Monday Afternoon (Mar. 9)

The polar jet has disappeared for awhile, so the cold air will stay far north this week.  The Subtropical (Southern) Jet rules the week ahead.  This jet is far weaker than the Polar Jet, but does have its foot in the Gulf of Mexico, so plenty of water is available.

Rains today over the south-central U.S.  will ride the jet slowly northeastward tonight.  Rain should begin after midnight and continue off and on most of the day tomorrow.  As this system is short on energy, no excessive rains are likely.  The NAM puts us around 1.5″ of rain but the GFS pushes the heaviest rains over southern KY.  Although the NAM placed the rain and snow last week almost perfectly, I feel the GFS looks more realistic with the weaker system.

Looks like Wednesday should be dry and warm.  Temperatures should reach at least 60, but any 3-4 hour break in the clouds could push us to the mid to upper 60’s.

Thursday’s weather looks very questionable at this time.  The NAM wants very much to bring another of northward, much like tomorrow.  Meanwhile, the GFS pushes the moisture eastward during the day and then brings some rain northward to Louisville Thursday night into Friday.

Wednesday 11 P.M. (Mar 4)

Just measured the snow in my driveway – 5″- and heard that the airport has already hit 7″ so I guess I’d better try to repair my “blown out of the water (or snow) forecast”.  Models and radar indicates that light snow should continue until 1 or 2 A.M. with only minor accumulations after that.  Snow banding has been heavy just south of Louisville so I’d expect areas from southern Jefferson Co., Bullitt, Spencer, Shelby, Hardin, Breckinridge, Grayson, Franklin, Nelson and Mercer getting Double Digit snows (10″-13″).  Lower totals over the rest of Jefferson Co. and areas north.

We should get about 1″-2″ for the rest of the storm, so 6″ to 10″ looks good over the area north of the counties mentioned above.

You win some, you lose some, but there’s tomorrow to try again.

Wednesday Afternoon (Mar 4)

After looking over the most recent data, I feel like some changes are in order.  First of all, I was expecting a much longer period of sleet.  That didn’t happen, so less sleet means more snow.  More snow than sleet creates a deeper accumulation.

Second, the models have increased the amount of expected precipitation between now and midnight.  That, too, would lead to a little higher snowfall.

So, with those changes in mind, here’s my latest forecast:

Tonight:  snow likely, windy and cold…low…17.  Most of the snow should fall by midnight…about an inch or less after midnight.  SNOW ACCUMULATION:  3″ to 5″

Tomorrow:  Mostly cloudy in the morning, then partly cloudy.  Windy with a high near 24. Some snow flurries possible in the morning.

Tomorrow night:  very cold…low…near 3.

Midnight/early Wed (Mar 4)

Evening update showing some changes, mostly due to the continued “slowing”   of the models.  In essence, it now looks as though the snow shouldn’t begin until after the primary moisture source has passed by.  Thus, much less snow is likely than  currently being predicted.  My revisions  to my earlier forecast…

Overnight:  rain, perhaps heavy at times.  Minor urban flooding expected for rush hour. Temperatures falling into the 30’s

Morning: Rain likely probably changing to sleet by midday.

Afternoon:  Sleet likely.  Accumulation 1/2″-1″.  Sleet changes to snow by evening.  Temperatures falling into the 20’s during the day.

Tomorrow night:  snow, windy and cold…temperatures continue to fall.  Snow diminishes toward morning.

TOTAL SNOW/SLEET ACCUMULATION:  2″ TO 4″

Tuesday afternoon (March 3)

Weather patterns remain pretty much the same as yesterday (see March 2 blog), but the NAM’s much slower evolution of the weather pattern has definitely been the way to go.  In fact, the GFS has slowed to about match yesterday’s NAM while the NAM has slowed even more.

That may not sound like a big deal, but it is huge concerning potential snowfall tomorrow and tomorrow night.  One other major point mentioned yesterday is the continued lack of any “kicker” out of the cut-off southwestern trough.  That allows it to send in one more big chunk of moisture WITHOUT any significant energy to form a strong surface low along the cold front.  (A strong low moving along the front would kept warmer air here much longer than now expected.  Thus, snow expectations would have been much lower.

