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John1122

Winter Storm Threat: Jan 23rd-25th 2015

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Well, it's within 72 hours of beginning and modeling is looking more and more robust for potential snow somewhere in the Great Valley region. Right now 40 North and Plateau west look to be in the sweet spot with several runs in a row of the GFS really hammering those areas into Southern Kentucky. 

 

As of now, all major models are on board with the storm and are showing a near perfect track for widespread snow across our region. The main issue, as always, will be warm nosing causing boundary temp issues. This looks especially likely for the Eastern Valley, from Chattanooga to Knoxville. 

 

If the boundary temps  work out, this looks like it could be a nice one. It's also somewhat shown that the new GFS has the same NW trend that the old GFS exhibited. 

 

Here are some clown maps from tonights runs.

 

00z GFS Through 90 hours on top, then the GGEM that Jags already posted in the pattern thread. 

 

 

post-499-0-56716300-1421823999_thumb.png

post-499-0-45561000-1421824044_thumb.png

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A few meteograms:

 

I'd like to see middle and west reel this one in.  You folks are over due.

Me too.  I have a buddy just north of Nashville that has been giving me all kinds of grief about it not being able to snow in mid TN anymore (due to the snow dome), and saying "I thought you said we were going to get good snows this year"..........yada yada yada.  He's really been blasting me.  I'd like to see him get blasted this year, even if mby doesn't.

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12z NAM looks even colder through 42 in central and west TN.  Should see precip start breaking out shortly after 42 on the NAM when looking at 500.  Let's see if more of mid TN can get a paste job on this run.

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PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
403 AM EST WED JAN 21 2015

VALID 12Z WED JAN 21 2015 - 12Z SAT JAN 24 2015

...DAY 1...

...GREAT LAKES/MIDDLE ATLANTIC/SOUTHERN NEW ENGLAND...

A MODEST TROUGH OVER THE MIDWEST WILL MOVE EASTWARD WITH A REGION
OF UPPER LEVEL DIFFLUENCE DOWNWIND OF THE TROUGH AXIS ALONG THE
MID ATLANTIC COAST AND A REGION OF UPPER CONFLUENCE OVER NEW
ENGLAND. AS THE TROUGH APPROACHES THE MID ATLANTIC COAST ON
WEDNESDAY AFTERNOON...A WEAK SURFACE LOW OVER NORTH CAROLINA WILL
BEGIN TO DEVELOP AND MOVE EAST OF THE VIRGINIA COAST BY THURSDAY
EVENING. THE CONFLUENCE WILL KEEP THE QPF MOSTLY SOUTH OF SOUTHERN
NEW ENGLAND EXCEPT FOR THE IMMEDIATE COASTLINE. WHILE LIGHT SNOW
WILL CONTINUE TO CROSS THE UPPER OHIO VALLEY ON EARLY WEDNESDAY
AND MOVE ACROSS PENNSYLVANIA BY MID WEDNESDAY...AN AREA OF
RAIN/SNOW WILL DEVELOP FROM VIRGINIA NORTHEASTWARD ACROSS
MARYLAND/DELAWARE AND NEW JERSEY. WHILE MOST ACCUMULATIONS WILL
LIKELY RANGE FROM 1 TO 4 INCHES IN THIS AREA...THERE IS A
CONSENSUS AMONG THE 00Z OPERATIONAL RUNS THAT A SWATH OF MORE
SIGNIFICANT QPF MAY DEVELOP FROM EASTERN VIRGINIA/DELMARVA INTO
SOUTHERN NEW JERSEY. SOME OF THE QPF MAY BE A MIX OF RAIN/SNOW BUT
THERE IS A LOW PROBABILITY THAT 4 OR MORE INCHES OF SNOW MAY FALL
FROM ACROSS SOUTHWEST PENNSYLVANIA AND THE APPALACHIANS FROM SW PA
INTO EASTERN WEST VIRGINIA...AS WELL AS NORTHEAST
MARYLAND/SOUTHEASTERN PENNSYLVANIA/DELAWARE INTO NEW JERSEY. IN
GENERAL...THE MODEL BLEND USED TO GENERATE THE FIRST GUESS
INCLUDED THE 12Z ECMWF/18Z GFS/18Z GEFS MEAN AND THE BIAS
CORRECTED SUPER ENSEMBLE.

