Wednesday 12/11 SNE Snow Threat

[weatherwiz]

Just now, dryslot said:

Coating to a trace?

I wonder if you can forecast negative snow...since we measure snow that reaches the ground (a positive value) what about snow that evaporates before reaching the ground...or gets caught in the updrafts?..it's not falling to the ground...it's rising farther from the ground. 

[RUNNAWAYICEBERG]

5 minutes ago, weatherwiz said:

I wonder if you can forecast negative snow...since we measure snow that reaches the ground (a positive value) what about snow that evaporates before reaching the ground...or gets caught in the updrafts?..it's not falling to the ground...it's rising farther from the ground. 

You schooled the models and weenies on this one. Good work.

[dryslot]

8 hours ago, HIPPYVALLEY said:

@dryslot and I like to reference how many feet of Canadian modeled snow we have shoveled over the years.   Permanent back injuries from it all really... or maybe those injuries were from all the kegs we've moved?

Even yesterday torch temps can’t melt off last years Ggem’s snow pack, When  I see someone lifting a 1/2 bbl, I get numbness in my leg.

[weatherwiz]

5 minutes ago, RUNNAWAYICEBERG said:

You schooled the models and weenies on this one. Good work.

Thanks but it's not over yet haha. If the Pats can come back from down 28-3...anything can happen lol. 

[OceanStWx]

13 hours ago, The 4 Seasons said:

Light snow accumulation means sub advisory for that forecast period i.e. around 1", 1-2, 1-3, 2-3

Moderate means advisory for that period

Heavy means warning for that period

Adding an inch to say 1-3 yields about 2-4ish. That's generally how that works in my experience. @OceanStWx can correct me if im wrong.

Light, moderate, heavy are the three categories and its usually stated outside of a time when exact numbers come into play.

More or less correct. It's different between the zone forecast (which the local office can modify) and the point and click (which is nationally implemented). 

But you have the categories correct I think. Light = 1=3", moderate = 3-6", and heavy = 6+

[RUNNAWAYICEBERG]

Just now, weatherwiz said:

Thanks but it's not over yet haha. If the Pats can come back from down 28-3...anything can happen lol. 

Not saying there’s no chance of snow we could get like 1-2” still but you and others raised some flags that some of us read and learned from. 

[OceanStWx]

25 minutes ago, weatherwiz said:

I wonder if you can forecast negative snow...since we measure snow that reaches the ground (a positive value) what about snow that evaporates before reaching the ground...or gets caught in the updrafts?..it's not falling to the ground...it's rising farther from the ground. 

I really, really wanted to keep any accumulating snow basically offshore with yesterday afternoon's forecast, but alas I had to try and shoehorn in around 2 inches to match up with neighbors. Didn't like getting dragged a bit on twitter for "ignoring" southern NH.

Just looking at our midnight shift grids and I'm going to have to chop even more than they did.

[Ericjcrash]

13 minutes ago, weatherwiz said:

Thanks but it's not over yet haha. If the Pats can come back from down 28-3...anything can happen lol. 

If Mark Sanchez can win a playoff game in Foxboro, literally nothing is off the table.

[Whineminster]

3 to 5 inches would be a nice treat. 20% chance.

[weatherwiz]

10 minutes ago, RUNNAWAYICEBERG said:

Not saying there’s no chance of snow we could get like 1-2” still but you and others raised some flags that some of us read and learned from. 

What I've learned from here over the years is that the best method/approach to forecasting is to account for everything...especially flags. When flags start to arise, that's when you need to pump the brakes and start asking yourself questions in your head...questions such as "how does this alter the potential outcome" or "what does this offset". What I then do is try and paint a visualization in my head of how everything will look as the event is unfolding (especially regarding radar). 

This does burn me often b/c I will be conservative more times than not, however, I have learned that there are some things I may place too much emphasis in or that my understanding of what I was interpreting was just flat out wrong. One example of this is RH in the DGZ. For some reason I was using 90+% as a threshold, however, upon reading up, I was way too high...threshold seems to be more in the 80-85% range...so when I would see less than 90% I would think it was too dry for good snowgrowth and I would underforecast. 

I also suck at not necessarily analyzing charts like 500 vorticity, but I really suck at understanding how the pieces work together and how subtle changes in placement, structure, track influence everything at the surface. This BURNED me last year...remember the weekend where we had a storm Friday and sunday or Monday...I completely played up the Friday one and and downplayed the second one...we got little Friday and slammed Sunday. 

