February 8-12 2016 Cold and Possibly Snowy

[John1122]

NAM is starting to come into range with this one. At 84 my sounding is 37 degree surface temp, 28 degrees at 850, 8 degrees at 700mb. But the NAM has a narrow band of moderate rain falling.

 

The GFS run was also a little worse for most of the valley areas due to rain initially. Now showing similar to what Stove said the Euro was showing. 2-4 along the border counties and Plateau. 1-2 central areas and 40 corridor. 1 inch or less south of 40.

[Stovepipe]

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. 

 

Based on what I've seen, I don't think it'll be particularly good for my area either, although I don't buy the rain.  It'll be snow showers that don't stick for hours because of warm surface temps, then once we get cold a dusting to an inch piles up.  It very well may be enough to close some schools though.  Might be a feast or famine band situation for some.  I'd love to be wrong but that is how I see it right now for the central and southern valley based on the modeling and how I've seen similar storms pan out.

[Runman292]

David Aldrich is giving an early prediction of 1-3 inches total in the valley, with higher amounts in the usual areas (plateau and mountains).

[JayCee]

MRX's morning AFD is somewhat less enthusiastic about the 2-4" area wide snow they were calling for earlier this week for next week. 

 

 

LONG TERM /SATURDAY THROUGH THURSDAY/...
AN UPPER TROUGH WILL MOVE ACROSS THE AREA SATURDAY...BUT DYNAMICS
AND MOISTURE WILL REMAIN WELL SOUTH OF THE AREA ACROSS THE GULF OF
MEXICO. AT THE SURFACE... RIDGING WILL DOMINATE FOR SATURDAY AND
SUNDAY PRODUCING DRY CONDITIONS.

THE MAIN WEATHER STORY WILL BE MONDAY THROUGH WEDNESDAY AS A DEEP
UPPER TROUGH DEVELOPS OVER THE EASTERN HALF OF THE NATION. THERE IS
STILL A GOOD DEAL OF UNCERTAINTY IN REGARD OF HOW FAR SOUTH UPPER
LOW GOES INTO THE APPALACHIANS AND THE ASSOCIATED STRENGTH OF THE
UPPER JET ACROSS THE REGION. THE LATEST ECMWF IS THE STRONGEST
BRINGING A PERIOD OF GOOD LARGE SCALE ASCENT ON MONDAY. ALSO...AS
UPPER/MID-LEVEL CHILL OFF...LAPSE RATES REALLY STEEPEN ON MONDAY.

WILL CALL FOR LIKELY CHANCES OF PRECIPITATION MONDAY AND MONDAY
NIGHT. PRECIPITATION TYPE IS TRICKY AND WILL BEGIN AS RAIN IN THE
VALLEY AND MIXTURE OF WINTRY PRECIPITATION PLATEAU/MOUNTAINS...THEN
CHANGING TO ALL SNOW DURING THE AFTERNOON. SNOW ACCUMULATIONS
LIKELY HIGHER ELEVATIONS...BUT UNCERTAIN FOR THE VALLEY DUE TO
TIMING OF THE DAY. WILL HIGHLIGHT THIS WITHIN THE HWO AND SPS.

FOR TUESDAY...NORTHWEST FLOW OROGRAPHIC SNOW ANTICIPATED WITH
FLURRIES AND SNOW SHOWERS ANTICIPATED AREA-WIDE. AGAIN...HIGHER
ELEVATIONS SNOW ACCUMULATIONS LIKELY.

FOR WEDNESDAY...ANOTHER SHORT-WAVE MAY MOVE ACROSS THE SOUTHERN
APPALACHIANS BUT CONFIDENCE LOW ON STRENGTH AND MOISTURE
AVAILABILITY.

 

[ShawnEastTN]

I was holding out hope that the 0Z run of the GFS was more of a one off from its earlier consistency, however both 0Z and 6Z are showing a more progressive look with the low and moving it fairly quickly out of the Great Lakes.  My better feeling about this from yesterday after multiple runs that were consistent is fading.   May be eating my words sooner rather than later from yesterday evening.  

[Stovepipe]

The 0z Euro was very similar to it's previous 12z in terms of accumulation; 2-4 on the western edge of the plateau into the highland rim/upper Cumberland, northern plateau and TRI, mountains 6+ and dusting to an inch in southern and central valley.  One encouraging thing, the 0z EPS mean snow is double that of the OP for central valley areas (2.4 inches), about the same as OP elsewhere.

