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Wednesday, December 24, 2014

Christmas to New Years +4

1-4 - results.  GFS had lakes cutter consistently first, Euro bopped back and forth.  Euro and GFS blew the temp forecast as it just got to 51 here on a forecast of 58.  NAM got the surface temps right.  Snowed four hours or so, accumulating 1.5 inches before freezing rain set in.  Temps hovered around 33 for the better part of the night, and snow remained on the ground until the stronger southerlies came in this afternoon. Not much rain during the daylight today, though thick fog in the morning, less than .1 mile vis. 

1-3  Make the start time early afternoon. Snow on radar approaching at 12:30 with reports of heavy snow in NJ. Temp at 33 with DP of 23 makes a period of snow and sleet likely. Not a lot of virga reported despite DPs.

1-2  Models still agree on the setup of warm air overrunning cold air.  Details as to how much  of the moisture arrives before or after the warm air are still up in the air.  All models show some snow, but is it a quick change or do we get an inch, or several inches?  One change since the last post is that the moisture seems more spread out, rather than front loaded.  Forecast remains a mostly rain event on Sunday, starting late Saturday afternoon or evening as snow, one or two inches to be safe.  But still need to watch.  Euro and snow map below.

Euro 0z

NAM 6z

12-31 - Models still agree on primary storm track up the St Lawrence, a little difference on when, where and if a secondary forms.  GFS and long range NAM are indicating a CAD (cold air damming) event where we could get thumped with snow.  Both 6z gfs and 12z nam are forecasting snow for the areas north of NYC.  Upton, Taunton and Albany offices of NWS are also onto this and have mentioned possibly heavy snow prior to changeover.  So this isn't dead just yet.  Text from GFS shows at least .27 qpf in Danbury before changeover.  What we don't know is how much of the .75 the following 6hr period is snow v. sleet v. freezing rain v rain.  GFS and Euro are notoriously quick in warming the surface during CAD events, so that 1.0 for 2m temp is likely a -1 or 0 and the 5.6 is possible by 12z, but more likely 1 or 2.  The temps aloft will warm though, and eventually the surface, but potentially not until most of the precip has fallen.edit - 12z gfs in much warmer now, but still keep an eye on.  

GFS 0.5 Degree FORECAST FOR:  LAT =  41.38  LON =  -73.46

                                            06Z DEC31   * - APPROXIMATED
                 2 M     850     SFC     SFC     700    6 HR     500    1000 
                 TMP     TMP     PRS     RHU     RHU     QPF     HGT     500 
                 (C)     (C)    (MB)    (PCT)   (PCT)   (IN)    (DM)     THK 
SUN 06Z 04-JAN   1.0    -2.9    1030      95      95    0.27     569     545    
SUN 12Z 04-JAN   5.6     6.9    1017      99     100    0.75     569     555    

12-30 Euro flips back to a storm heading to the Great Lakes, or at least north west of us, so now all models in agreement 5 days out.   With today not warming up (27 degrees at 1230) I'll be curious as to how the cold air holds.  Some hints (6z gfs) that cold air dammning may be in place for the interior.  Could be icy Sat night.

12-29   Euro shunts storm to south still.  GFS still brings it up to the lakes. JMA hits us with a quick weak storm, moves it just to our south.  CMC flipped from a wave to the south, to a storm to the lakes.  UKMET just coming into range...but looks like its going to our west.  The parallel GFS though is like the JMA in that it goes just to our south. 
12z euro snow
12z CMC snow

12z GFS snow

Parallel GFS

12-28  0z euro has nothing until the 3rd/4th as the storm goes to the lakes.  Cold air blasts in behind it, perhaps changing to snow, but not likely.  Northern stream wave crosses the country, sparks a weak LP off NJ for what looks like a minor snow event on the 6th.  12z run has completely different look once past 132hr.  At the 500mb level, an upper low now cuts off, so without the digging trough, the northern and southern streams keep separate, allowing the norther stream to suppress the surface storm as it brings it over KY, VA and off the coast ENE.  The cold air is marginally in place, with 6" of snow on the snow map for most of PA, N NJ, HV, CT, RI.  4 panel maps below make it easier to compare. The 12z run has several northern stream snow opps afterwards as well. Euro has a bias for holding energy over the SW though, so I am suspicious. 
12z euro
0z Euro

GFS on the other hand is sticking with the storm going to the lakes.  It also is waffling with the strong cold air coming in afterwards.

CMC splits the difference with the Low coming closer to our area or just west. 

12-27 Evening - 12z euro backs of the idea below. Storm remains in the apps and does not reform at the coast, bringing rain to the EC.

