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Windspeed

Freeze to Thaw, Winter Wx, Feb. 20th-21st, 2015

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A thread to discuss the Winter Storm threat for Feb. 20th and 21st. A large area will start out with Winter Wx on Friday and transition to all rain on Saturday afternoon. The timing and location of the system is still in question, as are the p-types and durations of those types in certain areas. Some areas may experience significant icing.

 

ANOTHER WEATHER SYSTEM DEVELOPS TO THE WEST FRIDAY...SPREADING
CLOUDS AND SNOW INTO THE SOUTHERN APPALACHIANS AND EASTERN
TENNESSEE VALLEY FRIDAY AND EARLY SATURDAY. SNOW ACCUMULATIONS OF 2
TO 4 INCHES ARE POSSIBLE BY SATURDAY MORNING. AMOUNTS MAY BECOME
HIGHER PRIOR TO PRECIPITATION CHANGING TO SLEET AND FREEZING
RAIN.
..BEFORE WIDESPREAD RAIN WORKS NORTHWARD THROUGH EAST
TENNESSEE ON SATURDAY. SOME AREAS...ESPECIALLY NORTHEAST TENNESSEE
AND SOUTHWEST VIRGINIA VALLEYS...MAY EXPERIENCE A FEW HOURS OF
FREEZING RAIN PRIOR TO THE CHANGE OVER TO ALL RAIN.
ABUNDANT
RAINFALL AND WARM TEMPERATURES SHOULD RELIEVE ANY ICING PROBLEMS.
LOCALIZED FLOODING MAY BECOME A PROBLEM DUE TO RAPIDLY MELTING SNOW
PACK.

 

 


Winter Storm Watch
URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE NASHVILLE TN
254 PM CST WED FEB 18 2015

...WINTER WEATHER ADVISORY FOR THE EAST THROUGH 6PM...DANGEROUS
WIND CHILLS TONIGHT INTO THURSDAY AND ANOTHER WINTER STORM FOR
FRIDAY AND FRIDAY NIGHT...

.LIGHT SNOW SHOWERS WILL CONTINUE ACROSS THE REGION THROUGH
6PM...BUT COULD LEAD TO MINOR ADDITIONAL ACCUMULATIONS OVER HIGHER
ELEVATIONS IN EASTERN MIDDLE TENNESSEE. FURTHER...THE COLDEST AIR
OF THE SEASON WILL USHER INTO THE REGION TONIGHT AND INTO THURSDAY.
WINDS TONIGHT COMBINED WITH BITTER COLD TEMPERATURES AT OR BELOW
ZERO WILL PRODUCE WIND CHILLS DOWN TO -15 TONIGHT INTO MIDDAY
THURSDAY. YET ANOTHER WINTER STORM WILL IMPACT MIDDLE TENNESSEE ON
FRIDAY...WITH SNOW...SLEET AND ICE ACCUMULATIONS POSSIBLE INTO
FRIDAY NIGHT BEFORE CHANGING OVER TO ALL RAIN SATURDAY.

TNZ005>008-023>028-056>063-075-077-093>095-190600-
/O.NEW.KOHX.WS.A.0002.150220T1800Z-150221T1800Z/
/O.CON.KOHX.WC.Y.0003.150219T0000Z-150219T1800Z/
STEWART-MONTGOMERY-ROBERTSON-SUMNER-HOUSTON-HUMPHREYS-DICKSON-
CHEATHAM-DAVIDSON-WILSON-PERRY-HICKMAN-LEWIS-WILLIAMSON-MAURY-
MARSHALL-RUTHERFORD-CANNON-BEDFORD-COFFEE-WAYNE-LAWRENCE-GILES-
INCLUDING THE CITIES OF...DOVER...CLARKSVILLE...SPRINGFIELD...
GALLATIN...ERIN...WAVERLY...DICKSON...ASHLAND CITY...NASHVILLE...
LEBANON...MOUNT JULIET...LOBELVILLE...CENTERVILLE...HOHENWALD...
FRANKLIN...BRENTWOOD...COLUMBIA...LEWISBURG...MURFREESBORO...
WOODBURY...SHELBYVILLE...TULLAHOMA...MANCHESTER...WAYNESBORO...
LAWRENCEBURG...PULASKI
254 PM CST WED FEB 18 2015

...WIND CHILL ADVISORY REMAINS IN EFFECT FROM 6 PM THIS EVENING
TO NOON CST THURSDAY...
...WINTER STORM WATCH IN EFFECT FROM FRIDAY AFTERNOON THROUGH
SATURDAY MORNING...

