OBS-NOWCAST for the Probable period of Hazardous wintry weather for a portion of the NYC sub forum centered on Wednesday Dec 8, 2021

[wdrag]

Many models have a little snow or ice for our area next Wednesday the 8th, possibly ending as rain?  WPC Friday afternoons forecast has a half inch+ of qpf for our area next Wednesday and a 30-49% chance of 3+" of snow or 1/4 inch combined sleet/snow. Click the graphics. That's not too bad for a day5-6 forecast. 

I may have overreached on  PROBABLE hazardous????  I do think there should be a little ice, at a minimum over the I84 high terrain. The rest of the area much more uncertain. 

We should be close to the  right rear quad of an upper level jet core centered near Nova Scotia (130 knots 200-300MB) next Wednesday (see EPS 18z Wednesday 300MB), this behind the strong negative tilt short wave departure of Monday.  A weakening 500MB short wave from the upper Midwest Wednesday morning crosses into northern New England by Thursday morning.  The 850 Low is north of our area.  Snow thicknesses are marginal especially south of I84, so that snow amounts this far in advance are VERY uncertain and likely to be less than 3" rather than more.  Some sort of light to possibly moderate ice-snow event should occur in parts of our interior Wednesday Dec 8.

One consideration is the qpf being less than currently advertised which would reduce amounts. 

This thread is posted to focus anyone's interest into the discussion.  LI-coastal NJ--- primary modeling may eventually favor your area but for now, I think the primary ensemble considerations for a 6 to 18 hour period of hazardous wintry weather next Wednesday is to the northwest of I95.

TAGS and Thread title may change this weekend or early next week. 717PM/3 Dec 2021

 

6AM Wednesday the 8th: converted this thread to OBS-Nowcast.  No other change. 

[Albedoman]

agree to all statements. The thing here is model consensus.  I have never seen so much chaos in the models in the past two weeks both in long and short range with the raging Pac jet in the last 15 years. At least there appears to consensus at this point in the long range models that a light snow/ice accumulation event especially west of the Delaware River is now apparent.  To have a 3+ inch plowable snow event though, threading of the needle has to be achieved for sure.  Temps on Wednesday morning have to be several degrees below freezing at sunrise, otherwise a simple lawn covering snow/ice rain  event is all that will happen. Anway, the snow will be gone by the end of the following weekend with the quick 60 degree warmup south of the NY/PA state line

 

[MJO812]

First run of the 0z regime

 

Icon

[MJO812]

Euro says what storm

Cold and offshore 

[MJO812]

[MJO812]

Eps

[MJO812]

6z icon

[MJO812]

Crush job for New England on the gfs. It is colder than the 0z Run .

[SnoSki14]

16 minutes ago, MJO812 said:

Crush job for New England on the gfs. It is colder than the 0z Run .

Trending towards a very weak system.

Not sure if they'll be too much with this but it's better than nothing.

[wdrag]

As noted above 00z/4 EC and UK are much weaker or nothing.  For now, take that with a grain of salt.  BUT, does tell us that uncertainty continues large and prepare for less than desired.  

I checked the 00z/4  NAEFS and it's still on board-the bigger concern I have is the marginal thickness. I can see sleet/freezing rain as more of a problem than snow.  

03z/4 WPC probs for significant snow/.ice  remain the same, but that is without the toned down EPS.    

I sure hope the EC/EPS comes back in the next few cycles, otherwise have to think wasted thread. 

[bluewave]

11 minutes ago, wdrag said:

As noted above 00z/4 EC and UK are much weaker or nothing.  For now, take that with a grain of salt.  BUT, does tell us that uncertainty continues large and prepare for less than desired.  

This will be the first test of the newly upgraded Euro with a coastal storm in the winter. It had been having suppression issues with coastal storms in recent years. So if the models like the GFS and CMC are right about a track closer to our area, then they weren’t able to address this issue on the upgrade. But if the CMC and GFS go south then we’ll know the issue was fixed. While the Euro has been the top scoring global model in recent years, I have never seen any official statistics for East Coast storm track performance. Maybe the model is tuned for performance in Europe? Even though the Euro has struggled with East Coast storm tracks in recent years, it still does good with the EPS 500 mb teleconnection patterns. My only critique is that it can be too weak with ridges along the East Coast and show too much ridging  near Alaska. This was the case recently with it having too weak a +EPO and too slow a Pacific Jet. It also seems like the GFS was a little faster to show the Pacific Jet flattening the Western Ridge and big -PNA drop. 

