February 8-12 2016 Cold and Possibly Snowy

[Runman292]

00z with ratios factored was pretty big for a lot of us.

I'd be happy with this.

[John1122]

Good write-up from MRX this morning. 

 

 

 

THE MAIN STORY IN THE EXTENDED WILL BE THE WINTRY WEATHER AND ARCTIC
AIR THAT WILL MOVE INTO THE AREA EARLY NEXT WEEK. MODELS HAVE BEEN
HOLDING CONSISTENT WITH AN EXTREMELY COLD AIR MASS MOVING INTO THE
AREA NEXT WEEK. LATE SUNDAY INTO EARLY MONDAY AN UPPER LEVEL TROUGH
WILL DIVE OUT OF THE NORTHERN PLAINS INTO THE TENNESSEE VALLEY WITH
IT BRINING IN THE FULL BRUNT OF THE ARCTIC AIR MASS. THE LATEST
00Z SUITE OF MODELS HAVE TRENDED A BIT QUICKER WITH THE ONSET OF
PRECIPITATION. THE LATEST MODELS INDICATE THAT PRECIP. WILL BEGIN
BETWEEN MIDNIGHT AND 6AM ON MONDAY MORNING. IF THIS WERE THE
CASE...EXPECT TEMPERATURES WOULD COOL ACROSS THE REGION THROUGHOUT
THE DAY MONDAY WITH MOSTLY SNOW ACROSS THE AREA. THE LATEST 00Z GFS
MODEL SOUNDINGS INDICATE THAT THE FREEZING LEVEL IS NO MORE THAN 1
KFT AGL ACROSS THE VALLEY WITH TEMPERATURES QUICKLY COOLING ALOFT
ON MONDAY. THE LAPSE RATES WITH THE SYSTEM CONTINUE TO BE
IMPRESSIVE AND EXPECT ALL SNOW WITH SURFACE TEMPERATURES OF 36-38
DEGREES BASED ON THESE LAPSE RATES. THE UPPER TROUGH CONTINUES TO
AMPLIFY ACROSS THE EASTERN CONUS AS THE LOW BECOMES CLOSED OFF.
SEVERAL SHORTWAVE TROUGHS WILL CONTINUE TO ROTATE THROUGH THE MAIN
SYSTEM WITH SNOW SHOWERS CONTINUING TUESDAY AND INTO WEDNESDAY.
REGARDLESS OF THE AMOUNT OF SNOW...TEMPERATURES WILL BE MUCH COLDER
THAN AVERAGE WITH HIGHS BELOW FREEZING AND LOWS IN THE TEENS
WEDNESDAY AND THURSDAY MORNINGS. IN FACT...SOME LOCATIONS MAY NOT
GO ABOVE FREEZING BETWEEN MONDAY AND THURSDAY AFTERNOONS. MODELS
CONTINUE TO HOLD TRUE TO THIS SOLUTION WITH ARCTIC AIR AND
WIDESPREAD SNOW SHOWERS MOVING INTO THE AREA EARLY NEXT WEEK.
MONDAY LOOKS TO FEATURE THE HIGHEST POPS BUT FOR THOSE LOCATIONS
NORTH OF I-40 AND IN THE FAVORED UPSLOPE REGIONS...LIGHT SNOW COULD
LINGER AS LATE AS WEDNESDAY NIGHT. FOR NOW EXPECT A 2-4 INCH SNOW
ACROSS THE AREA WOULD BE REASONABLE WITH THE LOWEST AMOUNTS ACROSS
THE SOUTHERN VALLEY AND HIGHER AMOUNTS NORTH OF I-40 AND IN THE
FAVORED UPSLOPE REGIONS. WILL CONTINUE TO HIGHLIGHT THE MENTION OF
SNOWFALL IN THE HWO BUT PLEASE CONTINUE TO CHECK BACK WITH SEVERAL
MORE MODEL RUNS TO COME BETWEEN NOW AND MONDAY.

[John1122]

They do seem fairly optimistic with temperatures. My high on the GFS Tuesday is around 23 and on Wednesday it's 18. MRX is about 8 and 13 degrees warmer on those days as of now. But if there's 3-4 inches of snow around, I can see numbers closer to the GFS verifying. Especially if the air is so frigid aloft.

