December 6-7: Rainy Frontal Passage or a Wintry Wave?

[Damage In Tolland]

Why can't you just not post crap?

Huh? I requoted his post. What do you mean?

[CT Rain]

For Scooter and Ryan

 

Thanks - I'll use my own model analysis. Verbatim you are lucky to get 1-2" on the Euro... I'm not sure why that is so hard for you to acknowledge. 

[CoastalWx]

Huh? I requoted his post. What do you mean?

 

He never said several inches to HFD and PVD. This is how stuff gets misinterpreted.

[Damage In Tolland]

He never said several inches to HFD and PVD. This is how stuff gets misinterpreted.

Dude. enough...he said a couple.. a couple is several. They mean the same thing

 

Anyway moving on.. wave looks healthy off to the SW

[ORH_wxman]

Ya'll are splitting hairs anyway.

 

The difference between a C-1 or 2 inches is not discernible on models like the Euro that do not have hourly resolution.

[weathafella]

He never said several inches to HFD and PVD. This is how stuff gets misinterpreted.

Dude. enough...he said a couple.. a couple is several. They mean the same thing

Anyway moving on.. wave looks healthy off to the SW

No! A couple is 2. Several is 3+

[Tropopause_Fold]

Dude. enough...he said a couple.. a couple is several. They mean the same thing

 

Anyway moving on.. wave looks healthy off to the SW

no.

[ORH_wxman]

Dude. enough...he said a couple.. a couple is several. They mean the same thing

 

Anyway moving on.. wave looks healthy off to the SW

 

"Several" to me is like 3-4.

 

 

Looks like "webster's dictionary online agrees:

 

¹sev·er·aladjective \ˈsev-rəl, ˈse-və-\

: more than two but not very many

: different and separate

 

http://www.merriam-webster.com/dictionary/several

[SnowMan]

awwww wham bam thank you NAM pic.twitter.com/OWAVxCmfji

lol....you're reaching...

[Damage In Tolland]

Oh my God

[CT Rain]

Ya'll are splitting hairs anyway.

 

The difference between a C-1 or 2 inches is not discernible on models like the Euro that do not have hourly resolution.

 

He said the Euro and the NAM were the same - that's absolutely not accurate and that's how stuff gets misconstrued. Verbatim the NAM approaches warning criteria for BDL while the Euro would struggle to drop 1-2". 

[CoastalWx]

Thank you. So much for not hyping.

 

ANyways, GFS is still not as enthusiastic, but we'll see what the other guidance does. Pretty good 12z set of guidance so far.

[ORH_wxman]

The difference between like an inch or two or 4"+ in the advisory area is going to be like 2 hours...with about a quarter inch of liquid equivalent falling between 03z-06z.

[CoastalWx]

There is still a decent band progged on the GFS near the Pike at 06z, but it looks like lift is certainly going to dictate how and when spots change over. It wasn't really much drier. The bigger difference is more eastern MA. There is probably going to be a time where the precip is rather light south of the MA/CT border because fronto forcing is lacking. So basically you are going to have to wait until that approaches, but at the same time it's moving east rather quickly as cold air advection finally comes from the north. The reason why this is more a nrn MA deal is because as the wave moves along the front...the cold air advection slows it's progress south until the wave moves through and then the cold acclerates SE. This slowing down is what helps create the frontogenesi.

[TauntonBlizzard2013]

awwww wham bam thank you NAM pic.twitter.com/OWAVxCmfji

Bastardi is nothing short of irresponsible for posting that. He knows his target client group though, many people going to bed expecting a foot of snow when they wake up

[CT Rain]

Goodbye Cano. Enjoy Seattle and a fate similar to Pujols.

What do people think about starting time for snow tonight?

 

Should start as light rain for us around 7 or 8. 

[CT Rain]

GFS looks like it has cooled a bit. 

[CT Rain]

This is what we're going with at the station. Seems reasonable to me. 

[ORH_wxman]

This is what we're going with at the station. Seems reasonable to me. 

 

 

That looks pretty reasonable...I could see some 4"+ in the Norfolk area, but given about 14 people live there, you'd be forecasting for the black bears anyway.

[dryslot]

No! A couple is 2. Several is 3+

 

I thought when you got married, It was as a couple not 3 or 4.................lol

[CT Rain]

Here's what I'm thinking - I'm glad the GFS is trended cooler.

