Potential winter threats

[Kaner587]

they start coming out on raliegh in 5 minutes

I heard they are very similar to 00z maybe slightly east...still a major signal

[Isotherm]

nobody. the storm may not even occur. it's very, very possible it will be supressed/way out to sea given the setup. these posts are really not needed until <3 days out.

Agree, I don't think we should get caught up in the details at this point considering it may or may not happen . Step #1 is getting the models to agree on a system for that time period. Once we get within 4-5 days, then we can get concerned about track, and within 3 days, potential amounts.

[SnoSki14]

Well if it happens, this would be a huge win for December and of course JB and Henry. But we know how these models work. If it shows a cutter 8 days out, that's what will happen, if it shows a coastal storm 8 days out, we never get our coastal.

[Kaner587]

Well if it happens, this would be a huge win for December and of course JB and Henry. But we know how these models work. If it shows a cutter 8 days out, that's what will happen, if it shows a coastal storm 8 days out, we never get our coastal.

lol finally something I agree with. Although you gotta give it to the EURO who nailed the pattern in its weeklies as well as this current storm a wk out (OP not weeklies)

[A-L-E-X]

i would say your fine, the low goes from the pt of long island to boston, east of the ct river would likely change over. at hr 174 the frz line goes from sw corner of the state to the northeast corner of the state going right over hfd, 850s are souteast of that. 180 the storm is over bos and the frz line is on the eastern border of ct and rhode island. If you do even change over you get a havey front end dump and a good bit on the back end.

We should be fine here on western long island-- remember the Millenium storm passed west of the above track and was still all snow up to Islip.

[A-L-E-X]

HPC sees it...

EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

225 PM EST SUN DEC 12 2010

VALID 12Z WED DEC 15 2010 - 12Z SUN DEC 19 2010

THE BASIC SURFACE ISOBARIC PATTERNS AND METEOROLOGICAL REASONING

WERE LEFT UNCHANGED IN OUR FINAL EDITION.  

THE MODELS ARE SHOWING AN UNUSUALLY ANOMALOUS UPPER HIGH

RETROGRADING FROM GREENLAND TO CENTRAL CANADA DURING THE MEDIUM

RANGE PERIOD. FAIRLY DEEP MEAN TROFS OFF EACH COAST THIS PERIOD

WILL BE BOOKENDS TO A VERY FLAT MEAN RIDGE OVER THE ROCKIES. THE

NEW SET OF 00Z/12 ENSEMBLE SPAGHETTI PLOTS SUPPORTED THE REASONING

OF THE PRELIMS. AN UPPER CYCLONE OVER THE GULF OF ALASKA SLOWLY

PIVOTS TOWARD THE PACIFIC NORTHWEST WHILE ASSOCIATED SHORTWAVE

TROUGHS ON ITS S SIDE MOVE ACROSS CA/THE GRT BASIN/THE ROCKIES.

GUIDANCE SHOWS CONSIDERABLE SPREAD DEVELOPING WITH THESE SHORTWAVE

FEATURES THU AND BEYOND IN THEIR TREK ACROSS THE LOWER 48 STATES.

BELOW NORMAL TEMPS WILL PREVAIL MOST PLACES OVER THE ERN HALF OF

THE CONUS WHILE MILDER AIR OVER THE WRN STATES STRUGGLES TO

PENETRATE THE COLD PATTERN OVER THE EAST. THE MAIN THRUST OF

MILDER AIR MAY BRING PRECIP TO THE SERN CONUS THU OR FRI. THE

PACIFIC NW WILL SEE FREQUENT INTERVALS OF PCPN IN ONSHORE FLOW

WITH HEAVY PCPN EXPECTED AS FAR S AS THE NRN HALF OF CA BY FRI DAY

5. FARTHER E...LAKE EFFECT SN WILL BE THE MAIN WEATHER STORY UNTIL

THU...WHEN AN ILL-DEFINED YET SIGNIFICANT AREA OF PCPN DEVELOPS S

OF THE OH RIVER IN CONNECTION WITH WHATEVER WAVES MIGHT BE

CROSSING THAT REGION.

