Category Archives: forecast

Daily chance for snow ahead

Friday, Jan. 25, 2019

Clippers coming at a rapid pace.

Models continue to bring small clippers into the U.S. once per day through the weekend.  They all appear weak, but still could bring us some light snow.  Last night’s clipper produced nothing but clouds and tonight’s might even be able to a produce some light snow from the clouds.  But even that looks like no more than the potential for a dusting of snow.

Tomorrow night’s clipper looks more promising.  This one seems to have the potential for a small accumulation, maybe a half inch or so.

Sunday’s clipper barely shows up on the models, so it looks like an “off” evening for snow chances.

But, Monday night’s clipper looks like the real thing.  It’s predicted to be quite strong and move across Wisconsin and Michigan Monday night and Tuesday.  Ordinarily Clippers don’t produce much precipitation south of the system’s storm track.  This time, however, the GFS has focused some rain and snow along the strong cold front sweeping south of the clipper.  There looks to be a potential for 1″-3″ of snow Monday night into early Tuesday.  It ought to be interesting.

Too early to tell about the snow, but one thing looks fairly certain – it’s really going to get COLD next Wed/Thu as nighttime lows should be the coldest (by far) this winter.

Think snow!

Cold weather continues

Thursday, Nov. 24, 2019

Daily chance for flurries/light snow

Now that cold air has reestablished itself, the open question remains – what about snow?

Helping to bring in  the new cold air mass is a brisk northwesterly jet stream flow from northwestern Canada into the central and eastern U.S.  Little pockets of even higher energy move along with this jet on a roughly daily basis.  One is passing over us tonight and will bring only clouds.  If it were a little stronger, it might squeeze out some flurries or light snow.  That’s another big question.  How strong will they be?

Being small, these Alberta Clippers (as we commonly call them) are hard for the computer models to resolve well.  As of now, the system due tomorrow night looks a little stronger – some flurries and very light snow possible.  Story looks about the same for Saturday night.  The GFS especially likes the chances for light snow from a Clipper Sunday AND one on Monday night/Tuesday.

Meanwhile, it’s far too early to get a handle on Sunday and Tuesday’s Clippers.  If the Tuesday storm works out similar to the GFS model’s forecast, the coldest air of the season will follow.  We’re almost certain to get that “single digit” temperature that has been talked about a couple of times recently.  Perhaps even a trip down to near zero.  But, that’s next week – plenty could change.  Meanwhile…

Tonight

Back to current times, the clouds should hold most of the night, but skies should clear by sunrise.  Westerly winds appear likely to stay above 10 mph.  Those two features should be enough to keep temperatures in the lower teens.  Probably it’ll drop to 12-13 here in Louisville.  A few degrees colder west of Louisville since skies will clear earlier there.

Lots of sun tomorrow, but not much warming.  Highs in the mid 20’s.

Stuff

Here’s another cool aurora shot from spaceweather.com

A little snow tonight

Wednesday, Jan. 23, 2019

Rain may hang around long enough for the cold air to arrive

The slow-moving cold front crossing the region now has been an active rain-maker for KY/IN.  As mentioned before,  the main part of the cold air won’t arrive until tomorrow.  Meanwhile, the models have slowed the tail-end of the precipitation by 3-5 hours since yesterday.  That should give time for the slowly advancing cold air to arrive in time to produce a little snow tonight.

Current thinking is that the rain will change to snow for a short time around 10-11 P.M. tonight.  Temperatures will still be above freezing, so no accumulation is likely on roadways.  However, grassy areas may get a dusting or even a “generous dusting”, but a half-inch looks like a top limit.

Later this week

A large mass of cold air will be dominate our weather scene from tomorrow into the weekend.  The upper air flow will be from the northwest.  That usually produces an almost daily chance for an Alberta Clipper to drop south from Canada into the midwest.  Clippers are hard to predict, but this morning’s GFS indicates that our best chances to get any snow from them will be Sunday and Tuesday.  Stay tuned.

Stuff

If you haven’t seem the pictures of the rare snowfall on the Sahara Desert, just click on them in the column to the right.  They’re worth it.

Winter wonderland plus the aurora!

from Chad Blakley

Wet and Warm Wednesday

Tuesday, Jan. 22, 2019

Rainy day tomorrow

As usual, the models have changed a little in the past day.  The most significant change is that a little pocket of energy has dropped out of Canada to enhance the northern part of the positively tilted trough moving slowly eastward over the central U.S.  That change will have two primary effects.  First, the western Great Lakes will get more snow than previously predicted.  Second, the weak cold front moving our way will probably be a larger rain-maker than I indicated.  Looks like about one inch plus or minus a quarter inch.