 

 

[Tropopause_Fold]

Should start as light rain for us around 7 or 8. 

will be interesting to see how quickly it flips. the marginal zone from C CT to the Pike or so...you could argue its snowing pretty quickly or that it's a tedious process...and you'd have good points to stand on, on both sides. 

[CT Rain]

will be interesting to see how quickly it flips. the marginal zone from C CT to the Pike or so...you could argue its snowing pretty quickly or that it's a tedious process...and you'd have good points to stand on, on both sides. 

 

I wrote more about it on my blog - http://ryanhanrahan.com/2013/12/06/snow-and-sleet-tonight/

 

Considering if it flips to snow it would be 1-2"/hour kinda stuff getting that changeover timing exact is critical. 

[eduggs]

awwww wham bam thank you NAM pic.twitter.com/OWAVxCmfji

That map includes snowfall from both storms, no?

[Typhoon Tip]

Now-cast on cold shows that it's coming in quickly despite the laissez faire character to the wind field.  Noticing PSF is already 36/34, and some of the PD mesonet obs that are elevation along the spine of the Berks' and Greens' are showing the coldest numbers; it's cooling aloft and that's the key.  Now nearing freezing, showing that just off the deck the air mass is getting chilly.  

 

12z NAM colder ... 900mb of -1C prior to onset of meaningful QPF, with +2C at 800mb, however notable cooling differential underway, and the next interval has .32 liq-equiv. in the bucket at Logan, with all levels, 980, 900, 800mb, at or less than 0C!   Another .30 occurs up through the next interval, again ... all levels at and less than 800mb, less than 0C.  

 

Not sure where these other products are originating/derived, but that's 6" of snow at 10::1.   Why the consternation/conservatism?   Seeing a lot of "might go as high as 3"" -type content, and I'm wondering what folks are looking at, then I figure it must be that there is a tendency to toss the NAM altogether?    Yeah ... okay to do so, if that's one's prerogative -- the model's given more reasons to take pause in the past.  I'm not willing to do so, though.  

 

This is a different sort of scenario than the more typical error-prone ANA depiction in my mind.  Namely because the west Atlantic ridge is simply not eroding here... The front is clearly/currently paralleling the flow, and is not likely to move a whole heck of a lot more SE than it already has...(probably just off the Island or thereabouts).  Meanwhile, there is a lot of strong mid-level SW flow back west of the boundary, setting up particularly ideal overrunning construct.  Adding to, there is even subtle vort-max perturbations modeled to pass through western NY, and that should assist a slant-wise ingest along the elevated frontal slope, so it not hard for this Met to visualize where the persistent NAM-modeled notion of QPF field is coming from.   

 

That ,.. and looping IR shows a large baroclinic leaf already is moving NE out of the MV at current hour, and the axis of lift has SNE in the cross-hairs.   It appears this is coming together...  

 

Buuut, I'm will to compromise a little with consensus and go with 3-5" away from SC and SE zones, where I'm not sure lower BL thickness will cooperate in time.  But places like BED-FIT-ORH-PSF and even down to HFD, ...I feel reasonably confident in a burst of moderate snow lasting several hours (as in more than 2, Kevin).

[eduggs]

This is what we're going with at the station. Seems reasonable to me. 

Seems very reasonable within CT.  But there is certainly bust potential on the high side, especially in NWCT, where model progs give roughly .5-.75 LE with marginal mid levels and near or just above freezing surface temps.  I don't think this is a typical anafrontal snow scenario that is typically underperforming.  The cold front is already pretty far south through SNE with a moisture laden frontal wave approaching.  Someone should get a good burst of snow.  Probably just north of CT, but it's going to be close.  I like starting conservative but I suspect forecast snowfall gets upped this evening.

[Typhoon Tip]

ALB  39 32 3117G22

[ORH_wxman]

Now-cast on cold shows that it's coming in quickly despite the laissez faire character to the wind field.  Noticing PSF is already 36/34, and some of the PD mesonet obs that are elevation along the spine of the Berks' and Greens' are showing the coldest numbers; it's cooling aloft and that's the key.  Now nearing freezing, showing that just off the deck the air mass is getting chilly.  

 

12z NAM colder ... 900mb of -1C prior to onset of meaningful QPF, with +2C at 800mb, however notable cooling differential underway, and the next interval has .32 liq-equiv. in the bucket at Logan, with all levels, 980, 900, 800mb, at or less than 0C!   Another .30 occurs up through the next interval, again ... all levels at and less than 800mb, less than 0C.  

