Author Archives: wx

Bitterly cold air by midweek

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Sunday, Jan. 27, 2019

No significant snow with the cold front

Basically no change today from yesterday’s models.  Strong cold front will cross central IN/KY tomorrow evening.  Ahead of the front tomorrow, we’ll see a windy mild day with temperatures reaching the upper 40’s to low 50’s during the afternoon.  As the front crosses I-65 tomorrow evening (around 6 – 9 P.M.)  it will probably squeeze a little moisture out of the air.  A little rain is possible with the front, then as the cold air rushes in, any rain should change to a brief period of light snow.  Little, if any, snow accumulation is expected locally.  However, !-2″ of snow will be possible east of I 75 thanks to some help from the higher terrain.

The upcoming cold air mass this week has been well promoted, so it should not come as a surprise to anyone.  However, temperatures in the low single digits with wind chills below zero Wednesday and Thursday mornings will be shocking on our systems.

By the weekend, however, it looks like temperatures once again bounce back into the 40’s and 50’s.

 

Snow chances are not very promising

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Saturday, Jan. 26, 2019

Flurries tonight, Monday night is still a possibility

We’ve had some very light flurries early this morning, after sunrise, and again this afternoon.  Still, nothing to show for the effort.  But, this evening’s clipper may give us at least a dusting.

The weak clipper has be producing very light snow across southwestern Indiana this afternoon and is moving eastward.  It’s also weakening.  Very little snow (if any) will drop south of I-64 tonight, so this system will be mostly north of Louisville.  We’ll probably see some flurries twice this evening – centered around 6 and 11 P.M.  No more than a dusting is expected anywhere near Louisville.  Low tonight in the upper 20’s and not much increase tomorrow with highs about the mid 30’s.

Monday into Tuesday

For the past several  posts, I’ve been pointing toward a strong Alberta Clipper expected to move into the western Great Lakes early next week.  Models are now projecting the primary snow chance for us Monday evening.  South of Clipper Monday, we’ll see see strong southwesterly winds and a quick warming into the 40’s.  The cold front trailing the clipper will push across central IN/KY Monday evening.  That will bring us the coldest air mass of the season Tuesday through Thursday.  Temperatures should drop to the lower single digits a couple of days.

What about snow?

Yesterday I mentioned the (to me) unusually high amount of precipitation the GFS was projecting with that front.  The weather south of clippers is usually quite dry.  Today, the GFS forecast reduces the rain/snow totals considerably.  The NAM is also low.  That seems much more reasonable to me.  But, it also reduces the snow potential to less than an inch.  It’s early, things could change.

Daily chance for snow ahead

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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

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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

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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

Snow on the Sahara!

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Tuesday, Jan. 22, 2019

Amazing pictures

I missed these photos about two weeks ago, but they are certainly worth a look.  The little Algerian town near where the snow fell has only had snow three times in its recorded history…the past two years and 45 years ago!

This is from a web site known as Earther.   https://earther.gizmodo.com/it-snowed-in-the-sahara-and-the-photos-are-breathtaking-1821884950?utm_medium=sharefromsite&utm_source=gizmodo_copy&utm_campaign=top

 

 

Wet and Warm Wednesday

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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.

 

Correction to previous post

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Jan. 21, 2019

Previous post accidentally described the next system to reach us as a negatively tilted trough.  That is incorrect.  Trough is positively tilted.  In general, positively tilted troughs produce weak weather systems.  Negative tilted troughs are far more energetic.

Sorry for the mistake.

Click on the corrected post (to the right).

Cold air highlights the week ahead

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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!

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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!