Arctic Front/Lakes Fetch Snow Dec 20-23

jmundie wrote:

AndyP wrote:Which locations are best for down sloping? I live in Erwin for example, is that a good location. I guess I am just trying to understand down sloping a little better.

Downsloping is bad. Upsloping is good.

If you are in the valley - you rarely ever get nw flow snow showers, because the winds travel down from the plateau and the sinking air causes the precip to disappear the same way that winds blowing up a mountain creates enough lift for snow showers.

Thank you for the explanation! So in my case, up-sloping will help me out this evening and tomorrow.

heres my NWS forecast for tonight...i dont buy it AT ALL...

Rain showers, snow showers, and freezing drizzle likely before midnight, then a chance of snow showers and freezing drizzle between midnight and 2am, then a slight chance of snow showers after 2am. Cloudy, with a low around 27. Breezy, with a west wind 20 to 25 mph, with gusts as high as 35 mph. Chance of precipitation is 70%. Little or no ice accumulation expected. New snow accumulation of less than a half inch possible

they must have looked at my post then changed the forecast

Rain showers, snow showers, and freezing drizzle likely before 11pm, then a chance of snow showers and freezing drizzle between 11pm and 1am, then a slight chance of snow showers after 1am. Mostly cloudy, with a low around 27. Breezy, with a west wind 20 to 25 mph, with gusts as high as 35 mph. Chance of precipitation is 30%.

It has began..JKL has put all of eastern KY under a WWA

Code:

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE JACKSON KY
330 PM EST THU DEC 20 2012

...WINTER WEATHER ADVISORY FROM LATE THIS EVENING INTO FRIDAY FOR
MUCH OF EASTERN KENTUCKY...

.COLDER AIR WILL MOVE INTO THE REGION THIS EVENING BEHIND A COLD FRONT
TRAILING SOUTH FROM A LOW PRESSURE SYSTEM TRACKING ACROSS THE GREAT
LAKES AND INTO THE NORTHEASTERN UNITED STATES. WRAPAROUND MOISTURE
AND UPSLOPE FLOW WILL LEAD TO A PERIOD OF SNOW SHOWERS MOVING ACROSS
THE REGION LATE TONIGHT AND INTO EARLY ON FRIDAY MORNING. BANDS OF
SNOW SHOWERS WILL PERSIST AS LATE AS EARLY FRIDAY EVENING OVER FAR
SOUTHEASTERN KENTUCKY NEAR THE WEST VIRGINIA AND VIRGINIA BORDERS.

KYZ044-050>052-058>060-088-104-106>115-117>120-210430-
/O.NEW.KJKL.WW.Y.0010.121221T0300Z-121222T0000Z/
FLEMING-MONTGOMERY-BATH-ROWAN-ESTILL-POWELL-MENIFEE-HARLAN-
ELLIOTT-MORGAN-JOHNSON-WOLFE-MAGOFFIN-FLOYD-LEE-BREATHITT-KNOTT-
OWSLEY-PERRY-LESLIE-LETCHER-MARTIN-PIKE-
INCLUDING THE CITIES OF...FLEMINGSBURG...MOUNT STERLING...
OWINGSVILLE...MOREHEAD...IRVINE...STANTON...FRENCHBURG...HARLAN...
SANDY HOOK...WEST LIBERTY...PAINTSVILLE...CAMPTON...
SALYERSVILLE...PRESTONSBURG...BEATTYVILLE...JACKSON...HINDMAN...
BOONEVILLE...HAZARD...HYDEN...WHITESBURG...INEZ...PIKEVILLE
330 PM EST THU DEC 20 2012

...WINTER WEATHER ADVISORY IN EFFECT FROM 10 PM THIS EVENING TO
7 PM EST FRIDAY...

THE NATIONAL WEATHER SERVICE IN JACKSON HAS ISSUED A WINTER
WEATHER ADVISORY FOR SNOW AND BLOWING SNOW...WHICH IS IN EFFECT
FROM 10 PM THIS EVENING TO 7 PM EST FRIDAY.

* SNOW SHOWERS WILL MOVE INTO THE REGION TOWARD MIDNIGHT AND PERSIST
  INTO EARLY ON FRIDAY MORNING. ISOLATED TO SCATTERED SNOW SHOWERS
  WILL PERSIST INTO EARLY ON FRIDAY EVENING. GUSTY WINDS WILL LEAD TO
  BLOWING OF FALLING AND FALLEN SNOW AT TIMES FURTHER LIMITING
  VISIBILITIES TO A QUARTER OF A MILE AT TIMES.

