Is #TeddySnowsevelt turning into #DwightDIcenhower?

Current Temps and Radar

1:04 AM Update

Sleet — almost exclusively sleet — has been falling in Clarksville since around midnight, glazing elevated surface and icing roads. Most of this went N of us, except for poor Joelton.

That’s just the beginning. Reports in E Arkansas and W Tennessee were also of sleet with corresponding and typical icing problems. That system is coming our way.

The bulk of this precip will arrive in Nashville around 5 or 6 AM. With surface temps below freezing, but temps aloft barely above freezing, sleet is expected. HRRR, NAM4, and GFS models all agree sleet will be the predominate precipitation type. This means slippery, slushy roads progressively worsening through the day.

All this sleet means very little snowfall. I’d expect less than 2″. This is expected to be a sleet event.

HRRR runs of late have pushed the surface freezing line really close to, but not encroaching, S Williamson County. The NAM4 also has the freezing surface temp dividing line running tangent to, but not in, Williamson County. The 0z run of the GFS has also kept freezing surface temps well south of us. So, even though it’s really close, we’re expected to barely stay below freezing at the surface, which is bad news for travelers and commerce in general.

Temps will only briefly flirt with the freezing mark. After 4 PM or so, temps will level off, then begin to tumble through the 20°s Monday night, freezing everything again. Travel will likely be treacherous again early Tuesday morning.

In fact, record cold temps are on the way. After bottoming out at 15° Wednesday morning, we’re forecast to shatter two records Thursday morning: (1) coldest temp ever for February 19, we’re forecast to -3°, the record is +5°. (2) We’ve never had a subzero temp in February.

Will will be up and tweeting @NashSevereWx by 4 AM.  By then, the midnight shift should have a new suite of forecast products.

9:24 PM Update

NWS-Nashville just released a forecast update. If you want to read it for yourself, click here. Otherwise, I’ll paraphrase.

Remember the “it’s all about that track of the low pressure center” theme from a few days ago (and this morning)? Well, that low continues to track North, as verified by the latest run of the NAM model. This north track is in keeping with other models and prior runs. This northern track “continues the trend of working warm air aloft into our approaching winter storm during the day on Monday.” However, the warmest air aloft is expected to be in counties to the south and the east of us.

We remain annoyingly right on the line.

This northern trend will work to keep the best chance for the most significant snowfall of 2″ to 4″ confined largely to a relatively narrow band near the Kentucky border.

“Latest NAM data also suggests that snow amounts over the north might not be quite as great as previously expected. However, will have to wait for the GFS to come in before jumping whole hog into that idea. The NAM still shows at least 2 inches and 4 inches likely over parts of the extreme north during the day tomorrow. So, at least a narrow strip of the north is still vulnerable to significant snow accumulations on Monday. Again, even where snow is not that significant, the sleet will be coming down in bucket fulls.

High temperatures along I-40 tomorrow look to be between 30° and 32°. All parts of Middle Tennessee should see hazardous driving conditions develop late tonight and on Monday.

In addition, the NAM model shows the most widespread snow occurring Monday night, when almost all areas could get an additional 2 inches to 4 inches.

No changes to the forecast suite are expected. The midnight shift at NWS-Nashville might decide to make changes after enjoying the benefit of the 0z suite of forecast models. For now, I think it’s fair to expect 2″ south of 40, more than that north of 40. But, that’s just snow. We still expect a lot of sleet!

8 PM Update

Answers to Your Questions!

1.  WT in the F…after all this, there won’t be snow!?!?

No one is saying that. We think it will be a sleet and snow mixture. More snow north of 40, more sleet less snow south of 40.

2.  Do you think travel will be worse in the AM or later as the event goes on? & How badly will this effect the roadways for the morning commute?

The commute is going to suck. We can’t find a single weather model that brings our surface temperatures above 32°. It was cold enough today to ready the roads to accept and freeze all forms of precipitation.

3.  Would it be best to go in to work early and then leave around lunchtime?

I think that’s a bad idea, unless you work at a hotel and bring a toothbrush. Conditions are expected to deteriorate during the day. Travel home should be a mess.

4.  First we heard 10″ then 7″ then 4″ now ice. So safe to say nothing is coming???

I hope the first thing you heard was that the forecast was going to change, and the number you were given at the time was the best estimate. Here we are less than 12 hours from the event, and no one thinks we will get nothing. A few of you are demanding expressions of certainty and levels of detail which exceed the state of the science. We just aren’t that good. However, we get better the closer we get to the event. I wish the science was better than that.