3 minutes ago, OceanStWx said:

I really, really wanted to keep any accumulating snow basically offshore with yesterday afternoon's forecast, but alas I had to try and shoehorn in around 2 inches to match up with neighbors. Didn't like getting dragged a bit on twitter for "ignoring" southern NH.

Just looking at our midnight shift grids and I'm going to have to chop even more than they did.

That certainly presents a major challenge for you...and everyone else really. It has to be tough when forecasting along the boundaries of CWA's in questionable situations...you think 1-2'' but just across the border they're going like 4-6''...huge difference and that does the public no good. People really thought you were ignoring southern NH...lol

[OceanStWx]

3 minutes ago, weatherwiz said:

That certainly presents a major challenge for you...and everyone else really. It has to be tough when forecasting along the boundaries of CWA's in questionable situations...you think 1-2'' but just across the border they're going like 4-6''...huge difference and that does the public no good. People really thought you were ignoring southern NH...lol

I think the grand irony there is that we probably pay more attention to southern NH than we should just because that's where all our population lives. 

[TalcottWx]

Yeah, I'd go sit on my computer and look at this one, but the posts are telling me the story lol

[RUNNAWAYICEBERG]

17 minutes ago, Ericjcrash said:

If Mark Sanchez can win a playoff game in Foxboro, literally nothing is off the table.

Canadian models butt fumbled this event.

[Baroclinic Zone]

Native American Swamps stealing all the 's snow.

[Baroclinic Zone]

Your Euro  snows

[SnowGoose69]

3 minutes ago, Baroclinic Zone said:

Your Euro  snows

Back after that Euro upgrade in 2014 or so this was an auto shift 50 miles west.  It was terrible the first 2 years or so off that upgrade being too dry and flat with anything that wasn’t a heavily amped system but after the latest update it seems to be about as good as it has ever been.  I haven’t even been seeing it’s 90-120 overamped tendency the last 6-8 months. 

[Typhoon Tip]

 

Starting to see why the models are backing off a bit as we get closer .. 

The problem is that the wind velocity at mid levels ahead of the western OV [ apparent ] short wave are not actually differentiating with respect to S/W enough because of that antecedent velocity surplus... S/W 'disappears' in streams that are already fast and that's it.. game over ( in relative amounts that is..). 

Anyway, I've tried to explain this a thousand times and it doesn't seem to be very well-received - probably ignored because it's bad news whenever the topic needs to come up... But, when the flow is very fast, S/W's get absorbed.. .and when they get absorbed, they don't have mechanical ability to trigger restoring jet structures... which in this case, is the post frontal up-glide -- destablization and breakout of lag QPF... etc... Go find the S/W over the western OV and notice the wind swell ahead of it are already modeled over 110 kts everywhere! 

I've been discussing at length across recent years ... that velocity surplussing in the atmosphere is a detriment in some cases because it is, in a 2ndary sense of it, a destructive wave interference in the relationship between large scale base-state synoptics, when then placing S/W spaces into said field that is already screaming. 

The large scale 'cancels' out the power of the smaller scales... There is only so much mechanical energy available to the atmosphere, which we know to be true. The Earth only rotates so fast and the density of the atmosphere is a constant... such that PV=NRT combined with the Corriolis in the equations of atmospheric motions can only result in so much .. .Well, if the large scale already expresses all that strength, the S/W are screwed - one way to think of it.  So, this OV S/W is having trouble in the models inducing the upglide over the west side of the front.  

   

[weatherwiz]

22 minutes ago, OceanStWx said:

I think the grand irony there is that we probably pay more attention to southern NH than we should just because that's where all our population lives. 

I feel like there are people who just browse social media 24/7 and stalk either local news stations or NWS and troll. My roommate from school works on TV in Bangor, ME and the comments he gets are ridiculous. One viewer was claiming she measured like 26'' of snow in the last storm and was upset b/c when he mentioned a range of totals that fell on air her total wasn't in the range lol

[eduggs]

All guidance has been shifting towards the ICON for 2 days now.  It has consistently shown limited post-frontal precip. west of I-95 from MD to EMA.  Underrated model.  We'll see how it shakes out.  There could still be surprises.  

[weatherwiz]

6 minutes ago, Typhoon Tip said:

 

Starting to see why the models are backing off a bit as we get closer .. 