[John1122]

12z ratio adjusted still says 2-5 from the 40 corridor and north, Highland rim and east. Around 1.5 in Nashville. 1 in NE Alabama, .5 to 1 from Chattanooga to around Cleveland.

[Stovepipe]

12z Euro virtually the same as 0z.

[jaxjagman]

Yeah not much difference in the euro qpfs.Leaves Mem with nothing,nothing much here.Best is to the east.Pulling for the GFS here.Though even if that at best looks nothing more than a dusting right now here.Probably a roof storm for us.

[Snowless in Carrollton]

FFC saying there could be a good amount of snow in North GA on Mon/Tues. I assume the same is the case for TN ?

[John1122]

FFC saying there could be a good amount of snow in North GA on Mon/Tues. I assume the same is the case for TN ?

 

Probably in the mountains and favored areas north of I-40. I assume that FFC is referring to the NE Ga mountains? I'd say they could get 3-5 in the favorable areas with more at the tops of the mountains.

[John1122]

MRX is being rightly non-commital on amounts. I've generally found their light accumulation wording to mean 1-3 inches.

 

 

 

THE MAIN STORY FOR THE
LONG TERM WILL BE THE AMPLIFICATION OF AN UPPER LEVEL TROUGH OVER
THE EASTERN U.S. SUNDAY NIGHT THROUGH TUESDAY WITH A DEEPENING UPPER
LOW FORMING ACROSS THE UPPER MIDWEST AND THE NORTHERN OHIO VALLEY. A
COUPLE OF SHORT WAVES WILL SHIFT SOUTHEAST ACROSS THE SOUTHERN
APPALACHIANS LATER SUNDAY NIGHT INTO MONDAY IN ASSOCIATION WITH THIS
AMPLIFYING UPPER LOW. THE EXTENDED PERIOD OF STRONG NORTHERLY FLOW
IN THIS REGIME WILL PULL ARCTIC AIR INTO THE DEEP SOUTH LIMITING
HIGH TEMPERATURES TO THE 30S ACROSS MOST OF THE FORECAST AREA BOTH
TUESDAY AND WEDNESDAY WHILE SOME MODIFICATION OF THE CHILLY AIR IS
EXPECTED THURSDAY INTO FRIDAY. A FAIR AMOUNT OF MOISTURE WILL
ACCOMPANY THE ARCTIC AIR ON ITS WAY INTO THE EASTERN THIRD OF THE
COUNTRY AND THIS SHOULD BE LIFTED INTO A PATTERN OF SNOW SHOWERS
ACROSS THE FORECAST AREA LATE SUNDAY NIGHT ALL THE WAY THROUGH
WEDNESDAY. IT APPEARS A LIGHT ACCUMULATION IS POSSIBLE IN THE GREAT
VALLEY WITH PERHAPS SEVERAL INCHES OF ACCUMULATION IN THE HIGHER
TERRAIN DUE TO RELATIVELY STRONG OROGRAPHIC LIFT THROUGH THE THREE
DAY PERIOD. GENERALLY IMPROVING WEATHER IS EXPECTED TOWARD THE END
OF THE WORK WEEK HOWEVER...PLACED A SLIGHT CHANCE FOR A COUPLE SNOW
SHOWERS OR SPRINKLES IN THE MOUNTAINS OF SOUTHWEST VIRGINIA AND
EXTREME NORTHEAST TENNESSEE THURSDAY NIGHT INTO FRIDAY WITH THE
PASSAGE OF A WEAK WAVE.

[nrgjeff]

Looks like a good time on the Plateau and Mountains, and perhaps favored areas the far upper end of the Valley. JC may do OK but this is tricky for Kingsport. Virginia and NC Mountains will do great. Should be a moist fetch at times with lots of PVA and cyclonic curvature upstairs. For the higher elevations this is Making Northwest Flow Snow Great Again!

 

I appreciate the positive thoughts for Chattanooga, but I am not holding my breath. Looks like a showers to flurries deal. Regardless of model output we have 1,500 FT more column to cool than Signal Mountain, where I think they get accumulation again. Enough energy and PVA (500 mb vorticity advection) is north to keep the boundary layer too warm in town. I know PVA goes south later Monday, but lead PVA is at/north of town before 12Z Monday and some other PVA lingers north all day (Ohio Valley). PVA is just the general rule; 850 front is strong this time, but the boundary layer will suffer from downslope with the northwest wind component. 

 

Tough to call Knoxvegas this set-up; obviously, chances are better than in Chatty. Then you have places like Maryville, Sweetwater and Athens TN barely above 1,000 FT that could do better than either Knox or Chatty. First wild guess 4 days out: dusting Chatty, if that; half inch Knox, inch if lucky; about an inch above 1,000 FT, more if lucky; 2+ inches Signal Mountain and far Upper Valley; A few inches Upper Plateau, locally several possible; NWFS fun in the Mountains, esp higher elevations.

[Runman292]

Looks like a good time on the Plateau and Mountains, and perhaps favored areas the far upper end of the Valley. JC may do OK but this is tricky for Kingsport. Virginia and NC Mountains will do great. Should be a moist fetch at times with lots of PVA and cyclonic curvature upstairs. For the higher elevations this is Making Northwest Flow Snow Great Again!

I appreciate the positive thoughts for Chattanooga, but I am not holding my breath. Looks like a showers to flurries deal. Regardless of model output we have 1,500 FT more column to cool than Signal Mountain, where I think they get accumulation again. Enough energy and PVA (500 mb vorticity advection) is north to keep the boundary layer too warm in town. I know PVA goes south later Monday, but lead PVA is at/north of town before 12Z Monday and some other PVA lingers north all day (Ohio Valley). PVA is just the general rule; 850 front is strong this time, but the boundary layer will suffer from downslope with the northwest wind component.

Tough to call Knoxvegas this set-up; obviously, chances are better than in Chatty. Then you have places like Maryville, Sweetwater and Athens TN barely above 1,000 FT that could do better than either Knox or Chatty. First wild guess 4 days out: dusting Chatty, if that; half inch Knox, inch if lucky; about an inch above 1,000 FT, more if lucky; 2+ inches Signal Mountain and far Upper Valley; A few inches Upper Plateau, locally several possible; NWFS fun in the Mountains, esp higher elevations.

How about a guess for North Knoxville?

[John1122]

How about a guess for North Knoxville?

I've seen in the past with enough moisture and the right flow that a band will set up from Cross Mountain in Southern Campbell and Northern Anderson and stretch into parts of Northern Knox. Cross Mountain is almost 4000 feet, it's the highest elevation on the Plateau and is easily the snowiest area outside of the Smokies/Far Eastern Mountain areas in Tennessee. It averages around 48 inches of snow a year and picked up 24 inches in the two storms last month.

[Carvers Gap]

Looks like a good time on the Plateau and Mountains, and perhaps favored areas the far upper end of the Valley. JC may do OK but this is tricky for Kingsport. Virginia and NC Mountains will do great. Should be a moist fetch at times with lots of PVA and cyclonic curvature upstairs. For the higher elevations this is Making Northwest Flow Snow Great Again!

 

I appreciate the positive thoughts for Chattanooga, but I am not holding my breath. Looks like a showers to flurries deal. Regardless of model output we have 1,500 FT more column to cool than Signal Mountain, where I think they get accumulation again. Enough energy and PVA (500 mb vorticity advection) is north to keep the boundary layer too warm in town. I know PVA goes south later Monday, but lead PVA is at/north of town before 12Z Monday and some other PVA lingers north all day (Ohio Valley). PVA is just the general rule; 850 front is strong this time, but the boundary layer will suffer from downslope with the northwest wind component. 

 

Tough to call Knoxvegas this set-up; obviously, chances are better than in Chatty. Then you have places like Maryville, Sweetwater and Athens TN barely above 1,000 FT that could do better than either Knox or Chatty. First wild guess 4 days out: dusting Chatty, if that; half inch Knox, inch if lucky; about an inch above 1,000 FT, more if lucky; 2+ inches Signal Mountain and far Upper Valley; A few inches Upper Plateau, locally several possible; NWFS fun in the Mountains, esp higher elevations.

 

 

So true.  If this is a purely northwest flow event...could be clouds w/ a few snow showers.  If actual pieces of energy accompany the northwest flow, we could see more than our usual northwest flow dusting.  In 1985, we did very well(on albeit frigid air) w/ pieces of energy rotating in but the moisture bands that stream off the Great Lakes almost always misses us since we don't have enough lift on this side of the Valley.  Rain shadow city.  Though one time in HS a piece rotated through and we ad 3" in two hours.  Really, very much like being in the lee of the Apps in North Carolina.

[ShawnEastTN]

I'm going to try to remain optimistic but after last few runs of GFS just not as enthusiastic as I had been.  Hoping there is enough lift to make a difference in the valley.  I was way more optimistic the last couple days.  Though I do believe the 6Z GFS is a little better than the previous 2 runs before it. 

[jaxjagman]

The euro did you guys right to the east..tys.43...tri .33,the only problem is there is some mixing.But these were what was shown for frozen not counting all the qpf's

[Runman292]

I'm not liking what MRX is saying. Here's the long term AFD:

UNSEASONABLY COLD

WEATHER PATTERN WILL BE IN PLACE THROUGH MUCH OF THE EXTENDED PERIOD

WITH THE ADVERTISED AMPLIFICATION TO THE UPPER LEVEL FLOW WHICH

UNFORTUNATELY WILL BE A STRONG NORTHERLY FLOW PATTERN. THE DEEPENING

TROUGH BUILDS SOUTH THROUGH THE EASTERN HALF OF THE NATION MONDAY

THROUGH WEDNESDAY WITH AN ARCTIC BOUNDARY DROPPING INTO THE SOUTHERN

APPALACHIAN REGION DURING THE DAY MONDAY. THE ARCTIC REGIME SHOULD

BEGIN AROUND LATE MORNING THROUGH THE AFTERNOON ON MONDAY WITH

PRECIPITATION CHANGING FROM LIGHT RAIN TO LIGHT SNOW. THE AIR WILL

BE SO COLD ALOFT THAT THERMODYNAMICS SHOULD PLAY A ROLE IN

INITIATING SOME DECENT SNOW SHOWERS FROM NORTHWEST TO SOUTHEAST FROM

LATE MORNING INTO THE LATE AFTERNOON HOURS. THE LIGHT SNOW SHOWERS

CONTINUE MONDAY NIGHT INTO TUESDAY AS SEVERAL DISTURBANCES BUILD

SOUTHEAST OUT OF CANADA AND ROTATE THROUGH THE BASE OF THE DEEP

EASTERN U.S. TROUGH. STILL TWO TO THREE DAYS OUT SO SNOWFALL

ACCUMULATION A LITTLE TOUGH TO PINPOINT BUT THROUGH THE LENGTHY

PERIOD BEGINNING DURING THE DAY MONDAY AND ENDING LATER WEDNESDAY

INTO WEDNESDAY EVENING...PERHAPS THREE TO FIVE INCHES (OR MORE) OF

ACCUMULATION IS POSSIBLE ON THE HIGHER TERRAIN FEATURES WITH A

DUSTING OVER MUCH OF THE GREAT VALLEY (EXCEPTION BEING NORTHEAST

TENNESSEE WHERE TWO INCHES IS POSSIBLE THROUGH THE EVENT). OF COURSE

OROGRAPHICS WILL PLAY A LARGE ROLE IN MOUNTAIN SNOWFALL ACCUMULATION.

THE FORECAST AREA GETS A CHANCE TO DRY OUT SO TO SPEAK THURSDAY AND

THURSDAY NIGHT WITH THE SLIGHT POSSIBILITY OF ADDITIONAL WINTERY

PRECIP WITH A WEAK WAVE PASSAGE FRIDAY THROUGH FRIDAY NIGHT. IT MAY

BE DRY AGAIN FOR SATURDAY. AS STATED BEFORE...IT WILL BE A COLD WEEK

WITH HIGHS A GOOD FIFTEEN DEGREES BELOW NORMAL IN THE LOWER 30S FOR

MUCH OF THE REGION TUESDAY AND WEDNESDAY WITH A BIT OF A "WARMING"

TREND FOR THE REMAINDER OF THE WEEK.

[jaxjagman]

NATIONAL WEATHER SERVICE NASHVILLE TN
245 PM CST SAT FEB 6 2016

.DISCUSSION...

SURFACE RIDGE ACROSS THE SOUTHEAST WITH MID AND UPPER LEVEL TROUGH
DOWN THROUGH THE AREA WILL PULL EAST THIS EVENING TAKING THE MID
AND UPPER LEVEL CLOUDINESS WITH IT. ANOTHER DISTURBANCE OFF TO
OUR NORTHWEST WILL MOVE THIS WAY AND BRING CLOUDINESS BACK INTO
THE MID STATE BEGINNING LATE SUNDAY MORNING INTO THE AFTERNOON.
TEMPERATURES TONIGHT NOT QUITE AS COLD AS LAST NIGHT BUT STILL
CHILLY WITH HIGHS ON SUNDAY IN THE 50S. LIGHT RAIN CHANCES RETURN
SUNDAY EVENING AS SYSTEM OFF TO OUR NORTHWEST GETS CLOSER WITH
RAIN BECOMING MIXED WITH LIGHT SNOW BUT NO ACCUMULATION EXPECTED
SUNDAY NIGHT WITH TEMPS REMAIN ABOVE FREEZING. COLD MONDAY WITH
HIGHS IN THE 30S WITH A GOOD CHANCE FOR LIGHT SNOW SHOWERS
POSSIBLY MIXING WITH LIGHT RAIN SHOWERS AT TIMES ACROSS THE AREA
DURING THE DAY AS COLD AIR ADVECTION REALLY KICKS IN WITH 850 MBAR
TEMPS DOWN IN THE -10 DEGREE RANGE AND EVEN COLDER DURING THE
AFTERNOON. BOUNDARY LAYER TEMPS WILL BE ABOVE FREEZING BUT I`VE
SEEN IT SNOW WHEN SURFACE TEMP WAS 43 DEGREES HERE IN NASHVILLE
IF THERE IS ENOUGH COLD AIR ADVECTION ALOFT IT CAN HAPPEN. SNOW
SHOWERS MONDAY NIGHT AND ON TUESDAY WITH EVEN COLDER AIR POURING
IN WITH LOWS TUESDAY MORNING IN THE LOW TO MIDDLE 20S WITH HIGHS
STRUGGLING TO REACH FREEZING WEST OF PLATEAU ON TUESDAY BUT
REMAINING BELOW FREEZING EASTERN AREAS AND ALONG PLATEAU. SNOW
ACCUMULATIONS ON THE ORDER OF 1 TO 2 INCHES LOOK POSSIBLE ALONG
THE PLATEAU ESPECIALLY IN THE UPPER CUMBERLAND AND IN NORTHEAST
MIDDLE TENNESSEE.

DRY WEDNESDAY INTO THE WEEKEND WITH NO MAJOR WARM UP IN SIGHT.

[John1122]

Will have to see how much moisture works down with each wave, but the forecast is not going to play out here how it's written. Which is  that it will start snowing here late Sunday night, switch to rain up into mid-morning, then switch back to snow. It's too cold aloft for the precip to change back to rain if it starts as snow. So it will either be all snow or it will start as rain then change to snow. I've never seen snow change to rain with well below 0c 850s and surface temps in the 30s. 

[jaxjagman]

Will have to see how much moisture works down with each wave, but the forecast is not going to play out here how it's written. Which is  that it will start snowing here late Sunday night, switch to rain up into mid-morning, then switch back to snow. It's too cold aloft for the precip to change back to rain if it starts as snow. So it will either be all snow or it will start as rain then change to snow. I've never seen snow change to rain with well below 0c 850s and surface temps in the 30s. 

yeah temps aloft being shown at around -30 at 500mb,i'd be skeptical at rain changing over to snow back to rain

 

Edit:especially higher up

[John1122]

The GFS has been locked on with ratio adjusted totals of 3-5 inches for the Plateau and NE areas with more in the mountains.

 

The latest couple have beefed up totals back into the 1-3 inch range from the southern to the central valley after showing .5-1 inch at earlier runs.

[ShawnEastTN]

Canadian was generous this afternoon at 10-1 map.  Canadian and Euro seem to be the most generous for the Great Valley, GFS in the middle and NAM the stingiest. 

[John1122]

Slight uptick/variations but overall a fairly steady picture of potential snowfall through Wednesday evening. 12z then 18z.

 

 

[jaxjagman]

Seen many times when these temps drop around 500mb the models underestimate the cold air aloft to the surface in the Valley,we'll see.The 500mb drops to -31C in mid Tn at 12z Mondayand doesnt fall below -30c until thursday 6z

[John1122]

The RGEM is getting into range with this, it's showing pretty much all snow from the onset. Approaching 1-2 inches over parts of the area by Monday at 1 pm. It'll be towards Monday until the RGEM gets the entire event in it's window. It was the first model that really started showing good snows from wave 1 a couple weeks ago.

[Runman292]

Slight uptick/variations but overall a fairly steady picture of potential snowfall through Wednesday evening. 12z then 18z.

Is this a 20-1 ratio?

[John1122]

Seen many times when these temps drop around 500mb the models underestimate the cold air aloft to the surface in the Valley,we'll see.The 500mb drops to -31C in mid Tn at 12z Mondayand doesnt fall below -30c until thursday 6z

There's excellent cold through the entire column for top down cooling to occur quickly. If it rains at all it will be super cooled rain drops that fall almost all the way to the surface as snowflakes. That should do the trick with no midlevel warm nosing being forecast.

[John1122]

Is this a 20-1 ratio?

It should be ratio adjusted for the entire event.