But, the changes , if anything, have reduced our already meager snow chances for late tomorrow.

Tonight

Increasing clouds and increasing temperatures tonight.  Rain arrives around 4 A.M. or later.  Temperatures rise to near 50 by morning.

Tomorrow

Rain, possibly heavy at times, during the morning.  Temperatures in the 50’s.  Rain tapers off during the afternoon and temperatures slowly fall into the 30’s. Rain ends about sundown – possibly changing to a little snow before ending.  No snow accumulation is expected, but a few areas could see a dusting.

Thursday+

A cold air mass will be rolling in all day.  A shot for some light Friday and the weekend.

 

Cold air highlights the week ahead

Monday, January 21, 2019

After Saturday’s Hall of Shame forecasting by the majority of local prognosticators, the cold air has settled in and calmed our weather for awhile.  Next system in line will be the remains of another large storm that blasted the Pacific northwest over weekend.  This system is diving into the southern  Rockies and then will slide eastward.  Unlike a couple of similar systems (the past two weekends), this one isn’t given much hope of regeneration.  The upper level parent trough is projected to remain, as we meteorologists say, positively tilted.  In this case, very strongly tilted.  That translates into normal people-talk as weak energy levels and very little development.

Tomorrow and Wednesday

The trough, however, will begin brisk southwesterly winds over the midwest and Ohio Valley tomorrow and transport moisture our way quickly.  Increasing clouds tomorrow with much warmer temperatures (into the 40’s).  Rain will return around midnight tomorrow night and continue into midday Wednesday.  Similar to Saturday night, the cold air behind this new system will be late to join the action.  In fact, the true blast of cold air won’t arrive until Thursday.  So there could be some snowflakes Wednesday afternoon, but no accumulation is expected.

Note:  The NWS is forecasting 1″-2″ of rain for us from this system.  That seems pretty high considering the upper support.  Probably closer to one inch than two.                                                                                                                                                                                                                   Later this week

With wintry air again dominating our weather, little active weather is anticipated.  Computer models are hinting at a couple of very weak Alberta Clippers drifting into the area Thu-Sat with periods of cloudiness, but not much chance for any significant snow.

Note:  The GFS is developing a strong Clipper into the western Great Lakes by early next week. Although not posing much of a rain and/or snow threat for us, the clipper is gathering a very potent cold air mass in its wake.  It might be the coldest air mass we’ll see this winter and probably bring along some light snow along with it.  Of course, that’s a week away – a lot of model changes can happen in that time.

Stuff

I see the Courier Journal has gotten even smaller.  The USA Today section has gone off the digital world.  So, there’ll be less paper in the “paper.”  At least the dimensions of the physical paper haven’t shrunk, as they have in recent years.

 

 

It’s all about the physics!

Saturday, Jan. 19, 2019

Model snow solutions are far apart.

Weather forecast models…you rely on then, you love them and sometimes you hate them.  Today, I’m very confused by them.

A little background:  Models are an attempt to explain/predict the future weather conditions.  The atmosphere is extremely complicated and certainly not fully understood.  Nevertheless, we’ve taken various laws of physics and developed equations to explain the atmosphere’s behavior as best we can.  Then, we have problems with data collection (it’s far from perfect) and fitting the data to a three-dimensional grid.  So then we put the imperfect data into the imperfect physical model, adjust it to the forecast grid, and let the computer do its magic.  In spite of the weaknesses of the “initialization” the results are extremely good – most of the time.

We have have a lot of different models and model schemes.  They all have the same goal – a correct portrayal of the upcoming weather.  The two big workhorses of the National Weather Service (for forecasts of a few days) are the GFS (a global model) and the NAM (North American regional).  We have two very short term models that model 18-21 hours ahead.  These are the RAP and HRRR.  The GFS and NAM run every six hours while the higher resolution models run every hour

Different Physics Packages!

Each model has a different physics package at its core.  Sometimes the results match almost perfectly.  Other times, they don’t.  It’s up to the human forecasters to try to figure out what the best solution is.  Model differences are wide apart today.

Let’s get down to the nitty-gritty.  What we’re most interested in today is snow!  When and how much.  Last evening’s (7 P.M.) computer runs showed a wide divergence from earlier model runs.  All models increased their snow forecasts for tonight – some by several inches. (This much change is quite unusual so close to the weather system’s arrival.)  Since then, they’ve divided into two camps – the GFS/RAP are at the lower end of the spectrum with 1″ – 3″ inch forecasts while the NAM and HRRR are forecasting 4″-8″ overnight.  Quite a difference!

