Update  5:25 P.M.

The line of storms did strengthen, but not much.  Line should push across Jefferson County without any significant problems.  East of Jefferson County, the line should be stronger, with possibly a severe storm warning or two this evening.

On the positive side, the squall line will actually decrease the strong wind fields  for an hour or two

Update  4:45 P.M.

Radar IS showing a definite uptick in strength of the approaching thunderstorms.  Between now and 6 P.M., expect a line of strong thunderstorms to move across the metro area.  Expect brief heavy downpours, additional strong gust winds and possibly some hail.

4:15 P.M. Thurs., March 14, 2019

Line of storms still crawling eastward

As of 4 P.M. the only strong-to-severe thunderstorm left is racing across northern Clark Co. IN.

Elsewhere, the remaining narrow line of storms still lies west of the Louisville area.  No severe activity has been noted in the part of the line headed our way.

The items above have worked about as expected since the weakening trend noticed a couple of hours ago.  However, we are not out of the woods yet.  One of the two short-term models predicts the line to re-intensify as it approaches I-65 and become strong again east of I-65 for a few hours this evening. That’s the HRRR model.  It’s partner, the RAP, does not.

As of this time, local radar does not show any rebuilding… yet.  If that continues and the RAP is correct, we should have minimal effects from the squall line. However, we’ll have to watch out for any intensification of the line as that would increase the potential for possible severe wind gusts – especially along and east of I-65.

WOW

I just noticed that the airport reported 61 mph wind gusts earlier this afternoon.  Bowman Field’s top gust reached 56 mph.  Ft Knox topped out at 53 mph.  Mostly likely, if we do get thunderstorms in the next hour or two, they won’t match those winds!

2 P.M. update

Thursday, March 14, 2019

1).  Recent data shows the upper and lower atmosphere are beginning to “uncouple.”  That means the “sweet spot” of atmospheric conditions that has spawned the severe weather to our west for the past few hours is beginning to fade.

2).  The weakening has enabled the line of storms to slow its eastward progression.

3).  New “best estimate” for pushing through Louisville Metro is now 4:30 to 6 P.M.

4).  Until then, surface winds will continue to be very gusty – up to around 40-45 mph.

5).  When thunderstorms arrive, the primary threat will be strong wind gusts – up to 50 mph or so.  Tornado threat has lowered.

1 P.M. update

Supercells still forming over west KY into SW IN.  Several tornadoes have been reported.

Adjust time of arrival in Louisville area to 3 P.M. – 5 P.M. Otherwise, discussion below still looks okay.

March 14, 2019  Noon

Potentially Damaging Storms late this afternoon

One change since yesterday’s post is the addition of additional moisture into the equation.  The very strong wind fields are still in place.  Now with the added moisture, it looks like nature’s two primary severe weather producers – dynamics and thermodynamics – will interact for a few hours this afternoon.  Luckily for us, the worst should be over before reaching the Louisville area.

Super cells are moving along the Ohio River in western KY and southern IL.  Several warnings have already been issued.  This area of severe weather will move rapidly northeast into southwest IN and then central IN over the next few hours.  It will not affect the Louisville area.

With afternoon heating, additional super cells are likely to form.  Models continue to put the primary threat north of the Ohio River.  However, I wouldn’t be surprised to see additional development over western KY early this afternoon.  Any super cell will be capable of producing large hail and tornadoes.

The threat to Louisville area will be between 4 P.M. and 7 P.M.  as a scattered to broken line of thunderstorms moves through.  Primary threat by that time should be strong winds, but depending upon how things evolve over the next few hours, it could get worse (or better).

Updates to follow…

Noon, Sat. Feb.23, 2019

Rain, thunder late this afternoon into the evening

Some quick notes…

1).  The forecast for the Ohio River flood in Louisville has lowered about four FEET since yesterday.  Rise above flood stage about midday tomorrow…crest just over 25 feet Tuesday.

2).  Strong storm over the upper midwest will push a cold front through the area this evening.  Showers and thunderstorms will be likely between about 4 P.M. and 10 P.M.  Rain: between .5″ and 1″.

3).  Severe weather is not likely, but we will have strong winds during the night.  Wind gusts are likely above 30 mph over much of the area.  Some gusts could reach into the 40+ mph range near thunderstorms.

4). Strong winds continue overnight and tomorrow – we could see gusts into the 35-45 mph range tomorrow morning.

6 P.M. Fri., Feb. 22, 2019

Model differences continue

First, we’ll take a look at rain.  The GFS and NAM have lowered their rain forecast for tomorrow, but the GFS is still about a half-inch heavier.  However, both models are way down from earlier this week.  (If memory serves me, I think the NWS was talking about a 5″-8″ total for the week.  About 2″ fell earlier this week.)  Now, the GFS is around an inch and the NAM is closer to a half-inch!  Current Ohio River forecasts, which include higher rainfall for tomorrow, call for the river to reach flood stage (23′) in Louisville tomorrow late afternoon and crest early next week about 15″ lower than last week’s crest.  If current rain forecasts are correct, that crest forecast will be revised downward.  Good news for the “river rats.”

Over the next 24 hours or so, we’ll see two episodes of rain.  Plenty of heavy rain will fall over southern KY tonight.  Some of the leftovers will push through northern KY/southern IN toward daybreak tomorrow.  That’s the easy part.

Later tomorrow

I hope you’ve heard of the 3 feet of snow at Flagstaff AZ (most in a 100 years) and the 1″ at Phoenix (almost unheard of).  That potent storm is now crossing the southern Rockies and will wreck havoc over the nation’s midsection tomorrow and tomorrow night.  The storm center will stay far to our northwest, but the cold front sweeping eastward south of the storm center is expected to create severe storms late tomorrow.

The highest concentration of severe weather is expected to be over western Tennessee.  The Storm Prediction Center has dropped the northern edge of its “slight risk” area down about 200 miles since this morning.  The western half of KY is in the slight risk area, but IN has been dropped.  But, will severe weather reach as far north as us?

That’s where the models diverge again.  There is no argument about the strong wind fields associated with this storm.  But the GFS and NAM don’t agree that warm, humid air is going to get this far north.  Sometimes the strong dynamics can overcome weak thermodynamics to create strong storms, but usually you’d like go see some help from both sides of the equation.

On that point, the GFS expects the thermodynamics requirement to be met and it’s statistical output prints out a high probability for severe storms around Louisville late tomorrow afternoon or evening.  On the other hand, the NAM holds sufficient moisture south of us and has a much lower severe storm threat for the Louisville area.

This is a gross simplification, but here’s what to watch for tomorrow afternoon.  The NAM is predicting a high tomorrow around 60 – not enough to free much thermodymanics.  Meanwhile, the GFS this morning was saying upper 60’s (latest is 66).  Upper 60’s would significantly rise chance for severe storms.  Still iffy in the mid 60’s, but the lower the “high”, the lower the chance for severe.  So, watch the temperature tomorrow afternoon.  The higher it gets, the higher the storm chance goes.

So, we have the GFS’s erratic behavior lately, the NAM’s accuracy recently, and the SPC backing away from the northward moisture expansion.  As the cold passes through late tomorrow, expect to see a line of heavy showers and some thunderstorms mixed in.  Strong winds will be possible, but “severe” storms are only a small possibility.

NOTE:  By definition, a severe thunderstorm must have at least 58 mph wind gusts.  Many Severe Thunderstorm Warnings are issued for storms that never reach that strength.