* AROUND 1 INCH OF SNOW IS ANTICIPATED...WITH LOCALLY HIGHER AMOUNTS
  AS HIGH AS 2 TO 3 INCHES WHERE PERSISTENT BANDS OF SNOW SHOWERS
  OCCUR AND ON SOME OF THE HIGHER RIDGES. THE LIGHTEST AMOUNTS ON
  AVERAGE WILL OCCUR IN THE DEEPER RIVER VALLEY LOCATIONS.

* ROADS MAY BECOME SLICK OR SNOW COVERED OVERNIGHT TONIGHT OR DURING
  FRIDAY. THE SNOW AND BLOWING SNOW WILL LEAD TO REDUCED VISIBILITIES
  AND LONGER TRAVEL TIMES DURING...ESPECIALLY DURING THE MORNING
  COMMUTE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER WEATHER ADVISORY FOR SNOW AND BLOWING SNOW MEANS THAT
VISIBILITIES WILL BE LIMITED DUE TO A COMBINATION OF FALLING AND
BLOWING SNOW. USE CAUTION WHEN TRAVELING...ESPECIALLY IN OPEN AREAS.

And MRX seems to be climbing on board. I think they they will have to issue advisories for at least the northern parts of the plateau and the northern parts of the smokies. Also MRX seems to think dowsloping will end after the front pulls through.

Code:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
252 PM EST THU DEC 20 2012

.SHORT TERM (TONIGHT THROUGH FRIDAY NIGHT)...STRONG SURFACE LOW
PRESSURE SYSTEM WILL MOVE NE INTO MI TONIGHT AND ENE THROUGH THE E
GREAT LAKES ON FRIDAY. COLD FRONT BOWING THROUGH THE E TN VALLEY
WILL MOVE THROUGH THE SOUTHERN APPALACHIANS TONIGHT. PREFRONTAL
DOWNSLOPING WINDS WILL END AS WINDS SHIFT SW BEHIND THE FRONT. AREAS
OF PRECIPITATION WILL TAPER OFF BEHIND THE FRONT. WINDS WILL SHIFT
TO THE NW THIS EVENING AND REMAIN BREEZY AND BECOME STRONG OF
FRIDAY. NEAR POST FRONTAL RELATIVE HUMIDITY REMAINS SHALLOW WHILE
COLD AIR ADVECTION IS STRONG. LIGHT SHOWERS AND DRIZZLE WILL CONTINUE
IN CYCLONIC FLOW ESPECIALLY ACROSS THE NORTHERN PART OF MRX CWA.
FREEZING LEVEL FALLS HARD AFTER 21/00Z. THE LIGHT PRECIPITATION WILL
LIKELY SHIFT BRIEFLY TO FREEZING DRIZZLE AS DEPTH OF RH DOES NOT
EXTEND INTO THE SNOW GROWTH REGION. WRAP AROUND MOISTURE MOVES INTO
THE AREA AFTER 21/06Z WITH HIGHER RH EXTENDING UP INTO THE SNOW
GROWTH REGION CONTINUING INTO MID DAY FRI. THIS WILL ALLOW FOR SOME
LIGHT SNOWFALL ACROSS NE TN/SW VA. TEMPERATURES WILL FALL INTO THE
20S TONIGHT. STRONG NORTHWEST WINDS WILL KEEP WIND CHILL VALUES
BELOW FREEZING FRIDAY. A WIND ADVISORY WILL BE REQUIRED AREAWIDE
WITH AN ADDITION WARNING POSSIBLE ACROSS THE HIGHER ELEVATIONS.
LIGHT SNOW AND CLOUDS CONTINUE TO SCOUR OUT FRIDAY NIGHT WHILE
TEMPERATURES CONTINUE TO FALL TO BELOW NORMAL WITH WIND CHILLS
RANGING FROM THE SINGLE DIGITS TO THE TEENS.


Some awesome discussion coming from MRX today..I will probably do a map to show the areas where I think accums will be possible later on tonight

Here's my call..I may put some discussion with it later on tonight when I get time

Cold advection has began here in earnest..just had a 31mph gust out of the NW!!