Nothing other than a dusting for the end of the year.  Euro does change on the 3-5th time frame. It has the storm from the 3-4th going to the lakes, weak.  But it also forms a storm  over LA, rides up the apps and transfers off the coast 0z the 5th. By that time some high pressure has tried to come in behind the first storm to the lakes, bringing cold enough air in to have it snow a little.  The ensemble control keeps the main storm over the lakes and doesn't form the one over the gulf.  The operational puts out a foot for areas just to our south.
Loading Maps... But no such luck on the GFS although it does sneak some light snow into the mid atlantic on the 30th.  GFS runs the storm to the lakes, keeps it strong, as does the CMC, though the GFS is ont he 3rd, CMC on the 5th.  Still don't buy any pattern change based on the last few days of runs.  There are runs with cold air, but its transient and not matched with precip. Any sustained cold on the runs is gone by the next model run.  Just keeps getting pushed back and back.  Was supposed to turn cold for good in mid Dec, per many mets.  But I don't even see it changing by mid Jan.  See the previous post as to why we need snow in December.

12-26  Euro has storm forming on front, but sliding to our south, with just a little precip on the 29th. Next shot a storm on the fourth heading to the lakes.0z GFS doesn't form storm to south, just a wave and slides it off.  The 4th storm is a bit warm, but does exit the CONUS to our SE so a rain to snow event. 6z GFS has the 4th storm going right over us.  CMC has first wave on the 29th brushing the area, with the 4th hitting NYC dead on. 

12-25 - Still no snow until maybe the 3rd, on GFS.  Nothing on Euro this morning.

12-24  Post Christmas, warm air will stay in the Northeast as a weaker low heads NNE through the Great Lakes.  It looks like a cold front will pass through around the 28th.  That front looks to stall somewhere along the MidAtlantic and a wave (or waves) of lp will ride along it.  The location of the front and the strength of the cold air will determine what, if anything, we get from the 28th to the 1st.  0z GFS shows an inch or two, Euro 2 or three inches.  But the 6z gfs keeps the front to our south.  CMC is showing a better chance as gulf moisture streams up the front and forms better lp.  DGEX as well.  But the boundary is really close.  All models show more seasonably cold, if not below normal, temps following New Years. 

update: afternoon Euro and GFS suppress all the waves to our south.  CMC is further south, but still brings some snow.  Colder than normal air does not  hit us on those runs as a low runs up the Appalachians during the Jan 2-4 time frame, bringing rain. 

Monday, December 22, 2014

We need snow in December

Back in 2011 I did a little research into snowless Decembers.  Using POU as they usually have 6 inches in Dec and rarely didn't, I discovered when it doesn't snow in December, it doesn't usually snow close to normal.
As of right now, there is no snow in the long range models for the rest of the month. Using Poughkepsie stats with average being 35-40 inches, here are some other years without snow in December and how they turned out:
2006 - Jan('07) 1.5"; Feb 17.5"; Mar 3.2"
1994 - Jan ('95) 0"; Feb 4"; Mar 0"

And years with under 1.5 inches of snow in Dec:
2004 - Jan(05) 22"; Feb 11"; Mar 16"
1999 - Jan(00) 6.4"; Feb 2.1"; Mar 0"
1998 - Jan (99) 15.9"; Feb 1.5"; Mar 1.9"
1997 - Jan (98) 0"; Feb 13"; Mar 1.6"

Now I only went back to 1993 since that was the most the AccuProsite let me. But with the exception of 2004, if we didn't get snow in December, we ended way below normal snowfall for the year.

The results for 2011-12 winter were by month in POU
Dec: .4
Jan 3.4
Feb  5.5
Mar 0

So that analog held, though there was a positive NAO from 11-16 to 1-12, which is unusual.  The NAO is more typical this year moving in cycles.

The only year out of the 7 years with under 1.5" of snow which was above normal was 2004.  POU had 1.4" of snow that December.  Currently at POU its 1.4"  of snow and +2 for temp.  Three storms after the Christmas Eve storm, all seem to be rain right now.  I'm a little nervous about the calls for a snowier and colder than normal winter. 

After reposting on AW forums, Noreaster, another poster who was following this line of thought did some more research.  Most recently,  "Since records began in 1880, 35 yrs in Pittsburgh had less than 3" of snow in December. Only 3 of those 35 years ended the season with above normal snowfall.  AND  "25 of 65 years, at the CT coast, December had less than 3.5” of snow. Not including this year.. yet. This year we have 0.7". Of those 25 years, 23 of them ended the season at or below normal. Only 1 well above normal (1993-94)Going further, of the 21 that ended up below normal, They all stayed under 2 feet of snow."

Tuesday, December 16, 2014

Christmas time

12-25 - results: just under .5" rain with high temp of 61 around midnight.  Christmas day is currenlty 50 with NW winds 10-15mph

Afternoon  - 12z run of Euro has more realistic precip of under 2"  Actually, 12z GFS and 12z Euro not far apart anymore.

morning  Biggest question now is how much rain and flooding- below are qpf pics from now until Christmas night.  Most rain is over by 7am Christmas morn.

