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.

Midday Friday  (Feb.20)

I’ll have more details later, but here’s my current thoughts on weather tonight through tomorrow.  (There’s still a fairly large difference between the NAM and GFS, so there’s a pretty large “margin of error” this close to the event.)

1)  Increasing clouds this afternoon…high in mid 20’s.

2).  Periods of light snow begin after 7 P.M.  Snow becomes heavier after 10 P.M. with an accumulation of 2″-4″ by 3A.M.

3).  3A.M.-7A.M.  Sleet mixes with snow and eventually becomes all sleet (and possibly freezing rain.

4).  7A.M. – Noon    Temperatures warm to around 32 degrees around Noon.  Meanwhile sleet changes to freezing rain and then to liquid rain.  (Rain/freezing rain could be heavy at times, but no major (damaging)  ice accumulations expected.

5).  Afternoon:  Temperatures rise above freezing for several hours.  Rain continues, but lightens as time wears on.

6).  Some snow flurries are possible as temperatures drop below freezing again

5).

THURSDAY AFTERNOON

Unbelievable!!!  After a badly busted forecast of this morning’s lows, local weather authorities are poised to do it again tomorrow.  My guess is that they haven’t learned anything from this morning’s fiasco.  Anyway, they’re shooting for -11 tomorrow morning while four of their major forecast tools predict 3, zero, -2 and 5.  On average, slightly warmer than their forecasts for today.  This morning, the busted forecast was due to the winds.  Tonight it’ll be due to increasing clouds  after midnight.

NOTE:  Missing a temperature forecast by 9 degrees or more has become a real rarity these days.  I’d guess it happens less than 10 times a year here.  Coming with all the Watches and Warnings in place (dependent on the forecast), it was a real embarrassment for us forecasters.

Friday-Saturday storm

We’re getting close enough to the arrival of the next storm to be able to try to make some sense out of it (although a few doubts remain).

In general, the models are thinking along the same lines although the NAM is faster (and cooler) than the GFS models.  The upper trend is for another polar jet disturbance to sink southward over the western Plaines and Rockies.  Unlike the past several storms. this trough will hold back in the western U.S. and send us ripples of energy over the weekend.  But, the main part of the system does not play a major role in the weekend’s activities.

Meanwhile, the subtropical jet is available to send plenty of  moisture our way.  Here’s how it’s shaping up:  Increasing clouds begin tonight with a cloudy cold day Friday.  We could see some very light snow or flurries during the afternoon.  High near 24 degrees.  Temperatures continue rising tomorrow night as snow becomes heavier.  In fact, 2″-4″ of snow appears likely before a changeover to sleet and freezing rain Saturday morning.  By Saturday afternoon temperatures will rise above freezing so freezing rain will change to rain and begin a long cleanup.

Doubts:  models have backed off a bit on the 1″-2″ rain totals, so the prospect for flooding will be much lower.  HOWEVER , many urban streets/intersections will flood because the storm sewers will be blocked by snow.

Biggest question mark remaining is the duration of the sleet and freezing periods.  At this time, it looks like the freezing rain will be the biggest threat – a lot of ice is possible, especially if the NAM is better than the GFS.  More tomorrow.