December 14/15 winter storm threat

[eduggs]

I'm not sure what was so bad about last night...unless you want a stronger low running up into SE MA with a risk of a changeover. Or if you are up in NNE and you miss the best QPF.

 

Granted, a changeover isn't necessarily bad if its a few hours of sleet after a big hit of 8-10" of snow, but you risk changing over to rain on closer setups too. I would think last night's solutions are exactly where the CP folks would want it. This isn't going to keep trending SE...there's a fat SE ridge that is only going to allow so much concession.

The upper level support with the "southern stream" and its associated PVA and jet dynamics have weakened since yesterday in the guidance.  That increases the risk of largely light precip and a possible miss from any developing coastal low center.

[powderfreak]

CMC seems reasonable to me.  And in my opinion it has been the most consistent of the group.  

 

http://collaboration.cmc.ec.gc.ca/cmc/cmdn/pcpn_type/pcpn_type_gem_reg.html

 

I'd take that all day long.  Feeling pretty decent for a widespread advisory level 3-6" or 4-8" potential in NNE.  We'll take this time of year.

[CoastalWx]

Looks like over ACK. What's with the ensembles being so far NW compared to operational guidance?

 

I think it's keying on the srn stream developing the low last minute. It didn't look impressive on the mean...but there might be a few members amped up that are messing with it too. Or, they could be correct.

[ctsnowstorm628]

I think it's keying on the srn stream developing the low last minute. It didn't look impressive on the mean...but there might be a few members amped up that are messing with it too. Or, they could be correct.

Gotcha. In my several years of model watching, I'd always associated ensembles NW of the OP as a red flag, especially when its both the GEFS and Euro Ens.

 

I was amazed when I compared the 12z Euro yesterday and 00z today it was so much slower at 500mb. Literally every feature was weaker and 50 miles west.

[mahk_webstah]

There is nothing better than a 36-48 hour continuous snowfall..just non-stop accumulating snow

dec 08

[powderfreak]

Looks like over ACK. What's with the ensembles being so far NW compared to operational guidance?

 

I'm interested in how both the CMC and GFS have what is generally looking like a little lighter QPF back across our area of NNE (but still a solid Advisory type QPF), however, they both seem to have this almost second band or burst way NW of the low.

 

I mean we've seen it happen before, but you have the main precip shield and then another band far NW... GFS has it pretty close to the -10C H85 isotherm, and this is the CMC with it:

 

Heavier snow immediately NW of the rain/snow line, but then there's an almost banded like feature NW as the northern stream H5 vorticity pours into NNE.  Could be some high ratio stuff that might make up for some lighter QPF.

 

[moneypitmike]

LoL I think our town used a 1/4 of ours back during that non-event in November - treating the 38f roads during the rain.

 

Classic!

 

Ensembles are still maybe just SE of ACK, but look more intense then the op.

 

Scott--is there much spread or clustering that's driving the further west look of the ensembles?

[ORH_wxman]

The upper level support with the "southern stream" and its associated PVA and jet dynamics have weakened since yesterday in the guidance.  That increases the risk of largely light precip and a possible miss from any developing coastal low center.

 

 

Yes...it also decreases the risk of a warmer storm with lots of rain for southern New England. So there's obviously a happy medium in there. Many of the colder overrunning events have had dampening shortwaves moving northeast in a fast flow enviroment.

[Clinch Leatherwood]

Classic!

 

 

Scott--is there much spread or clustering that's driving the further west look of the ensembles?

 

Wrong Scott I know but:

 

Ensembles may be keying on something based on the broader grid that may not be there.  Be interesting to see if there's a ton of spread.  IE, fast flow favors SE.

[ctsnowstorm628]

I'm interested in how both the CMC and GFS have what is generally looking like a little lighter QPF back across our area of NNE (but still a solid Advisory type QPF), however, they both seem to have this almost second band or burst way NW of the low.

 

I mean we've seen it happen before, but you have the main precip shield and then another band far NW... GFS has it pretty close to the -10C H85 isotherm, and this is the CMC with it:

 

Heavier snow immediately NW of the rain/snow line, but then there's an almost banded like feature NW as the northern stream H5 vorticity pours into NNE.  Could be some high ratio stuff that might make up for some lighter QPF.

 

I_nw_g1_EST_2013121112_093.png

It'll be interesting. -12- -16C in the DGZ is 20:1 stuff in NNE. Lift is marginal but the temp profile aloft is prime for fluff.

[Typhoon Tip]

Subtle variances in the handling of jet interactions is playing havoc with the deteministic coherence to put it nicely ... Basically, the GFS ...as of 06z, decides to back off the "digginess" of the N-stream, as the TV S-stream S/W skirts by underneath.  The somewhat better N-stream digging of previous runs caused the whole scale flow to "tilt" more meridian-like along the EC, and that foisted the S-stream S/W more normal to the thermal fields/BL cold ...inducing better/stronger cyclogenesis.   

 

The 00z Euro appears to have a slightly more sheared out system for different reason altogether, regarding an overall weaker appeal with the Pacific intermediate stream wind max.   (I think that is also what confused some folks into thinking triple phase earlier in this thread?)  Anyway, that piece of wind dynamics phased in with the S-stream S/W more proficiently in the previous runs, and therefore when the total of it all turned the corner you had more energy aloft coming to the party (so to speak...)

 

Actually, now that I checked again, the 06z and 12z oper. GFS also has slightly less intermediate stream relay off the Pac (if the N-stream concerns were not enough...).

 

Ugh.  Oy vay.  What a big flappin' cluster this whole thing is turning into.   

[dendrite]

Keep in mind this is the GFS...but yet look how sick that thermal ribbon is. Reality probably would bring that front to near BOS.

avn_sfc_st_99.gif

Yeah...I may have snow falling in the single digits briefly here.