Loading Maps...
Euro 1.5 - 4" for most of the area

Loading Maps...
GFS 1.5 - 2" for most of the area

Loading Maps...
JMA 1-2"
CMC/GEM 2-4"

ho ho ho ho ho ho ho ho ho ho ho ho ho ho ho ho ho ho ho ho ho ho ho ho ho ho ho ho ho ho ho
12-19 East trend halted, still need to go further for snow.  Models not completely aligned with placement of low (upper and surface) yet.  Some pics of the differences from the 0z run effective Christmas Eve 7pm

Only the DGEX has the upper low going further south and east (and it actually moves to our south eventually, although its still too warm to produce meaningful snow)
Lastly, some snow maps for Christmas night - snow on ground or accumulated. Most of the snow on ground already exists .

Dgex snow

Euro snow

GFS snow

12-18  Still mostly if not all rain, but a shift east takes place, will the trend continue.

0z Euro transfers energy from lakes storm, to spawn storm over the EC.  This is similar to the 18z GFS run from yesterday.  This results in a 984 low right over us 7pm 12/24 and down to 976 over Portsmouth at 1am and 970 over Quebec by 18z 12/25.   No accumulating snow in our area.

0z GFS almost transfers into a new low, similar to Euro, but the GL low maintains control. 980 low over same area of Quebec, which then heads NW and deepens to 964.  Same for the most part on the 6z run

CMC  - more like Euro, storm develops on EC, goes to 984 over NYC and then bombs slowly northeast.  A little more chance of some snow on this run.  Can't tell how deep it gets as there are too many lines.  Actually its 977 off Tropical Tidbits, and it shows rain for the most part. 

DGEX 6z agrees with Euro, keeps the storms separate until it hits our area and gets pulled NW into the upper low.

12-17 Brown Christmas

0z GFS has 984 low over GL spawning secondary 980 lw over the east coast, too far west for us to have snow. It deepens  to 978 to our north and stacks with cold air flowing in.  Maybe some snow at the end. You know how often that works. 6z run is more traditional GL storm which gets to NY, but then is recaptured and heads back over the lakes as a 968 low.

Euro on the other hand sees the northern stream and the upper disturbance but it focuses more on developing a storm over MS and TN where it gets caught by the upper low and bombs to 972 as it heads N into the GL.

1217 0z gfs
12-16  With there remaining two events between now and Christmas, I'm separating the thread.  Christmas forecast is complicated with separate N and S branch systems.  The main character not forecast to enter US until Saturday/Sunday, so expect variation until then.

Todays Euro runs for Christmas - 0z has system entering WA on Saturday, then by Monday there is a 1000 slp over IA,  and another over CO, with a slug of moisture in the Gulf.  By Tuesday night, its 992 over WI, so it doesn't move much.  Meanwhile that slug of Gulf moisture starts moving across FL and over to the ATL. By midday Christmas Eve, there is a mess on the map with the slp over Lake Superior.  A lot of rain heading up the east coast. Snow moving through OH and Western and Central PA and NY State.  Then by Christmas morn the low off the coast forms over Cape Cod and up into Maine. Possibly snow showers for Christmas, otherwise nothing by rain.
12 run way different. It has a 998 slp over N Minn. on Monday, and Tues.  The slug of gulf moisture heads more over the SE, then on Wed a low forms over TN which moves to PA.  Looks like a 980 low over State College 6z thurs. Then it moves almost due east.  Looks like it stacks with an ULL, then moves SE after it passes us.  Amazingly has snow just to our north, but wow does it sock NH

GFS has another take.  0z run has slp stay north of the US, but send a bunch of moisture into our area Christmas eve, and the thicknesses look good.  A storm does form in the Gulf but it slides out to sea.  But... another storm forms once that moisture form the N Branch reaches us. A 996 slp forms over the benchmark.  So it snows a few inches/. 6z run is similar, but the gulf storm comes up coast further, we still get that moisture from the north. 12z run sends low to MN like 12z Euro, then spins it out. Secondary lp forms way off NC, then rotates into New England.
12z gfs
CMC has something in between


Saturday, December 13, 2014

Mid Dec to Christmas

12-21 - dusting so far, light snow on and off from 3:30 on the 20th through now (10am 12/21)

12-19 No real changes, UKMEt has nothing, Euro has an open wave, yesterdays late JMA had a benchmark storm with no cold air. GFS shunts it out to sea.  Nothing more to see here, no further posts unless there is a change.

12-18 - this mornings models show either rain or nothing.  I think the storm on Christmas is overpowering it and pulling in a lot of warmer air.  CMC doesn't even have a storm.  Euro blows the weak  storm off to our south, but continues to warm up.  GFS actually develops the storm, brings it over the benchmark, but the flow aloft ahead of the storm is from the south.  Once the 850 low forms, the incoming Christmas storm doesn't allow it to pull in colder air.  So it results in rain.

