Jan. 21, 2019

Previous post accidentally described the next system to reach us as a negatively tilted trough.  That is incorrect.  Trough is positively tilted.  In general, positively tilted troughs produce weak weather systems.  Negative tilted troughs are far more energetic.

Sorry for the mistake.

Click on the corrected post (to the right).

Friday, July 20, 2018 Noon

…we’ll probably get lucky.

Unusually strong summer system is dropping southeast from the western Great Lakes and should trigger numerous strong-to-severe thunderstorms this afternoon/evening.

Morning rains set up the higher moisture, now the upper dynamics have plenty to work with.  Lucky thing for us is that the next big surge of upper energy is approaching rapidly and probably won’t get enough heat energy to kick off storms until it is either right over us or to our east.

Storms should start organizing between 2-3 P.M. near I-65 and move rapidly southeast.  Some scattered severe activity is possible in the I-65 corridor, but these storms will get better organized and much more dangerous east of I-65.  Widespread severe weather is likely over the eastern half of KY this afternoon/evening.

Luckily, most (if not all) of the damaging weather will be east of the Louisville metro.

Watch the skies this afternoon.

Thursday, May 31, 2018  5:45 P.M.

Development to our west is still slow.  Primary development, as expected, will stay south (where the energy is) with heaviest storms over western TN.  A weaker bit of energy may still work its way up the Ohio River tonight, but that looks like it’ll be later than I originally thought…probably arriving around 11 P.M. to Midnight.  No problems with this system, if it arrives.

Comment:  This has been a really bad month for Louisville area forecasters.  It’s only fitting that the  current NWS forecast seems destined to join the faulty list.  My guess is they haven’t taken into account the changes caused by this afternoon’s storm system.

3:30 P.M. 5/26/2018

Rain/thundershowers over southern IN have remained weak and are not showing any indication of dropping into KY.  So, there will still be a slight  chance for a shower later today or tonight, but most, if not all, of  the Louisville area will stay dry through the weekend.  But, it’ll be hot!  Have fun!

Tuesday, March 20, 2018  2 P.M.

Another big nor’easter is on track to pound the eastern U.S. from northern West Virginia, north Virginia and northern Maryland northward into New England.  4″ to 8″ of snow will be likely over a large area while some spots could record a foot of snow, or more.

Meanwhile, we’ll be on the back side of this big snow-maker.  The computer forecast models are predicting about a 2″ – 4″ snow in about a 100 mile wide swath from southern Indiana and extreme northern KY  northeastward toward Lake Erie. That swath could reach 6″ or more over east-central IN and northwestern Ohio.  The Louisville National Weather Service’s forecast includes Louisville in that 2″ – 4″ snow area.  But, don’t count on that much snow here.  I have two good reasons for predicting why our Louisville snowfall total should be lower.

First,  the western side of Northern Hemispheric storms is a weaker precipitation-maker than the warmer eastern side.  The northwest side of these systems has to “wrap around” moisture from the active eastern side of the storm. That’s a hard job to pull off. Nevertheless, it does work.  Whatever moisture that does make the wrap around is rather small, but efficient.  As it reaches the northwest quadrant of the storm, it encounters colder air which squeezes out some moisture.  Little, if any, moisture can get far enough around to reach the southwestern quadrant of the storm.  The problem here is that the Louisville area will be in the Southwestern quadrant of the system by Midnight-2 A.M.

Second,  several models are predicting a weak low pressure to form west of the primary storm center.  This development is expected over east KY and West Virginia.  When that happens this evening, it will interfere with the wrap around precipitation mechanism of the parent storm.  So, we have another problem with the potential snowfall here.

With all that to consider, here’s my forecast:  a light rain/snow mix will begin during the afternoon rush hour and quickly  turn over to snow this evening.  Periods of light snow will continue overnight changing to flurries by daybreak.   Temperatures will remain in the 30″s all night, so roads should remain mostly wet with just a few slick spots.

How much snow?

Louisville area: !” to 2″ on grassy areas

South of Louisville: less than 1″

Southern Indiana: 2″ to 4″ north of the Ohio River.  4″+ over south-central counties northeast to the Ohio border.