12Z MODELS: THE MAIN PROBLEM CONTINUES TO BE RESOLVING THE PACIFIC

SHORTWAVES CROSSING THE CONUS UNDERNEATH THE RETROGRADING CANADIAN

BLOCK  THU DAY 4 AND BEYOND. THE 12Z/12 GFS IS FAIRLY CONSISTENT

WITH ITS OWN 00Z/12 CONTINUITY IN MOVING A NRN STREAM UPPER

LOW/SHORTWAVE ACROSS THE NERN QUARTER OF THE NATION DAYS 3-5 AND

DOWNPLAYING THE SRN STREAM. ON THE OTHER HAND...THE NEW

CANADIAN/UKMET SUGGEST OTHERWISE...COMING UP WITH A FORECAST QUITE

AT ODDS WITH THAT OF THE GFS. THE UKMET AND CANADIAN BOTH ROUGHLY

FOLLOW OUR PRELIM ECMWF/ECENS MEAN CONTINUITY THU/FRI...YET STILL

DIFFER SIGNIFICANTLY FROM EACH OTHER THOSE DAYS. THE UKMET GIVE A

BETTER FIT TO OUR CONTINUITY DAY 4 WHILE THE CANADIAN GIVES A

BETTER FIT DAY 5. THE UKMET APPEARS TO TRACK A WAVE TOO FAR NE FRI

DAY 5 GIVEN THE MEAN DEEP TROF OFF THE E COAST. THE NEW 12Z ECMWF

SUPPORTS THE FLATTER CANADIAN SOLUTION. THESE MODEL DIFFERENCES

LEAD INTO THE UNCERTAIN TIME FRAME NEXT WEEKEND OFF THE SE COAST

OF THE CONUS. AM NOT TERRIBLY CONFIDENT OF ANY SOLUTION NOW. THE

NEW 12Z ECMWF HAS ITS MAIN ERN CONUS SHORTWAVE ENERGY SLOWER DAYS

5-6 THAN THE CANADIAN...SLOW ENOUGH TO LEAD INTO THE CHANCY

CYCLOGENESIS OFF THE SE COAST NEXT WEEKEND DESCRIBED BELOW.  

00Z/12 ENSEMBLE 500MB SPAGHETTI PLOTS HIGHLIGHTED AN AREA OF

POSSIBLE CYCLOGENESIS OFF THE SE COAST OF THE CONUS LATER SAT 6

AND BEYOND. IT WAS MOSTLY ECMWF ENSEMBLE MEMBERS THAT WERE

SUPPORTING CYCLOGENESIS OFF THE SE COAST NEXT SAT OR SUN. THE

06Z/12 GFS RUN SEEMED TO BE PICKING UP ON THIS POSSIBILITY FOR

NEXT SAT/SUN....BUT THE NEW GFS RUN HAS GONE BACK FLAT. RECENT

RUNS OF THE ECMWF HAD EARLIER SHOWN A CHANCE FOR CYCLOGENESIS NEXT

WEEKEND OF THE SE COAST BUT THE MOST RECENT RUN HAD BACKED OFF

FROM IT. NOW THE 12Z/12 RUN OF THE ECMWF IS BACK ON

BOARD...DEVELOPING A MAJOR SNOWSTORM NEXT WEEKEND FROM INTERIOR NC

TO NEW ENG. IF CORRECT...IT COULD LAY DOWN A HEAVY BLANKET OF SNOW

IN THE SAME AREAS AS THE BIG SYS LAST YEAR...ALMOST TO THE DATE! A

WHITE CHRISTMAS FOR THAT AREA 6 DAYS LATER WOULD BE HIGHLY FAVORED

IN THE PERSISTENT COLD PATTERN.

FLOOD

Hmmm so possible analogs for the upcoming system would be: December 1966, December 1995 (both la ninas) and December 2009 ?

[Chris L]

Hmmm so possible analogs for the upcoming system would be: December 1966, December 1995 (both la ninas) and December 2009 ?

I don't think it will be like 2009....... that was pure STJ driven...

[atownwxwatcher]

Ensemble means are definitely east

http://raleighwx.americanwx.com/models/ecmwfens/12zecmwfens850mbTSLPNA168.gif

http://raleighwx.americanwx.com/models/ecmwfens/12zecmwfens850mbTSLPNA192.gif

[whiteoutwx1796]

Hmmm so possible analogs for the upcoming system would be: December 1966, December 1995 (both la ninas) and December 2009 ?

