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Dec 12 Snow/ice threat


ORH_wxman

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I'm seeing a subtle variation throughout the NAM's synoptic (chart) evolution re lower level features in this thing, on this 12z run.

There appears to be more "sag" in the weak sort of secondary trough that extends east from perceived primary at ~ 48 hours.  Previous runs gave an impression of that trough axis establishing farther N into SNE proper compared to this run, which has that axis at that interval more like NYC'ish. That gives the allusion of more boundary layer forcing/CAD conservation going on up this way.

I'm looking at the T1, T3 and T5 temperatures intervals on the FRH grid (FOUS) for BOS and it's not exactly top heavy with warm there folks.  It's like +5 (granted, ...inferno) at T1, but is only +2 C (overcome-able in heavy falls rates) at 900mbs and then -1 C at 800mb.  So that's really like 39 F with cat paws at the surface at the warmest interval out in the Harbor at Logan Airport, where every lives and cares...

When I see that and factor in common wisdom with these sort of things ... you get out west of the city along I95 over eastern MA and that's what?  probably 34 F or colder, and likely 31 in the deep interior with a N drifting ageostrophic flow ... where at both places you have aggregated snow fall in various sizes and wetness (given that sort of sounding and total synoptic evolution). 

Buuut, that's all just talking about the NAM of course...

EDIT: heh, I'm a dipschit - I got my intervals backward.. it's actually the 12z run that is more aggressive with the trough axis.  Probably doesn't matter. This model still has time to correct. But the stuff about the FRH grid is still true.

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12 minutes ago, Typhoon Tip said:

 

I'm seeing a subtle variation throughout the NAM's synoptic (chart) evolution re lower level features in this thing, on this 12z run.

There appears to be more "sag" in the weak sort of secondary trough that extends east from perceived primary at ~ 48 hours.  Previous runs gave an impression of that trough axis establishing farther N into SNE proper compared to this run, which has that axis at that interval more like NYC'ish. That gives the allusion of more boundary layer forcing/CAD conservation going on up this way.

I'm looking at the T1, T3 and T5 temperatures intervals on the FRH grid (FOUS) for BOS and it's not exactly top heavy with warm there folks.  It's like +5 (granted, ...inferno) at T1, but is only +2 C (overcome-able in heavy falls rates) at 900mbs and then -1 C at 800mb.  So that's really like 39 F with cat paws at the surface at the warmest interval out in the Harbor at Logan Airport, where every lives and cares...

When I see that and factor in common wisdom with these sort of things ... you get out west of the city along I95 over eastern MA and that's what?  probably 34 F or colder, and likely 31 in the deep interior with a N drifting ageostrophic flow ... where at both places you have aggregated snow fall in various sizes and wetness (given that sort of sounding and total synoptic evolution). 

Buuut, that's all just talking about the NAM of course...

EDIT: heh, I'm a dipschit - I got my intervals backward.. it's actually the 12z run that is more aggressive with the trough axis.  Probably doesn't matter. This model still has time to correct. But the stuff about the FRH grid is still true.

There's definitely secondary signals over SE MA area from appearing east of NJ. That would fit climo. Fwiw RGEM is decent in the Boston area. Seems like it argues 2-3" for the city. 

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1 minute ago, CoastalWx said:

There's definitely secondary signals over SE MA area from appearing east of NJ. That would fit climo. Fwiw RGEM is decent in the Boston area. Seems like it argues 2-3" for the city. 

yeah, I tend to agree - RGEM that is.

that model is like the one gem that comes out of the Canadian office and I tend to rely on it more so than our own version, the NAM for these tedious BL contention events. 

anyway, not that you asked ...that is.  :)    I think this is a WAA burst ending as freezing snitzel right up to I95 and probably a wetter snow for the coastal plain ending as drizzle.  QPF being what it is...

It moves off then we await the 15th for another sub 4" micron of interest haha

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1 minute ago, CoastalWx said:

Gfs really goes to town between like 9z-13z or so. I think places like ORH and even int NE MA could grab several inches during that time in addition to what falls prior to 9z.

It's prob enhanced by like the 925mb warm front. You can the defined front on the maps. 

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3 minutes ago, ORH_wxman said:

It's prob enhanced by like the 925mb warm front. You can the defined front on the maps. 

Yeah A lot of forcing from lower levels...but should be able to lift right up through the column. Deep layer saturation on the soundings too, so would not shock me if the GFS advertises brief S+ in a few spots.

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1 minute ago, Damage In Tolland said:

Canadian looks like mostly snow north of the Meritt. Drops 4-7 roughly north of there up past I-90

Can we trust the Canadian though?  That's a nice lil event in Central and N. Ct if that is close to correct????   I dunno though??  If the Euro comes out with something close to that, that would lend much more confidence in that 4-6 inch idea for interior CT.

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Still not expecting more than 2-3 for myself or Kevin.  Perhaps Litchfield county can tap into some 4-5 amounts as the secondary placement may hold the cold air a little longer in that area.  Berks and perhaps northern ORH could see some 4-6 type amounts the way I'm seeing things with perhaps the area NW of 84 and south of the Pike and west of ORH with a 2-4 inch snowfall. I'll take 2 inches and call it a day.  

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22 minutes ago, 512high said:

Scott, Can I still assume a 3-6" for my city, without rain involved(for salting purposes on the properties we maintain), thanks ahead of time

Yeah I think so, although it may end as a bit of drizzle. It may get into 30s which will melt a bit before freezing up Monday night.

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26 minutes ago, CTValleySnowMan said:

Still not expecting more than 2-3 for myself or Kevin.  Perhaps Litchfield county can tap into some 4-5 amounts as the secondary placement may hold the cold air a little longer in that area.  Berks and perhaps northern ORH could see some 4-6 type amounts the way I'm seeing things with perhaps the area NW of 84 and south of the Pike and west of ORH with a 2-4 inch snowfall. I'll take 2 inches and call it a day.  

agreed and 1-2 is still very possible for us

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