Winter Pattern Discussion 2014-2015 (December/January)

[Carvers Gap]

Nothing set in stone five days out. Looks like temps are marginal no matter what the scenario. Euro appears to have switched back to the track it has been showing for a few days. Again, I think anything prior to Christmas is just a bonus. With no blocking in place yet, this weekend's storm could still shift north or south again on the models.

[jaxjagman]

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1109 PM EST MON DEC 15 2014

VALID 12Z FRI DEC 19 2014 - 12Z TUE DEC 23 2014

...SNOW POSSIBLE FOR PORTIONS OF THE MID-SOUTH EASTWARD INTO THE
CENTRAL/SOUTHERN APPALACHIANS...

...OVERVIEW...

ACTIVE PATTERN TO CONTINUE INTO NEXT WEEK AS UPPER RIDGING SLOWLY
BUILDS JUST OFFSHORE CALIFORNIA. PATTERN SHIFT IS FORECAST TO MOVE
THE MAIN RIDGE/TROUGH CENTERS ABOUT A HALF WAVELENGTH DOWNSTREAM
IN THE MEDIUM RANGE... AS THE RIDGE IN CENTRAL CANADA MOVES TO
EASTERN CANADA AND THE RIDGE TO THE NW OF HAWAII MOVES CLOSER TO
CALIFORNIA. THIS SHOULD FAVOR TROUGHING IN THE SW CONUS MOVING
EASTWARD PAST 100W BY NEXT TUESDAY. A LEAD SYSTEM IN THE SOUTHEAST
QUARTER OF THE CONUS WILL PUSH AWAY FROM THE
SOUTHEAST/MID-ATLANTIC LATE THIS WEEKEND BUT ITS LATITUDINAL
EXODUS IS UNCERTAIN.

...GUIDANCE EVALUATION AND PREFERENCES...

IN THE EAST... THE MODELS/ENSEMBLES HAVE OFFERED A VARIETY OF
SOLUTIONS OVER THE PAST FEW DAYS FROM A VERY LOW AMPLITUDE AND
FLAT WAVE MOVING THROUGH THE SOUTHEAST TO A WRAPPED UP SFC LOW
HUGGING THE COAST INTO NEW ENGLAND. THE ECMWF ENSEMBLE MEAN HAS
OFFERED THE BEST CONSISTENCY AND HAVE CONTINUED TO RELY ON ITS
ROBUSTNESS. THE DETERMINISTIC ECMWF HAS BEEN LESS STABLE IN ITS
DETAILS BUT BY NO MEANS UNUSABLE... AND IN FACT USED A 50/50
WEIGHTING BETWEEN IT AND ITS ENSEMBLE MEAN FOR THE FIRST PART OF
THE FORECAST -- FRIDAY THROUGH SUNDAY -- AS THE LOW PUSHES THROUGH
THE SOUTHEAST AND THEN TURNS NORTHEASTWARD AND HEADS INTO THE
ATLANTIC... LIKELY PASSING JUST SOUTHEAST OF THE 40N/70W
BENCHMARK. AGAIN... ENSEMBLES STILL SPAN AN AREA ROUGHLY 500 BY
500 MILES JUST OFF THE DELMARVA EARLY SUNDAY.

FOR THE WEST... GOOD AGREEMENT EXISTS THROUGH ABOUT THE WEEKEND AS
THE TROUGH OFF THE COAST SPLITS AND THE SOUTHERN PORTION DROPS
THROUGH THE GREAT BASIN AND INTO THE FOUR CORNERS REGION. FROM
THERE... THE GEFS MEMBERS ARE QUICKER TO MOVE THIS ENERGY EASTWARD
TOWARD 90W BY NEXT TUESDAY WHILE THE ECMWF ENSEMBLE MEMBERS LAG
BEHIND BY ABOUT 10 DEGREES LONGITUDE. THE CANADIAN ENSEMBLES LIE
EVEN FARTHER WEST INTO NW MEXICO. ONE FACTOR OF INFLUENCE IS HOW
STRONG AND EAST UPPER RIDGING BECOMES OFFSHORE CALIFORNIA... ALSO
RELATED TO UPSTREAM CENTRAL PACIFIC TROUGHING DOWNSTREAM OF A
STRONG JET OFF JAPAN EARLY NEXT WEEK. WITH THE TENDENCY TOWARD
MORE AMPLIFICATION OVER THE PACIFIC... WOULD TEND TO FAVOR THE
SLOWER SOLUTIONS -- ECMWF ENSEMBLES -- OVER THE QUICKER GEFS
MEMBERS. THE NAEFS MEAN CORRELATES WELL WITH THE ECMWF ENSEMBLE
MEAN GIVEN ITS BALANCING QUICKER VS MUCH SLOWER MEMBERS... AND
TRENDED THE FORECAST TO A 50/50 WEIGHTING BY NEXT TUESDAY.