THE NATIONAL WEATHER SERVICE IN NASHVILLE HAS ISSUED A WINTER
STORM WATCH...WHICH IS IN EFFECT FROM FRIDAY AFTERNOON THROUGH
SATURDAY MORNING.

* WIND CHILL ADVISORY IMPACTS...WIND CHILL VALUES WILL DROP DOWN
  TO AS LOW AS -15 AT TIMES FROM 6PM TONIGHT THROUGH NOON
  THURSDAY.

* WINTER STORM WATCH TIMING...A WINTER STORM WATCH IS IN EFFECT
  FROM FRIDAY AT NOON UNTIL SATURDAY AT NOON.

* MAIN WINTER STORM IMPACT...A MIX OF ACCUMULATING SNOW...SLEET
  AND ICE WILL BE POSSIBLE FRIDAY AND FRIDAY NIGHT BEFORE CHANGING
  OVER TO ALL RAIN MIDDAY SATURDAY.

* OTHER IMPACTS...UNTREATED ROADS WILL REMAIN TREACHEROUS THROUGH
  THE REST OF THE WEEK. IF YOU MUST TRAVEL...USE EXTREME CAUTION.

 

 

 


TNZ067>069-071-073-083>086-099>101-190900-/O.EXP.KMRX.WW.Y.0008.000000T0000Z-150219T0000Z//O.CON.KMRX.WS.A.0002.150220T2100Z-150221T2100Z/ROANE-LOUDON-KNOX-NW BLOUNT-NORTH SEVIER-RHEA-MEIGS-MCMINN-NORTHWEST MONROE-HAMILTON-BRADLEY-WEST POLK-INCLUDING THE CITIES OF...KINGSTON...LENOIR CITY...KNOXVILLE...MARYVILLE...SEVIERVILLE...DAYTON...DECATUR...ATHENS...MADISONVILLE...CHATTANOOGA...CLEVELAND...BENTON715 PM EST WED FEB 18 2015...WINTER STORM WATCH REMAINS IN EFFECT FROM FRIDAY AFTERNOONTHROUGH SATURDAY AFTERNOON......WINTER WEATHER ADVISORY HAS EXPIRED...* EVENT...A WINTER STORM SYSTEM MAY APPROACH BY LATE  FRIDAY...BRINGING A THREAT OF WINTRY PRECIPITATION INTO SATURDAY.* TIMING...PRECISE TIMING OF THE POTENTIAL WINTER STORM REMAINS  UNCERTAIN. PRECIPITATION WITH THIS STORM IS EXPECTED TO BEGIN  LATE FRIDAY.* IMPACTS...SNOW ACCUMULATION MAY RESULT IN HAZARDOUS TRAVEL  CONDITIONS ON UNTREATED ROADWAYS. GUSTY WINDS MAY RESULT IN  ADDITIONAL POWER OUTAGES AND TREE DAMAGE IN AREAS THAT  RECEIVED SIGNIFICANT ICE ACCUMULATION ON MONDAY.PRECAUTIONARY/PREPAREDNESS ACTIONS...A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANTSNOW...SLEET...AND/OR ICE ACCUMULATIONS. FUTURE DRIVINGCONDITIONS MAY BECOME HAZARDOUS...SO CONTINUE TO MONITOR THELATEST FORECASTS.

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0z NAM clown:

 

61l65yW.gif

it's a shame it would be washed away so quickly once the rain starts. I nice glaze of ice should slow it down some to start but not long. looks to have beefed up precip some from previous runs as well.

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The Hi-Res NAM seems to be more freezing rain and less snow than regular NAM based on meteograms and p-type maps.

I'm thinking it's gonna be closer to 2 inches of snow, maybe 3, 1/2 inch or so of sleet then .10 or so of freezing rain based on model blends. MRX is just saying they've no idea how much of anything will fall.

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Tropical seems to count all frozen as snow, which seems to be common for a lot of clown generation programs.

 

This one is a little closer to reality but probably still not exactly in line with the model output.

 

USA_ASNOWI24_sfc_063.gif

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MRX is a little confusing on this...not even a WWA for NETN, with expectation of advisory snow and ice...but a WSW for central and southern valley with no more expectation of totals than for northern valley.