12-17  0z Euro run develops a new coastal after the impulse brings light snow/rain in the area.  This coastal moves from 1016 off OBX, to 1012 in the pocket and 1008 over Cape Cod.  All rain for tristate.
Euro 1012 in pocket

0z GFS slides the first system out to sea off SC with nothing for us.  But now it also is forming another storm.  1012 off obx, but it moves east, but has an inverted trough/warm front hitting us Tuesday.  6z has more moisture for the original light snow event, also has a weaker low off NC heading NE which looks to throw back some moisture, but again, while at first it looks like an inverted trough, I'm thinking the moisture is actually from the warm front ahead of the Christmas storm.

12-16  GFS and Euro in agreement on nuisance snow Sunday, DGEX further east with rain. NWS at 40% chance.  Thinking light snow, but still keeping an eye on it. Euro went negative tilt with the trough causing moisture to fall back in

Euro still has1-3/2-4 inch event for the 21st.  0z run was a trace-1" but the 12z came back with more.  Thickness and temp profiles look like all snow for most of the area, except perhaps coastal areas and SNJ.  Storm is weak and slides off the coast, SE of the BM, but leaves some moisture
Loading Maps...
12z Euro qpf 21st

GFS agrees, QPF similar to Euro, snow map as well
Loading Maps...
GFS Snow

JMA has an interesting map  -it throws back a lot of moisture
Loading Maps...

6z dgex looks much further east
Loading Maps...

12-15 afternoon - ideas of snow fade away
12z GFS 12-21
GFS showing snow showers T-1" of snow on the 21st.
JMA shows a nice hit, .5 or so precip, has 1014 low over PA and OBX  at 144hr and bombs out to a 988 low at 42N65W at 168hr.  900mb, 850mb and 700mb temps below freezing all of the area for hrs 144 and 168 (what happens in between, can't tell).
12z Euro is a miss for the TriState area and north.  Brushes Cape Cod and SNJ, but not measurable.
UKMET positions the low over the Delmarva, should be close enough for precip, mostly snow.
Canadian is out to sea
 Euro ensemble agrees with the UKMET with placement over delmarva

For Christmas...
Euro has a 998 low going right to our west, influenced by a low over the GL. Rain late on the 24th.  Ensemble agrees with GL low idea
Canadian has a GL low, but forms another one far off the coast.
GFS takes a low out to sea to the SE of us - Jacksonville to 100miles east of OBX, but then the GL low blasts through,  see below. Snow map has nothing though.

12-15 morning
0z Euro has storm on 21st moving up to the Delmvarva from SC, but then ENE out to sea, bringing snow to SNJ, and perhaps a little snow further north. Christmas storm now on Euro comes from the Lakes and probably isn't more than a dusting-2".  Last frame is Christmas eve.
0z and 6z GFS have the storm on the 21st very weak, with two sections moving NE, one hits us, one misses.  Total precip.25 to .5 so a 2-4 inch event.  Both runs have the Christmas storm moving to our west now.  0z gfs has a 980 low over Michigan moving north.

Loading Maps...
GFS precip for 12-21
0z euro det not much on the 17th, mostly light rain.  still a hit, though a little off the coast for the 21st
12z euro closer in and brings to 988mb.  850's are a little warm for LI, southern half CT and Southern NJ for a frame, but 700mb, 925mb and surface temps support frozen.  The track is dubious -VA/NC border 0z sunday, to Cape May, to just off ACY, to inside ACK (nantucket) - each spot 6 hrs later.  .75-1 qpf.  12+ from KY, WVA, Central PA to Catskills.  9-12 NNJ, EPA, WCT, HV, 6 elsewhere in New England.
 Euro EPS has the 21st storm a little to our west, with a mix, and a northern branch shortwave hitting us on Christmas for a nice couple of inches.


0z  17th some scattered rain showers, 21st a minor snow event/borderline rain, but it crushes the NE on Christmas - goes from 988 100 miles east of Cape May to 972 low over Boston with 1.2 of qpf.  925mb layer is above freezing for part of it resulting in sleet/fr rain mixing in. But surface temps, 850 and 700 all below freezing.
Merry Christmas

 The 12z run has rain on the 17th, a small snow, snow to rain event on the 21st as it has a northern and southern system to our north and south.  Then for Christmas, the low from the 0z run is 500 miles or so west, over the Great Lakes, but somehow reforms over Boston and hits us with a little snow on the backside.

12z gfs snow on Christmas

0z - light rain on 17th, nothing on the 21st, shortwave in Northern branch for snow on Christmas
12z doesn't really develop it and sends a weak storm out to sea off SC

 update  12z euro hits NJ/NY/CT/PA on the 21st

18z GFS hits on Christmas

12-13  Multiple opportunities through Christmas

The 17th has some precip coming through, looks like rain, but some runs have a storm forming as the front passes.  Worst case snow scenario would be 2" or less and thats a long shot.  Euro and GFS have this feature - NWS has mix forecast, but again its light.