Since last night the GFS and (today) the RAP have been trending down while the NAM and HRRR have been trending upward.  Go figure!

So, what’s going to happen?

Good question.  I don’t know for sure, but I think I’ve got a pretty good idea.  Yesterday’s blog pointed out some problems I had with the NWS forecast.  The rain looks like it’ll end at the lower end of expectations.  The cold air system and the rain system have still not gotten together and it looks like the phasing of the two systems won’t happen until after midnght.  And, the falling temperatures this evening will take several hours – so no concern about the much-feared “flash freeze.”  Temperatures will fall.  Snow will fall.  Roads will become slick.  Just like always.

So, the GFS inspired forecast from yesterday has worked very well.  There are just more things I like about today’s GFS than the other models, so I’m sticking with it.  The GFS has upped its snow forecast from yesterday and seems quite reasonable to me. So…

Snow forecast:

1″ -2″ metro Louisville.  Up to 3″ north of the Ohio River.

Rain should change to snow around 9-10 P.M. and it will be quick – most of the snow should be over by 1-2 A.M.

Note:  This is my “best guess.”  The National Weather Service is at 3″ – 5″ and some of the model forecasts discussed above go even higher. This could turn out to be a snow-lovers dream.  I’m just not buying it, yet.

Think snow!

Wet and icy Saturday ahead.

 

Colder weather by Saturday night

Models haven’t changed much since yesterday.  GFS is really playing down the snow for tomorrow while the NAM is still hinting at about 2″ along and north of the Ohio River.  The NAM was better last weekend, but that was unusual.  Both models have continued to lower their rain predictions with which I agree.  So, here’s my latest thinking…

Saturday

Rain moves in before daybreak and continues through about midday.  During the afternoon rain will diminish to light rain/drizzle.  Rain may even quit for a few hours.  Temperatures will likely reach the mid 40’s.  Rainfall totals should be in the .50″ to 1.25″ range – most of Louisville area will be an inch or less with the heavier totals south and east of us.

Saturday night

Around 6-7 P.M.  the cold air will make its entry.  Temperatures will drop quickly and drop below freezing by 9-10 P.M.  – on their way to near 20 by morning.  Winds will be very strong overnight with gusts over 30 mph.

The cold air will bring some moisture with it.  A quick rain to snow changeover will happen during the early evening.  Any snow should move out of the area before midnight.  There won’t be much snow – probably an inch or less.  But, over the years we’ve certainly learned that even a small amount of snow can create big road problems. Some icy spots are likely on area roads tomorrow night.

Sunday plus

Winds gradually diminish during the day, but it’ll still be a cloudy, cold day with temperatures remaining in the lower 20’s during the day.  Monday morning lows in the city will be in the low to mid teens, slightly colder in rural areas.

 

Another weekend…another storm

Thursday, January 17, 2019…4 P.M.

Subtle changes

If you’re a snow-lover you’re not going to like the small changes to Saturday’s forecast.  Both the GFS and NAM have drifted in the same direction, so I’ve got pretty good confidence the solution they are pointing toward looks realistic.

We’ve been tracking a storm system blasting northern California and a large chunk of Arctic air moving south from Canada.  Original thought was these two systems would merge over the Ohio Valley/midwest on Saturday.  The result of the merged system would bring us plenty of rain (2″-3″) Saturday.  Then, as the cold air rushed in Saturday night, we’d see an inch or two of snow.  I’ve heard talk of heavier snow, a “flash freeze,”  and single-digit temperatures (even sub-zero).

That’s all nonsense if the current model trends are correct.  The new idea is that the west coast trough and the cold air system will not get “in phase” until the primary surface storm system passes east of the Louisville area.  That means the storm system will not get to its rapid development stage until it gets to Ohio or beyond.

Consequences of the recent changes

1).  Rain remains likely most of the day Saturday.  But it won’t be as much.  Totals will probably range in the 1″ to 1.5″ range.

2).  Rain should end by Saturday evening and we’ll probably see some snow flurries and/or snow showers overnight.  Accumulation, if any, should be less than 1″.

3).  The initial surge of colder air will be slower to arrive.  Temperatures will not fall rapidly enough to allow a flash freeze.  Icy spots, however, will form on roadways during Saturday evening.

4).  Sunday will be very cold…probably near 20-22 all day.  Because the primary storm system will intensify north/east of Louisville, the cold air transport southward will be weaker.  Thus, it appears the local temperatures won’t drop into the single digits in the Louisville area either Monday or Tuesday morning.  Rural areas especially in southern IN could see lows below 10 degrees.)

