Potential Thanksgiving Event

[NCCatawba]

How unusual is it for Louisiana to be under a Winter Storm Watch this time of year with a Ice Storm Warning pending? Winter Storm Warnings down to the Mexico border.

 

I think its always a good indicator to read their details talking about the mix bag of precip and how it will play out. May end up very similar here.

[John1122]

JKL AFD on GFS vs Euro.

 

 

 

GFS SEEMS TO REMAIN THE OUTLIER. THIS IS FURTHER
SUPPORTED AFTER LOOKING AT THE GFS ENSEMBLES AS ALL OF THE ENSEMBLE
MEMBERS EXCEPT ONE SUPPORT A SOLUTION CLOSER TO THE 00Z ECMWF. WITH
THIS IN MIND...THOUGHT IS THE OPERATIONAL GFS IS AN OUTLIER AND CAN
LIKELY BE DISREGARDED AT THIS TIME. GIVEN THE CONSISTENCY OF THE
ECMWF...OPTED TO KEEP THE FORECAST VERY CLOSE TO THIS SOLUTION.

[Cold Rain]

I think you meant the Euro.

I wish I did.

[tnweathernut]

MRX has went with ZR/sleet as their frozen precip type of choice and is actually predicting all rain in the highest elevations of the Smokies.

 

As for the clown maps, I've noticed some show all frozen precip as snow accumulation. Not sure if that's what the WB map is doing or not.

If you look at 500, the maps from various models would support a switch back to snow for northeast TN.  Whether it happens or not remains to be seen, but I'd say that's more likely than staying freezing rain/rain and sleet for the duration.  JMO

[Brick Tamland]

JKL AFD on GFS vs Euro.

 

So how can one time the GFS is an outlier, and the next time the Euro is? It seems whichever one shows a less impressive system is always the outlier, as if going for the most conservative forecast is always the right way to go.

[Brick Tamland]

I wish I did.

 

Why? Just because it is less impressive? The Euro was wrong last time when it showed a big storm and caved to the GFS eventually. Why can't it be wrong this time, too?

[Cold Rain]

Why? Just because it is less impressive? The Euro was wrong last time when it showed a big storm and caved to the GFS eventually. Why can't it be wrong this time, too?

It can, but it probably won't.

[John1122]

So how can one time the GFS is an outlier, and the next time the Euro is? It seems whichever one shows a less impressive system is always the outlier, as if going for the most conservative forecast is always the right way to go.

The Euro has been very consistent in showing the same solution for their forecast area and the GFS has flipped all over the place, notice the mention that the GFS op didn't even have it's ensembles supporting it.  That's why they are using it.

[Brick Tamland]

It can, but it probably won't.

 

 

And why do you say that? Just because it is less impressive? Do we just say whichever one doesn't show snow is the one to go with now?

[Brick Tamland]

The Euro has been very consistent in showing the same solution for their forecast area and the GFS has flipped all over the place, notice the mention that the GFS op didn't even have it's ensembles supporting it.  That's why they are using it.

 

I thought earlier the Euro showed the big storm while the GFS didn't, and now they have switched.

[Brick Tamland]

And with these models going back and forth and one time one shows snow and the other doesn't, and the next time they switch places, how can they be that reliable at all? Seems all they can do is show a potential and whatever happens with snow around here is really anyone's guess.

[John1122]

Even though they are neighboring offices, share similar terrain, and have 5 counties that touch, JKL and MRX are at completely different odds on zr vs snow, and higher elevation precip types. 

 

This is JKL's take,

 

 

 

WE COULD SEE THE POTENTIAL
FOR A 1 TO 3 INCHES OF SNOW ACROSS THE MAJORITY OF THE AREA (PERHAPS
EVEN HIGHER IN THE HIGHEST TERRAIN). HIGHEST AMOUNTS WILL REMAIN ON
THE COLDER RIDGETOPS WITH SLIGHTLY BETTER LIQUID TO SNOW RATIOS. AS
I WAS WRITING THIS...JUST CAUGHT A GLIMPSE OF THE 12Z ECMWF AND IT
NOW HOLDS ONTO THE BETTER MOISTURE THROUGH WEDNESDAY...SUPPORTING A
BIT MORE SNOWFALL. THIS COULD YIELD HIGHER SNOWFALL TOTALS.
HOWEVER...THIS IS THE FIRST RUN THE ECMWF HAS SHOWN THIS KIND OF
POTENTIAL FOR SNOW...SO WILL ONLY ADJUST SNOWFALL TOTALS UP SLIGHTLY
FOR THE TIME BEING...BUT WILL CONTINUE SNOW CHANCES THROUGH
WEDNESDAY EVENING.

