99 replies to this topic

[robbbs]

I think most of us are starving for a winter storm and have been scouring various sources for any information that might lend support to the notion that this weekend may bring a wintry event to the metro region. Monday's 18z GFS run was a tease as it had a near perfect scenario and track for a widespread moderate to heavy snow event for virtually our entire region. Unfortunately, that scenario lasted all of 6 hours until the 00z run came out and started a succession of northward shifts of the midwest low, running it well to the northwest of us to the Great Lakes and Canada. The last gfs run, today's 18z, shifted the low track slightly further east, but still well west of us. While there will be a reinforcing shot of cold air on Saturday, if Sunday's track stays west of here, southeast winds will erode the cold air for most of us before any significant precip can occur. The models do have a  secondary forming on the coast, but the 18z GFS has the coastal developing off Boston, too far north to be of any help here. Under the latest GFS run, IMO most of us would see some kind of frozen precip at the onset, but with a quick change to rain. It is only Wednesday, and a number of posters on the board today correctly indicated there's still time for the model tracks to shift to something more favorable, not to mention that we're not even within the NAM's range for Sunday yet. Not looking great right now but, as many posted today, too early to shut it down.

[LongIslandWthr]

Thanks for summing that up robbbs, indeed it is too early to tell but we should have a some what better handle of this storm by Friday evening/night with many I presume pulling an all-night-er watching the models..  :smile:

[dragons1225]

haha not me ill be in baltimore all weekend for the army/navy game


go army beat navy!  :biggrin:

[NYBrit]

Great summary Sat!  I think you got everything  :laugh:
Now can someone please give us some good news about this weekend storm?

[devilsfan0405]

Good summary, Robbs. Let's keep our fingers crossed.

[Stormchaser]

Great summary Robbbs. Outlines the scenario quite nicely.

I would agree that it's not yet time to write the storm off; however, there's more bad than good in terms of the overall synoptic-scale set-up. Three main aspects of this pattern through Day 7 are unfavorable: 1) Placement of the Polar Vortex, 2) No 50-50 low near Newfoundland, 3) Lack of a neg NAO block in the north atlantic.

The strength of the late week clipper is, IMO, our only hope for widespread snow this far south. If the system can intensify enough to temporarily raise heights over SE Canada, forcing the polar front further south, thereby resulting in a storm track further south -- then there's a chance for some winter weather. Current depictions on virtually all guidance, including the NAM, aren't too pretty. Yes, the NAM is a bit better but not much.

I'm going to attempt to break this down in visual format - with my hideous drawings. Below is the 18z GFS 500mb depiction for Sunday:

[img width=600 height=419]http://i7.tinypic.com/6s8m9hl.jpg[/img]

Things to note:

1) Lack of blocking near greenland, in fact, the NAO is solidly positive with a powerful low to the east of Canada. What this means is any high pressure over SE Canada is going to have a difficult time holding its ground as there's nothing downstream to block its movement. If a BLOCK was in place near greenland, that HP in southern Canada would have NOWHERE to go, thereby preventing a low cutting thru the Great lakes. However, we don't have that.

2) Polar vortex position is in SW Canada, thus a SWLY upper flow across the Mid-west. Not favorable for east coast snow -- it teleconnects to ridging over the southeast US as one can see on the map posted above.

3) Trough is negatively tilted in the Mid-west already - bad sign. We want a neg tilted trough on the east coast as that promotes cyclogenesis/bombogenesis. However, seeing this in the center of the country is often a precursor to rains along the coastal plain.

Hopefully this helps as to why it's not a good set up right now.

I'm not saying it can't change -- as the 18z GFS is a bit south. Our only shot is my first point from above -- we NEED a STRONG CLIPPPER, to pull down the cold air and force a more southern track, or we're done.

[metfan4life]

good writeup

[snowfreak188]

this stom is basically done for now for us a few flakes to rain

[metfan4life]

i hope not  >:(

[Stormchaser]

Where's your Christmas spirit snowfreak? Miracles are possible.  :biggrin:


Would be foolish to write something off 5 days in advance, even if it doesn't look too great now.

[snowfreak188]

Quote

Where's your Christmas spirit snowfreak? Miracles are possible.  :biggrin:


Would be foolish to write something off 5 days in advance, even if it doesn't look too great now.

after what i just saw on the nam maybe im speaking to soon am i rite?

[summer]

This storm looks like even as fat west as buffalo might have rain...

[wxtracker93]

Quote

Great summary Robbbs. Outlines the scenario quite nicely.

I would agree that it's not yet time to write the storm off; however, there's more bad than good in terms of the overall synoptic-scale set-up. Three main aspects of this pattern through Day 7 are unfavorable: 1) Placement of the Polar Vortex, 2) No 50-50 low near Newfoundland, 3) Lack of a neg NAO block in the north atlantic.

The strength of the late week clipper is, IMO, our only hope for widespread snow this far south. If the system can intensify enough to temporarily raise heights over SE Canada, forcing the polar front further south, thereby resulting in a storm track further south -- then there's a chance for some winter weather. Current depictions on virtually all guidance, including the NAM, aren't too pretty. Yes, the NAM is a bit better but not much.