Spitting out a few flurries here. Seems to be a sleet/snow flurry mix.

NW North Carolina mountain counties are now also under a WWA.

Code:

URGENT - WINTER WEATHER MESSAGE...CORRECTED
NATIONAL WEATHER SERVICE BLACKSBURG VA
634 PM EST THU DEC 20 2012

...SEVERE WINTER WEATHER CONDITIONS FRIDAY AND SATURDAY...

.DEEP LOW PRESSURE WILL MOVE THROUGH THE UPPER MIDWEST TONIGHT
AND INTO NEW ENGLAND ON FRIDAY. THE COLD FRONT ASSOCIATED WITH
THIS WINTER STORM WILL MOVE THROUGH THE REGION EARLY TONIGHT...
BRINGING MUCH COLDER TEMPERATURES AND BLUSTERY CONDITIONS FOR
FRIDAY AND SATURDAY. WRAP AROUND MOISTURE ON THE BACK SIDE OF THE
WINTER STORM WILL RESULT IN A 36 TO 48 HOUR PERIOD OF SNOW AND
BLOWING SNOW ACROSS SOUTHEAST WEST VIRGINIA...WITH HEAVY SNOW
ACCUMULATIONS POSSIBLE ALONG THE WESTERN SLOPES IN THE HIGHER
ELEVATIONS...BEGINNING LATE TONIGHT AND CONTINUING INTO SATURDAY.
VERY STRONG WINDS WILL COMBINE WITH THE SNOWFALL TO PRODUCE
BLOWING SNOW AND POTENTIALLY NEAR BLIZZARD CONDITIONS IN SOME OF
THESE MOUNTAINOUS AREAS. LIGHT ACCUMULATING SNOW...IN ADDITION TO
BLOWING SNOW...IS ALSO POSSIBLE ACROSS FAR WESTERN VIRGINIA AND
INTO THE HIGH COUNTRY OF NORTH CAROLINA...SNOW AMOUNTS
CONSIDERABLY LESS THAN WHAT IS EXPECTED TO OCCUR IN WEST
VIRGINIA.

MEANWHILE...IN ADVANCE OF THE MAIN STORM SYSTEM SLATED TO MOVE
INTO THE AREA FRIDAY AND SATURDAY...A BAND OF SHOWERS...MIXED WITH
SLEET...IS MOVING ACROSS THE REGION THIS EVENING. WHILE SURFACE
TEMPERATURES ARE ABOVE FREEZING IN MOST AREAS...LOCATIONS EAST OF
A LEWISBURG...BLACKSBURG LINE ABOVE 2500 FEET ARE AT OR JUST BELOW
FREEZING. IN THESE AREAS...SOME MINOR SLEET ACCUMULATIONS HAVE
BEEN REPORTED RESULTING IN ICE COVERED AND SLICK ROADS AT THESE
HIGHER ELEVATIONS.

NCZ001-018-VAZ009-015-210745-
/O.CON.KRNK.WW.Y.0014.121221T0500Z-121222T0500Z/
ASHE-WATAUGA-SMYTH-GRAYSON-
INCLUDING THE CITIES OF...WEST JEFFERSON...BOONE...MARION...
INDEPENDENCE...WHITETOP...TROUTDALE...VOLNEY
634 PM EST THU DEC 20 2012

...WINTER WEATHER ADVISORY REMAINS IN EFFECT FROM MIDNIGHT
TONIGHT TO MIDNIGHT EST FRIDAY NIGHT...

* LOCATIONS...THE HIGH COUNTRY OF NORTH CAROLINA AND INTO THE
  HIGHER TERRAIN OF FAR WESTERN VIRGINIA.

* HAZARD TYPES...SNOW AND BLOWING SNOW.

* ACCUMULATIONS...SNOW ACCUMULATION OF UP TO 1 INCH.

* TIMING...RAIN WILL CHANGE TO SNOW AROUND MIDNIGHT TONIGHT...
  WITH SNOW SHOWERS AND BLOWING SNOW CONTINUING THROUGH THE DAY
  FRIDAY. THE SNOW IS EXPECTED TO TAPER TO FLURRIES FRIDAY NIGHT.

* IMPACTS...ACCUMULATING SNOW ALONG WITH AREAS OF BLOWING SNOW
  AND WIND CHILLS IN THE SINGLE DIGITS AND TEENS.