Although we got nice accumulating snows it still was a glancing blow for the 5 boros. To the east it was a different story.

[Alpha5]

Ensemble means are definitely east

http://raleighwx.ame...mbTSLPNA168.gif

http://raleighwx.ame...mbTSLPNA192.gif

As to be expected...at least they have the storm there

[A-L-E-X]

Although we got nice accumulating snows it still was a glancing blow for the 5 boros. To the east it was a different story.

Might mean a closer in track with the la nina-- just dont want it to get too close.  I dont know what happened in the Dec 1966 la nina, but I do know we had a KU event.... but in the Dec 1995 la nina storm, 15-20 inches was predicted, but the storm came too close and changed to sleet for a time overnight before changing back to snow the next morning.  It lasted for two days however, with the tremendous block in place and was followed by the most sustained period of arctic cold that winter saw.  NYC and JFK got 7-8 inches of snow (and a plane skidded off a JFK runway and into Jamaica Bay on the second day of the storm), ISP got 12" and LGA got 14"  I've always wondered how NYC got half what LGA got-- back then snowfall was measured more accurately at the airports lol.  Ditto with the temps at NYC. 

[CooL]

As to be expected...at least they have the storm there

Agree...I mean, with no room for this to come any further west, alot of models and ens are going to be pretty far east...Which is actually not a bad thing...But this storm is going to need alot of ingredients to come together at the right time with a perfect track.

[earthlight]

144-156 hr GGEM ensemble mean has a pretty favorable look for those who have access. Not too shabby for this range.

[jrodd321]

As to be expected...at least they have the storm there

Yep. Euro ensembles were WAY east the entire time leading up to the cutter last week remember?

[Chris L]

We got the pattern setup for us.

Now let's see what it can do...

Keep an eye on the vortex... if that wants to dive in.....

[CooL]

Yep. Euro ensembles were WAY east the entire time leading up to the cutter last week remember?

True, good point Jrodd, the euro ens remained stiff on there "coastal low" for this current storm, which obviously did not come into fruition

[winterwx21]

Not sure about all the excitement for next weekend. The Euro is showing pretty much perfect timing with a phase, which seems pretty unlikely to me considering the pattern. No big ridge out west and the flow looks kind of zonal. It's a situation that requires PERFECT timing. We really have to thread the needle and I think the chance is slim. But at least it's something to watch.

[earthlight]

Not sure about all the excitement for next weekend. The Euro is showing pretty much perfect timing with a phase, which seems pretty unlikely to me considering the pattern. No big ridge out west and the flow looks kind of zonal. It's a situation that requires PERFECT timing. We really have to thread the needle and I think the chance is slim. But at least it's something to watch.

Not in agreement at all with this post. This is a very active Pacific flow, and the vortex in Southeast Canada is sitting there waiting to amplify into one of the shortwaves shooting across the CONUS. The blocking to the north of this polar vortex, over Central and Northeast Canada and towards Greenland, is actually retrograding westward over the next 5 to 10 days. If this first storm doesn't occur, the Polar Vortex will amplify into the next shortwave and phase--the Euro has another storm just off the coast at Day 10 with a very similar synoptic setup. This is a ticking time bomb, not a thread the needle.

[Kaner587]

Not sure about all the excitement for next weekend. The Euro is showing pretty much perfect timing with a phase, which seems pretty unlikely to me considering the pattern. No big ridge out west and the flow looks kind of zonal. It's a situation that requires PERFECT timing. We really have to thread the needle and I think the chance is slim. But at least it's something to watch.

ya man i'm not really sure what you're seeing...

[Alpha5]

144-156 hr GGEM ensemble mean has a pretty favorable look for those who have access. Not too shabby for this range.

Yeah looks good, UKMET looks ok at 144, low over the interior southeast, H5 trough looks a bit west

[phlwx]

Not in agreement at all with this post. This is a very active Pacific flow, and the vortex in Southeast Canada is sitting there waiting to amplify into one of the shortwaves shooting across the CONUS. The blocking to the north of this polar vortex, over Central and Northeast Canada and towards Greenland, is actually retrograding westward over the next 5 to 10 days. If this first storm doesn't occur, the Polar Vortex will amplify into the next shortwave and phase--the Euro has another storm just off the coast at Day 10 with a very similar synoptic setup. This is a ticking time bomb, not a thread the needle.

