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.

1 P.M. Sunday (Mar 1)

Looks as though the expected rain for most of the day has already wrapped up.  Some light showers this morning have moved away with little left to our west to dampen the afternoon.  Still rain south and east of Louisville early this afternoon, but that is moving away.

So, for the rest of the day:  cloudy and cold with just a 30% chance for a few light showers…high…42.

Tonight:  Cloudy and cold…low…28.  20% chance for rain and /or flurries.

Monday:  Mostly cloudy and cold…high…40.

Midnight update  (Feb. 22)

A couple of hours of very light snow have moved east of the area.  We should be dry for the next few hours, then light rain takes over and continues off and on through most of Sunday.  No snow or ice accumulations anywhere within a 30 mile radius of Louisville.

Saturday afternoon (Feb. 28)

Weak atmospheric energy “ripple” coming our way tonight and tomorrow.  The rain/snow line should be at least 30-40 miles north of Louisville, except at the beginning. Here’s my point of view:

Tonight:  Cloudy and cold…temperatures holding in 33-35 range.  Some periods of light snow are possible beginning after 10 P.M.  Snow should change to rain by 2 A.M.  Little, or no, snow accumulation expected.

Sunday:  Cloudy and cold with rain most of the day…high…40.  Rain should end by late afternoon.  Colder a few flurries tomorrow night.

  Wednesday Afternoon (Feb 24)

Cold air is still hanging around, but the rest of our weather certainly has been calmer this weekend.  A couple of posts ago, I mentioned the southern storm track would be active this week.  The second storm this week is bringing “winter” to the deep south today and the southeast tonight/tomorrow.  That storm has spread moisture far to the north today (the clouds we’ve been seeing) and could drop perhaps an inch or two of snow tonight over far southeastern KY.  Nothing for us from this system.

However, the northern stream is planning another big mass of unseasonably cold air for the lower Ohio Valley tomorrow.  As that new cold air supply drops in tomorrow, we could see some snow flurries and perhaps a few snow showers.  Most likely time for any snow will be afternoon and early evening.  Little, if any, accumulation expected.

Earlier, I had mentioned the possibility of  a third southern stream system phasing with a northern system to create a major storm system early next week over the central and eastern U.S.  But, as always, things change.  Strong indications now are that the northern system will be dominant and “cut off” the southern system without merging with it.  The southern system will still feed in some moisture for some moderate rains early next week (possibly beginning Sunday).  The lack of merger of the two systems is good news with respect to severe thunderstorms.  Some severe weather will still be possible from TX/OK eastward Mon/Tue, but much less of an outbreak than it looked earlier.

Forecast
Tonight: cloudy and cold…low…24

Tomorrow; mostly cloudy, windy and  cold…high…30.  Snow flurries and/or snow showers likely tomorrow afternoon and evening. Little or no snow accumulation expected.

Tuesday Evening (Feb 24)

Unseasonably cold weather will continue until the weekend when some warmer weather should return for a few mild, wet days early next week.

Main storm track should continue over the Gulf Coastal states through late week.  Meanwhile the northern (Polar) jet does bring us yet another shot of very cold weather Thursday.  That could also bring a shot at some snow flurries or snow showers Thursday.

Both the northern and southern jets show signs of getting much more energetic by late in the weekend, but they should phase into one very strong storm over the central U.S by Mon/Tue.  Actual surface feature will pass north of us, so rain, not snow, will hit us.  If things continue to shape up they way the models currently portray, we could well see the first big severe weather outbreak over the southcentral and southeastern U.S. Mon/Tue.

Wednesday Forecast

Becoming cloudy overnight…low…24

Partly cloudy tomorrow with a high of 34.