Tuesday, 2/2/2016

First, the Wind Advisory…

...WIND ADVISORY IN EFFECT FROM 1 PM THIS AFTERNOON TO 7 AM EST
WEDNESDAY...

.THIS AFTERNOON...CLOUDY WITH SCATTERED SHOWERS AND
THUNDERSTORMS. HIGHS AROUND 70. SOUTHEAST WINDS 10 TO 20 MPH.
GUSTS TO AROUND 40 MPH IN THE AFTERNOON. CHANCE OF PRECIPITATION
40 PERCENT.
.TONIGHT...BREEZY. SHOWERS AND THUNDERSTORMS. SOME THUNDERSTORMS
MAY PRODUCE DAMAGING WINDS. LOWS AROUND 50. SOUTH WINDS 10 TO
25 MPH WITH GUSTS TO AROUND 40 MPH. CHANCE OF PRECIPITATION NEAR
100 PERCENT.

Now, here is the NWS definition for a Wind Advisory…

Wind Advisory

A Wind Advisory is issued when the following conditions are expected for 3 hours or longer.

1) sustained winds of 31 to 39 mph    

AND/OR

2) wind gusts of 46 to 57 mph.

Notice anything unusual?  Yes, the forecast doesn’t came anywhere close to the definition.  And, this is the third time they’ve done this in the past couple of months!

So, let’s put it this way…it’s going to be noticeably windy this afternoon and tonight.  But, Wind Advisory criteria?  Very doubtful.

Severe weather situation

As a massive winter storm moves slowly NE out of Kansas toward the western Great Lakes, a major outbreak of severe storms is expected along the Mississippi Valley late this afternoon into early evening.  The western third of KY and southwestern IN could be hard-hit.  But for the Louisville area the situation is much different.

As is often the case with winter severe storm outbreaks, the dynamics (wind fields, etc) are very strong.  But the thermodynamics (temperatures, moisture, etc) are weak.  Sometimes, the dynamics can overwhelm the weaker thermo and wreak havoc.  That is expected late this afternoon and early evening along and near the Mississippi River.  Severe storms and some strong, long track tornadoes appear possible.

During that time, the thermodynamics will be at their peak.  But, the models never bring any positive thermos into central KY or southern IN.  Any instability dies quickly to our west after 6 P.M.  As the cold front slowly advances eastward, the expected severe storm areas consolidate into the line of gusty winds and very heavy rainfall as it approaches the I-65 corridor.  Biggest threat for our area should be flash flooding.  It’s possible we could see 2″-3″ of rain in a few hours, so watch out for flooding in low-lying areas.  If flooding is going to occur, it should be Midnight or later

As for the timing of the windy, rainy and possibly stormy weather…  For the Louisville area, the primary squally system should pass the area between 10 P.M. and 2 A.M.

Note:

The definition of the severe thunderstorm is Winds reaching 58 mph or higher and/or one inch hail.  I don’t believe either of those items will occur in the Louisville area tonight.  NEVERTHELESS, I do believe a Severe Thunderstorm Warning will be issued locally.  After all, can anybody remember the last time a moderate to strong line the thunderstorms has passed Louisville WITHOUT a warning being issued?  (It’s kind of like that Windy Advisory thing.)

Stuff:

I was happily impressed with the Cardinals win over UNC last night.  Good testament to the character of the team to bounce back from Saturday’s game with UVA.  It also speaks well for a team, such as UVA, that can completely change a game with their exceptional defense.

6 P.M. Fri 1/22/2016

I am flabergasted at the new NWS forecast…just cannot believe it.

A few more tenths of an inch possible before this wraps up by 7-9 P.M.  But, we’ll see plenty of blowing and drifting snow tonight.

Friday, 1/22/2016

Snow intensity is winding down. but periods of light snow should continue until around 7-8 P.M. Radar shows the northern edge of the light snow is slowly drifting from southern IN toward Louisville.  It’s going to be tough to measure from here on out because of the strong winds and blowing snow, but any additional accumulations will be less than one inch for the Louisville area.

Snow totals appear to be highly variable, but nothing extreme.  At SDF the snow depth was measured at 7 A.M. and showed 3″ and at 1P.M. the snow depth was also 3″.  My driveway had 2.4″ around 1 P.M. and little snow since then.

It’s hard to imagine the NWS is still maintaining the Winter Storm Warning and the 4″-6″ snow forecast for Louisville.

But then, as Yogi Berra famously  said, “It ain’t over ’till it’s over.”