Significant changes in past few hours.

Models have been running the precipitation farther north this evening.  It now appears the southern one-quarter of KY will stay snow free.  Heaviest snow band looks to be between a few miles south of I-64 to southern KY.  Basically, Bullitt Co and south.

Also, models are predicting faster movement of the storm (should leave Louisville area by 3 AM.  Faster movement means lower precip. totals for us.

Another change:  Models are now predicting colder temperatures overnight.  That means slightly more accumulation of snow AND possible road problems for Louisville.

So, for Louisville area:  some rain, but mostly snow.  Louisville could see an inch of snow on grassy areas with some slush on roads.  Major roads, however, should have few problems

Monday, Jan. 15, 2018

Not much to worry about this afternoon

A cold front pushing toward us has been producing some nice snow over southwestern IN this morning.  However, current short-term models are forecasting a considerable weakening of the snow field this afternoon as it passes through the I-65 corridor.  Plus, southerly winds have pushed temperatures to around 32 degrees and they should stay there this afternoon.

As a result, my forecast needs a little revision:

Light snow should begin around 1 P.M. and be mostly over by 5 P.M.  Flurries will continue overnight.  This afternoon’s snow will mostly melt on roadways, so this evening’s rush hour will only have a few slick spots.  As always, drivers will find those slick spots and we’ll have some accidents.  Overall, however, things should be pretty good considering holiday traffic will be lighter than usual.

Snow accumulations will be light.  Within a 30 mile radius of Louisville, the Ohio River will be a dividing line.  On the Kentucky side of the river, snow accumulations should run around 1″ on grassy areas (little, if any, on roads as discussed earlier).  South and east of Jefferson County snow totals will diminish to less than an inch.  On the Indiana side of the Ohio River, snow totals will be higher – 1″-2″ in the counties touching the Ohio.  Farther north and west, it’ll probably be more like 2″-3″.
NOTE:  I wasn’t surprised to see snow overnight.  However, the amount of snow really surprised me.  Best I thought nature could do was around .1″, maybe .2″  The half inch sure fooled me.  I’m hoping the prediction described above will be better.

Sunday, Jan. 14, 2018  11 P.M.

Evening models have all increased their forecasts for snow Monday.  Still a possible dusting overnight; then afternoon snow Monday should average around 1″ with some isolated spots perhaps as high as 2″.

Friday, Jan, 12, 2018

Icy weather takes a break

All of a sudden the freezing rain has quit and will not return for 2-3 hours.  As a result, the icy mess I talked about a couple of hours ago ISN’T GOING TO HAPPEN.

With this break, we’re back to a mostly snow situation.  Sleet and (mostly snow) will return by 4 P.M., just in time to foul up rush hour traffic.  Snow will continue through rush hour and gradually end before midnight.  Total snow accumulation: 1″-3″.

This sudden halt in the icy weather has given us a tremendous break!

Friday, Jan.12, 2018 11 A.M.

Sleet/freezing rain will cause more problems than snow.

This afternoon is going to be a real mess.  Yesterday, I discussed the quicker timing on the current weather pattern.  So far, that has worked okay…with one exception – cold air.  Temperatures were expected to remain in the 30’s until late afternoon.  But, the really cold air (20’s) has swept across the area much sooner than that.  It’s already here.  So, the consequence of that is much more trouble.

With temperatures aloft still well above freezing, rain will be the primary precipitation until late afternoon.  As that rain falls into the cold near-surface air we’ll see a 4 to 6 hour period of freezing rain gradually changing to sleet.  If freezing rain dominates, it could cause big problems with tree limbs, power lines, etc.  If sleet dominates the main problems will be with the roads.  Sleet should be the dominate precipitation, but a longer than expected period of freezing rain isn’t out of the question.

The snow part of the equation hasn’t changed.  The precipitation should change to snow by 3-5 P.M.  Snow will wind down this evening and end by midnight.  It’ll be hard to measure with all the ice already on the ground, but the Louisville area should see an accumulation of 1″ to 3″.  Higher snow totals are likely north and west of town.