...SENSIBLE WEATHER HIGHLIGHTS...

SOUTHERN/EASTERN SYSTEM LATE THIS WEEK INTO THE WEEKEND SHOULD AT
LEAST BRING WET AND SOME WHITE CONDITIONS TO THE
MID-SOUTH/SOUTHEAST INTO THE CENTRAL/SOUTHERN APPALACHIANS AND
MID-ATLANTIC. LACK OF ARCTIC AIR OVER THE CONUS SPELLS A MARGINAL
WINTER P-TYPE EVENT BUT POTENTIAL EXISTS FOR AT LEAST A FEW INCHES
ON THE N/NW SIDE OF THE PRECIP SHIELD AS IT ADVANCES EASTWARD.
TEMPERATURES IN THE WAKE OF THE SYSTEM SHOULD BE BELOW AVERAGE BY
5-10 DEG F.

WESTERN TROUGH AND SFC BOUNDARY LATE THIS WEEK WILL BRING A GOOD
1-3 INCHES OF QPF TO THE COASTAL RANGE AND THEN A SECOND SYSTEM
EARLY NEXT WEEK SHOULD PUSH THE PRECIP EASTWARD PAST THE DIVIDE
WITH A MORE ZONAL FLOW. DEPENDING ON HOW QUICKLY THE SOUTHERN
TROUGH MOVES EASTWARD OUT OF THE SW/TX RAIN SHOULD EXPAND IN AREAL
COVERAGE IN S TEXAS AND THE LOWER MS VALLEY NEXT TUESDAY.

FRACASSO

[jaxjagman]

LONG TERM(FRIDAY THRU TUE)...
ACTIVE WX IS EXPECTED FOR FRIDAY THROUGH SUNDAY MORNING WITH WIDESPREAD
PRECIPITATION OVER THE REGION. A SHORTWAVE TROUGH WILL MOVE FROM THE
SOUTHERN PLAINS...ACROSS THE TN VALLEY TO THE MID ATLANTIC REGION...AS
A SURFACE LOW WILL MOVES ACROSS THE DEEP SOUTH. THERE IS STILL A GOOD DEAL
OF VARIABILITY AMONG MODELS WITH THE STRENGTH AND PHASING OF THE UPPER SYSTEM
AND TRACK OF THE SURFACE LOW. IT IS POSSIBLE THAT SOME SNOW COULD OCCUR IN
MID TN THIS WEEKEND...BUT ENSEMBLE BLENDS AND TRENDS OF OPERATIONAL MODELS
SUGGEST THE BEST CHANCE FOR SNOW ALONG THE FRINGES OF THIS SYSTEM WILL BE
NORTH OF OUR AREA. GIVEN THE UNCERTAINTIES...WE WILL INCLUDE THE POTENTIAL
FOR SOME SNOW TO MIX WITH THE RAIN OVER OUR NORTHWEST COUNTIES FRIDAY NIGHT
INTO SATURDAY...AND AGAIN SATURDAY NIGHT. ELSEWHERE...WE WILL LIMIT THAT
POTENTIAL TO JUST LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THIS POINT...
EVEN THE COLDER LOOKING SOLUTIONS ARE MARGINAL FOR ANY MEASURABLE SNOW
ACCUMULATION. AT THIS POINT...THE BEST BET IS FOR A CHILLY RAIN...MIXED WITH
SOME FLAKES NORTH OF I 40 AND PLATEAU. STAY TUNED.

SUNDAY AFTERNOON THROUGH MONDAY SHOULD BE DRY AND SEASONABLY CHILLY.
ANOTHER SHORTWAVE WILL BRING A CHANCE FOR SHOWERS TUESDAY.