Thursday morning, 1/21/2016

Quick update after a glance at morning GFS and NAM model runs.  The trends remain the same as yesterday afternoon’s update mentioned – the primary storm track still looks to be on a track too far south to bring the really heavy snows as far north as the Ohio River.  Things are running a little slower as snow may hold off until around late morning or Noon tomorrow. (Makes the Winter Storm WARNING going into effect at 7 P.M. tonight look rather silly, doesn’t it? )

Still looks about the same – 3″- 5″ or 6″) in Louisville area.  Rapidly increasing totals up to 6″-12 south of the metro (across central KY).  Rapid drop in accumulations north of the Ohio.

More later.

Friday afternoon (Mar 6)

After a beautiful snow forecast, the NWS fell back into it’s recent trend of big-time errors on low temperatures.  Early yesterday, it was all about the record lows we’d be having.  Didn’t happen.  Didn’t even come close.  But, in fact, a record MAY have been set!

First, yesterday’s high, predicted to be 17, reached the mid 20’s.  But the crowning event was to be the low this morning.  (see yesterday’s blog)  Yesterday’s overnight forecast, issued at 3:41 P.M. predicted a low temperature of -5 to -10 degrees.  This morning’s low was 8 deg. ( In forecasting, an error of +/- 3 degrees is considered a “hit”.)  So, the official forecast had an error range from 13 degrees to 18 degrees!  In today’s world, a miss of 10 deg. or more probably only happens a handfull of times a year.  But, a miss of 18 deg. is  virtually unprecedented.  So, indeed, a new record may have been set this morning – worst low-temperature forecast ever.  However, I don’t imagine that such records are kept, so we’ll never know.

Weekend

Southerly winds and partly cloudy skies will contribute to dry, warming weather.  That’s good news for most of us, but not for those who live in flood-prone areas.  Highs in 40’s may sound good, but that’s still below normal for early March.  Next week we’ll have some days in the 50’s and some reach the 60’s.

Tonight…partly cloudy and cold…low near 20 this evening, then slowly rising temperatures overnight.

Tomorrow and Sunday:  partly cloudy with highs in the mid to upper 40’s.

  Wednesday 11 A.M (Mar 4)

I see the Weather Service has started to back down on their snow forecast, so I suppose the media folks will as well.  However, I still think the NWS step backward is far too small.

Quick look at morning data runs confirms (to me anyway) that my forecast posted last night is right (almost) on target – 2″-4″ of snow/sleet by tomorrow morning.  However, I have one subtle change to make.  It looks to me that we’ll see a prolonged period of sleet this afternoon.  We could see up to an inch (or so) of sleet before a change to snow this evening, probably between 6 P.M. and 9 P.M.  After midnight, snow should begin to taper off to a few flurries by morning rush hour.

Another update this afternoon.

P.S. Why is JCPS closed today???

Sunday Evening

A post last week discussed the poor forecasting (and thus the badly misleading wind chill information) of overnight lows for Louisville last week.  Well, they are at it again tonight.

1).    Wind Chill Advisory from Midnight until 9 A.M. Mon A.M.  Okay, that’s the headline.  For Louisville, the Wind Chill Criteria for an advisory is -10 deg. to -25.

2),  The NWS forecast for Jefferson County is for a low of 8 degrees and a wind chill of +1 to -9.  The forecast doesn’t agree with the headline (Wind Chill Advisory)

3).  Once again, the NWS  forecast low (8) is far below available guidance.  Latest I’ve seen say either 13 or 14 degrees).  Even though the winds will be northerly (bringing us colder air), the models all expect a large amount of cloudiness to linger most of the night, reducing radiational loss.  Thus, to me the guidance looks to be much better.  I’ll give it a low of 12 by 8 A.M. tomorrow.  Assuming the warmer temperatures, wind chills will be even farther away from advisory “criteria.”

Week ahead

Weather remains very cold, but calmer conditions should return for most of the week.  The next two “major” storms should move across the Gulf Coastal states this week.  That’ll keep the big problems south of us.  A couple of northern stream disturbances will cross over us.  One tonight and the second late Tuesday.  Each one will serve to reinforce the cold weather, but will have only enough moisture to perhaps produce some snow flurries.

The third major storm to push out of the southwest this week should come in two sections.  The first (Friday) could bring a little snow but the major energy with the system should arrive Sat. night/Sunday.  Too early to tell whether it’ll bring rain or snow OR the whole mixed bag like this weekend.