southern boundary was about 40 miles NORTH of the Ohio River near Louisville, where it should have been.

So what happened?  In recent years local Weather Service offices have been given the leeway to “alter” the SPC Watches.  So today they decided to change the prediction to include the Louisville area.  Seems to me we saw another case of CYA this afternoon.

To the uninitiated, CYA is a long-running acronym for “Cover Your A–”

Good job SPC!  Not so good, locals.

No severe weather expected tonight

6 P.M. Monday 6/6

Storm cluster weakening

Satellite, radar and lightning data all have shown a rapid decrease in storm intensity in the northern half of the convective system moving across the region.  A couple of severe storms could still pop over far southern KY, but the rest of us will receive a good soaking this evening.

Widespread severe storm outbreak this evening/tonight

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

Quick update on tonight’s snow forecast

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.

Winter makes a brief comeback

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.

Storm updates

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.

Very Windy afternoon

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.

New terminology for an old excuse

5:30 P.M. Sat., Feb. 5, 2022

Got a good laugh from this morning’s CJ.  When asked by a reporter, “What happened to the big ice storm?, a National Weather Service forecaster replied that the storm had “underachieved.”   Essentially saying that our forecast was correct and nature was wrong.  Give me a break.

A little background

When I arrived in Louisville in 1969, I heard many stories about a long-time Head of the local “Weather Bureau”, as many people called it back then. O. K. Anderson was his name and he was closely associated with phrases like, “It was coming our way, then this darned Ohio Valley changed its path and ruined everything.”  “This darned Ohio Valley” got blamed for all the missed forecasts.

He was correct, the Ohio Valley does alter weather systems.  My reasoning, however, was that the Ohio Valley has been basically the same for thousands of years.  Shouldn’t it always alter weather patterns the same way?

It took several years (and some pretty bad forecasts), to start seeing patterns of behavior difference between the forecast models and reality.  After awhile, I developed enough confidence to actually use those observed differences in my forecasts.  What an improvement that made.

But, back to my original point.  Over many years, forecasting improved a good bit but winter storms still were the source of quite a few “misses.”  And snow and ice forecasts were far more noticeable than anything else.  It’s like this:  if you forecast rain, it doesn’t really matter whether it rains .1″ or 1″,  it still “rains.”  But if you predict one inch of snow and you get 10″, everybody notices.

When forecasts didn’t pan out, I kept hearing two specific phrases.  “We got lucky” and “We dodged the bullet”  are still used regularly.  I’ve been telling people for decades, if you hear either one of those phrases, what they are actually saying is, “I was wrong.”

So, we’re back to 2022 and we have a new entry to our list of excuses.  At least twice this winter I’ve read from the NWS, a storm underachieved.  So now, you can blame a missed forecast on “the Ohio Valley”, “we were lucky”, “we dodged the bullet” or “the storm underachieved.”  Any way you say it, it means “I blew it.”

Note 1:  We’re all human.  We all make mistakes.  Some people just can’t admit it.

Note 2:  This is exactly the same reason that has brought us the so-called “climate crisis.”

A Eureka moment?

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.