I'm going to attempt to break this down in visual format - with my hideous drawings. Below is the 18z GFS 500mb depiction for Sunday:

[img width=600 height=419]http://i7.tinypic.com/6s8m9hl.jpg[/img]

Things to note:

1) Lack of blocking near greenland, in fact, the NAO is solidly positive with a powerful low to the east of Canada. What this means is any high pressure over SE Canada is going to have a difficult time holding its ground as there's nothing downstream to block its movement. If a BLOCK was in place near greenland, that HP in southern Canada would have NOWHERE to go, thereby preventing a low cutting thru the Great lakes. However, we don't have that.

so without a block, that means that the storm could easily be carried up into Canada, correct?

[summer]

sorry - as "far" west as buffalo
has anyone seen more of an easterly - southerly tract?

[Stormchaser]

Quote

after what i just saw on the nam maybe im speaking to soon am i rite?

00z NAM is a good bit cooler than the GFS. If extrapolated, it would probably be a good front-end dump of snow/ice, especially for inland areas. Notice the NAM is more bullish on the late week clipper thus a colder foundation for the precip. Not to mention a 1036MB high in a perfect position. I'm fairly confident some parts of New England will get hammered with this system (snow/ice). It's a question of how far southeast.

[Stormchaser]

Quote

so without a block, that means that the storm could easily be carried up into Canada, correct?

Brett,

Yes, and that's what the GFS, Euro, UKMET are depicting at this time. However, the NAM is sensing a stronger late week clipper, which would allow a colder airmass into the Northeast prior to the arrival of the storm. We don't need a -NAO for snowstorms in the NE, that's one of the reasons why I haven't written this off. High pressure placement is good - only improvements I'd like to see is a Polar vortex further east in Canada (would aid in forcing the low south).

All in all I think this is far from resolved.

[snowfreak188]

Quote

Brett,

Yes, and that's what the GFS, Euro, UKMET are depicting at this time. However, the NAM is sensing a stronger late week clipper, which would allow a colder airmass into the Northeast prior to the arrival of the storm. We don't need a -NAO for snowstorms in the NE, that's one of the reasons why I haven't written this off. High pressure placement is good - only improvements I'd like to see is a Polar vortex further east in Canada (would aid in forcing the low south).

All in all I think this is far from resolved.

oh boy do i hate that PV lol :wacko:

EDIT: just checked the 00z and seems like its a whole 10-20miles east lets keep the trend lol

[summer]

nick gregory - 10:05am "is there snow in store for this weekend?"  total sell job to get us to come back - snow sells and this is why when the mets call for rain - take it... if there was a sniff of a big snow they would shout it from the rooftops and all the bread and milk would be gone

[lab94]

Quote

Great summary Robbbs. Outlines the scenario quite nicely.

I would agree that it's not yet time to write the storm off; however, there's more bad than good in terms of the overall synoptic-scale set-up. Three main aspects of this pattern through Day 7 are unfavorable: 1) Placement of the Polar Vortex, 2) No 50-50 low near Newfoundland, 3) Lack of a neg NAO block in the north atlantic.

The strength of the late week clipper is, IMO, our only hope for widespread snow this far south. If the system can intensify enough to temporarily raise heights over SE Canada, forcing the polar front further south, thereby resulting in a storm track further south -- then there's a chance for some winter weather. Current depictions on virtually all guidance, including the NAM, aren't too pretty. Yes, the NAM is a bit better but not much.

I'm going to attempt to break this down in visual format - with my hideous drawings. Below is the 18z GFS 500mb depiction for Sunday:

[img width=600 height=419]http://i7.tinypic.com/6s8m9hl.jpg[/img]

Things to note:

1) Lack of blocking near greenland, in fact, the NAO is solidly positive with a powerful low to the east of Canada. What this means is any high pressure over SE Canada is going to have a difficult time holding its ground as there's nothing downstream to block its movement. If a BLOCK was in place near greenland, that HP in southern Canada would have NOWHERE to go, thereby preventing a low cutting thru the Great lakes. However, we don't have that.

2) Polar vortex position is in SW Canada, thus a SWLY upper flow across the Mid-west. Not favorable for east coast snow -- it teleconnects to ridging over the southeast US as one can see on the map posted above.

3) Trough is negatively tilted in the Mid-west already - bad sign. We want a neg tilted trough on the east coast as that promotes cyclogenesis/bombogenesis. However, seeing this in the center of the country is often a precursor to rains along the coastal plain.

Hopefully this helps as to why it's not a good set up right now.

I'm not saying it can't change -- as the 18z GFS is a bit south. Our only shot is my first point from above -- we NEED a STRONG CLIPPPER, to pull down the cold air and force a more southern track, or we're done.

Great job! Even I get it now. :biggrin: I do have a question. Where and what causes this SE ridge we always hear about? Is it that big H near south Fl

[snowfreak188]

992MB low in the west already on the gfs :ohmy: