Little Snow Tonight?

Current Temps and Radar

Tonight: Snow Sliding In?

As we wrote this morning, rain systems will pass to our south over the next 2 or 3 days.

The first comes tonight/overnight.

To deal with this I decided to make this low quality YouTube video (where went the HD button?):

If you can’t watch it: as the system moves closer to us, it’ll encounter drier air. We think there may be a brief dusting S of I-40, but even that is unlikely. “Dusting at most.”

Monday – Below Freezing – Wake Up 19°, High 29°

Wake up wind chills Monday morning will be in the single digits, and won’t warm past the teens all day.

24 hours after Sunday night’s iffy snow event, an almost identically iffy/light snow event is possible. That system looks like it’s going to pass even further to our south.

Rest of the week: BLERG.

Friday-Sunday, the following pattern remains possible:

1. Rain/Snow mix at night.

2. Transitioning to light snow after midnight.

3. Then transitioning to rain during the day.

Long term, we think temps will finally make it to the 50°s.

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

When Will the Blerg Break?

Current Temps and Radar

Let’s start with an overview:

That’s pretty blerg.

The Blerg looks like it’ll break after next weekend:

Today – Little More Melting (High 39°), Cloudy, Chance of Rain/Snow Tonight

Rivers and streams are still rising a bit. The Harpeth River at Bellevue got a Flood Advisory early this morning water levels moved into action stage:

A Flood Watch remains until noon today.

Over the next 2 or 3 days, rain systems will pass to our south. Some of them may wander north into Middle Tennessee.

The first of those comes tonight/overnight.

There’s low confidence in this snow. If the system passing to our south wobbles south at all, we won’t see anything. This is very light precip. It would only be a “very light nuisance” per NWS.

Monday – Below Freezing – Wake Up 19°, High 29°

Wake up wind chills Monday morning will be in the single digits, and won’t warm past the teens all day.

24 hours after Sunday night’s iffy snow event, an almost identically iffy/light snow event is possible:

Friday-Sunday, the following pattern is possible:

1.  Rain/Snow mix at night.

2.  Transitioning to light snow after midnight.

3.  Then transitioning to rain during the day.

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

Rain Clearing Away, Freezing Temps Return

Current Temps and Radar

At 6 PM, the back edge of the rain was approaching downtown Nashville, and finally signaling the end of the soaking rainfall we’ve endured today.

A Flood Watch remains in effect until noon Sunday.

Radar estimated rain totals were between 1″ and 3″:

A Flood Advisory has been issued until 10:15 PM to account for all this rain and the snow melt. Don’t drive over water-covered roads. Also consider that with the ice, days of subfreezing temperatures, and all this rain, there are many new potholes and other structural problems with the underlying asphalt. This will compound what is already a bad decision to drive across a water-covered road.

A south wind helped temperatures climb steadily all day. Our high was 45°.

The end of the rain around 7 PM signals the return of a north wind…and colder temps.

Sometime after midnight, we will drop back below freezing, refreezing the standing water and slushmelt.

Meanwhile, with all the snow melt, the temperature and dew point will be very close together. This presents a fog concern. In addition, any fog forming over roads and sidewalks during freezing temperature will add yet another glaze of black ice. However, that concern is secondary to the traditional: water + freezing temperatures = ice equation.

Sunday – Blerg – Wake Up 30°, High 40°

A little more snow melt is expected, but it won’t be much. We are going to have to endure a brisk North wind around 15 mph, sending wind chills into the low 30°s by noon, low 20°s by 6 PM, and close to 10° by midnight.

There was a slight mention of snow in the forecast, but it’s not showing up at all on the short range weather models.

Sunday night around midnight, the NAM4 model thinks we will see snow showers along and south of I-40.

Other models aren’t so sure about this. It will be watched carefully, but this does not look to be a big or otherwise meaningful event. As this is happening, surface temperatures will crash through the 20°s, before settling into a Monday morning low of 17°. This will refreeze remaining water and any new wintry precipitation.

Monday – Cold – Wake Up 17°, High 26°

Wind chills aren’t expected to rise above 16°. However, we may see the sun peek through.

Extended Blerg: additional snow chances will present themselves throughout the week, but right now there is low confidence in saying we are going to have more snow and ice.

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

Ice Storm Warning: I Will Now Dodge Your Questions

Current Temps and Radar

Let’s dispense with the normal blog format.

An Ice Storm Warning is in effect beginning at Noon today.

Don’t miss the “Main Impacts” in this graphic:

  • Ice and snow will make travel hazardous. Rain will add to ice it is already on trees and surfaces, and will cause damage.
  • Tree limbs are likely to fall and power outages are likely.
  • Major disruptions to travel Friday afternoon through Saturday morning.
  • Warming temps and heavy rainfall will bring chances for localized flooding Saturday.

When

Snow is expected before the freezing rain begins. Snow should be light and intermittent, with accumulations not more than 1″. The HRRR illustrates this well. At 1 PM, we expect:

WeatherBELL Models _ Premium Weather Maps - Mozilla Firefox 2015-02-20 11.09.49

6 hours later:

7 pm

Between 1 PM and 7 PM the snow will slowly transition into a brief period of sleet before becoming all freezing rain.

NWS thinks snow/sleet will begin to transition into freezing rain between 6 PM and 9 PM tonight.

It will start in the southwest and work its way east and northeast. That means Fairview and Spring Hill are expected to see freezing rain before Brentwood, Nashville, Hermitage, Goodlettsville.

The NAM4 model thinks we will see more snow and much more freezing rain than is shown by the HRRR above.

Note: Freezing rain is RAIN, that freezes on contact with the ground. Do not fool your self into thinking it’s just cold rain!

If possible, I would advice heading home from work before 6 PM to avoid getting stuck in traffic when the we transition into freezing rain.

How Bad Will It Be?

Frankly, I’m encouraged by the off-and-on precipitation depicted by the HRRR model. I have a feeling we may be revising, up or down, the ice totals as we get closer to the evening.

Nevertheless, this looks to be a lot of ice. 0.25″ to 0.50″ does not sound like much, but when it sits on trees and power lines already weakened by Snowbama and OldSlickory, and winds at 10mph – 15mph (gusts 20 mph), there is concern we could downed tress and power lines… Power outages are possible.

Be sure to report any downed trees, power lines, and ice/snow accumulations using #tSpotter

Tell Me About the Sperry-Piltz Ice Accumulation Index!

Try to be cool. Everyone calls that “SPIA.”

When you add 0.3″ of ice to 12 MPH wind gusts, you score a 2 on the SPIA Index.

A “2” means ” scattered utility interruptions possible… Typically lasting less than 12 hours.”

When Will It Change To Rain?

This is the real question. There is a LOT more rain coming overnight and through Saturday. Getting that freezing line to lift north of us means everything.

The NAM4 thinks it’ll be 4 or 5 AM before we get above freezing. This will allow for more ice to accumulate. This model presents a much more concerning scenario because it thinks we will see 12 hours of icing. However, this model seems to be the outlier.

HRRR seems to be suggesting the freezing line, approaching from the south, will arrive much sooner — around midnight. The problem is this model only extends out to 15 hours, so we really are not in its range right as I write this. The good news is that the GFS model has us above freezing around midnight. So do the HRW-A and HRW-N models. This is pretty encouraging, but there still will be ice and it will be dangerous.

Can I Drive In It?

You shouldn’t. Right now, I’d want to be in my house by 3 PM. That’s just my estimate right now. No promises. Your results may vary.

What about if I’m going from X place to Y place?

Don’t drive in it.

What if I take Q road and Z route?

Don’t drive in it.

What About My Flight?

I don’t know. I wish I could help you. I can’t give you info I don’t have. The airlines make those decisions.

So When Can I Safely Drive?

When the freezing rain changes to “regular rain,” and there is sufficient time for it to melt. I can’t say exactly how much ice we will see, so I certainly can’t tell you what will be safe to travel. Check TDOT Smartway. In general, we think we will see improvement in road conditions Saturday after 9 AM, and possibly before. I’m planning on being out and about Saturday afternoon.

Rain/Flooding Saturday

With ice and snow melt, along with at least another inch of rain (and probably more), localized flooding could be a concern.

qpf 1-2 ...

We will be closely watching this throughout the day tomorrow.

What About Sunday?

Snow is possible Sunday and Monday. Then again Thursday.

Do You Sleep?

No.

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

Winter Storm Warning Details

Current Temps and Radar

NWS-Nashville has issued a Winter Storm Warning from noon Friday until 9 AM Saturday.

Friday Morning & Afternoon

Very light and intermittent snow in the morning. (615 PM Update: the two short range weather models, the HRRR and RAP, do not send us any morning snow. The NAM4 model sends us some very light snow, but even if it makes it to us, it will encounter a very dry environment and produce very little impact. The main hazards will develop sometime after noon and rapidly worsen through the evening).

Heavier snow should arrive around mid afternoon and continue into the evening.

About 1″, maybe 2″ of snow expected. We don’t think it will be accumulating until the afternoon.

Friday Evening Into Early Saturday Morning

Warm air aloft (yes, a “warm nose” similar to what we saw Monday) will arrive, with freezing temps at the surface. This will change snow to sleet, and then to freezing rain, sometime Friday night and lasting until around Midnight. Significant icing is expected across Middle TN. We expect 1/4″ of additional ice along I-65, a bit less west of 65, a bit more east of 65. “This additional ice is likely to cause major problems.”

Sometime between 3 AM and 7 AM, we should change from sleet/freezing rain to “all rain.”

Saturday Morning

Rain will continue from daybreak through the rest of the day Saturday, presenting potential for localized flooding.

Total precip this weekend will be between 1.5″ and 3″.

Light snow is expected late Sunday night, but it’s not expected — at this time — to be significant.

This website supplements @NashSevereWx on Twitter, which you can find here. Multiple updates and additional nuggets of information will not be here, but rather found on Twitter. As always, consult multiple reliable weather sources multiple times.

Arctic Temps Tonight & Winter Storm Watch Details

Current Temps and Radar

First, a PSA:

Observe the top of the car following you. If you’re not sure it’s clear, it is a good idea not to follow too closely.

Is the Snowdome Dead?

We thought so this morning. We stopped the #Snowdome clock this morning at . . .

. . . based on information we had 1.2″ of snow. Turns out that was at the NWS-Nashville office (they ended up with 1.6″), not at the airport, where official records are kept. The above streak counts official totals at BNA only.

Multiple places in Nashville measured 1″ or more of snow. But with BNA only at 0.7″ and unlikely to get to 1″ from afternoon flurries, we think the streak lives. As long as the streak lives, Snowdome lives. It’s the only objective way to go about it. Reasonable minds disagree, but I’m willing to live with that.

The Clock is restarted!

The question is: will it survive Friday? More on this below.

Arctic temperatures are arriving tonight and overnight. This will produce crazy-cold temps for us. NWS has issued a Wind Chill Advisory from 6 PM tonight through noon Thursday.

The official forecast low temp is -1°. The wind chill (that’s the “feels like” temperature) will bottom out as low as -14°.

Minus. Fourteen.

Thursday’s high is 17°.This forecast verifies, it will set records for the coldest low and coldest high temperatures

The snow and ice melt we enjoyed this afternoon will refreeze.

Winter Storm Watch

When:  Noon Friday through noon Saturday.

What:  A bunch of stuff.

Disclaimer! As was made painfully obvious this previous weekend, weather models aren’t perfect that good at pinpointing exact timing on transitions from snow to sleet to freezing rain to rain. That timing makes all the difference in accumulations. So, please note we expect this forecast to change.  Uncertainty reflects understanding, not a lack of skill or effort in trying to get the forecast “right” (whatever that means). As we get closer to the event, the forecast improves, so please check multiple reliable weather sources multiple times as we approach this event.

The following represents our best forecast. We are being vague with the times because we’re not really sure exactly when these transitions will occur. However, this represents the order of events and the potential accumulation for each.We’re omitting what would be a tedious review of the model data.

I made this graphic. Not an official NWS graphic.

NWS issued the Winter Storm Watch because “there is a potential for major impacts, but confidence is not yet high. Remember that watches signal to the public that there is something to prepare for. Some watches are upgraded to advisories or warnings as the events approach, or they may turn into nothing at all. Expect many updates to yet another challenging winter weather forecast.”

The biggest fear with this storm is the icing potential. During this past Monday’s #snowbama (or #UlysleetsSGrant #OldSlickory if you prefer), we had a good amount of ice, but it came relatively quickly and with very little wind. Friday night’s event may come with almost 2/10″ of ice plus 11 mile-per-hour winds. This causes concern not just for travel, but also for the integrity of already-heavy-from-ice trees and power lines.

Consider this Ice Accumulation Index:

 

The Weekend

Rain, and a lot of it. Temps in the 40s will assist and possible achieve total ice melt.

1″+ is expected. Right now, we do not anticipate a flooding event, although localized flooding may occur.

Then, as if that’s not enough to deal with, as the rain is pulling east of us it may change into a light mix of snow late Sunday night into Monday morning.

With cold weather the rest of the week.

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

Winter Weather Advisory Wednesday Morning: A Little Snow

Current Temps and Radar

Today’s sunlight helped the melting process. Roads improved a bit.

But here comes a clipper system located in Missouri at 4 PM:

Is this another

of the ice and snow?

Not really. This isn’t a repeat of the system we just had to deal with. This one is much, much smaller.

This clipper system is going to (1) refreeze some of the ice melt we saw today and (2) top that off with another 1″ or less of snow.

Models have consistently put the ETA of the snow around around 3 AM. Here’s the HRRR:

Snow/flurries should taper off around 7 AM:

For this reason, this afternoon NWS-Nashville issued a Winter Weather Advisory effective Tuesday night at midnight through noon on Wednesday.

NAM4, SREF, GFS, Euro models all think we will get less than 1″, but those models assume a 10:1 Liquid Ratio, and our NWS thinks the real ratio will be closer to 16:1, which could nudge the totals closer to 1″. All in all, still a minor event.

The NAM4 is picking up on flurries arriving in the afternoon, but that shouldn’t do much to add to our accumulation.

Wednesday’s high temperature is 24°. Of some concern will be the arrival of a cold west/northwest wind ranging between 11 and 17 MPH. This will drive wind chills into the single digits. There is still some concern about iced over trees and maybe a few power lines coming down.

Wednesday night, legit arctic air finally arrives, and will drive our temperature down to 6° at midnight, 2° at 3 AM, and briefly and potentially all the way down to -1° or -2° just before the sun comes up Thursday morning. We have never seen subzero temperatures this late in February in Nashville.

The forecast doesn’t get much better after that.

The next system looks like it could start as snow on Friday afternoon/evening, then transition to sleet overnight, before turning to a soaking rain Saturday as temperatures rise above 40°.

This forecast will be similar to this past weekend: it’s all about the track of the low pressure center. If it tracks one way, it will just be a rain event. If it tracks another way, it will be a snow event. Current indications still suggest the low will track right over our area, and produce a snow-to-rain event. Right now, we don’t think this will be a winter storm, but as it was made painfully obvious this weekend, weather models aren’t good enough to pinpoint the exact track of a low pressure center to enable a forecaster to communicate any meaningful level of confidence in precipitation type this far away. Uncertainty reflects understanding, not a lack of skill or effort in trying to get the forecast “right” (whatever that means).

A few other things:

Those looking for road conditions can click here or, more specifically, review the TDOT Smartway traffic cameras scattered all over the city. We are very uncomfortable advising you to drive, or not to drive, somewhere. So, we won’t do it. Also, we do not track weather conditions and certainly not road conditions outside Davidson and Williamson Counties. It’s not that we don’t want to answer your questions, it’s that we don’t have enough information to do so in a responsible way.

Flight info can be found here.

We do not comment on the potential for schools to close. Yes, like everyone else, we have opinions about whether they should be closed or not, but we keep those opinions to ourselves. One small concern is that someone might mistake our opinion about closing school with an official decision. More than that, we don’t have people driving all over both counties before dawn trying to determination if roads are passable.

Finally, thank you to all of you for your kind words. It’s our privilege and blessing to be able to share with you the weather information we love to nerd out on.

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

Maybe a Little Snow Overnight

Current Temps and Radar

Today’s sunlight is helping the melting process. The problem is temperatures. We are not forecast to get above 30° today. It’s going to get even colder tomorrow. Above-freezing temperatures are not expected until Saturday.

Today we are watching a clipper system approach from the midwest.

Here it is at 9:40 AM:

We think it will arrive tonight/overnight, and bring a little bit of snow. Models are in general agreement on this.

By 11 PM, the HRRR has it approaching the Mississippi River:

The NAM4 model thinks the snow will turn on sometime around 3 AM…

…then continue off-and-on through about 10 AM. All indications are that this snow will be less than 1″, probably much less. This is nevertheless obviously unwelcome considering we are trying to melt and clear the ice we already have.

After the sun goes down Wednesday night, temperatures will tumble into the teens, and then into the single digits. The low temperature Thursday morning in Davidson County is -2°. Williamson County’s low is -3°.

It’s going to be hard to melt our ice considering the potential of an additional glaze of fresh snowfall, followed by subzero temperatures. We have never seen subzero temperatures this late in February in Nashville.

Our focus then turns toward yet another weather system expected Friday night into Saturday. For now, this looks like it could start as a snow on Friday afternoon/evening, then transition to sleet overnight, before turning to a soaking rain Saturday as temperatures rise above 40°.

This forecast will be similar to this past weekend: it’s all about the track of the low pressure center. If it tracks one way, it will just be a rain event. If it tracks another way, it will be a snow event. Current indications suggest the low will track right over our area, and produce a snow-to-rain event. Right now, we don’t think this will be a winter storm, but as it was made painfully obvious this weekend, weather models aren’t good enough to pinpoint the exact track of a low pressure center to enable a forecaster to communicate any meaningful level of confidence in precipitation type this far away.  Uncertainty reflects understanding, not a lack of skill or effort in trying to get the forecast “right” (whatever that means).

A few other things:

Those looking for road conditions can click here or, more specifically, review the TDOT Smartway traffic cameras scattered all over the city. We are very uncomfortable advising you to drive, or not to drive, somewhere. So, we won’t do it. Also, we do not track weather conditions and certainly not road conditions outside Davidson and Williamson Counties. It’s not that we don’t want to answer your questions, it’s that we don’t have enough information to do so in a responsible way.

Flight info can be found here.

We do not comment on the potential for schools to close. Yes, like everyone else, we have opinions about whether they should be closed or not, but we keep those opinions to ourselves. One small concern is that someone might mistake our opinion about closing school with an official decision. More than that, we don’t have people driving all over both counties before dawn trying to determination if roads are passable.

Finally, thank you to all of you for your kind words. It’s our privilege and blessing to be able to share with you the weather information we love to nerd out on.

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

Ice Storm Warning Until 9 AM Tuesday

Current Temps and Radar

At 2:11 PM, NWS-Nashville canceled the Winter Storm Warning in Davidson County and replaced it with an Ice Storm Warning effective until Tuesday at 9 AM. Williamson County is also under the same Ice Storm Warning until 9 AM Tuesday.

Widespread significant icing has already occurred. See #tSpotter on Twitter to submit and review other storm/accumulation reports, or just click here. Some additional freezing rain is possible into the evening before it changes to sleet and snow, then tapers off. As I write this, the main batch of frozen in freezing precipitation is moves east of I-65, but a few lingering sleet and snow showers will be possible until dark. Both HRRR and NAM4 models have all the precip gone by dark.

By 6 PM, temps which once were flirting with freezing are forecast to drop back into the upper 20°s. By midnight, we’re expected to be 21°, on our way to a low temp of 16° in the wee hours of Tuesday morning. Tomorrow’s high is only expected to reach 30°.

The biggest concern is the weight of the ice sitting on trees and power lines. Interruptions to power, with an inability to drive safely to a place with power/heat, continues to be the main concern.

Should you attempt to drive tonight or tomorrow morning? If you’re asking me:

Will it melt tomorrow? Probably not. We’re going to be mostly cloudy, and although every little bit of sunlight helps, with temperatures as cold as they are and considering the amount of sleet and freezing rain we’ve seen, travel is discouraged. Most reports I’ve seen suggest treated roads are hazardous, and untreated roads resemble a hockey rink, but I haven’t driven anywhere today and I’m not a transportation expert, so I claim no authority on the topic. It just seems logical driving is a bad idea.

In fact, even colder air is on the way Wednesday and into Thursday. As this reinforcing blast of arctic air arrives, it might produce a little Wednesday afternoon snow, with little/no meaningful accumulation. We will probably set a record low cold temperature Thursday morning. I don’t know if if you will be able to make it to the Predators game Tuesday night or whether school will be canceled for the rest of the week. I won’t speculate on either.

We are not forecast to get above freezing until Saturday.

11:51 AM Update

At 10:25 AM, NWS-Nashville noted that above-freezing temperatures at and near 5000 feet continue to stream into Middle Tennessee. These temperatures are why it’s not snowing, but sleeting instead. As this warmer air aloft continues to stream in, most precipitation should be freezing but not frozen, meaning we should see more rain mix in with the sleet. This will continue through the early afternoon.

Meanwhile, temperatures at the surface are hovering right at, but mostly just below, freezing. This is promoting the accrual of ice, which will continue this afternoon for most locations. We now expect between 1/4″ and 1/2″ of ice in both counties, not just Williamson County.

The exact amount of ice accrual will depend on a few factors. First, elevation. Some will see more, others less. Second, the location of the heavier precipitation bands will influence the amount of ice accumulation. Your results will vary.

As we go into the late afternoon and evening, colder air will sweep southeastward and bring a transition back to sleet and, yes, a little bit of snow, across all of Middle Tennessee.

Models think this will end around 6 PM or so. Until then:

However, as this is happening, the moisture will be decreasing, such that snowfall totals for this event will be generally less than 1 inch south of I 40, with amounts around 1 inch along I 40, increasing to as much as 5 inches at the Tennessee/Kentucky line.

The sleet is ruining our chances for massive accumulating snow.

Why? The “warm nose” of temps at 5,000 feet we’ve been talking about since early Sunday morning, seen here on data collected from this morning’s weather balloon:

It appears your kid will have to sled like this. Wear a helmet!

Model guidance also suggests the precipitation will end between 7 PM and 9 PM tonight. And then it’ll get colder!

This website supplements @NashSevereWx on Twitter, which you can find here. This website will be infrequently updated. All of our updates, etc. will be posted on Twitter. Consult multiple reliable weather sources multiple times today.

Ice Update

Current Temps and Radar

Sleet and freezing rain has arrived. This is not what we ordered. Roads – especially untreated secondary roads – are a slippery mess. Car wrecks everywhere. It’s not safe to drive right now. Will says the treated roads are slushy, bad but passable with his Jeep, in 4WD, equipped with specialized snow tires. Untreated roads are much worse.

An Ice Storm Warning is in effect for most of Williamson County as shown by the the purple shaded area below. It runs generally from just south of Fairview, through Cool Springs, towards north of Nolensville:

The Ice Impact Index is an experimental product offered by NWS in an effort to quantify the impacts an ice storm will have on the power structure. There are 5 levels of impacts:

The area along and S of Highway 96 in Williamson County seems to be the dividing line between the first and second group. Those along and south of that line might expect scattered utility interruptions typically lasting less than 12 hours.

From HWY 96 north to I-40, some local utility problems are possible, lasting typically only a few hours.

This morning, the Storm Prediction Center issued a very technical discussion expressing concern that the sleet will change to rain…then freeze at the surface. You can read that here if you want.

For those north of the black line in the image above, including all of Davidson County, sleet and freezing rain is still expected, it’s just that we don’t think it will accumulate past 1/4″. This area remains under a Winter Storm Warning for the mix of sleet and snow expected to accumulate through the day. Significant ice accumulation is still possible.

The sleet is ruining our chances for massive accumulating snow.

In looking at the HRRR and NAM4 models, it looks like there will not be a transition to snow until later tonight, and only briefly. Right now, this looks to be primarily a sleet event. Why? The “warm nose” of temps at 5,000 feet we’ve been talking about since early Sunday morning, seen here on data collected from this morning’s weather balloon:

Model guidance also suggests the precipitation will end between 7 PM and 9 PM tonight. And then it’ll get colder!

This website supplements @NashSevereWx on Twitter, which you can find here. This website will be infrequently updated. All of our updates, etc. will be posted on Twitter. Consult multiple reliable weather sources multiple times today.