Next opportunity is the 21st.   Euro EPS has been on this, the operational slid it out to sea yesterday but is moving it NE now.  GFS 6z has a nice run for snow
6z GFS - storm on 21st

Christmas Eve/Day - Models loading a system in the Gulf which looks like it will run up NE around Christmas Eve. Euro EPS has a upper low dropping into the middle of the country, which implies the storm will go to our west, but there could be a redevelopment off the coast.   GFS says it wants to deluge us.
6z gfs storm Christmas eve

Wednesday, December 3, 2014

Dec 8-11

12-13  Results:  Heavy rain 2+ inches tuesday, drizzle tues night, light snow, snizzle and snow showers on and off from Wednesnday noon through last night (fri nite).  Euro and UKMET were closest, though not exact.  SLP tracked up to Cape Cod, not over NYC/CT per Euro/UKMET. But at least they had it close to the coast and caught by the upper low.  GFS caught on, but later, though its runs within 48 hrs had the slp positioned better.  


Going to award this one to the Ukmet.  Euro had it figured out too, but kept trying to get fancy with it, doing loops, multiple lows, etc.  Ukmet had it right along the coast, caught around NYC and then out.  GFS clueless again until 2 days before.  CMC had the 500mb low too far south and rotated the slp into NC when Euro/Ukie had it positioned correctly, so far.  JMA took benchmark on 12-5. 

Today was interesting in that the daytime high was 28, with winds NE to ENE all day, flurries in New Haven and Newtown and light snow over LI and SNJ.  As I write this tonite at 9:30, temp still 28 with DP of 20 and winds ENE (here and airport).   I wouldn't be surprised by freezing rain over night.  Precip is approaching Cape May now. HRRR is about 3 hours behind on the radar and it has radar returns here at 4am, but based on current timing, 1am seems right.  It also has temps rising above freezing here around 10z, which based on the wind direction does not make sense. There is still a strong high, winds from the N so not sure why the surface temps rise during the night.  850's yes, but there should be strong damming at the surface.  This could lead to freezing rain.  HRRR times the arrival of precip at the same time of the temp >32.  850s forecast >0c at 12z.  925s at 3z.  That makes more sense based on the ESE wind at that level.

 So what should happen is that the Poconos, Catskills, Berks, Greens and Whites get dumped.  What's been lost is the low hanging around.  We'll have to wait and see if that happens.  If it does, we may see some back end snow showers by Wed morn. Parts of Litchfield, Sussex, Dutchess, Orange may see 1-3/2-4, but stress may. 

Sadly, I'll be traveling on 12-9 so won't get to enjoy tracking this one during the event. 

12 -07 - summary. Euro's gone loopy, see below.

UKMET has the slp off NC, Off NJ to Boston, back to over DXR and then out to the NE.  Too close to shore for snow for us, but nice further west. Cavaet that with I don't know the upper air parameters for the UKMET, just slp and 500mb heights.
CMC looks to drive the slp due north up the coast, never having it caught by the 500mb low. Its low passes just east of NYC and just east of DXR.  It brings another low into main from the Atlantic on thurs. It is also too close for any serious snow for areas from west of the immediate path eastward.

0z gfs snow map hr 108
6z GFS is similar to Euro up to Wed, except further east.  It reforms the lp further east of NC, brings it up to 40N at 71W on 0z Wed.  The ULL is over VA at that time. 12z Wed the slp is over SE Mass, the ULL has caught it and by 18z the slp is over RI, at 996mb and stacked with ULL.  From there it moves NNE occluding over Maine on Thurs Night/Friday.  0z is similar, but further west with the ULL closer to DXR and the SLP centered over Eastern CT. 0z surface temps 1-2 above 0c through the event.  850's mostly above.  6z run has warmer surface temps, cooler 850's but still looks mostly rain with a few inches of snow wed night.  Just to our N&W, its a different with 12-18 inches. 