 

Not sure where these other products are originating/derived, but that's 6" of snow at 10::1.   Why the consternation/conservatism?   Seeing a lot of "might go as high as 3"" -type content, and I'm wondering what folks are looking at, then I figure it must be that there is a tendency to toss the NAM altogether?    Yeah ... okay to do so, if that's one's prerogative -- the model's given more reasons to take pause in the past.  I'm not willing to do so, though.  

 

This is a different sort of scenario than the more typical error-prone ANA depiction in my mind.  Namely because the west Atlantic ridge is simply not eroding here... The front is clearly/currently paralleling the flow, and is not likely to move a whole heck of a lot more SE than it already has...(probably just off the Island or thereabouts).  Meanwhile, there is a lot of strong mid-level SW flow back west of the boundary, setting up particularly ideal overrunning construct.  Adding to, there is even subtle vort-max perturbations modeled to pass through western NY, and that should assist a slant-wise ingest along the elevated frontal slope, so it not hard for this Met to visualize where the persistent NAM-modeled notion of QPF field is coming from.   

 

That ,.. and looping IR shows a large baroclinic leaf already is moving NE out of the MV at current hour, and the axis of lift has SNE in the cross-hairs.   It appears this is coming together...  

 

Buuut, I'm will to compromise a little with consensus and go with 3-5" away from SC and SE zones, where I'm not sure lower BL thickness will cooperate in time.  But places like BED-FIT-ORH-PSF and even down to HFD, ...I feel reasonably confident in a burst of moderate snow lasting several hours (as in more than 2, Kevin).

 

 

I think an argument can be made for going both bullish or bearish on this system....you make a good bullish argument. The bears can point to the parallel flow with the marginal pesky warm layer betweem 700-800mb as being a limiting factor and taking too long to get washed out. Big omega overruning the front can overcome that though and certainly that is where a lot of the uncertainty lies.

[Damage In Tolland]

Now-cast on cold shows that it's coming in quickly despite the laissez faire character to the wind field.  Noticing PSF is already 36/34, and some of the PD mesonet obs that are elevation along the spine of the Berks' and Greens' are showing the coldest numbers; it's cooling aloft and that's the key.  Now nearing freezing, showing that just off the deck the air mass is getting chilly.  

 

12z NAM colder ... 900mb of -1C prior to onset of meaningful QPF, with +2C at 800mb, however notable cooling differential underway, and the next interval has .32 liq-equiv. in the bucket at Logan, with all levels, 980, 900, 800mb, at or less than 0C!   Another .30 occurs up through the next interval, again ... all levels at and less than 800mb, less than 0C.  

 

Not sure where these other products are originating/derived, but that's 6" of snow at 10::1.   Why the consternation/conservatism?   Seeing a lot of "might go as high as 3"" -type content, and I'm wondering what folks are looking at, then I figure it must be that there is a tendency to toss the NAM altogether?    Yeah ... okay to do so, if that's one's prerogative -- the model's given more reasons to take pause in the past.  I'm not willing to do so, though.  

 

This is a different sort of scenario than the more typical error-prone ANA depiction in my mind.  Namely because the west Atlantic ridge is simply not eroding here... The front is clearly/currently paralleling the flow, and is not likely to move a whole heck of a lot more SE than it already has...(probably just off the Island or thereabouts).  Meanwhile, there is a lot of strong mid-level SW flow back west of the boundary, setting up particularly ideal overrunning construct.  Adding to, there is even subtle vort-max perturbations modeled to pass through western NY, and that should assist a slant-wise ingest along the elevated frontal slope, so it not hard for this Met to visualize where the persistent NAM-modeled notion of QPF field is coming from.   

 

That ,.. and looping IR shows a large baroclinic leaf already is moving NE out of the MV at current hour, and the axis of lift has SNE in the cross-hairs.   It appears this is coming together...  

 

Buuut, I'm will to compromise a little with consensus and go with 3-5" away from SC and SE zones, where I'm not sure lower BL thickness will cooperate in time.  But places like BED-FIT-ORH-PSF and even down to HFD, ...I feel reasonably confident in a burst of moderate snow lasting several hours (as in more than 2, Kevin).

Nice disco Tippy..Sounds like a couple to several inches for all!!

[eduggs]

Here's what I'm thinking - I'm glad the GFS is trended cooler.

I love that method of snowfall forecasting.  It's probably too complex for the average weather consumer, but I wish all forecasts were more probability based like that.  So when there is a big bust on either side, say 0" or 10", people can't just complain that forecasters are terrible.  There would be more understanding of the range of possibilities.