But, the big picture hasn’t changed much – heavy rain expected tonight.  Rain totals could range as high as 2″ to 4″ before the changeover  to snow.  The NAM still keeps the axis right along the Ohio River while the GFS continues to place Louisville on the northern edge of  the heaviest rain area – with the heaviest rain axis about 60 miles south of the river.  Either way, we’ll probably have a major water mess for rush hour tomorrow.

Now, the snow potential.  In spite of the timing differences between the NAM and GFS, they are a lot closer together with the potential snowfall.  Without explaining all the different scenarios from the models, I’ll just go right to my  current “working theory.”

CURRENT FORECAST IDEAS:  Heavy rain and widespread moderate urban flooding tonight.  Temperatures begin falling after midnight and and reach the 30’s by 7 A.M.

Tomorrow morning  rain changes to sleet, which should continue until at least mid-afternoon.  A change to snow is likely by late afternoon.

Tomorrow night:  SNOW, probably heavy at times through the evening and early morning hours.  Any significant snow should be over by 8 A.M.  Light snow/flurries could continue Thursday.

TOTAL SNOW ACCUMULATION:  6″ to 10″ for the Louisville area.  lower totals north of Louisville and heavier snows south of Louisville.

NOTE:  My prediction is based on the expectation of at least several hours of sleet tomorrow.  If the change to snow occurs sooner, snow totals could reach 8″-12″.  (The most recent “new” GFS model says 7.6″.

Monday afternoon (March 2)

The very heavy rains expected tomorrow and especially tomorrow night have been long advertized and they should happen.  Earlier rain estimates suggested 2″-3″ for the Louisville area.  Most recent forecasts are pushing totals even higher, more like 3″ to 4″.  Either way, we should be prepared for a lot of lowland flooding tomorrow night/early Wednesday.  It looks like we’ll see quite and mess with the excessive rainfall.  Overall, the NAM is a little slower with the timing of this system (heavy rain potential continues until at least midday Wednesday.  The NAM continues to focus the heaviest rain right along the Ohio River and about 75 miles north and south of the river.  Meanwhile, the GFS is faster with any heavy rains over by midnight tomorrow night.  The GFS also places the axis of heaviest rain south of Louisville – over central KY with Louisville on the northern edge of the 2″ + zone.

For several days those heavy rain forecasts have come with a tantalizing suggestion that the rain will turn to snow before ending.  As we’ve drawn closer, snow is looking like a very good possibility.  As I mentioned last week, the key to this part of the forecast was whether the southwestern U.S. upper trough would phase, and merge, with the stronger northern system.  As expected, rather than merging, the southwest system “cut-off” from the main system.  As a result, there will be no strong surface low at the end of this winter storm.  Just frequent ripples of energy, but no strong center of the storm system to dominate the action. But the SW system will provide ample (more than ample) moisture to the northern system’s energy.  Thus our threat for flooding rains.

But with no strong energy surge to come along and clean things out, it greatly enhances our chances for snow.  In fact, it is settling into a rather classic pattern that usually puts down  a 1″-3″ snow cover as cold air changes the rain to snow for the last few hours of precipitation.  As wet as the storm looks to be and as cold as the air is behind the cold front, it could easily jump up a notch to 2″ to 4″ of snow.  Big question, however, is where is the snow going to accumulate with all the water all over the place?

So, trying to smooth out the variations between the models, here’s my latest forecast:

Tonight:  Increasing cloudiness and cold.  Temperatures rising into the upper 30’s by morning.

Tuesday:  Warmer, with light rain developing during the morning.  Rain will become heavy at times during the late afternoon.  High…53.

Tuesday night:  Rain, heavy at times.  Widespread minor flooding likely.  Temperatures rising to the upper 50’s, but then falling after midnight into the low 30’s by morning.  Rain changes to snow overnight with a possible accumulation of 2″ to 4″ by midday Wednesday.