...DAYS 1 TO 3...

...SOUTHERN ROCKIES/SOUTHWEST/SOUTHERN HIGH PLAINS/TENNESSEE
VALLEY/APPALACHIANS/MID ATLANTIC...

A POTENTIALLY HIGH IMPACT STORM FIRST AFFECTING THE SOUTHERN
ROCKIES/SOUTHWEST AND SOUTHERN PLAINS ON DAYS 1 AND 2 BECOMES A
SIGNIFICANT SNOW/ICE THREAT FOR THE TENNESSEE
VALLEY/APPALACHIANS/MID ATLANTIC BEGINNING ON DAY 3.

TWO TROUGHS...ONE OF THE THE DESERT SOUTHWEST AND THE OTHER DIVING
SOUTHWARD FROM THE NORTHERN ROCKIES WILL MERGE ON WEDNESDAY AND
THURSDAY INTO A SIGNIFICANT UPPER TROUGH OVER THE SOUTHWEST. SNOW
IS DEVELOPING THIS MORNING ALONG THE FRONT SLOPES OF THE COLORADO
ROCKIES AND WILL SPREAD SOUTHWARD ACROSS SOUTHERN COLORADO/MUCH OF
CENTRAL/NORTHERN AND EASTERN NEW MEXICO/SOUTHWEST KANSAS/THE
PANHANDLES OF OKLAHOMA AND TEXAS/WESTERN OKLAHOMA/WESTERN TEXAS
AND AN AREA ALONG THE RED RIVER VALLEY BETWEEN OKLAHOMA AND TEXAS.
THE HEAVIEST SNOW IS EXPECTED TO DEVELOP ALONG THE FRONT SLOPES
OF THE ROCKIES FROM CENTRAL AND SOUTHERN COLORADO ACROSS PARTS OF
THE SAN JUAN AND SANGRE DE CRISTO RANGES...WHERE THERE IS A HIGH
PROBABILITY OF AT LEAST 8 TO 12 INCHES OF SNOW.  AMOUNTS IN EXCESS
OF A FOOT OF SNOW IS EXPECTED IN PORTIONS OF SOUTHERN
COLORADO/NORTHEAST NEW MEXICO AND THE WESTERN PANHANDLES OF TEXAS
AND OKLAHOMA.

AS THE TROUGH MOVES EASTWARD AS A POSITIVELY TILTED TROUGH ON
THURSDAY INTO EARLY FRIDAY...SNOW WILL LINGER ACROSS SOUTHEASTERN
NEW MEXICO AND WESTERN TEXAS AND BEGIN TO SPREAD EASTWARD ALONG
THE RED RIVER VALLEY BETWEEN OKLAHOMA AND TEXAS. THERE IS A LOW TO
MODERATE PROBABILITY OF SNOWFALL EXCEEDING 4 INCHES ACROSS
SOUTHEAST NEW MEXICO AND WESTERN TEXAS. THERE ARE SIGNIFICANT
DIFFERENCES IN THE AMOUNT OF SNOW FORECAST FOR THE RED RIVER
VALLEY...WITH ONLY LIGHT ACCUMULATIONS PREDICTED BY THE GFS/ECMWF
AND ENSEMBLES WHILE THE LATEST 00Z NAM/21Z SREF MEMBERS FORECAST
MUCH HIGHER AMOUNTS.  AS A RESULT...THERE IS A LOW PROBABILITY OF
GREATER THAN 4 INCHES OF SNOW ALONG THE WESTERN RED RIVER
VALLEY...ALTHOUGH WPC FORECASTERS TENDED TO IGNORE THE NAM/SREF IN
FAVOR OF THE ECMWF/GFS SINCE THE QPF AMOUNTS SEEMED TO BE BETTER
CORRELATED TO A WEAKER SYSTEM THAN FORECAST BY THE NAM.