 

http://forecast.weather.gov/product.php?site=OHX&issuedby=OHX&product=AFD&format=CI&version=1&glossary=1

[Carvers Gap]

Uhh, folks.  Someone might want to take a look a the Euro.  Marginal temps for northern sections on this weekend's storm.  Christmas storm is a hybrid miller A/B it appears...or it may be a true miller B.  Looks like it attempts to phase as energy gets handed off.  A step in the right direction in my opinion for the second storm.  

[tnweathernut]

Uhh, folks. Someone might want to take a look a the Euro. Marginal temps for northern sections on this weekend's storm. Christmas storm is a hybrid miller A/B it appears...or it may be a true miller B. Looks like it attempts to phase as energy gets handed off. A step in the right direction in my opinion for the second storm.

It is interesting in that it shows a snowfall Christmas eve night, probably after the kids will have gone to bed.

Not that it will stay the same,, or that I am saying the timing won't change, but how awesome (and magical) would it be if you go to bed that night as a child..... with no snow on the ground, and wake up with a few inches?

I agree that it is a step in the right direction.

[Carvers Gap]

I'll take another helping of the 18z GFS.  I know. I know.  18z.  But enjoy the Christmas Eve run at least once for your own viewing pleasure.

[1234snow]

I'll take another helping of the 18z GFS. I know. I know. 18z. But enjoy the Christmas Eve run at least once for your own viewing pleasure.

I must be missing something. Just looked like a frontal passage to me with the cold chasing the moisture on the 18z GFS.

[valkhorn]

I must be missing something. Just looked like a frontal passage to me with the cold chasing the moisture on the 18z GFS.

 

It looks good on the 850s, but the boundary layer temps don't support snow at least for Knoxville, or most of the East TN area anyways.

[Carvers Gap]

This far out, I would advise looking at the pattern. That is what I was looking at... We get a low in that position somebody is going to get snow IMO. Was not just a cold frontal passage when a low winds up to your east...

[Carvers Gap]

Looks like this weekend and Christmas day now look like non-events on this AM's model runs for TN, 0z Euro and 6z GFS. Euro banks the cold out west, maybe an error IDK. GFS drops the hammer shortly after Christmas.

[valkhorn]

Looks like this weekend and Christmas day now look like non-events on this AM's model runs for TN, 0z Euro and 6z GFS. Euro banks the cold out west, maybe an error IDK. GFS drops the hammer shortly after Christmas.

 

Well back end flurries look possible during Christmas Day, so if they are I'll take it. It's better than a blowtorch christmas.

 

EDIT: The 06z para GFS changes the precip briefly to snow before exiting. I'll take a few token flakes.

[tnweathernut]

If we get this look in the 11-15, which is the 26-30th, and there isn't a widespread winter event for some (maybe many) in the mid-south, it would be just plain unlucky...

Photo courtesy of Allan's (RaleighWx) twitter.

[1234snow]

Looks like this weekend and Christmas day now look like non-events on this AM's model runs for TN, 0z Euro and 6z GFS. Euro banks the cold out west, maybe an error IDK. GFS drops the hammer shortly after Christmas.

The Euro had one of the strongest storms I've ever seen modeled last night. 522 dm heights just west of us and a bombing 965 mb low when it gets to Michigan. This will be a Christmas Eve nightmare (or miracle) for someone in the Ohio Valley. I don't think we are out of it just yet. We need the trough further east though.

[jaxjagman]

ImageUploadedByTapatalk1418822131.791823.jpg

If we get this look in the 11-15, which is the 26-30th, and there isn't a widespread winter event for some (maybe many) in the mid-south, it would be just plain unlucky...

Photo courtesy of Allan's (RaleighWx) twitter.

 

Little add on

[BNAwx]

4panel.png 1024×1024 .png

 

Little add on

 

-EPO ruled the roost last year...

[John1122]

The Christmas timeframe threat is catching the eye of local NWS offices.

 

From JKL.