[Typhoon Tip]

Btw,  ...if for muse only... take a look at the NAM... It shows that 24-hour period of snow grains/flurries, if not light snow, breaking out along the arctic drape during the run-up hours, really nicely.

[radarman]

Btw,  ...if for muse only... take a look at the NAM... It shows that 24-hour period of snow grains/flurries, if not light snow, breaking out along the arctic drape during the run-up hours, really nicely.

 

Agreed.  Some weak convergence and lift starting Friday overnight really.   In the valley I'd guess we'd be fighting dry air with that kind of drain but at the very least would provide that snow sky to enhance the anticipation.

[Mr. Windcredible!]

Btw,  ...if for muse only... take a look at the NAM... It shows that 24-hour period of snow grains/flurries, if not light snow, breaking out along the arctic drape during the run-up hours, really nicely.

 

That's what I'm most interested in at this point. Assuming this comes together, I have a hard time seeing how the coastal plain avoids rain for the bulk of the main event...so best to hope for some decent WAA snows ahead of it. Unfortunately, I feel the models usually hit that up hard at this range then often back off as the event gets closer. 

[Randy4Confluence]

Yeah even the light stuff at the onset will stick on impact after the Thurs/Fri cold snap unlike the snowfall yesterday that didnt stick to the roads even up here because of marginal ttemps.

[OceanStWx]

2/2/11 had some awful meteorology being put out. 20-24" in srn NH with H7 goin through NY.

 

I moved to GYX shortly after that one...

 

I'm a sucker for the cold sounding overrunning snows with a deep saturated snow growth layer. As I mentioned before (and I know you've said it too)...those can be really efficient snow producers.

 

 

There's obviously still risk that we get screwed on this system and everything goes into the meat grinder initially and then the follow up wave stinks too...but overall I'm pretty encouraged. You'd rather have a system to your southeast at this time range during this type of pattern than the other way around.

 

For a brief time the GFS has BOS with a several hundred mb deep DGZ. The 12z GFS Cobb output gives ORH a solid 21 hours with ratios greater than 17:1.

[Typhoon Tip]

That's what I'm most interested in at this point. Assuming this comes together, I have a hard time seeing how the coastal plain avoids rain for the bulk of the main event...so best to hope for some decent WAA snows ahead of it. Unfortunately, I feel the models usually hit that up hard at this range then often back off as the event gets closer. 

 

It depends what part of the CP we are opining about...  Cape and the Islands...sure.   I think even BOS is okay in this, though.  

 

Not that my opinion means much, but this reminds me of Dec 5, 2003.   It is no analog, I repeat, no analog... But why it reminds me of that is the "freshness" of the polar-arctic air associated with the high, which remains parked ideally during the duration of ...what ever this turns out to be.  I remember having this debate with a poplar Boston on-camera Met in the days just before that big event, and wound up right... The coastal boundary hit a brick wall just NW of the Sagamore bridge, and never even made it to Logan.  

I was living in Winchester at the time, which is on the west side of Rt 93, about 10 clicks N of the city as the crow flies, and we never made 20!   We had NNE wind carrying occasional whiteouts champaign, while Logan parachuted at 33F, and Brockton had glop for a an hour at 35...  Both there and former collapsed well below freezing from mid event on.  

[Damage In Tolland]

It depends what part of the CP we are opining about... Cape and the Islands...sure. I think even BOS is okay in this, though.

Not that my opinion means much, but this reminds me of Dec 5, 2003. It is no analog, I repeat, no analog... But why it reminds me of that is the "freshness" of the polar-arctic air associated with the high, which remains parked ideally during the duration of ...what ever this turns out to be. I remember having this debate with a poplar Boston on-camera Met in the days just before that big event, and wound up right... The coastal boundary hit a brick wall just NW of the Sagamore bridge, and never even made it to Logan.

I was living in Winchester at the time, which is on the west side of Rt 93, about 10 clicks N of the city as the crow flies, and we never made 20! We had NNE wind carrying occasional whiteouts champaign, while Logan parachuted at 33F, and Brockton had glop for a an hour at 35... Both there and former collapsed well below freezing from mid event on.

Harv?

[weathafella]

Euro starts snowing Saturday morning now.

[Typhoon Tip]

Harv?

 

No name dropping please

[weathafella]

Bitter cold with snow Saturday on euro

[powderfreak]

Can we get some descriptions of the ECM as it comes out for all of New England today, lol? 

[weathafella]

Damn...euro looks excellent for mby!

[eduggs]

Yes...it also decreases the risk of a warmer storm with lots of rain for southern New England. So there's obviously a happy medium in there. Many of the colder overrunning events have had dampening shortwaves moving northeast in a fast flow enviroment.

Totally agree.  I just think lots of people look for big, intense storms in the guidance... rapid deepening, cutoff 500mb lows, mature deformation.  This has trended away from that (although I think it could still come back).

 

But I'm with you, I enjoy long duration snows, especially with a cold column.  But ideally the snow is heavy enough to accumulate at least a little bit.  The initial 12 hours of overrunning on the GFS and Canadian could turn out to be scattered flurries.

[Damage In Tolland]

Temps near 15 and snow Saturday. Wow

[SnowMan]

Damn...euro looks excellent for mby!

No one but you cares about your backyard according to Dendrite lol

[weathafella]

Powder... Always starts in sne earlier in the modeling. You're snowing nicely Saturday night as is mpm.

[jamesnichols1989]

I can see how the northern stream vortex gets involved more in the storm and this becomes colder and less WAA.  But I also see how this is a rain event for the Cape and Islands.  Which would stink, but its only December 11th.

[ORH_wxman]

Euro is essentially a long duration high end advisory to low end warning snow for most of SNE and CNE.