[Mr Bob]

Overnight ensemble runs are more supportive of what MRX has with EPS running about -10 of normal and GEFS running about -15...Only operational GFS has it so frigid while the Op Euro is probably a little too warm....We will probably end up above what we hit in Jan by a couple of degrees, IMO....

[JayCee]

With these type of terrain driven snows, amounts over East Tennessee can be highly variable depending on location.  Upslope-vs-downslope has already been talked about, and I’ve witnessed how changeable it can be while driving home from KY many times.  Along I-75 on the Plateau, I’ve seen heavy snow falling, but break out into sunshine immediately south the Plateau near Caryville and Rocky Top (formerly Lake City).  Then, as I’ve traveled southeast toward Knoxville, the clouds and snow showers rebuild, and once I get home east of Sevierville, the snow is falling steadily again--but usually not as heavy as on the Plateau itself.  The rain/snow shadow caused by the Plateau seems to affect valley areas the greatest nearest the Plateau (areas just south and east of it), but once you drive some distance away, the shadow is somewhat less pronounced.  If the plateau was as high as the Smokies, the whole valley would probably never see snow with these CAA (Cold Air Advection) type snow events.  I’ve noticed that most areas in North/South Carolina east of the Smokies can be in full sunshine while areas in east Tennessee are having snow.  The 5,000-6,000 peaks along the TN-NC border effectively block any moisture from making it over those mountains. 

[Greyhound]

Saw a twitter post from last night stating that thunder snow could be a possibility on Monday for parts of the valley.  Can some of the smarter guys elaborate on this?  I've seen/heard it twice and would love to experience it again....but prefer not to have Jim Cantore in our area either. 

 

Edit:  they did mention it was WAY early, but a possibilty based on a skew T and Cape levels

[ShawnEastTN]

Some of the models insist on showing rain with this system and I can't understand quite why. Look at this panel of the GGEM. Note the 528 dm line south of the area. I'm sure most of us know that 540 thickness is 50/50 for snow at 1000 feet in elevation with snow actually possible at 546 the higher up you go. I'd think at below 528 it's far more likely to be a snow precip type than a rain precip type. Especially with nw winds, surface temps in the mid 30s, which are shown here, and 850s at around -5 or lower over the area, the 700 mb are -15 to -20 which is excellent for snow growth. Even the 925 temps are around 0 or below. It literally seems to be spitting out rain with the entire column below freezing from 700 down to almost the surface and the surface about 3 degrees above freezing. The odder part to me is that it's showing snow further east, which is actually the warmest area on this panel from 700 all the way to the surface.

 

 

 

We've been seeing that for multiple runs now.  It as though its looking only at 2M Temps, though as you mention on the eastern portion of that map showing as snow and actually warmer doesn't make a whole lot of sense.  Whats interesting to me is we all know as advertised that isn't going to be rain.  So with the clowns we are seeing they likely aren't counting that which is showing as liquid as being accumulating snow.  Which is actually likely cutting the totals on the clown maps.

[ShawnEastTN]

Saw a twitter post from last night stating that thunder snow could be a possibility on Monday for parts of the valley.  Can some of the smarter guys elaborate on this?  I've seen/heard it twice and would love to experience it again....but prefer not to have Jim Cantore in our area either. 

 

Edit:  they did mention it was WAY early, but a possibilty based on a skew T and Cape levels

I would say unlikely for most to see that out of this, but convective type snow showers are common in events like this especially for the Mountains and Plateau, however I wouldn't bank on thunder snow for most.  I've only been through it twice in my life.  The blizzard of 93 about 2 to 3AM here in East TN, and a couple years ago in Lincoln Nebraska.  It is an awesome sight and sound, also eerie.  Most convective snowshowers creating lightning during the day are never noticed though.

[Daniel Boone]

The American models are as alot of things have gotten, an embarrassment to the United States.

The "official" stations that are used in the model ingest system are inaccurate, therefore resulting in inaccurate forecasts.

The last"upgrade" of the gfs, although looking more precise, is far from it and much of it probably due to the aforementioned.

[Daniel Boone]

I have experienced thundersnow several times here. The most extreme, vivid was during the January 2013 dumping. I heard a couple claps then told my wife of which hadn't experienced it. So, we went outside and while out there in heavy snow a blinding flash with booming thunder nearly simultaneously! Needless to say, wife hurried back inside.

[Stovepipe]

The American models are as alot of things have gotten, an embarrassment to the United States.

The "official" stations that are used in the model ingest system are inaccurate, therefore resulting in inaccurate forecasts.