 

 

 

A MUCH MORE IMPRESSIVE STORM SYSTEM IS SHOWING UP IN THE COMPUTER
MODELS FOR THE MIDDLE OF NEXT WEEK...WITH DECENT AGREEMENT ON AN
IMPACTFUL SYSTEM JUST IN TIME FOR PEAK HOLIDAY TRAVEL. AN UPPER
LEVEL TROUGH WILL DIG IN OVER THE PLAINS EARLY IN THE WEEK AND
BECOME NEGATIVELY TILTED OVER THE OHIO VALLEY MID WEEK. THIS CAUSES
EXPLOSIVE DEEPENING OF A SURFACE LOW PRESSURE WHICH IS PROGGED TO
DEVELOP AND TRACK OVER US OR VERY CLOSE TO US ON ITS WAY NORTH TO
THE GREAT LAKES. THIS SYSTEM IS STILL WAY TOO FAR OUT IN THE FUTURE
TO PINPOINT EXACTLY WHAT TYPE OF WEATHER WE WILL BE DEALING
WITH...BUT RAIN...WIND AND SNOW ARE ALL ON THE TABLE FROM TUESDAY
THROUGH WEDNESDAY...AND POTENTIALLY BEYOND.

[John1122]

MRX already has me with a 60% chance of snow for next Wednesday. It's extremely rare for them to go above 30 percent more than 3 days out.

[1234snow]

MRX already has me with a 60% chance of snow for next Wednesday. It's extremely rare for them to go above 30 percent more than 3 days out.

It would not surprise me if we got into some good upslope with the magnitude of this system.

The #SantaBomb (yes I know I know) was deeper on today's models. Lowest pressures was 960 on the GFS and 965 on the Euro from what I could tell.

Very wild pattern coming up even if it turns out not favorable for us.

Edit: 958 Mb on the 12z GFS

[jaxjagman]

MRX already has me with a 60% chance of snow for next Wednesday. It's extremely rare for them to go above 30 percent more than 3 days out.

Strange,the same with Nashville,40% Surprised it's not snow/rain

[max100]

James Spann sure doesn't think much of anything happening.  He is going very conservative after what happened this year in Bham and ATL>

[Carvers Gap]

Just an opinion, but the Euro just looks too wound-up. The GFS is much less so for Christmas Eve.  Hate to go against Dr. No, but it looks overdone.  The next two days will shed some light on things. 

[1234snow]

Just an opinion, but the Euro just looks too wound-up. The GFS is much less so for Christmas Eve. Hate to go against Dr. No, but it looks overdone. The next two days will shed some light on things.

To be honest I think the GFS will end up winning the battle with this "storm" in a few days. The Euro was way too amped and too cold and is conceding to the GFS. (I'm talking about the 19th-21st time frame)

Now for the Christmas Eve storm the 18z GFS does spit out a few inches for Far East Tennessee and the mountains. The storm track was on the east side of the mountains this time and up into New York. Hopefully the GFS is onto something.

[valkhorn]

00z operational and parallel say no snow for east TN on Christmas. Oh well.

[Carvers Gap]

The 0z Euro spits out yet another variation of the mid-week storm. Most energy stays north. Looks like a blizzard for the upper MS Valley...like way up there. It again places the cold air out west. 6z is zonal after the initial cold shot. I don't think we get snow next week and has always been a bit of a long shot. I am more concerned with where this storm goes. Can it set up the cold delivery mechanism that we need? 50/50 low?

[Stovepipe]

00z operational and parallel say no snow for east TN on Christmas. Oh well.

 

Not that I'm expecting snow on Christmas, but the GFS meteogram for Knoxville shows it for 00z and even more for 06z.

 

 

 

[tnweathernut]

The 0z Euro spits out yet another variation of the mid-week storm. Most energy stays north. Looks like a blizzard for the upper MS Valley...like way up there. It again places the cold air out west. 6z is zonal after the initial cold shot. I don't think we get snow next week and has always been a bit of a long shot. I am more concerned with where this storm goes. Can it set up the cold delivery mechanism that we need? 50/50 low?

Not all that worried, OP's will be all over the map next week or so.

Ensembles look good around day 6-8z

[BNAwx]

Not all that worried, OP's will be all over the map next week or so.

Ensembles look good around day 6-8z

 

 

 

 

 

I really like that look.  Should not only allow for cold but storminess as well..

[Carvers Gap]

The 12z Euro looks very good.  Talking pattern folks, not specific events.  Is lining up now w/ the GFS and is not holding the cold out west.  Cross polar flow.  Nice run.

[Carvers Gap]

Specifically towards the end of the run a strong -NAO, a frontal boundary draped across the upper south running east to west, and cold dropping into the Plains.  NA is cold on this run. 

[John1122]

The GFS was also very cold in the extended and appear to be delivering severe cold into the east at the end of it's run. -20 to -30 in the mid-west with 20+ mph north winds blowing throughout the South and the 0f line approaching Western Kentucky.