[NCCatawba]

The Euro has been very consistent in showing the same solution for their forecast area and the GFS has flipped all over the place, notice the mention that the GFS op didn't even have it's ensembles supporting it.  That's why they are using it.

 

Winner Winner Chicken Turkey Dinner!

 

The only solution left for the GFS to surprise us with is a solution that falls inline with the euro. We shouldn't complain tho its just a short drive up the mountains if anyone wants to see some accumulations.

[Chattownsnow]

well the NAM shows snow for Baton Rouge, LA. so we know we can throw it out the window lol.

[Cold Rain]

And with these models going back and forth and one time one shows snow and the other doesn't, and the next time they switch places, how can they be that reliable at all? Seems all they can do is show a potential and whatever happens with snow around here is really anyone's guess.

Brick, the atmosphere is not a binary system.

[griteater]

The Euro has been very consistent in showing the same solution for their forecast area and the GFS has flipped all over the place, notice the mention that the GFS op didn't even have it's ensembles supporting it.  That's why they are using it.

 

If they are referring to the 12z GFS Ensemble members, they are blind.  On the Euro, the northern stream more or less phases/captures the southern stream when the southern stream wave is the vicinity of MS/AL.  10 of the 12 GFS ensemble members show stream separation in that location.  I don't know which model will be right, but they are wrong in saying that the GFS ensemble members do not support the operational run and are more like the Euro.

 

http://www.meteo.psu.edu/~fxg1/ENSHGT_12z/ensloopmref.html#picture

[tarheelwx]

I think they we referring to the 00z run maybe?

Tw

[griteater]

It's also funny that the Raleigh discussion says that the GFS has been consistent...which I tend to agree...both models have been fairly consistent...Euro phased and north, GFS non-phased and south...right?  I don't remember every run.

[griteater]

I think they we referring to the 00z run maybe?

Tw

Could be, and if that's the case, they have old data as of their 2:30PM disco

[GaWx]

I'm just guessing, and I figure Larry will put me in my place, but I'd say one or two in ten years we'd see single digits, maybe more.  Saw a lot in the 60's.  Recently not so much, but even in the 80's and 90's it wasn't so rare.  0 or below, much more rarefied air in my parts of Ga. Over the fields, and thru the woods, on mammoth back we'd go.  Everyone laughed, and smiled and sang, as the stars shone upon the snow....

 

Tony's pretty close. Back to 1879, it is about 3 years in 10 for singles or colder. Below 0 is ~1 in 20 years.

 

KATL: Period/# yrs. singles or lower/# yrs. subzero

 

1879-1900: 12/3

1901-1920:: 7/0

1921-1940: 8/0

1941-1960: 4/0 (1950, 51, 58, 59)

1961-1980: 8/2 (62, 63, 66, 67, 70, 72, 76, 77)

1981-2000: 8/2 (81-3, 85-6, 89, 94, 96)

2001-2012: 1/0 (2003)

 

So, about one every three years since 1879 has had a single or lower. Average coldest of year is in the low to middle teens.

 

Decade with most years with singles or colder: 1980's with 6 (actually 6 in 9 years). However, 9 year period with most was 1893-1901 with 7.

 

Most years in a row with singles or colder: 4 (1884-7).

 

No singles or lower:

 

1/29/1940-11/24/1950:  10 years, 9 months, 27 days

2/3/1951-2/16/1958: 7 years, 14 days

***1/25/2003-present: 10 yrs., 10 months...new record long (since 1879) just beating 1940-50 but still counting. But the general idea is that we're in the midst of a relatively warm period not unlike 1941-57. However, snowwise, it has been much snowier recently since 1941-57 had only 12.1". 1996-2013 has had 31.7" since the singles lows in 2/96!

[John1122]

Could be, and if that's the case, they have old data as of their 2:30PM disco

 

They say they were looking at the 12z GFS and the 00z Euro, I'm not sure when the 12z ENS come out, but the 12z Euro came out while they were writing the AFD. 

[Tyler B]

On the 18z NAM did it slide east a bit from 12z? To me it looks like it did not much but some?

[tarheelwx]

When do 12z gfs ensembles come out?

Tw

[NEGa]

So when are we going to see the GFS or Euro cave to the other? They can't keep being totally different all the way up to Thanksgiving.

oooh yes they can lol.  you should know better than that  

 

finally dropped out of the 50s (barely) - looks like still a chance at a little zr before the rain takes over.  not bad at this point to have something that hasnt completely disappeared as we approach the start time (at least not yet)

[griteater]

When do 12z gfs ensembles come out?