The last"upgrade" of the gfs, although looking more precise, is far from it and much of it probably due to the aforementioned.

 

Do you have verification scores that show American models are significantly less accurate than foreign models?  If so I'd like to see them.  There are many things that embarrass me in this country.  Weather models are not one of them, but to each his own.

[ShawnEastTN]

I have experienced thundersnow several times here. The most extreme, vivid was during the January 2013 dumping. I heard a couple claps then told my wife of which hadn't experienced it. So, we went outside and while out there in heavy snow a blinding flash with booming thunder nearly simultaneously!

If you are up near the Cumberland Gap, you would definitely have higher odds of that than the Valley.  Elevation absolutely helps in that scenario.

[Daniel Boone]

Do you have verification scores that show American models are significantly less accurate than foreign models?  If so I'd like to see them.  There are many things that embarrass me in this country.  Weather models are not one of them, but to each his own.

Hey stovepipe. Actually, have been told by a chief NWS Met. that the FAA governs the airport stations and that they allow as much as 4 degrees either side of actual with calibration. Also, NWS doesn't fund these nor can afford their own , they have to let things go as they are. There's alot more I could tell you.

Also, don't trust those scores either. They're judged up against the same flawed stations. So, of course they're going to verify decent, lol.

[ShawnEastTN]

Hey stovepipe. Actually, have been told by a chief NWS Met. that the FAA governs the airport stations and that they allow as much as 4 degrees either side of actual with calibration. Also, NWS doesn't fund these nor can afford their own , they have to let things go as they are. There's alot more I could tell you.

Also, don't trust those scores either. They're judged up against the same flawed stations. So, of course they're going to verify decent, lol.

 

I would wager there is some reasoning in allowing temperature variance of actual measured at many airports wx reporting stations.  The biggest one I can think of is the amount that all the pavement around most of these urban stations, let alone the airports themselves must take into consideration reflective radiation of heat locally at the site.  Though that would just be my guess, and this probably belongs in banter.  I wouldn't imagine that though being a major issue when you think about the many balloon launches daily around the country in varying urban and rural areas for data.  Just throwing my 2 cents in.   

[ShawnEastTN]

Loving the position of the Great Lakes Low on this run...  Mostly hanging out in SE Michigan keeping nice fetch of moisture streaming out of the Lakes, plus moisture from the Atlantic being pulled back from the coastal low to our lakes low to inject more moisture for several frames before the coastal absorbs the lakes low.  Basically snow and snowshowers early monday through late wednesday for most.

[Daniel Boone]

Yeah, the balloons for upper air but, how do you know if those are accurate? I have spoke with an Faa official regarding the Bell county station(k1a6) and he was basically rude, care less about the problem there. Even though kjkl nwsfo had contacted them of the + temperature bias of that station.

[ShawnEastTN]

MRX mentioning steep lapse rates seems plausible with 2 of the waves passing through the initial frontal passage and then again late that night into Tuesday morning.  Could see moments of moderate snows at times.

 

GFS loop:

[Stovepipe]

Hey stovepipe. Actually, have been told by a chief NWS Met. that the FAA governs the airport stations and that they allow as much as 4 degrees either side of actual with calibration. Also, NWS doesn't fund these nor can afford their own , they have to let things go as they are. There's alot more I could tell you.

Also, don't trust those scores either. They're judged up against the same flawed stations. So, of course they're going to verify decent, lol.

 

Earlier you said your beef was with the American models, that is what I was responding to.  The data might be a legit concern, but I'm sure that same data is fed into the foreign models as well so from a modeling perspective it looks to be a wash.  Anyway, this belongs in banter so let's keep the flizzard discussion going.

[Stovepipe]

12z Euro is not very impressive.  The surface freezing line is north of the Ohio river when the best precip comes through.  Mountains, plateau, and upper Cumberland finagle 2 to maybe 4 inches while most other areas are a dusting to an inch.  Downsloping is evident in the central valley.

[tnweathernut]

I guess we will just have to wait and see how robust each impluse is and if there is an enhancement from the lakes.  Some of that will be poorly modeled and I am guessing there will be surprises, both good and bad, along the way.  Nice little period of winter coming at us regardless of the amount of snow seen.  