Euro snow 0z 12-7 run at 108 hrs

12-7  0Z Euro puts out one of the strangest winter runs I've seen in the nearly 10 years of watching winter storms.  I tried to video this - watch as the front comes through today, a piece is left behind and as the next UL system comes in forms a 014 LP off SC/NC, sends that LP up to  a 1002 lp off DE by 18z Tue.  All is normal so far.  The white lines indicate the upper level heights.  You can see the upper level low coming in at 18z Tues, slp (surface low) is off ACY at 0z on Wed.  At 6z the surface low is 998 mb and still off ACY. The upper low is approaching the Baltimore area.  Its hr 84, where a second 1004 slp forms out at sea in response to the ULL, that is crazy.  The original slp starts moving WSW toward the ULL over Baltimore. By 0z on Thursday the original slp is stacked with the ULL,  the second slp is heading around the ULL and deepens to 996.  Its actually going to cross the Benchmark (40/70) from the SE.  The ULL drifts north and almost captures the now 992-994 slp hitting LI and ACK.  Instead of continuing on its NW course, it then heads SW as its captured by the ULL which is now stacked with the second SLP just south of Long Island.  A move west over NYC in the next frame 18z thurs, when the storm occludes.  By 18z Friday,  the slp and ull are still over NJ. By Sat the slp is gone, but the ULL remains over VA and ANOTHER 1010mb slp forms east over the Atlantic.  That moves west toward the ULL,  so that by Sunday there is a 1004 slp off the coast of SC, with the ULL over SC.  They stack on 0z Monday as the slp drops to 1000.   This time there is no occlusion as the ULL/slp moves slowly NE  passing 40N at 64W, still stacked and at 998mb.  And thats the last frame.  10 days of one ULL and the three slps it spawns.

Well, the video didn't turn out that well, but you can see the white lines of the Upper level low and how it behaves - all other models have it moving NE once it stacks over us. 

12-6  Not much change from yesterday, still looking at a lot of rain in our area. There is a cooling trend, but the storm needs to hang up south of Montauk to bring snow to the tristate.  Right now, longitude is crucial as the 850 line looks n-s. Areas west, wet snow.  East, rain. 

Euro keeps the low off NJ in the 12z run.  850's cool from a max of 6.9 to 4.  Whats different from yesterday is its a little east, but there's a second system forming in the ocean that rounds the UL and hits Maine on Thurs.  About 2" qpf as rain, then snow showers thurs and fri.  Ensemble mean though still has storm east of our longitude, and cold enough for snow.  But the ens trend is west.  And the ensemble control is where the operational is.  I'd look for Euro to move a little more east in the operational, and a little more west on the mean ens but don't think it will be enough to blast us with snow.  West of the hudson, different story.
Warm and West Euro operational

Colder and more east ensemble mean
UKMET has shifted slightly east in its 12z run over the 0z run.  Just from the Del river to NJ coast.  Still mostly rain

JMA still has a classic noreaster track.  Its 850's and 925 temps are favorable for snow west of Waterbury
Loading Maps...

NAM is also on board, granted through 84 hrs. It allows for the temps to crash once the UL and surface are stacked.  Giving far N&W suburbs a chance of white. 
Loading Maps...

CMC  - 0z run looked like Euro/UKIE and yesterday.  12z run loses the phase of the UL low and surface low.  Instead it still forms a strong low and brings it past Montauk at 996 mb.  If the UL were there, it would be snow, but it keeps on going and rain is ended by Tuesday evening. CMC is also pretty warm, so its all rain.  It doesn't stack until its over Nova Scotia

CMC Tues morn

That leaves the GFS.  Its kinda out on its own, none of the four model runs look the same.  Some stack the low over us, some not until NH, one doesn't even close off the low.  They are all east of the Euro, but bring only a mix of rain/snow. The 18z run closes the UL right over us, but the surface low to the east, with the 540 thickness showing snow, but the 850 showing rain. Then there is the snow map!

GFS 4panel 12z Wed

GFS 18z snow map

                                  sfc c      850 c                                                                      qpf          snow
TUE 06Z 09-DEC   0.7    -3.5     130    6979    05010     SN    0.01    0.00    
TUE 12Z 09-DEC   1.7     0.4     131    5118    04010     ZR    0.03    0.03    
TUE 18Z 09-DEC   3.2     1.2     131    5543    02013     RA    0.18    0.03    
WED 00Z 10-DEC   2.5     2.0     131    5448    35015     RA    0.34    0.03    
WED 06Z 10-DEC   2.4    -0.9     131    3522    32018     RA    0.42    0.23    
WED 12Z 10-DEC   2.0    -2.1     130    2109    31015     RA    0.61    0.73    
WED 18Z 10-DEC   1.4    -2.3     130    1359    32013     SN    0.41    1.05    
THU 00Z 11-DEC   0.4    -1.6     130     615    31014     SN    0.04    1.05    
THU 06Z 11-DEC  -0.4    -0.9     130     438    31012     SN    0.06    1.08 

Euro/UKMET east, UL and surface stack over NYC.
GFS - east. runs all over with UL/surface relationship.  18z run gives us a foot
JMA - east. looks classic, cold for snow
CMC - middle looks classic, too warm.
Hate to say this, but its going to be a mixed bag.  Keep monitoring trends


Euro quasi trop systems

 12-5  Prolonged storm event, despite pos nao. 

Euro becomes more believable.  Instead of taking the LP from OK to PA then driving it SE and having it loop back NW, the LP shears out and is mostly absorbed by this semi tropical system in the atlantic near 60/30.  Front pushes down behind that, along with a strong upper level low.  NEW low forms off NC coast and travels north in a more traditional manner. The lows become stacked, and believe it or not, drag that first low back into the new system (which is still an odd solution).  Actually, the frame below is after the low hits LI and goes SW into the UL. 