5.  NWS Nashville’s site says 3-7 inches of ice/snow. Still think that’s accurate?

I expect that to be tweaked a little bit tonight. When it is, we will tweet it. I think Joelton, Madison, Hendersonville are good for about 5″, maybe more (7″ is reasonable), with Thompson’s Station and Spring Hill mostly a mess of slushy sleet with snow mixed in. Everyone else somewhere in between. We think this makes the most sense, but, we don’t really know.

6.  Are we expecting Monday morning commute problems?

Absolutely.

7.  What about [flights; somewhere other than Davidson & Williamson Counties]?

I’m too busy getting Davidson and Williamson County wrong to venture outside our territory and get your forecast wrong, too. Also, I know as little about flights as you do. I wish I knew more.

8.  Why do

Sorry, what was that? Music’s on too loud.

9.  When will it all end?

We think it’ll all and before midnight tomorrow night.

10.  Have you heard from PanicCatfish?

No. I’m worried about him. He faxed (yes, dude faxes) me this a few hours ago. No note.

That’s not even him, and there’s a reference to lures in the corner. I’m pretty worried.

11.  Publix and Kroger thank you all for your participation…..

My Milk & Dairy Overlords would not permit a written response, but I think I can slip a wink and a GIF past the censors:

4:57 PM Update

Here’s where we are:

We think #Snowbama will be in full swing by 5 AM:

Will It Be Sleet, Or Snow? The models continue to think the 850mb temps — that’s the 32F air at 5,000 feet — will push toward I-40 when the precip arrives. Surface temps are still expected to be below freezing. So, the issue isn’t “will we,” but “what kind” and “how much.”

The further N you go, the more likely you’ll see more snow.

The further S you go, the more sleet you’ll see (thanks to those barely-above-freezing temps at 5,000 feet), and therefore less snow.

The determining factor will be the actual location of the 850mb freezing line. Go south of that line, you’ll get mostly sleet and freezing rain. Go north of that line, and it’ll be all snow.

The problem with this forecast is that the models disagree exactly where the line will be.

The NAM4 puts the line N of us around noon. This would give us a sleet event:

The GFS has it over here:

The Euro is somewhere in between.

So, a wiggle north or south will make a dramatic difference. Right now, this looks like a sleet and snow event for us, not the all-snow mother of all snowfalls.

Still thinking 0.25″ of ice is possible, with around 2″ to 3″ of snow near Spring Hill, and 5″ to possibly 7″ N of I-40. The models are still showing 9″ and 10″, but we think that’s way too high.

NWS will update snow and ice accumulations tonight. We’ll pass those along here and on Twitter @NashSevereWx.

@kylemcreamer sent us this. Hilarious.

This website supplements @NashSevereWx on Twitter, which you can find here. Lots more/updated information will be posted there.

#Snowbama! #SnowverCleveland! The President’s Day SnowStorm!

Current Temps and Radar

1:00 PM Overview

From the NWS-Nashville Conference Call:

Ice remains a concern. New from NWS-Nashville:

This has produced a downward adjustment in snow totals, but has also increased the range of possibilities.

Expect more snow the further north you go, and more sleet/ice the further south you go.

We still think all this will start after midnight.

What about tomorrow night? This:

10:07 AM Update

To get snow, temps aloft and at the surface have to be below freezing.

However, this morning we’re seeing the models continue to predict the arrival of at/above freezing air at around 5K feet (plus or minus a few thousand feet) when this all starts after midnight tonight. That would transition this from an “all snow” event to a “sleet and/or snow” event.

With the introduction of sleet into the equation, expectations for massive snow accumulations should go down. This is what we were concerned about earlier this morning (the purple line shown in the below models). Seems we are always on the freezing line one way or the other. Usually, the factor preventing snow is “too warm” surface temperatures. With #Snowbama, the issue is warmer temps aloft with colder/below freezing temps at the surface. So frustrating. It’s what we get for living in a mid-latitude city.

It want to emphasize surface temperatures are expected to remain below freezing. Whether it’s snow, sleet, or maybe even rain falling from the sky, when it falls to us, it’s going to encounter freezing temperatures and freeze to anything and everything.

Here’s the latest thinking on timing and type:

This remains a very big storm and a definite threat to all types of travel Monday into Tuesday. Forecast temperatures for us are not expected to get above freezing until Friday afternoon (although it’ll be close tomorrow afternoon).

This website will be updated periodically throughout the day (because stuff will change!). The latest information will be always be found on Twitter @NashSevereWx. This website operates to supplement what we do on Twitter. Consult multiple reliable weather sources multiple times today.

7:44 AM Update

NWS-Nashville put this link on its front page this morning:

They led this morning’s forecast discussion with “southern storm system will bring wintry weather to Middle Tennessee tonight through Monday with the potential for some of the heaviest snowfalls in more than 10 years.”

“Winter Storm” for Nashville is defined as 3″+ of snow, and/or 0.5″ of sleet, and/or freezing rain. This morning, a Winter Storm Warning was issued to account for the 3″ of snow expected between 9 PM tonight through 6 PM Monday.

This Winter Storm Warning is for all of NWS-Nashville’s area. See the shaded counties above.

We’re interested only in what’ll happen in Davidson and Williamson Counties. We think the snow will start falling later tonight, sometime between 11 PM and 2 AM.

As the graphic above says, when the snow starts to fall way overhead, it will encounter dry air. This dry air will evaporate/gobble up the snowflakes before they reach the ground. But, the dry air can only eat so much, and once it’s “full” (meaning, the air is saturated), nothing will stop the snow from falling.

The NAM4 model kicks off the snow in the middle of the night, around 2 or 3 AM. The GFS does the same thing. HRRR is also following this trend. Expect our snow to start after midnight.

If you’re traveling anywhere, go tonight. Not tomorrow.

How Much?

Predicting snow totals is exceptionally difficult. If the system wobbles a little bit this way or that way, it’ll make a big difference in accumulation. For this reason, consult multiple reliable sources of weather information multiple times leading to and continuing through this event.

Right now, NWS-Nashville is emphasizing TREMENDOUS UNCERTAINTY EXISTS, then dropping a half foot on us:

This forecast will adjust multiple times. Please don’t stop checking back with the weather. The models have been wobbling this system north and south over the past few days. It’s currently wobbling a bit north, but still, we expect the end of #Snowdome.

The Models!

The GFS has a good depiction of the wobble problem/concern:

But, as it’s currently modeled, the GFS thinks we’ll see this:

But if that L moves those 5,000 ft (850mb) temps 50 miles north or south, it will make a huge difference. it could cut our snowfall accumulations in half. Right now, though, the storm is perfectly oriented to bury us. Thanks, #Snowbama! (I’m calling this #Snowbama because “President’s Day Snowstorm” is too wordy. We also liked #SnowverCleveland, but felt that was too long.)

Let’s just look at one more model: a regional model (GFS is a global model). Our friend, the NAM4!

Anyway, watch what the “wobble” north does to our snow accumulations:

Note this is the 6z run of the NAM. The new one was downloading but taking forever. We’ll be posting several model updates to @NashSevereWx all day.

Remember this graphic from a few days ago?

Still true!

The conceivable range here is 1″ to 11″, but those are outlier totals. Most likely is 6″. Watch the whole game, even up to the final play. Otherwise, you may miss it:

This website supplements @NashSevereWx on Twitter, which you can find here. Lots more/updated information will be posted there.

Wind Chill Advisory Tonight, Winter Storm Watch Tomorrow Night

Current Temps and Radar

If you aren’t panicking yet, WHAT ARE YOU WAITING FOR?

First, it’s going to get really cold tonight and tomorrow. So cold, NWS-Nashville issued us one of these:

Wake-Up temps Sunday will be in the teens. The afternoon high is 28°, but the wind chill will not get above 18° all day.

Then, we wait for ThePresident’s Day Snow of 2015 #SnOwBAMA.

It all starts as early as 8 PM, or possibly later than that. The first flakes will be battling the Dry Air Monster (not pictured).

This dry air battle will delay the onset of accumulating snow. We expect the meaningful snow potential to begin around 3 AM and extend until noon Monday.

NWS-Nashville says “confidence in snow amounts is still low at the moment, but improved over yesterday’s forecast. This is largely due to the differences in [moisture content] between the models as well as the drying out of the upper levels per model soundings.”

Model Forecast Accumulations Through Monday Night at Midnight

GFS model

NAM4

Euro (not pictured because terms of service do not allow it, and even if it did, I don’t know that I could bring myself to actually post it, so here’s this):

Short Range Ensemble Forecast (each line is its own regional model, the black line is the mean)

Those 4 models are just that…models. Models aren’t forecasts, but they’re consulted when making a forecast. Remember, NWS-Nashville’s “confidence in snow amounts is still low at the moment.” For now, they put us in the 3″ to 5″ range.

catshell

That much snow is hard to believe, isn’t it? It can happen:

But…9″, Euro?

Really hard to believe.

Go with 3″ to 5″.

It just feels wrong to expect this much snow. The only reason I can come up with to discount it is our 4 year history of busted snow forecasts. All the models are siding with the snow.

Even the Canadian!

For this reason NWS-Nashville has issued a Winter Storm Watch effective at 6 PM Sunday and lasting through 6 PM Monday. This is because we are forecast to get more than 3″ of snow during that 24 hour period.

All we need is 1″ to bury the #Snowdome. That looks like it’s going to happen. Our last 1″ snow was February 9, 2011. Four years, six days ago.

It appears cold temperatures will be lingering throughout the rest of the work/school week. A series of low pressure areas are believed to continue to slide our way and reinforce our cold air aloft. It’s likely temperatures at 5000 feet won’t get above freezing until Friday night. Meanwhile, surface high-pressure will probably keep us at/below freezing until Friday. With cloud cover, little sun, and 3″+ of snow on the ground, it’s going to be hard to warm us up past freezing to get a good snow melt.

Consult multiple reliable sources of weather information multiple times leading to and continuing through this event.

This website supplements @NashSevereWx on Twitter, which you can find here. Lots more/updated information will be posted there.

There’s no place like snow…. There’s no place like snow….

you thought she only dealt with tornados….

(Editor’s Note: this post was written by Friend of @NashSevereWx and fellow local weather nerd Justin Mundie. I thought you would enjoy and benefit from his thoughts on the approaching winter storm. As usual, nothing we write or Justin writes is an official NWS forecast unless it says so).

Good afternoon readers. I’m your guest host for the moment. My name is Justin Mundie. I’m a Realtor with Village Real Estate. 30 years old. 12 in Nashville. 27 years a weather nerd. But enough with introductions… lets get to the interesting weather we have on tap.

This morning, modeling has been moving towards a more consistent solution after having waffled around between no snow, 2 separate waves of precipitation, and now one, healthy wave Sunday Night through end of business Monday. The continuity between the computer models is helping to solidify confidence in the forecast. When we’re talking about something as complex as the atmosphere, there is always the possibility for a forecast to go terribly wrong. Snow is even more difficult than normal forecasting because a minor difference in total water content falling from the sky (that wouldn’t be noticed in an ordinary rain storm) can yield drastically different results as far as snowfall (not to mention temperatures being off a degree or two). Generally, 1/10 inches of liquid water equals an inch of snow. But that varies as well, which plays into the uncertainty.

Now for the big picture. The snowstorm that is set to blast Boston with another foot tonight is a big part of what’s going on with our weather down here. As it stalls off the coast of Newfoundland, it slows down the flow of weather systems across the country. We weather nerds call this a 50/50 low due to its proximity to that lat/long. This allows for the energy that spawns low pressure to move more south than east, a prerequisite for southern snow. It also works in tandem with cold high pressure over Michigan to funnel cold air into the southeast, another necessary ingredient in for winter weather in these parts. On the other side of the country, a tall ridge of high pressure is off the west coast. This drives the jet stream up towards the north pole and then back down into the center of the country. Pieces of “energy” dive down this ridge underneath the cold air in the east, and as they start moving east instead of south, they act as a mechanism for transporting gulf moisture up and over the cold air that’s sitting on top of us. This is the perfect situation for heavy snow to fall in our area. You can see these features on this 500mb map:

gfs_namer_072_500_vort_ht

At the present time – modeling indicates that precipitation, in the form of snow, breaks out in southeast Missouri Sunday afternoon. As this disturbance dives south, it should tap the Gulf of Mexico, a rich source of moisture, and the radar should begin to fill in with heavy snow falls near Cape Girardeau (Missouri). Which makes me think of Lamberts, home of “throwed rolls”. (Its lunch time as I’m writing this. Sorry.)

(Editor’s Note: I cannot recommend this place more. Love it).

As the evening progresses, this strengthening low pressure system moves underneath the dome of cold high pressure over Michigan, and should bring somewhere between .3 and .6 inches of qpf (water) into our area. That should translate to roughly 3-6 inches of snow. Locally there could be areas with more wherever convective banding sets up (think the bright colors on the radar). Precipitation should end sometime in the afternoon Monday and temps will plummet behind the system. With healthy snow cover, low temperatures Wed and Thursday could get down into the low single digits. Yikes.

I like to qualify my forecasts with what could possibly go wrong. There are a few things I’m concerned about.

Dry air: The air will be dry and it’s possible that models are predicting precipitation that would fall into a more moist atmosphere. If there is too much dry air, we could end up with lots of virga, which is precipitation that’s evaporating before it hits the ground.

Sleet: If temperatures rise too much in the upper atmosphere, snowflakes that fall through it will melt and refreeze upon reaching the ground. The further you are towards the TN/AL line, the higher likelihood of sleet mixing in. While snowfall ratios are generally 10 inches of snow for 1 inch of water, sleet is more like 2 inches for 1 inch of water. So even a couple hours of sleet can really screw up predicted snow totals.

Model Error: The energy diving down may not be modeled correctly. There is energy in the southwest as well that appears to stay back and travel to our south on Tuesday. If there’s more interaction with this energy, or no interaction at all, we could end up with a drastically different solution.

Right now – I’d say my forecast confidence for 3-6 inches with locally higher amounts is about at 50%. Give me another 24 hours and I’ll feel a lot more confident. But, as you know if you’ve lived any time in Tennessee, the weather can surprise you.

Editor’s Additions

Thanks for that, Justin. Great job.

The official forecasts from NWS-Nashville:

Start Times

Snow Totals

The week ahead

More/Updated information will be posted on Twitter @NashSevereWx, which you can find here.

#Snowbama

Current Temps and Radar

TodayWarmish Afternoon & Then Rain/Flurries As Temps Crash – High 48°

A clipper system will race through Middle Tennessee around noon bringing a slight chance for rain and no worry flurries during the late afternoon. From NWS-Nashville:

clipper snow

The short range models are picking up on this chance for rain transitioning into light snow. Below is a look at what the HRRR is showing during the late afternoon.

no worry snowz

Overnight we will be clear and cold because of a high system pressure centered in the Great Lakes that will sage down into Middle Tennessee. Wind will become northerly at 10mph –  20mph!

Overnight temps will bottom out in the Lower teens and wind chills will get below 0 degrees!

Sunday

Sunday will begin in the lower teens and only reach the mid 20’s during the afternoon. Increasing clouds combined with northerly winds at 5mph – 15mph will allow the wind chill to get as low as -2° during the day.

President’s Day Snow, aka #Snowbama

Model overview: All the models are in agreement snow will begin Sunday night and continue into Monday. Then, for Monday, the the models diverge in their agreement…The GFS keeps snow possible in Nashville throughout the night into Tuesday. The Euro cuts the snow threat off overnight and keeps the activity off to the east of Nashville. While the NAM is in between these two on timing. The NWS believes that we will hold onto a slight chance for snow through Thursday because of a trough of low pressure that will stick around and allow for disturbances to race through it.

Details

The GFS has #Snowbama beginning around midnight.

nash snow gfs

With snow ending by Tuesday evening.

snowbama end

A slight chance for snow will continue through Thursday as a series of smaller disturbances race through Nashville.

smaller gfs

Snow chances will completely end early Thursday morning.

The NAM has #Snowbama beginning Sunday evening.

nam snowbama begins

#Snowbama’s first term ends by Monday afternoon.

NAM Snowbama

According to the NAM there will be a lull in the snow until #Snowbama’s second term begins Tuesday morning.

second term

The NAM doesn’t go out far enough to see the end of the second term.

The Euro has #Snowbama beginning early Monday Morning and ending Wednesday afternoon. It dumps about a half a foot on us. 6″!  This is the high end of the probability spectrum, and is NOT a forecast.

Probabilities/Amounts

Once we go through the day Monday…we get this:

So, what we have is a about a 5″ difference between the low-snow total models and the high-snow total models. As usual, the truth is probably somewhere in between. NWS-Nashville is splitting the difference, and says it’s possible we will see 3″ or 4″ on Monday.

THIS MAY CHANGE. IN FACT, IT PROBABLY WILL. CONSULT MULTIPLE RELIABLE SOURCES MULTIPLE TIMES FOR YOUR WEATHER INFORMATION.

The streak of days without an inch of snow appears to be coming to an end.

extended

Find more details throughout the day @NashSevereWx on Twitter.

Snow Streak In Jeopardy?

Current Temps and Radar

Today – Warmer Than Yesterday – High 38°

The high pressure that has been overhead the past couple of days will shift to the southeast and allow us to warm into the upper 30’s.

Overnight temperatures will get into the mid 20’s.

Saturday – Warmer Afternoon & Slight Chance for Flurries – Wake Up 26°, High 49°

Temps will warm into the upper 40’s.

After noon, a clipper system will be racing through Davidson/Williamson Counties, causing a cold NW wind to start gusting into the 20s.

During the late afternoon, the clipper system will bring a chance for a few no-worry-flurries. Here is a look at what the High Res NAM is showing at 2 PM Saturday:

no worry snow

Overnight we become partly cloudy and will — temporarily — lose our slight chance for snow. Temperatures will fall into the… teens!

Sunday – Warmer Afternoon & Chance for Flurries – Wake Up 12°(wind chill: 0°), High 26° (wind chill: Teens)

High pressure centered over the Great Lakes will build into Middle Tennessee which will help usher in a reinforcing blast-o-cold air.

Then, during the afternoon, a strong upper level disturbance will arrive.

All that ahead of what our NWS thinks is a “good chance” for snow late Sunday night/early Monday morning, with accumulation possible.

Sooner or later, our hair is going to be caught in the blender.

Is this that time?

The big picture is becoming slightly less fuzzy, but there remains plenty of uncertainty in the models. It’s fair to start breaking them down for you, but please remember: this is going to change. Perhaps dramatically. Do not unplug from the grid. Stay tuned. Consult multiple reliable sources for your weather info, preferably something a little more informative than your crapapp.

The NAM and the GFS are in relative agreement. They both believe that a few flakes could begin to fall during the late afternoon Sunday. According to both, the event will begin between 6 PM and midnight, but more likely closer to Sunday midnight/Monday AM than late Sunday afternoon.

NAM:

NAM Snow

GFS:

GFS SNOW yo

Both models believe the heaviest snow will fall around midnight and the the event will end before noon on Monday.

Editor’s Note: the reason I’m not jumping on board all the way with this event “happening” is the trend of the GFS model. Thing keeps trending south of us, and the available moisture content for what we think we may see keeps declining. Plus, we’re stil more than 48 hours away from the event. I’m very nervous this’ll bust. Please don’t tell everyone we’re sure it will snow, because we aren’t. We think it’ll probably snow. It’s important we give our intern this forum to handle this the way he sees fit, and I respect his opinions on it. We’ll offer another independent opinion on it tomorrow. 

Below is a look NAM’s modeled sounding using BUFKIT at midnight.

BUFKIT SNOW

The Sounding above makes me believe that the snow to liquid ratio will be above 10:1. During the event the ratio could be between 15:1  and 25:1. The NAM is predicting a total of 0.2″ of liquid to fall during the event. Based solely on the NAM/GFS and the ratios listed, we could see a few inches of snow. Remember this is only based on two models… Don’t panic.

What about the Euro?

This model thinks it all starts between midnight and 6 AM Monday morning and ending Monday night.  It also predicts higher snow amounts.

The Canadian Model is in agreement with the Euro on timing but not snow totals. The Canadian believes that the bulk of the snow will stay south of Nashville and along the MS/AL and TN border.

GEM snow

This is still alot of snow.

Summed up:

The models believe that the snow will begin overnight on Sunday and could continue through Monday afternoon, ending overnight. Snow accumulation is looking more and more likely but this far away I will not give a range. All I will say is that if I were a betting man, I’d put money on breaking the streak of days without 1″ or more of snow.

extended

The NWS believes we will have a slight chance for snow Tuesday through Wednesday night… It is starting to look like the snow will stay south of Nashville on those days.

Just for fun. This:

This website supplements @NashSevereWx on Twitter, which you can find here. Lots more/updated information will be posted there, including the results of the 2 PM conference call with emergency management, local media, etc.

 

Snow: All About That (Track of the Low Pressure Center)

Current Temps and Radar

What Was Up With This Morning’s Flizzard?

We missed it.

Last night’s forecast grids had a 5% probability of precipitation (POP) and no quantitative precipitation (QPF):

I went back and checked last night’s HRRR and NAM4 models: bone dry.

At 3:39 AM, NWS-Nashville mentioned the potential for flurries which were ongoing in central MO/IL.

At 7:25 AM, we noticed this in KY:

By 9 AM, it developed into a full-on flizzard:

When I saw it:

What happened? After the Arctic front blasted through, there was a little ripple in the upper levels of the atmosphere, which produced enough lift to set off no-worries flurries.

We missed that one not because we weren’t paying attention, but because it:

If you want perfection, read your Bible.

Friday, NWS thinks there’s a “very small possibility” we could have a re-do of the flizzard we saw this morning; however, any flizzard is expected to be smaller Friday than we saw Thursday.

Saturday, another arctic front will reinforce already-cold air, and may bring some light snow to the area. Officially, only flurries are expected — not accumulation. We’ll be watching this closely.

Sunday morning’s wind chills will be in the negatives.

“Enough Already! What About The Snow?”

My rant from earlier bears repeating. If you’ve read this already, scroll down to the purple words.

If you look hard or long enough, you’ll find some knucklehead posting model data with snowfall accumulation maps. These guys (usually guys, sorry ladies!) like to tweet, Facebook, Snapchat the model with the highest snow totals. A good example is the Canadian model, which has 15″ of snow falling across all of Tennessee, which is ridiculous. That’s a model, not a forecast, the same way that a brick is not a house.

For the record, I get it. I realize there are some websites that are going to make a “call,” and I really don’t have a problem with that. Most people just want weatherpeople to make the call, right? Like this?

What I don’t like about this is that there is a specific accumulation range listed.  This forecast is more complicated than that, and I think you’re all smart enough to understand and accept the uncertainties and probabilities that go along with it. So why not just lay it all out there? Just putting up a number and a percentage is an OK starting point to a discussion, but it should not be the end of the discussion. It should begin the discussion.

During this afternoon’s forecast discussion, we learned the models are still painting a fuzzy picture. (Translation below)

It’s all about the track of the low pressure system. The models aren’t exactly sure where it’ll track. It all depends on the track.

If the low tracks south, we’ll see more snow and less rain. On its current track, it’d be a pretty decent snow event for us.

But if it tracks too far south, we may not see anything.

And, if it goes back north, expect a mess of rain/sleet/snow.

NWS still says our “forecast confidence continues to be low,” which doesn’t sound like an 80% chance of 3″ to 5″ to me, either.

Earlier today, NWS-Nashville wrote this, worth repeating: “Emphasis must be placed on the very low confidence with this scenario as it remains over five days out and model guidance will likely shift in numerous times until the event gets closer.” This afternoon’s data is a good illustration of that.

And, yes, we could be looking at another clipper system making us some snow Wednesday night, but with low confidence in Mon/Tue snow, there’s no confidence in Wednesday’s forecast.

One of the more unusual components of this storm will be the sub-freezing temperatures expected after all the precipitation ends. It may not be until Friday afternoon that we rise above freezing.

This website supplements @NashSevereWx on Twitter, which you can find here. We’ll post updated info there.

SnowMageddon Next Week? Look at the whole board.

Current Temps and Radar

What Was Up With This Morning’s Flizzard?

We missed it. We all missed it.

Last night’s forecast grids had a 5% probability of precipitation (POP) and no quantitative precipitation (QPF):

I went back and checked last night’s HRRR and NAM4 models: bone dry.

At 3:39 AM, NWS-Nashville mentioned the potential for flurries which were ongoing in central MO/IL.

At 7:25 AM, we noticed this in KY:

By 9 AM, it developed into a full-on flizzard:

When I saw it:

What happened? After the Arctic front blasted through, there was a little ripple in the upper levels of the atmosphere, which produced enough lift to set off no-worries flurries.

Anyways, as for this afternoon: the clouds are clearing away. We didn’t get any accumulation, so it wasn’t a big miss. But, yeah, we missed that one not because we weren’t paying attention, but because it:

If you want perfection, read your Bible.

So anyway, most if you are reading this because you want to know what’s going on early next week. Believe me, so do we! So, I’m dispensing with the normal format. Here’s Friday-Sunday: It’s going to be cold. Especially Sunday (bundle up for soccer practice!):

SnowPocalyspeMaggedon 2015: Is The World Ending Next Week?

If you look hard or long enough, you’ll find some knucklehead posting model data with snowfall accumulation maps. These guys (usually guys, sorry ladies!) like to tweet, Facebook, Snapchat the model with the highest snow totals. A good example is the Canadian model, which has 15″ of snow falling across all of Tennessee, which is ridiculous. That’s a model, not a forecast, the same way that a brick is not a house.

For the record, I get it. I realize there are some websites that are going to make a “call,” and I really don’t have a problem with that. Most people just want wxpeople to make the call, right? Like this?

What I don’t like about this is that there is a specific accumulation range listed.  It’s more complicated than that. And I think you’re all smart enough to understand and accept the uncertainties and probabilities that go along with it, so why not just lay it all out there? Just putting up a number and a percentage is an OK starting point, but it should not be the end of the discussion. It should begin the discussion.

That discussion starts with NWS-Nashville’s AFD (area forecast discussion):

Everyone uses models (and experience, etc) to make forecasts. For Monday-Tuesday-Wednesday, these models “continue to struggle” and provide a “wide ranging forecast nightmare of potential wintry precip types.”

Hmmm. OK. It continues:

“Forecast remains quite complicated and of low confidence” doesn’t sound like an 80% chance of 3″ to 5″ to me, either.

So, when you read the below, you should do so in the context of the red and purple underlined text above, and then you should remember that 12 hours ago we missed that flizzard.

Anyway, our NWS currently thinks:

1.  Precipitation could arrive as early as Monday morning, and with the arctic air mass still hanging around, light snow or sleet would be most likely.

2.  During the day Monday and into Monday night, temperatures at the surface are expected to warm at the same time temperatures at 5000 feet will warm, changing the wintry precipitation to freezing rain and ice pellets, then eventually rain by Monday night.

3.  Rain would continue overnight Monday into Tuesday.

4.  Some time Tuesday, more cold air will arrive as the system is pulling away, and change the rain back to snow, ending Tuesday night or early Wednesday morning.

One of the more unusual components of this storm will be the sub-freezing temperatures expected after all the precipitation ends. It may not be until Friday afternoon that we rise above freezing.

“Emphasis must be placed on the very low confidence with this scenario as it remains over five days out and model guidance will likely shift in numerous times until the event gets closer.” (NWS-Nashville)

Let me illustrate something. The GFS “runs” 4 times a day. Let’s look at Tuesday morning at 6 AM.

Here is the latest run (snow):

Here’s the run — covering the same time as the one above — before that (rain):

This the same model, and even it doesn’t know if it’ll be raining or snowing.

This is why your app that says there’s an 80% of 3″ to 5″ is crap app.

We weather guys are Sam Seaborn. We are definitely not President Bartlet.

This website supplements @NashSevereWx on Twitter, which you can find here.

Prepare for Cold

Current Temps and Radar

Getting much colder. Watch the graph below. It’s going the wrong way.

Thursday – Colder. Much Colder – Wake Up 26°, High 31°

The wake up wind chill is 14°. Fourteen!

Overnight temps will drop into the teens. Ugh.

Friday – COLD – Wake Up 16°, High 37°

Just look at this:

So. Cold.

Monday/Tuesday snow potential:

Weather models spit out “solutions” (what it thinks will happen) on a daily basis. The GFS model “runs” 4 times a day. The Euro model runs twice a day. Not only do these not agree with themselves from run to run, but they also disagree with each other.

Here’s what NWS-Nashville noted about the model solutions for Monday/Tuesday:

Yeah. We don’t know either. Could be rain. Or snow. Or sleet. Or ice. Or all of this. Only thing we have some measure of confidence about: there will be precip.

This website supplements @NashSevereWx on Twitter, which you can find here.

Warmer Tomorrow. After that, Not Warmer. Definitely Not Warmer.

Today – Wind Chills in 30°s

Our afternoon high is 45°, but the north wind will cut the wind chill to the 30°s.

We expect some clearing this afternoon. Visible satellite:

Wednesday – Warmer – Wake Up 29°, Lunch 50°, High 56°

Thursday – No! – Wake Up 27°, Lunch 32°, 6 PM 27°

A cold front will arrive and restore February.

You might hear a slight mention of snow/flurries. That’ll be to our east, with nothing for us.

Typical February cold will settle in for the rest of the week, but it won’t be blergy (remember: blerg means 30°s, no snow, no sun; we’ll see the sun):

Pain returns Sunday in the form of a powerful cold front. NWS-Nashville calls it a “true Arctic airmass.”

Temps Sunday at 6 AM:

Wind Chill Sunday at 6 AM:

Snow? We don’t think so.

But maybe Monday. GFS and Euro models are cooking up hope for a snowstorm Monday/Tuesday. Way too far away to get excited about this. More details to follow over the next several days.

This website supplements @NashSevereWx on Twitter, which you can find here.