 

And on their grid, they show wind chill values for Friday of -1 to -11, with a temp of 24 and only winds at 5 mph? Does that sound right?

 

One more question: anyone else think it seems odd that the record low for tonight is 13? I would have though it would have been quite a bit lower for the record. All the local mets seem to be making a big deal that we will break our record tonight by close to 20 degrees...the 13 just doesn't seem right to me.

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MRX is a little confusing on this...not even a WWA for NETN, with expectation of advisory snow and ice...but a WSW for central and southern valley with no more expectation of totals than for northern valley.

 

And on their grid, they show wind chill values for Friday of -1 to -11, with a temp of 24 and only winds at 5 mph? Does that sound right?

 

One more question: anyone else think it seems odd that the record low for tonight is 13? I would have though it would have been quite a bit lower for the record. All the local mets seem to be making a big deal that we will break our record tonight by close to 20 degrees...the 13 just doesn't seem right to me.

 

I am sure it's been colder, but Tri hasn't been keeping records as long as Knoxville, who has a record of 8 for 2/20. As for no advisories, they mentioned that the timeframe is just a bit too far out for them in NE Tennessee. Which is another reason I believe the Winter Storm Watch has a good chance of being turned into an Advisory when it comes time, likely with the afternoon shift you'll see area wide advisories, although they could probably even hold off until Friday morning for NETN, SWVA.

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I am sure it's been colder, but Tri hasn't been keeping records as long as Knoxville, who has a record of 8 for 2/20. As for no advisories, they mentioned that the timeframe is just a bit too far out for them in NE Tennessee. Which is another reason I believe the Winter Storm Watch has a good chance of being turned into an Advisory when it comes time, likely with the afternoon shift you'll see area wide advisories, although they could probably even hold off until Friday morning for NETN, SWVA.

-2 here north of Nashville

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My point forecast is now 70 percent snow tomorrow afternoon, 1/2 inch snow. 100 percent tomorrow night of snow, sleet, then zr. 2-4 inches of snow and sleet and .10 of ice. That actually may result in a winter storm warning. Especially with the zr/sleet forecast until 1 Saturday.

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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NASHVILLE TN
349 AM CST THU FEB 19 2015

.DISCUSSION...
MOSTLY CLEAR AND VERY COLD CONDITIONS ABOUND THIS MORNING. THE
EARLIER SNOWFALL HAS ENDED ACROSS THE PLATEAU AREA. CURRENT TEMPS
ARE GENERALLY IN THE SINGLE DIGITS. STILL EXPECTING SEVERAL
LOCATIONS ACROSS THE NORTH TO FLIRT WITH THE ZERO DEGREE MARK FOR
LOWS. WINDS HAVE DECREASED AND ARE GENERALLY UNDER 10 MPH BUT WILL
KEEP THE WIND CHILL ADVISORY GOING UNTIL NOON AS NW WINDS OF 5 TO
10 MPH ARE EXPECTED TO CONTINUE.

TODAY...BROAD AND IMPRESSIVE THERMAL TROUGH WILL REMAINED ANCHORED
JUST EAST OF THE AREA. THE THERMAL AXIS THIS AFTERNOON WILL BE SET
UP ALONG THE ATLANTIC COAST. 850 MB TEMPS ACROSS THE PLATEAU AREA
WILL ONLY BE -20C AT 00Z. SO...FOR HIGHS TODAY...WE WILL ONLY SEE
THE MERCURY REACH 11F AT CSV...16 FOR CKV AND 19 FOR BNA.

TONIGHT...ALL EYES WILL BE ON THE DEVELOPING SYSTEM OVER TX. STILL
EXPECTING A SFC LOW TO BEGIN DEVELOPING WITH EASTWARD TROUGHING
DEVELOPMENT. PRECIP SHOULD BEGIN TO SPREAD OUR WAY AND IT LOOKS AS
THOUGH SOME SNOWFALL COULD REACH OUR WESTERN COUNTIES LATE TONIGHT.
HOWEVER...POPS WILL BE LOW.