ON DAY 3/FRIDAY INTO EARLY SATURDAY...THE POSITIVELY TILTED TROUGH
MOVES EASTWARD AND THEN BEGINS TO EVOLVE INTO AN INCREASINGLY
NEUTRAL AND THEN NEGATIVELY TROUGH MOVING ALONG THE GULF COAST
BEFORE STARTING TO HEAD NORTHEASTWARD ALONG THE ATLANTIC COAST.
WHILE AN AREA OF CONFLUENCE OVER THE EASTERN US IS ASSOCIATED WITH
RISING PRESSURES ALONG THE EASTERN US AHEAD OF THIS
SYSTEM...ALLOWING COLDER AIR TO PRECEDED THE STORM BEFORE MOVING
UP ALONG THE EAST COAST...THE CONFLUENCE SUBSIDES AND HIGH
PRESSURE MOVES OFF THE EAST COAST.  HOWEVER...THERE IS ENOUGH COLD
AIR THAT A THREAT OF SNOW/SLEET AND FREEZING RAIN REDEVELOPS ALONG
THE NORTHERN FRINGE OF THE PRECIPITATION SHIELD ON FRIDAY INTO
EARLY SATURDAY FROM THE TENNESSEE VALLEY INTO THE APPALACHIANS AND
ALONG PORTIONS OF THE MID ATLANTIC STATES.  BY SATURDAY
MORNING...THERE IS A LOW TO MODERATE CHANCE OF GREATER THAN 4
INCHES OF SNOW FROM NORTHEAST TENNESSEE/EASTERN KENTUCKY INTO THE
MOUNTAINS OF NW NORTH CAROLINA/WESTERN VIRGINIA INTO EASTERN WEST
VIRGINIA AND WESTERN MARYLAND. THE HIGHEST TOTALS ARE EXPECTED TO
BE IN THE 4 TO 8 INCH RANGE OVER THE ELEVATED TERRAIN OF EASTERN
WEST VIRGINIA AND WESTERN VIRGINIA BY SATURDAY MORNING...BUT THIS
IS ONLY THE START OF THIS STORMS TRACK ALONG THE EAST COAST. THERE
IS ALSO A CHANCE THAT A STRIP OF FREEZING RAIN WILL DEVELOP AS
WELL FROM EXTREME NORTHEAST GEORGIA UP ALONG THE SPINE OF THE
APPALACHIANS INTO PORTIONS OF THE MIDDLE ATLANTIC STATES...WHERE
THERE IS A LOW PROBABILITY OF GREATER THAN .25 INCHES OF ICE FROM
THE MOUNTAINS OF WESTERN NORTH CAROLINA INTO WESTERN VIRGINIA.
THE 00Z ECMWF/GFS/00Z GEFS MEAN AND THE 12Z ECMWF ENSEMBLE MEAN
WERE USED TO BASE THE FIRST GUESS OF THE SNOWFALL/ICE FORECAST.

THE PROBABILITY OF 0.25 INCHES OF ICE IS LESS THAN 10 PERCENT
ACROSS THE CONTIGUOUS US ON DAYS 1 AND 2.

KOCIN

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Hmmm thanks for the read Jax. If Paul Kocin is at least talking about the potential in the TN Valley, then I'm interested. There are not many out there that have his knowledge and skill at predicting Eastern US snowstorms.

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Hmmm thanks for the read Jax. If Paul Kocin is at least talking about the potential in the TN Valley, then I'm interested. There are not many out there that have his knowledge and skill at predicting Eastern US snowstorms.

Ditto, I agree.  Will be interesting to see what happens. I hope there are GOOD surprises along the way.

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The GGEM has an unfortunate waffle of the freezing line during peak QPF that greatly lowers snow totals.  1) I'll be interested to see what the higher resolution RGEM shows soon as we are almost in range and 2) just a little change in arrival time could make or break snow if the temps are right on the margin.  Regardless, I'd feel pretty good right now if I lived in northwest TN.

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12z Euro shows the cold air retreating as precip begins Friday and returning in time to make a snowy stripe of 2 to 4 inches extending from Jackson TN to northeast KY.  The stripe isn't even wide enough to get Nashville into the mix on that run.

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12z Euro shows the cold air retreating as precip begins Friday and returning in time to make a snowy stripe of 2 to 4 inches extending from Jackson TN to northeast KY.  The stripe isn't even wide enough to get Nashville into the mix on that run.

Started to wonder the GEFS went S this afternoon,the Euro followed

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Definitely close enough to watch like a hawk. Would be awesome if you guys could get hit with a 1-3, 2-4 type deal, then crushed at the end of the month/beginning of Feb.....