Stacked lows at 500 and surface

 All of this results in 2+ inches of rain for most of CT.  It gets more interesting west of the Hudson and in VT/NH. But the 850's are really close for West CT.  West of the Hudson is a mix, north of Mass there are some spots of 24+" .

 However, the ensembles have the low located closer to the BM rather than over NJ, which would cream most of the area. 500mb and 850 temps
Euro ens dream storm

UKMET looks similar to Euro, perhaps a little east, 50 miles or so. Its 12z run is similar.
UKMET hr 120 (it stacks shortly after)
CMC hangs onto the Euro original idea of rotating whats left of the original LP back west into NC then strengthening in response to the 500mb energy and moving it up through Delaware Bay, then NNE over DXR. Rain.

JMA looks like its the more traditional LP off NC to BM.  It cuts off the UL, but just off the NJ coast.  850's are really close

 DGEX from hr 84 brings the low straight up the coast with rain mostly east of the hudson and south of NY/NJ border.  Nothing but rain in East PA/NJ or New England.

NAVGEM cuts the UL off to our north.  Then has another UL form over FL/GA.  It blows the front through, then eddies some of the energy off the coast and brings it back up into the cut off to our north.  At  hr108 its moisture is east of the Hudson, the 850 line is at the CT/NY border, so perhaps Putnam/Dutchess see some snow for an hour or two.

GFS still doesnt buy it, mainly that the UL is going so far south.  The 12z idea was a surface LP coming through the lakes with the UL cutting off over Lake Erie or so on Tuesday.  As that UL deepens, it brings up surface energy from the Atlantic over us.  It never really deepens past 1000mb and it meanders in S Canada for several days.  There's not much precip in it for us, and its a little too warm.

18z GFS run seems to be slightly more like the Euro, but the UL cuts off too late and is not far enough south to give us snow.    And by the time the LP at off the coast deepens its near Maine. Good run for VT though.
Problem is that the GFS ens look very similar to the Euro ens - which is a very strong signal. That's spread to the north/north east.

0z Nam for 12-6 shows the Euro/CMC/Ukmet idea so far.  Its trough is strongly negative, but there is a lot going on at the 500mb level so I can't predict where it cuts off. 
 Summary:  JMA, Euro ens and GFS ens are aligned for a great snowstorm.  GFS operational is alone in its placement of ULL.  UKMET/Euro/CMC are bringing storm right along the coast or just inland for mostly if not all rain for most of the area. 

12-4  Euro changes a little.  12z run takes a low over OK on 12-5 through OH Valley on 12-6, then ESE over the OBX on Sunday.  Sometimes you see storms coming up the Apps and reforming off OBX to the ESE, but this doesn't seem to be the case.  This one looks like its shunted SE by a cold front clearing our area Sunday morning.  By Monday its still weak and spinning offshore NC at 34/72.   Interestingly the 0 line at 850 stops advancing south and decouples from the LP.   Then late Monday, the storm picks up some UL energy coming around the trough, the trough goes negative and the meandering low is comes back north.  As it comes north, it goes from a 1012 low  off NC at 0z Tues to 1000mb south of central LI by 12z Tues (see instant wx map below).  Then to a 992 low by 18z Tuesday sucking in the 850 line.  Then 988 over the Cape.  For areas north of the LI sound:  Mod snow starting late monday night, tues morn.  The next 6 hrs is a toss up - 850 line squiggles everywhere.  But by 18z tuesday western CT, western Mass, eastern NY, including the city and NE NJ are getting plastered with snow.   Temps are so marginal, only at the 850 level, that its again difficult to see where its snow vs sleet v freezing rain.  This mornings run, and yesterday had colder surface temps, leading to my concern about freezing rain (zr), but they are just above 0c this afternoon (I don't trust Euro surface temps during precip events). Euro snow map is fun too...don't trust it yet.   Euro ens control is east of the operational, still brings some snow (3-6), and is colder.
ECMWF Mean Sea Level Pressure Map Unavailable
euro snow dream

Canadian is similar to the Euro, except it brings the low as far south as SC latitude, then back  NNW over the OBX to the Chesapeake, right up NJ and spins it over NYC before bumping it back SE, then E then NE. It looks like all rain.

12z GFS says the storm over OK friday just moves on through the OH Valley until PA, when it broadens and looks more like a frontal passage for us.  The associated moisture gets as far as 64W before it turns around and heads N, then NE crossing 70W at 36N.   We get nothing.

UKIE bombs us - such a decieving hr 120 and then bam! We are under a 524 upper low stacked over a surface low.  I have not idea how cold it is, nor can I even see the pressure as the lines are too closely packed (means lots of wind).