Note:

The cold upper trough expected over the eastern parts of North America due to the Sudden Stratospheric Warning of late December is now in place.  This system should provide us with frequent snow opportunities and plenty of cold air for the next 2-4 weeks.  Forecasting should be lots of fun.

If you’d like a little more detail on what a Sudden Stratospheric Warming is, see my post from a couple of weeks ago.

Stuff:

We are constantly bombarded by the things that the climate change “hawks” want us to hear, so you probably missed the news that the U.S. is one of the world leaders in carbon emissions REDUCTION.  Yes, compared to the 2005 baseline, total U.S. emissions have dropped 11%, even though we had a small increase last year.  As a whole, Europe has dropped a little (1-3%) as well.  But, the rest of the world continues their rapid increases.  Roughly 80-90% of the nations which signed the Paris Climate Accord continue to increase their emissions.  China and India are by far the biggest offenders.

Let’s not blame China too much.  After all, they have a signed agreement with the U.S.  to keep increasing emissions as much as they want until 2030.  The Climate Gang praised that agreement as just about the greatest thing since (the proverbial) sliced bread.  I’ve always felt that the agreement gave China all the bread and the slicer.  Maybe we’ll get some crumbs out of the deal.

Snow is approaching!

Friday, Jan.11, 2019

Snow overnight…sloppy tomorrow

Today the various models are in close agreement with only some minor differences.  The biggest difference is with snow totals where the GFS is slightly higher than the rest.  Without getting into the various interplays/interpretations that COULD happen, I’m just going to lay out what I THINK will happen.

Tonight

Snow should arrive in Louisville shortly before Midnight.  Most of our accumulation will occur between 1 A.M. and 5 A.M.  After that snow will be lighter and gradually end around sunrise.  By 8 A.M. most of the Louisville area will have a snow cover between 1″ and 2″.  North of the Ohio River, some areas (especially west of I-65) may have up to 3″.  Untreated roads will be snow-covered for a few hours.  Treated roads will be slushy and wet.

Tomorrow

There’s a chance for a rain/snow mix for a couple of hours late in the morning.  Snow cover should actually be decreasing by that time.  The afternoon  should be generally dry.  During that time roads will clean up and overnight snowfall will continue to melt.

Saturday night

Rain moves in during the evening and continues lightly until late night.

Sunday

During the morning light rain/drizzle will change back to light snow/flurries  Any precipitation will fade away by early afternoon.  No more than a “dusting” is expected.

Monday morning

There’s a chance (30% )that we could see some light snow/flurries for the morning rush.  Little, if any, accumulation is expected, but some slick spots could develop.

That’s  my thinking, now let’s see how it works out.

Think snow!

Weekend Weather Prospects

6:30 P.M. Thursday, Jan. 10, 2019

Snow and rain likely.

Forecast models have changed little since yesterday, but that’s enough to bring our weekend forecast into better focus.  The primary change is that the NGM and GFS have both warmed a little.  My worry from yesterday about that prospect is looking like a realistic idea.  Consequences follow:

General situation remains the same…a weak system coming out of the southwest will drift ENE across the southern states.  It will start to regenerate Sunday, but that will be too late for us.  With the low center staying to our south, we’ll have a northerly component to our winds, so the colder air will hold in place with only a slight warming modification.

Heavy snow will break out over northern AR and southern Missouri tomorrow and march eastward into KY/IN tomorrow night.  Snow should begin in the I-65 region about midnight or later.  Temperatures should remain at or above 32 degrees overnight, so snow should accumulate ON GRASSY AREAS !”-2″ by morning.  Roads will have only a small accumulation of slushy/wet snow, but,as always, drivers will find the icy spots.  Luckily, since it’ll be Saturday traffic should be light.

Saturday most of the overnight snow will melt away and roads will improve rapidly.  It’s also looking like little or no precipitation will fall during the day.  If anything falls from the sky during the day, it’ll be light rain.

Part 2

Light rain/drizzle moves in Saturday night and continues off and on until early Sunday.  During Sunday, the surface storm system pulls eastward and drags colder air back into the Ohio Valley.  Some light snow/flurries are likely during the day, but little, if any, accumulation is expected.

We need babies!

Read an article today about the slowing birth rate in the U.S.  In general, the thought goes, our female population needs to produce  2.1  children during her lifetime in order to keep our population stable.  Our current rate has dropped to about 1.7.  So, in spite of what we’re being told, we need those immigrants!