Tw

wow or allan could better answer that, but for the 12z runs, I believe the GFS Ensemble mean comes out in the noon-1PM time range....with the individual members coming out in the 1-1:30PM timeframe

[griteater]

Good write-up from Greenville...

THE FORECAST MODELS STILL EXHIBIT QUITE A BIT OF SPREAD WITH THE H5LOW TRACK FROM TX THROUGH THE GULF COAST TUE THROUGH TUE NIGHT. THENAM/CMC AND NOW THE 12Z ECMWF...EXHIBIT MORE OF A DEEP OPEN WAVE BYTUE...WHILE THE SLOWEST GFS HAS MORE OF A CLOSED SYSTEM. THE GFSWOULD LIMIT QPF THROUGH TUE AS DEEP GULF COAST CONVECTION MIGHTINTERRUPT MOISTURE TRANSPORT INTO THE REGION. THE GEFS AND ECMENSEMBLES REPRESENT A COMPROMISE WHICH WILL BE FOLLOWED TO BRINGPRECIP ONSET IN FROM THE GULF MAINLY DURING THE EARLY MORNING HOURSTUE...WITH QPF RAMPING UP THROUGH THE DAY ON THE STRENGTH OFISENTROPIC LIFT AND UPPER JET DIVERGENCE EAST OF THE TROUGH.REGARDING PTYPE...THERE APPEARS TO BE A MODEST 850 MB WARM NOSETHROUGHOUT ON ALL MODEL PROFILES AROUND ONSET TIME TUE MORNING. WETBULB PROFILES WILL BE TRICKY AT THE HIGHER ELEVATIONS AND ALONG THENRN BLUE RIDGE WHERE SOME SNOW AND SLEET COULD BRIEFLY MIX IN FOR ANHOUR OR TWO AFTER ONSET...LEADING TO LIGHT ACCUMULATIONS.HOWEVER...VERTICAL PROFILES AND THICKNESS SCHEMES ALL INDICATE THATFREEZING RAIN AND ASSOCIATED ICING WILL PROVIDE THE MAIN HAZARD FORTHE BULK OF THE QPF TUE MORNING...BEFORE PRECIP CHANGES OVER TO ALLRAIN FROM THE S. THERE NOW APPEARS TO BE THE POTENTIAL FOR ADVISORYLEVEL ICE ACCUMULATIONS FROM THE GA/SC MTNS TO THE NW NCPIEDMONT...AND POINTS NW. THE COLDEST MTN LOCATIONS COULD SEE ICEACCUMS IN EXCESS OF ONE TENTH OF AN INCH. WILL CONTINUE TO HIGHLIGHTTHE ICE POTENTIAL IN THE HWO.

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...AS OF 245 PM SATURDAY...THE MEDIUM RANGE PICKS UP IN THE MIDDLE OFTHE WEATHER EVENT...WITH COPIOUS MOISTURE AND AMPLE FORCING FORCONTINUED PRECIP INTO THE OVERNIGHT HOURS. IT SHOULD BE RAINING JUSTABOUT EVERYWHERE AT 00Z WEDNESDAY...BUT THAT IS ABOUT THE LIMIT OFCONFIDENCE WITH THE BACK END OF THIS SYSTEM. THERE REMAINS SOME BIGISSUES WITH CONTINUITY AND CONSISTENCY WITH THE GUIDANCE THROUGHWEDNESDAY...ALTHO THE OPERATIONAL GFS HAS COME AROUND TOWARD THE 00ZRUN OF THE ECMWF IN THAT IT HANGS ON TO A DEFORMATION ZONE ANDPRECIP OVER THE WRN CAROLINAS THROUGH WEDNESDAY NIGHT. WOULD LIKE TOSEE SOME MORE CONFIDENT NUMBERS FROM THE MOSGUIDE FOR THE TUESDAYNIGHT AND WEDNESDAY TIME PERIOD BEFORE WE HANG ONTO A CATEGORICALFOR ANOTHER 24 HOURS. SO...THE PRECIP PROBABILITY WILL BE RAMPEDDOWN INTO THE LIKELY CATEGORY TUESDAY NIGHT AS A MEASURE OFUNCERTAINTY INCREASING WITH TIME...BUT THE LIKELY WILL BE STRETCHEDINTO THE WEDNESDAY MORNING PERIOD MOST PLACES...AND THE AFTERNOONOVER THE NC PIEDMONT. PARTIAL THICKNESSES AND FCST SOUNDINGSINDICATE A SUBSTANTIAL WARM NOSE OVER THE ENTIRE FCST AREA. THE NEWECMWF ALSO SUPPORTS THE IDEA THAT MTN PEAKS MIGHT ACTUALLY BE WARMERTHAN VALLEYS. SO...THINK THE PRECIP WILL BE ALL RAIN ACROSS THEENTIRE FCST AREA THROUGH TUESDAY NIGHT. IT WON`T BE UNTIL WEDNESDAYWHEN SOME OF THE COLDER AIR STARTS TO SPILL IN. THE ECMWF IS MOSTAGGRESSIVE WITH ITS PLUNGING THICKNESS. THE FCST LEANS MORE TOWARDTHE GFS WHICH KEEPS THE MID LEVEL THICKNESS WARMER. THIS SHOULDRESULT IN A CHANGEOVER TO SOMETHING OTHER THAN RAIN...WITH THE MOSTPROBABLE CATEGORY BEING FREEZING RAIN FOR WEDNESDAY AFTERNOON ANDEVENING ACROSS THE NORTHERN ZONES. THIS IS VERY LOW CONFIDENCE...ASIT OFTEN TAKES TOO LONG FOR THE COLDER AIR TO MAKE IT OVER THE MTNSAS THE PRECIP IS PULLING OUT. IF THE ECMWF IS CORRECT...THEN MORETHAN LIKELY IT WILL END AS A BRIEF PERIOD OF LIGHT SNOW. THIS WILLBE SUBJECT TO CHANGE OVER THE NEXT FEW MODEL CYCLES.