AS WE MOVE INTO FRIDAY...SNOW IS EXPECTED TO OVERSPREAD THE MID
STATE. BY AFTERNOON...THE PRECIP WILL BEGIN TO CHANGE TO SLEET AND
FREEZING RAIN FOR WESTERN AREAS. ON FRIDAY NIGHT...THE TRANSITION
WILL CONTINUE FROM WEST TO EAST. IT LOOKS AS THOUGH THE PRECIP WILL
CHANGE TO ALL RAIN ACROSS SOUTHWESTERN AREAS AROUND 03Z...CENTRAL
AND NW AREAS 06Z-09Z...PLATEAU AREA 12Z TO 15Z SATURDAY MORNING.
AFT 15Z...RAIN WILL PERSIST INTO SATURDAY NIGHT. IN FACT...1 TO 2
INCH RAINFALL AMOUNTS CANNOT BE RULED OUT.

AS FOR THE SNOW AND WINTRY ACCUMULATION...LOOKS AS THOUGH 1 TO 2
INCH SNOWFALL AMOUNTS COULD OCCUR ON FRIDAY...PRIOR TO THE SNOW
TRANSITIONING TO SLEET AND FREEZING RAIN. SLEET ACCUM COULD BE
AROUND 1/4 INCH...AND ICE ACCUM BETWEEN 1/10 INCH AND 1/4 INCH.
THE FACT THAT THE OVERALL LIQ EQUIV OF FROZEN/FREEZING PRECIP LOOKS
TO BE IN THE .25 TO .35 RANGE...THE WINTER STORM WATCH WILL
CONTINUE.

FOR THE EXT FCST...THINGS KIND OF QUIET DOWN A BIT. WE COULD SEE
SOME LIGHT SNOW SUNDAY NIGHT AND MONDAY ON THE BACK SIDE OF THE BIG
WEEKEND SYSTEM. THEN...FOR NOW...THE GULF MOISTURE REMAINS WELL
SOUTH OF OUR AREA AND TN LOOKS DRY. TEMPS WILL STILL RUN ON THE COLD
SIDE FOR THE MIDDLE OF NEXT WEEK BUT IT WILL BE NOTHING LIKE IT IS
TODAY.

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So, what do you all have for the (none HIRES) 12z NAM? Looks like it takes its time getting the Valley to the freezing mark Fri-Sat. Looks like significant precip before it switches.

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So, what do you all have for the (none HIRES) 12z NAM? Looks like it takes its time getting the Valley to the freezing mark Fri-Sat. Looks like significant precip before it switches.

 

Yeah looks juicier and colder.  I'll post the clown and meteograms once it finishes rolling out.

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12z NAM clown for Friday/Saturday:

 

RfI37RJ.gif

 

Juicy. I wonder how much of that is freezing rain and sleet in TYS. Also, it would be pretty nice to have a nice thump and have it melt so that the ice can at least go away a bit.

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Juicy. I wonder how much of that is freezing rain and sleet in TYS. Also, it would be pretty nice to have a nice thump and have it melt so that the ice can at least go away a bit.

Yeah, surely some of that is ice pellets and zr, right? I wouldn't complain if that happens but that seems like an awful lot of snow. I am also going to assume ratios would be lower due to the impending warm air.

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Meteograms for 12z NAM show:

 

TYS:

Snow:  0.70

ZR:  0.31

Sleet:  0.39

 

TRI:

Snow:  6.5 

ZR:  0.23

Sleet:  0.06

 

BNA:

Snow:  0.70

ZR:  0.18

Sleet:  0.36

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Meteograms for 12z NAM show:

 

TYS:

Snow:  0.70

ZR:  0.31

Sleet:  0.39

 

TRI:

Snow:  6.5 

ZR:  0.23

Sleet:  0.06

 

BNA:

Snow:  0.70

ZR:  0.18

Sleet:  0.36

Stovepipe can you provide KCHA numbers?

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I am not sure that I buy the 12 NAM yet.  That was a big shift in our favor this time.  The totals are dependent on two things:

 

1.  Precip moves in before the cold moves out(that I think is correct...but how much?)

 

2.  Precip shield is south(after the last storm, I am a little iffy on this one, but synoptics may favor this)

 

Temps tomorrow will be around zero tomorrow morning.  Will be tough for any system to erode the cold quickly.  Going to be very dependent on how quick the precip moves in.  If it is slow, this could be next to a non-event.  If it is quick, like the NAM...game on.  So, let's see what model support the NAM has and what would counter it.  Anyone have any maps that would support it from short range models?

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