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The 12z Euro ensemble mean looks very similar to the operational run for the Friday system in terms of snow.  The control is also pretty similar but a bit more generous with snow throughout west TN including Memphis.

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The 12z Euro ensemble mean looks very similar to the operational run for the Friday system in terms of snow.  The control is also pretty similar but a bit more generous with snow throughout west TN including Memphis.

18Z NAM is N through h45

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Canadian is a hockey puck to the mouth and the European is a currency devaluation. American models had fewer changes at 12Z, just the usual wobbles run to tun. Last 24 hours situation has perhaps perked up a bit west.

 

First, southeast Tennessee is really going to struggle with warm air. 850 mb temps stay up due to downslope off the Apps. Plus 700 mb warm tongue works in Friday afternoon. Looks like a cold rain from Chattanooga to Knoxville, with flurries maybe snow showers Friday night in Knoxvegas. Perhaps Chatty ends as flurries Friday night. HSV to northwest GA may be all rain too far south. Tri Cities still looks okay for light snow Friday night but will also have to work through the warm nose first. Ditto Upper Plateau. TRI is my pick.

 

Nashville faces weak downslope off the Plateau. Though it is much less of an influence than the Apps, the Plateau can disappoint in Nashville too. Still I think Nashville should end as snow showers at least flurries. Memphis is interesting to watch today. Most guidance keeps 850 mb below freezing for the event, which would bring light snow, but surface temps stay above freezing. If not MEM northwest Tennessee into Middle Kentucky should get sticking snow. Cheers.

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Canadian is a hockey puck to the mouth and the European is a currency devaluation. American models had fewer changes at 12Z, just the usual wobbles run to tun. Last 24 hours situation has perhaps perked up a bit west.

 

First, southeast Tennessee is really going to struggle with warm air. 850 mb temps stay up due to downslope off the Apps. Plus 700 mb warm tongue works in Friday afternoon. Looks like a cold rain from Chattanooga to Knoxville, with flurries maybe snow showers Friday night in Knoxvegas. Perhaps Chatty ends as flurries Friday night. HSV to northwest GA may be all rain too far south. Tri Cities still looks okay for light snow Friday night but will also have to work through the warm nose first. Ditto Upper Plateau. TRI is my pick.

 

Nashville faces weak downslope off the Plateau. Though it is much less of an influence than the Apps, the Plateau can disappoint in Nashville too. Still I think Nashville should end as snow showers at least flurries. Memphis is interesting to watch today. Most guidance keeps 850 mb below freezing for the event, which would bring light snow, but surface temps stay above freezing. If not MEM northwest Tennessee into Middle Kentucky should get sticking snow. Cheers.

 

As always, thanks for sharing your thoughts Jeff.  :guitar:

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slowed down by the looks

 

The radar reflectivity with p-type actually looks kind of decent early Saturday morning from middle TN, across the highland rim, to the plateau.  But unfortunately the 12k resolution snow accumulation maps only show a dusting from it. 

 

Edit:  So basically that suggests some periods of decent flakage across a good part of the state late Friday night early Saturday with next to nothing to show for it.  Never even changes over in the central and southern valley.  But at least the clipper looks wet unlike the Euro.

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The radar reflectivity with p-type actually looks kind of decent early Saturday morning from middle TN, across the highland rim, to the plateau.  But unfortunately the 12k resolution snow accumulation maps only show a dusting from it. 

 

Edit:  So basically that suggests some periods of decent flakage across a good part of the state late Friday night early Saturday with next to nothing to show for it.  Never even changes over in the central and southern valley.  But at least the clipper looks wet unlike the Euro.

Who knows if the NAM is right,it popped a secondary that stole all the energy by the looks,first time i seen this :unsure:

 

Edit:who know,i just noticed the 18z did thing same thing on the NAM

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MRX says a couple of inches Plateau and Mountains with the deformation band, 1 inch or less central/northern valley, dusting southern valley. 

 

My forecast is now rain before 9 Friday night, then snow, with light accumulations possible, low 32.

 

I really hope the deformation band gives some vigorous rates and everyone gets at least an inch or two. Especially the Nashville area folks.

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