Both of you are right. You need everything to click right (strong 500 mb vort) to get Sunday's storm verbatim. It is a thread the needle in that regard. If it's not this storm, it *could* be the next storm. If you look at the 0z and 12z Euro there's a pretty sharp difference in evolution of the 500 mb vort over the Lakes...the weaker scenario shoves Sunday's threat out to sea and then sets up Day 10. The 12z has a much stronger 500 mb vort...hence a bomb and phase.

We've seen "potential" patterns in the past fizzle...not saying that will be the result in this pattern but it's not a slam dunk by any stretch that it's going to snow on Sunday or in ten days. Cautious optimism FTW?

With that said, it is an active pattern and there is a lot of potential...just not going to say definite on either threat.

[winterwx21]

Both of you are right. You need everything to click right (strong 500 mb vort) to get Sunday's storm verbatim. It is a thread the needle in that regard. If it's not this storm, it *could* be the next storm. If you look at the 0z and 12z Euro there's a pretty sharp difference in evolution of the 500 mb vort over the Lakes...the weaker scenario shoves Sunday's threat out to sea and then sets up Day 10. The 12z has a much stronger 500 mb vort...hence a bomb and phase.

We've seen "potential" patterns in the past fizzle...not saying that will be the result in this pattern but it's not a slam dunk by any stretch that it's going to snow on Sunday or in ten days. Cautious optimism FTW?

Very fair post. There are things for and against it. Again I don't like that there isn't a good ridge out west to amplify things on the east coast. I also fear that the 50-50 low and -NAO could be a little strong for a storm to turn up the coast. Seems like a pattern that doesn't favor a big coastal storm for us, but I REALLY hope I'm wrong.

[Voyager]

its a really tight gradient on the west side, but colder. You are in the .5-.75 on the euro.

Tight gradients killed us in just about every major storm last year. I hope this one will be different. I don't want to sit and watch NYC get buried the same way DC-Philly got buried last year while we sit on the fringe with paltry couple of inches.

[winterwx21]

ya man i'm not really sure what you're seeing...

LOL. Am I wrong about there not being a good ridge out west to amplify things for the east coast? There are some positive things, but also some real concerns. With lack of western ridge and strong negative NAO, there's the threat of it just being a flat wave. Some people that love snow just see what they want to see and ignore the problems. I love snow too, but I try to be realistic. There are major problems with the pattern for next weekend's potential.

[earthlight]

Tight gradients killed us in just about every major storm last year. I hope this one will be different. I don't want to sit and watch NYC get buried the same way DC-Philly got buried last year while we sit on the fringe with paltry couple of inches.

I can almost guarantee a tight gradient with a Polar Vortex phase.

[Isotherm]

There's going to be pro's and con's with every potential event, but I think we can say with certainty that the pro's outweigh the con's with this particular system. Things can go wrong, but it's less likely to happen with the historic blocking we have in place (which teleconnects to strong negative height field somewhere on the east coast). My confidence is high on there being a pretty decent sized storm near the EC next weekend, it's just a matter of the interaction b/t the PV and the short wave energy which will make all the difference wrt exact track.

[Kaner587]

LOL. Am I wrong about there not being a good ridge out west to amplify things for the east coast? There are some positive things, but also some real concerns. With lack of western ridge and strong negative NAO, there's the threat of it just being a flat wave. Some people that love snow just see what they want to see and ignore the problems. I love snow too, but I try to be realistic. There are major problems with the pattern for next weekend's potential.

I am not saying the set-up is perfect but I don't see these upcoming threats as threading the needle

[earthlight]

The ensemble means continue to indicate the potential for a light snow event at the end of this upcoming week...Thursday and Friday.

[earthlight]

Here are some of the SREF members, rather encouraging if you ask me. I will take whatever amount of snowflakes I can get.

[Colin]

gfs continues to be about as boring as it can possibly get...sometimes i have to wonder if it can be that far off in the longer range.