[John1122]

If the interaction with the Atlantic gets involved, that's where the snow will really be enhanced. JKL mentioned this. The reason thunder is possible is that these are convective snow showers, the winter equivalent of summer storms. JKL's forecast area had a lot of thundersnow last year out of an event like this that moved into SWVA with thunder snow in parts of that area too.

 

The running average of the snow clowns pretty much suggests 3-6 for the Plateau, SW VA, NE TN and Southern Kentucky, 1-3 for the almost the entire Valley in middle TN, Northern Alabama and East Tn, 6-10+ for the mountains in their favored areas. Probably end up being a long duration winter weather advisory type situation if the situation comes to pass as modeled.

[John1122]

Still not sure on why the temps warm into the mid 40s supposedly in areas on Monday. Even if they do it should be a rapid top down cooling event because the upper levels are all extremely supportive of snow being the precip type.

 

It's shaping up to be a classic shift battle at MRX. The overnight shift is always more bullish than the day shift when honking the snow horn, which played out in today's disco and forecasts,

[tnweathernut]

Still not sure on why the temps warm into the mid 40s supposedly in areas on Monday. Even if they do it should be a rapid top down cooling event because the upper levels are all extremely supportive of snow being the precip type.

 

It's shaping up to be a classic shift battle at MRX. The overnight shift is always more bullish than the day shift when honking the snow horn, which played out in today's disco and forecasts,

I was just looking at that.  It will be interesting to see how it plays out, but my gut tells me we never reach 40 and most areas stay in the 30's before falling back to around freezing.  Precipitation onset appears to be before or around dawn on Monday (if that holds)

[Chattownsnow]

I was just looking at that.  It will be interesting to see how it plays out, but my gut tells me we never reach 40 and most areas stay in the 30's before falling back to around freezing.  Precipitation onset appears to be before or around dawn on Monday (if that holds)

You guys up north of me might be fine but I have a feeling i'm going to see rain out of that band moving through. winds will be out of the W to WSW if the GFS is to be believed as well. I've been through situations like that before and it never is good for my area lol. 

[ShawnEastTN]

You guys up north of me might be fine but I have a feeling i'm going to see rain out of that band moving through. winds will be out of the W to WSW if the GFS is to be believed as well. I've been through situations like that before and it never is good for my area lol.

I think that is whats wrong here, the modeling of rain is odd.  As discussed earlier in the thread, the column above supports essentially all snow even at Chatt at start time of the event or rapid change to snow at the very least.  The surface at Chatt around start of snow is modeled by GFS to be 37-38 degrees or so.  With the very cold air above I would have a very hard time forecasting rain, if the mid and upper levels are being modeled correctly even for Chatt.  

 

I think I'm going to come out bullish on this one, and I know that is a gamble with a northern stream system, but there are so many interesting pieces with this one that to me really could make this almost one of a kind and not just another northern stream system.

 

Edit:

 

Roughly start time of precip temps from 18Z GFS:

 

Knox:                                            Chatt:

925mb = +1 C                               925mb = +1 C

850mb = - 4 C                               850mb = - 4 C

700mb = - 13 C                             700mb = - 15 C

500mb = - 33 C                             500mb = - 30 C

 

Knox 2M = +2 C                                Chatt 2M = +3 C

 

I just have a hard time with those producing rain with surface temps in the valley at start of precip being mid and upper 30s.  Those mid and upper 30s should crash quickly below freezing with precip falling. 

[Chattownsnow]

I think that is whats wrong here, the modeling of rain is odd.  As discussed earlier in the thread, the column above supports essentially all snow even at Chatt at start time of the event or rapid change to snow at the very least.  The surface at Chatt around start of snow is modeled by GFS to be 37-38 degrees or so.  With the very cold air above I would have a very hard time forecasting rain, if the mid and upper levels are being modeled correctly even for Chatt.  

 

I think I'm going to come out bullish on this one, and I know that is a gamble with a northern stream system, but there are so many interesting pieces with this one that to me really could make this almost one of a kind and not just another northern stream system.

If you have time, I would love to hear what you think makes this system different from others that have come through similarly to this one. You have more knowledge than me in the weather realm and would be interested to hear what you think. I looked at soundings and see 850 temps are clearly around -3C at hr90. 

 

I remember an event that was a total fail recently I think maybe the 12-13 winter that had a system similar to this that called for snow of 2-4 inches that ended up all rain besides the plateau and higher elevations. Wish I could remember the date but boy was it disappointing.  