[WeatherNC]

wow or allan could better answer that, but for the 12z runs, I believe the GFS Ensemble mean comes out in the noon-1PM time range....with the individual members coming out in the 1-1:30PM timeframe

 

Correct, the indv mems are avialble ~1pm on the model center, which is much faster than they used to roll, props John and Allan!  

 

The 12z UK does a pretty good job of spitting the difference between the GFS and Euro, with a tip of the hat towards the EC.  At 96hrs, it shows a primary slp ~996 just south of Long Island, with a trailing secondary, associated with the southern stream cutoff near Charleston SC.  The H5 maps match up nicely with the surface, southern parcel is still closed off through central AL, you can clearly see the northern stream punching down through TN/KY, it's late, but close enough to make the first wave riding up the EC dominant.  There is enough gap though for a secondary low to develop in response to the southern parcel, which could be a winter type wild card on its backside.

[griteater]

Correct, the indv mems are avialble ~1pm on the model center, which is much faster than they used to roll, props John and Allan!  

 

The 12z UK does a pretty good job of spitting the difference between the GFS and Euro, with a tip of the hat towards the EC.  At 96hrs, it shows a primary slp ~996 just south of Long Island, with a trailing secondary, associated with the southern stream cutoff near Charleston SC.  The H5 maps match up nicely with the surface, southern parcel is still closed off through central AL, you can clearly see the northern stream punching down through TN/KY, it's late, but close enough to make the first wave riding up the EC dominant.  There is enough gap though for a secondary low to develop in response to the southern parcel, which could be a winter type wild card on its backside.

Sounds good WeatherNC...a blend is probably the best way to go at this point

[FLweather]

RAH seems to favor a GFS 2 part solution.

 

 

 

COMPARED TO THE TREND OF THE GFS AND
ECMWF...THE NAM APPEARS TO OPEN AND LIFT NORTHEAST THE UPPER TROUGH
FASTER... PULLING THE SURFACE LOW WELL WESTWARD OVER THE WESTERN
CAROLINAS BY THE END OF THE DAY TUESDAY. THE LATEST ECMWF HAS ALSO
TRENDED THIS WAY...A SEEMINGLY LARGE SHIFT FROM ITS PREVIOUS RUN.
FOR THIS FORECAST...WILL PLAN TO CONTINUE LEANING TOWARD THE
CONSISTENCY OF THE GFS...WHICH ALSO MAINTAINS THE BASICS OF THE
PREVIOUS FORECAST...A PRUDENT POSITION GIVEN MODEL DIFFERENCES IN
SUCH A COMPLEX...YET TO EVOLVE SCENARIO.

 

[John1122]

WPC didn't seem to like any model runs as of their afternoon update and went with yesterday's runs.

 

 

 

DUE TO THE MODEL TIMING DIFFERENCES...AN ENSEMBLE RATHER THAN
OPERATIONAL SOLUTION WAS PREFERRED. AS OF NOW...A BLEND OF THE 00Z
ECMWF/ECMWF MEAN/PREVIOUS 18Z GEFS WAS PREFERRED FOR THE OVERALL
PATTERN HERE. THE NEW 18Z GEFS BASICALLY MIRRORS THE 12Z
GEFS....SO IT WAS NOT PREFERRED.