* WINDS...WEST 30 TO 40 MPH WITH GUSTS UP TO 75 MPH.

* TEMPERATURES...IN THE UPPER 20S.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS WINTER WEATHER ADVISORY MEANS THAT PERIODS OF SNOW AND
BLOWING SNOW WILL CAUSE TRAVEL DIFFICULTIES. BE PREPARED FOR
SLIPPERY ROADS AND LIMITED VISIBILITIES...AND USE CAUTION WHILE
DRIVING.

&&


MRX seems to be ignoring the need for WWA's in their counties that will likely see a few inches of snow! You would think the little episode they had on the plateau last winter would have made them a little more generous when issuing winter wx products. I also think their pops are WAYY too low for tomorrow and surrounding WFO's would agree with me.

I expect scattered snow showers off and on all day tomorrow and possibly into the night valley north of I-40... plateau and mountians. MRX seems to think precip will be gone around lunch while surrounding WFO's have snow chances into tomorrow night. Its been a while since I disagreed with their line of thinking but I am in full disagreement tonight!

Meanwhile the upper levels are cooling down very quickly with the deep LPS.

The 850 freezing line has almost cleared the state with the 925mb freezing layer right behind it

Snowing at my house in Halls, very fine but at a pretty good clip.
Car tops are turning white.

1st snowflakes here at house in morristown now. Pretty good sized.

32 with nickel and dime sized flakes roaring in sideways. Been snowing since about 7 pm.

Dont let the radar fool you tonight..there is snow falling on the Plateau area. Alot of folks in east TN often get fooled by this during winter. They see the snow in the valley moving out and no more moving in off the plateau when actually there is snow moving eastward off the plateau. John can explain this better than I can (That area is in between coverage and often times during winter the radar doesnt see the precip) and youve already heard John say its been snowing at his place since 7pm..so just a heads up that the radar is actually lying tonight..lol

I was wondering about that Toot. The flurries/snow showers here just seem to come and go, but seems to be about the same size as John-nickel and dime. Temp is 34, but dropping pretty fast. Maybe this can keep on across the plateau, and not downslope. Any late night thoughts Toot?

There will be an even better area for east Tennessee moving in around 2 or so. As for the radar, the further away you get the higher up it sees in the atmosphere. Most of the time in these snow situations the snow falls from lower in the atmosphere than the radar is seeing at that distance.

Oh, ok. Thanks John. Right now, flake size has decreased, but intensity seems to have increased. Pretty good clip out there. Temp 33 now, so not much more to go if this keeps up. Heres hoping for a surprise in the AM.

Jed33 wrote: Any late night thoughts Toot?

Not really..everything seems to be right on track. I see that MRX raised POPS area wide for tomorrow...lol

Radar and especially satellite images are pretty impressive. It wouldnt surprise me to wake up to dusting or so here in the northern valley if the winds dont keep it from accumulating. Satellite images tonight reveal a very powerful and mature mid latitude cyclone with a very large comma head.

John1122 wrote:There will be an even better area for east Tennessee moving in around 2 or so. As for the radar, the further away you get the higher up it sees in the atmosphere. Most of the time in these snow situations the snow falls from lower in the atmosphere than the radar is seeing at that distance.

Thanks for the explanation again John..It seems every winter I always forget what causes that phenomenon. Anyways.. is any of it trying to lay out that way.. or is the wind/warm ground hampering things?

Channel six showed around 1 inch in my area with up to .15 or so in Knoxville, which would be a heavy dusting. The heaviest snow is probably around Cookeville, to Crossville and points North and West of there right now.

Nothing is laying here yet Toot, we are getting NW winds at about 25-30 mph. Plus the ground is very warm still. If it gets into the middle 20s I'm figuring on .5 inches or so here.

Actually a heavy shower is going now and it's whitened the decks and vehicles.

Not sure why, winds are still out of the SW 15-20 here. Temp is 37.9.

Very heavy shower whitened the ground and road. It's very granular and I could actually hear it on my roof.

etnwx wrote:Not sure why, winds are still out of the SW 15-20 here. Temp is 37.9.

This is a really organized low pressure system and its almost vertically stacked up and down. Normally in this situation the center of circulation of the upper low would have already past our longitude to the ENE. Its so large and powerful that it has somewhat occluded as it has basically wrapped cold air almost all the way around it!