[Carvers Gap]

For this event you are going to do the best if you are on the Plateau and west side of the eastern Valley, specifically east of I-81 and north of say Greeneville.  I think we all see some flakes flying and maybe even an inch or two in Kingsport...But I would not be surprised for the usual areas to score 4-6".  John's area looks like money.

[ShawnEastTN]

If you have time, I would love to hear what you think makes this system different from others that have come through similarly to this one. You have more knowledge than me in the weather realm and would be interested to hear what you think. I looked at soundings and see 850 temps are clearly around -3C at hr90. 

 

I remember an event that was a total fail recently I think maybe the 12-13 winter that had a system similar to this that called for snow of 2-4 inches that ended up all rain besides the plateau and higher elevations. Wish I could remember the date but boy was it disappointing.  

My reasoning is really 2 fold.  In the instance of rain, say for Chatt the flow ahead is never really southerly, it is briefly SW but mostly W ahead of the system and even that is brief don't believe there is going to be a warm up enough to warrant rain or rain for very long at the very least.  Plus it may start before daybreak, which is always a plus.

 

Second there is enough lift rotating through to ensure even the valley gets something, now I'm not saying I think we get crushed in the valley, but I do believe even Chatt sees up to a couple inches by the time all is said and done.  This isn't a typical NW flow event.  In most of those there isn't any appreciable lifting mechanisms to give the valley anything at all but passing flurries at best.  There are at least 4 different waves which should provide enough lift for periods of light snow even down to Chatt.

 

Sure there will be more on Signal, Lookout and Monteagle than in Chatt and we lose a little moisture to the Plateau but I'm buying that this will not be moisture starved as are most northern stream systems.  Not to say it would ever compare to a southern stream system which is obviously superior for most of us unless you are John1122 up in Campbell County in a sweet spot for these.

 

I'm not a Met by any means and would hate to be in a position to forecast this because I believe there will be surprises hopefully good ones.  I may even have to eat my words on this one but I do believe i'm going to be liberal on this event considering possible Atlantic feeds in the last couple runs and a couple others further back, plus the ice free nature of the lakes this year and a strong low with robust waves rotating through.

 

My thoughts... Hopefully I don't have to eat my words.  If so not the first time I would have wagered and lost on these forums.

[Chattownsnow]

My reasoning is really 2 fold.  In the instance of rain, say for Chatt the flow ahead is never really southerly, it is briefly SW but mostly W ahead of the system and even that is brief don't believe there is going to be a warm up enough to warrant rain or rain for very long at the very least.  Plus it may start before daybreak, which is always a plus.

 

Second there is enough lift rotating through to ensure even the valley gets something, now I'm not saying I think we get crushed in the valley, but I do believe even Chatt sees up to a couple inches by the time all is said and done.  This isn't a typical NW flow event.  In most of those there isn't any appreciable lifting mechanisms to give the valley anything at all but passing flurries at best.  There are at least 4 different waves which should provide enough lift for periods of light snow even down to Chatt.

 

Sure there will be more on Signal, Lookout and Monteagle than in Chatt and we lose a little moisture to the Plateau but I'm buying that this will not be moisture starved as are most northern stream systems.  Not to say it would ever compare to a southern stream system which is obviously superior for most of us unless you are John1122 up in Campbell County in a sweet spot for these.

 

I'm not a Met by any means and would hate to be in a position to forecast this because I believe there will be surprises hopefully good ones.  I may even have to eat my words on this one but I do believe i'm going to be liberal on this event considering possible Atlantic feeds in the last couple runs and a couple others further back, plus the ice free nature of the lakes this year and a strong low with robust waves rotating through.

 

My thoughts... Hopefully I don't have to eat my words.  If so not the first time I would have wagered and lost on these forums.

well I appreciate you sticking your neck out there and giving us your take. I really don't believe we see anything down here but flurries and off and on snow showers with little to no accumulations but I hope I'm wrong! I do believe north of here and favored locations will do well. 

[ShawnEastTN]

well I appreciate you sticking your neck out there and giving us your take. I really don't believe we see anything down here but flurries and off and on snow showers with little to no accumulations but I hope I'm wrong! I do believe north of here and favored locations will do well. 

I understand that.  Hope you all do get something out of this, you all haven't had much this winter.  More ice than anything the first storm, and very little out of that Miller B.  I'm just excited to have something to watch, if I can't get a Miller I'll take what I can get.