The problem is that the wind velocity at mid levels ahead of the western OV [ apparent ] short wave are not actually differentiating with respect to S/W enough because of that antecedent velocity surplus... S/W 'disappears' in streams that are already fast and that's it.. game over ( in relative amounts that is..). 

Anyway, I've tried to explain this a thousand times and it doesn't seem to be very well-received - probably ignored because it's bad news whenever the topic needs to come up... But, when the flow is very fast, S/W's get absorbed.. .and when they get absorbed, they don't have mechanical ability to trigger restoring jet structures... which in this case, is the post frontal up-glide -- destablization and breakout of lag QPF... etc... Go find the S/W over the western OV and notice the wind well ahead of it are already over 110 kts everywhere! 

I've been discussing at length across recent years ... that velocity surplussing in the atmosphere is a detriment in some cases because it is, in a 2ndary sense of it, a destructive wave interference in the relationship between large scale base-state synoptics, when then placing S/W spaces into said field that is already screaming. 

The large scale 'cancels' out the power of the smaller scales... There is only so much mechanical energy available to the atmosphere, which we know to be true. The Earth only rotates so fast and the density of the atmosphere is a constant... such that PV=NRT combined with the Corriolis in the equations of atmospheric motions can only result in so much .. .Well, if the large scale already expresses all that strength, the S/W are screwed - one way to think of it.  So, this OV S/W is having trouble in the models inducing the upglide over the west side of the front.  

   

In a situation like this though, how important is that s/w? Too me, I don't think it is overly important (referring to that OV s/w)...that s/w lags the cold front quite a bit and it's this front (and associated frontal energy) as it pushes through which just yields a different atmospheric state (going from buoyant to subsident). Even if that s/w didn't really get absorbed and maybe the jet feature/speed was more favorable...would it do anything to help? If there was stronger moisture advection which could shoot in with some WAA as we lose the influence of the front...maybe it would be different? 

[CTWeatherFreak]

1 hour ago, weatherwiz said:

I wonder if you can forecast negative snow...since we measure snow that reaches the ground (a positive value) what about snow that evaporates before reaching the ground...or gets caught in the updrafts?..it's not falling to the ground...it's rising farther from the ground. 

Yes.. seems too me more than once weve  had 6" of virga.

[weatherwiz]

2 minutes ago, CTWeatherFreak said:

Yes.. seems too me more than once weve  had 6" of virga.

At least there is no virga when tracking severe 

[MJO812]

Nam looks juicier so far 

[Baroclinic Zone]

Rock out with the 12z NAM out Westerners.

[WeatherX]

Dumbfounded

[purduewx80]

4 minutes ago, weatherwiz said:

In a situation like this though, how important is that s/w? Too me, I don't think it is overly important (referring to that OV s/w)...that s/w lags the cold front quite a bit and it's this front (and associated frontal energy) as it pushes through which just yields a different atmospheric state (going from buoyant to subsident). Even if that s/w didn't really get absorbed and maybe the jet feature/speed was more favorable...would it do anything to help? If there was stronger moisture advection which could shoot in with some WAA as we lose the influence of the front...maybe it would be different? 

It has everything to do with it. That shallow wedge of dry air on a few models at 850 mb has nothing to do with why most guidance shifted southeast in the past 24 hours. 

[ORH_wxman]

NAM def looked better than 06z....RPM still looks like ka-ka.

[weatherwiz]

2 minutes ago, purduewx80 said:

It has everything to do with it. That shallow wedge of dry air on a few models at 850 mb has nothing to do with why most guidance shifted southeast in the past 24 hours. 

See...this is where I am a bit weak in analysis. 

Well...I get the southeast shift has little to do with the shallow edge of dry air at 850...

but what about the differences in the s/w relate to a farther southeast shift in precip. This is what I struggle to deal with visually on models. 

[STILL N OF PIKE]

haven't been following this closely last 24 hours but if the nam that i just peek'd at looks better than prior runs...this event is a well.....good luck to Ginxy-PVD-GHG 

Hope someone scores 3"

[ORH_wxman]

Just now, STILL N OF PIKE said:

haven't been following this closely last 24 hours but if the nam that i just peek'd at looks better than prior runs...this event is a well.....good luck to Ginxy-PVD-GHG 

Hope someone scores 3"

NAM has been one of the uglier models on this event for the past 3 or 4 runs, so it's useful that it trended better. I don't expect the RGEM or GGEM to verify though and give warning snows. SE MA and RI are def the best spots though for this one.