850mb temps




There is a closed upper low centred over Michigan and the the circulation all the way down to the surface is in sync. This makes the wind field behave alot like the wind field on tropical system would..very circular and organized.

500mb heights/winds




When you compare the 500mb level (above) with the surface the wind fields/direction is very similar. Normally in this situation this would not be the case

Surface wind direction/radar


Before I turn in for the night.. its 34 degrees with light snow trying to lay on car tops. Looking at long loop radar this baby is certainly booking it and it may be outta here quicker than I thought.. but then again radar can be very decieving at times.

Woke up with a good dusting on the ground..rooftops and such here in Morristown. Headin out to work it will be interesting to see where the heavier amounts are

Meanwhile MRX finally went with a WWA in its northern mountain counties

Code:

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE MORRISTOWN TN
419 AM EST FRI DEC 21 2012

...LIGHT SNOWFALL TODAY BEHIND PASSAGE OF A STRONG COLD FRONT...

.BRISK WEST TO NORTHWEST WINDS WILL BRING MUCH COLDER AIR INTO THE
REGION TODAY. LINGERING MOISTURE WILL FALL AS SNOW SHOWERS OR
FLURRIES...WITH A LIGHT SNOW ACCUMULATION EXPECTED OVER THE HIGHER
TERRAIN OF SOUTHWESTERN VIRGINIA AND THE NORTHERN MOUNTAINS OF EAST
TENNESSEE.

THE SNOW SHOWERS SHOULD END OR TAPER OFF TO FLURRIES BY EARLY THIS
EVENING.

TNZ018-043-045-047-VAZ002-006-008-211900-
/O.NEW.KMRX.WW.Y.0010.121221T0919Z-121222T0000Z/
JOHNSON-SOUTHEAST GREENE-UNICOI-SOUTHEAST CARTER-WISE-RUSSELL-
WASHINGTON-
INCLUDING THE CITIES OF...MOUNTAIN CITY...CEDAR CREEK...ERWIN...
ROAN MOUNTAIN...WISE...NORTON...LEBANON...ABINGDON
419 AM EST FRI DEC 21 2012

...WINTER WEATHER ADVISORY IN EFFECT UNTIL 7 PM EST THIS
EVENING...

THE NATIONAL WEATHER SERVICE IN MORRISTOWN HAS ISSUED A WINTER
WEATHER ADVISORY FOR LIGHT SNOW...WHICH IS IN EFFECT UNTIL 7 PM
EST THIS EVENING FOR THE HIGHER TERRAIN OF SOUTHWESTERN VIRGINIA
AND NORTHERN MOUNTAINS OF EAST TENNESSEE.

* EVENT...SCATTERED TO NUMEROUS SNOW SHOWERS WILL BRING A LIGHT
  SNOW ACCUMULATION OF 1 TO 3 INCHES TODAY...ACROSS THE HIGHER
  TERRAIN OF SOUTHWESTERN VIRGINIA AND THE NORTHERN MOUNTAINS OF
  EAST TENNESSEE.

* TIMING...PERIODS OF SNOW SHOWERS OR FLURRIES THIS MORNING...WITH
  BANDS OF LOCALLY HEAVIER SNOWFALL POSSIBLE THIS AFTERNOON.

* IMPACTS...BE PREPARED FOR POSSIBLE SNOW COVERED ROADS AND LIMITED
  VISIBILITIES. IF YOU MUST TRAVEL...SLOW DOWN AND ALLOW EXTRA TIME
  TO REACH YOUR DESTINATION. WINDY CONDITIONS WILL MAKE IT FEEL
  EVEN COLDER TODAY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER WEATHER ADVISORY FOR SNOW MEANS THAT PERIODS OF SNOW ARE
EXPECTED OR OCCURRING...BUT ACCUMULATIONS ARE EXPECTED TO BE LIGHT.
DRIVING AND WALKING MAY BE DIFFICULT ON UNTREATED ROADWAYS AND
SIDEWALKS.

There was flurries here in South Knoxville from about 3:30 A.M. But nothing stuck. Oh we'll hopefully we can get some more after Christmas!!

This system sure packed a puch with the wind field..some of the strongest and widespread non thunderstorm winds I have seen in a long time. It has been one raw day outside today