Thursday,March 19, 2020

Flash flooding likely: severe storms iffy

A fairly strong upper air disturbance will come across the lower Ohio Valley tonight.  Lucky for us, it’s focused mostly on Indiana.  With this upper system, we’ll see two clusters of thunderstorms overnight.  With the rains of the past two days, periods of heavy rain, especially over southern IN, will pretty much guarantee widespread pockets of flash flooding over northern KY and southern IN.  If you live in a flash flood-prone area, you know the drill.

The first cluster of thunderstorms will be over the area this evening.  The southern side is weak and will provide plenty of rain to west and central KY and initiate some of the expected flash flooding.  But no severe thunderstorms.

The first cluster of storms will be more noteworthy over the southern half of Indiana.  Severe storms are moving over southern Illinois and will race eastnortheastward.  Heavy downpours are likely and a few severe storms will be possible between, roughly, 8 P.M. and Midnight.  Primary threat will be strong winds and possibly some hail.

The second cluster of storms will move through the area between about 2 A.M. and 8 A.M.  This one is much stronger and is likely to produce an outbreak of severe storms from Arkansas, southeast Missouri and southern IL this evening.  By the time this cluster arrives in the Louisville region, it is likely to be weakening.  Plus, atmospheric instability will be diminishing. Also, the strongest dynamics will remain north of our area.

The result will be a very noisy night north of the Ohio River.  Flash flooding will probably become  a serious problem.  Storms will be strong, but probably not severe.  Along and south of the Ohio River, the primary line of thunderstorms most likely won’t arrive in Louisville until 5 A.M. or later.  They will not be very strong, but deposit enough rain to make a very messy rush hour before the exit the area by 8 A.M.

Strongest storms will stay south and west of Louisville

Thursday, March 12, 2020  4:45 P.M.

Latest radar trends and short term forecast models are strongly indicating that we’ll get plenty of rain this evening, but severe weather will not reach the Louisville area.  Severe storms are forming along the approaching cold front over western KY and dropping rapidly southeast.  That area of severe storms is heading toward central Tennessee.

Meanwhile, area of showers and non-severe thunderstorms has been expanding over  SW IN and is moving our way.  Cold front may produce some gusty winds as it passes through the Louisville area between 6:30 and 8:30 this evening.  Our biggest problem will be with heavy rain and possible areas of flash flooding.

Thursday, March 12, 2020  4 P.M.

Cluster of rain/thunderstorms in the area now is not showing any signs of severe weather,  Instability is very low, but the dynamics are quite strong.  Nevertheless, severe weather is not expected with this area.  However, stronger storms appear likely later this evening.

Current showers/t-storms are forming along a warm front slowly pushing north.  Once we get into the warmer/moister air south of the front, we’ll have the potential for slightly higher instability for a few hours.

During that time, a cold front will be moving over southern IN/western KY.  That system should pass through our area between 6 and 8 P.M.  The front is already creating severe weather to our west.  Instability should still be weak, but the wind fields will be strong enough to create a strong wind threat – possibly severe (58 mph or more) in a few areas.  Atmospheric structure favorable for tornadoes should remain south and west of Louisville.

After 8 P.M., threat for severe weather will move south and east of Louisville area.

Fri., Feb. 7,2020

Weak Clipper brings a little more snow

A weak Alberta Clipper dropping into the Ohio Valley tonight and tomorrow morning will leave a minor calling card in its wake.  Available moisture is lacking and the clipper does not appear strong enough to force much lifting this far south.  The clipper’s path is expected to pass over southern IL/IN.  That sets up central IN for a possible 1-3″ accumulation tonight and early tomorrow.

Meanwhile, south of a clipper’s path, not much happens.  In reaction to the clipper moving north of us, we’ll see southerly winds tonight.  That’ll hold temperatures in the low to mid 30’s.  Precipitation south of a clipper’s path historically is little or none.  So, even though some light snow is possible late tonight and tomorrow morning, accumulation will be in the “little or none” category.  Probability for measurable snowfall is about 50%.

Tomorrow morning marks the last snow chance for about a week, at least.

Wed., Jan 22, 2020 4 P.M.

Flip flops are the latest model fashion

Two weeks ago, the models were forecasting a major pattern reversal over North America.  Winter was finally on the way.  Seven days ago, the models had reversed themselves – abnormally warm weather would remain well into next month. Now, the models have undergone a “reversal reversal.”  In other words, the forecast again favors below normal temperatures taking over during the next 7-10 days.  This time, however, the Euro model is even colder than the GFS.

It’s all very confusing, but here’s what’s most likely for the next few days.  A deepening upper level low will push from the southern Rockies tonight to a position right over top the IN/KY by late Friday.  Ahead of the storm we’ll be mild with periods of rain from late tomorrow into Friday.  As the low moves over us rain showers will probably change to snow showers Friday night into Saturday.  It’ll be too warm for any accumulation on roads, but some minor accumulations are possible on grassy areas.

After that, warming will be back early next week followed by rain, then colder.  GFS and Euro predict another storm with rain to snow next Fri/Sat, but forecasts that far in advance this winter have met with pretty poor results.  We’ll see.

Thursday, Jan. 16, 2020

Not again?!

Today’s GFS is really cutting back on its pattern-reversal forecast.  Today’s runs push any cold phase arrival back a week, at least.  It’s quite a bit weaker than last weeks storm, but another west coast storm is developing and heading toward a northern cut across the central U.S. Saturday.  Following that, Sunday thru Tuesday will be the coldest days we’ve seen in almost a year.

That was supposed to be start of a long term cold period. But, now the GFS is predicting yet another major west coast storm moving into the central Plains the next weekend.  Even after that, it’s holding off on a pattern shift.

The Euro model has been a little hesitant on the magnitude of any pattern change for the past week.  Now, it too is backing off.

The GFS has been doing this to us for six months.  I’m still hoping that one of these times, it’ll actually happen.