DGEX has a more traditional storm forming over OBX and moving east of the BM.  Not a bad looking solution, though its showing us being too warm to snow.


GFS 120

Euro has interesting feature - Saturday morning  a warm front pushes over us, with a cold front following on Sunday morning.  Then on Sunday morning, a SW in Missouri on Saturday, forms a lp off NC/VA. That LP just lingers, spinning out moisture and doing all sorts of funky things with the 850 line (see below).  925 and 700 mb layers are cold enough for snow, but the 850 is very random.  It then moves north to south of LI, then NE over the CC canal.   But thats not all...  the stronger shortwave which  causes this odd behavior is over MN on Monday, MO on Tues and GA/SC on Wed when it spawns a second low which grazes us but smacks SE Mass.  CMC shows the first low, but dismisses it, focusing on the second low which it drives NW into Del. Bay. UKMET puts a 1040 high over Maine and has the cutoff low at hr 144 centered over TN
12z GFS has a low forming out to sea at hr 144 and doesnt have the strong UL as the CMC/UJIE and EUro have.  DGEX has the first storm like the Euro, but no second one and no strong UL. 

 These are the temps at various levels through the period at DXR.  Pretty cold surface temps but then there is that warm up at 850 on Monday evening. 
                             12Z DEC03
PRESSURE LEVELS  SFC  1000   925   850   700   600   500   400   300   200      
MON 12Z 08-DEC   -3    -4    -5     0    -4   -10   -19   -31   -48   -58       
MON 18Z 08-DEC   -3    -4    -5     0    -3    -9   -19   -31   -46   -58       
TUE 00Z 09-DEC    1     1    -1     4    -3    -9   -19   -32   -46   -57       
TUE 06Z 09-DEC   -1    -1    -2     4    -4   -11   -20   -33   -44   -54       
TUE 12Z 09-DEC   -1    -1    -3    -2    -5   -11   -22   -35   -45   -53       
TUE 18Z 09-DEC    1     1    -5    -4    -7   -15   -27   -36   -45   -51       
WED 00Z 10-DEC   -2     1    -4    -5    -8   -16   -26   -38   -47   -52       
WED 06Z 10-DEC   -5    -3    -6    -5    -8   -14   -25   -38   -49   -52       
WED 12Z 10-DEC   -6    -5    -5    -5    -8   -14   -25   -36   -51   -52       
WED 18Z 10-DEC   -1    -1    -7    -6    -8   -14   -25   -38   -53   -50       
THU 00Z 11-DEC   -2    -2    -7    -9    -9   -15   -25   -37   -53   -49       
THU 06Z 11-DEC   -6    -4    -8    -8   -10   -14   -24   -37   -52   -50       
THU 12Z 11-DEC   -6    -4    -8    -7    -8   -15   -24   -37   -52   -51       
THU 18Z 11-DEC    0     0    -6    -3    -6   -14   -25   -38   -49   -53 
Numbers with precip
                 sfc     850                            qpf
SUN 12Z 07-DEC   2.1     1.9    1027      72      72    0.18     565     544    
SUN 18Z 07-DEC   2.1     0.6    1029      41      39    0.03     565     542    
MON 00Z 08-DEC   0.1    -0.7    1030      48      57    0.01     565     541    
MON 06Z 08-DEC  -1.8     0.1    1027      59     100    0.05     563     541    
MON 12Z 08-DEC  -2.9     0.0    1023      82      97    0.25     560     542    
MON 18Z 08-DEC  -3.3    -0.3    1015      85      97    0.46     555     543    
TUE 00Z 09-DEC   0.6     3.7    1008      86      62    0.10     553     546    
TUE 06Z 09-DEC  -1.1     3.5    1005      88      73    0.06     547     543    
TUE 12Z 09-DEC  -1.5    -1.9    1006      86      69    0.03     545     540    
Lastly, GFS from 12z
SUN 12Z 07-DEC  -2.3     0.0    1032      74       6    0.00     564     539    
SUN 18Z 07-DEC   1.6    -1.2    1035      51      14    0.00     566     538    
MON 00Z 08-DEC  -1.7    -1.8    1038      68      26    0.00     568     539    
MON 06Z 08-DEC  -2.1    -1.8    1038      61      29    0.00     569     539    
MON 12Z 08-DEC  -2.2    -0.4    1038      73      20    0.00     568     538    
MON 18Z 08-DEC   2.8    -0.9    1033      77      12    0.00     564     538    
TUE 00Z 09-DEC   3.1    -3.4    1029      93      11    0.02     561     538    
TUE 06Z 09-DEC   4.2     0.6    1020      96      67    0.01     555     539    
TUE 12Z 09-DEC   4.4     1.1    1013      99      98    0.19     550     539    
TUE 18Z 09-DEC   6.1    -3.3    1010      76      28    0.02     542     535