[EasternLI]

3 minutes ago, bluewave said:

This will be the first test of the newly upgraded Euro with a coastal storm in the winter. It had been having suppression issues with coastal storms in recent years. So if the models like the GFS and CMC are right about a track closer to our area, then they weren’t able to address this issue on the upgrade. But if the CMC and GFS go south then we’ll know the issue was fixed. While the Euro has been the top scoring global model in recent years, I have never seen any official statistics for East Coast storm track performance. Maybe the model is tuned for performance in Europe? Even though the Euro has struggled with East Coast storm tracks in recent years, it still does good with the EPS 500 mb teleconnection patterns. My only critique is that it can be too weak with ridges along the East Coast and show too much ridging  near Alaska. This was the case recently with it having too weak a +EPO and too slow a Pacific Jet. It also seems like the GFS was a little faster to show the Pacific Jet flattening the Western Ridge and big -PNA drop. 

I would be really interested in seeing some model scores for east coast cyclogenesis. I don't recall ever seeing a product like that. Or even a study, though maybe one exists somewhere. Would be fantastic if a product like that existed. 

[bluewave]

37 minutes ago, EasternLI said:

I would be really interested in seeing some model scores for east coast cyclogenesis. I don't recall ever seeing a product like that. Or even a study, though maybe one exists somewhere. Would be fantastic if a product like that existed. 

They have a site called confluence that reviews how the Euro did with some individual East Coast storms. The case below was for the January 2016 blizzard. It had too much storm suppression keeping  the heaviest snows south of NYC.  That was the one of the biggest NAM wins that we ever saw. 
 

https://confluence.ecmwf.int/display/FCST/201601+-+Snowstorm+-+US+east+coast

5. Good and bad aspects of the forecasts for the event

• Early signal (from Sunday 17 Jan 00z) and very consistent forecasts
• Too low accumulation over NYC
• Question about snow density for the case

 

[wdrag]

1 hour ago, bluewave said:

This will be the first test of the newly upgraded Euro with a coastal storm in the winter. It had been having suppression issues with coastal storms in recent years. So if the models like the GFS and CMC are right about a track closer to our area, then they weren’t able to address this issue on the upgrade. But if the CMC and GFS go south then we’ll know the issue was fixed. While the Euro has been the top scoring global model in recent years, I have never seen any official statistics for East Coast storm track performance. Maybe the model is tuned for performance in Europe? Even though the Euro has struggled with East Coast storm tracks in recent years, it still does good with the EPS 500 mb teleconnection patterns. My only critique is that it can be too weak with ridges along the East Coast and show too much ridging  near Alaska. This was the case recently with it having too weak a +EPO and too slow a Pacific Jet. It also seems like the GFS was a little faster to show the Pacific Jet flattening the Western Ridge and big -PNA drop. 

Excellent considerations and we should see what happens.  I do find it very difficult to believe the 00z/4 EC nada p and therefore it's tame EPS. To me, the WAA pattern induced after the 00z/7 CFP for 12z/8 should do the trick for qpf.  Learning time...

I tend to favor the EC inside 6 days, though I'm aware it's far from perfect...just tending to be a little better than the GFS.  

I like the idea of regional scores and also scores at the surface or at least 850MB (wind, temp) ... that's where it counts but of course resources and capabilities may be too meager to attempt. 

[eduggs]

2 hours ago, wdrag said:

As noted above 00z/4 EC and UK are much weaker or nothing.  For now, take that with a grain of salt.  BUT, does tell us that uncertainty continues large and prepare for less than desired.  

I checked the 00z/4  NAEFS and it's still on board-the bigger concern I have is the marginal thickness. I can see sleet/freezing rain as more of a problem than snow.  

03z/4 WPC probs for significant snow/.ice  remain the same, but that is without the toned down EPS.    

I sure hope the EC/EPS comes back in the next few cycles, otherwise have to think wasted thread. 

Gut says this comes back north and agree that this feels like a potential ZR/IP situation. Cold surface in situ, especially around 925mb. And then the orientation of the upper levels with the longwave trof fairly far west and plenty of room for a strong southerly component to the mid-level flow.

[hudsonvalley21]

06z GFS  eye candy run for interior folks

 

[MJO812]

12z icon has a nice track and hits SNE hard

[NEG NAO]

The one model that has been consistent run after run is the CMC - snowstorms do happen in unfavorable patterns - IMO something to consider

[MJO812]

Gfs cooled once again 

Hits interior  hard

[EastonSN+]

Seems like 12 z shifted north. Would hate to have cold rain

 

[jm1220]

4 minutes ago, EastonSN+ said:

Seems like 12 z shifted north. Would hate to have cold rain

 

That’s exactly what I would expect if you live near the city or coast. Setup wise this isn’t one that favors us. Not sure where you are but if you’re near I-84 and north, sure. 

[MJO812]

9 minutes ago, EastonSN+ said:

Seems like 12 z shifted north. Would hate to have cold rain

 

Precip and cold shifted south.

Ukie is a miss 

Cmc is also flatter

[MJO812]

4 minutes ago, jm1220 said:

That’s exactly what I would expect if you live near the city or coast. Setup wise this isn’t one that favors us. Not sure where you are but if you’re near I-84 and north, sure. 

With the fast flow , a miss is more likely.

[snowman19]

6 minutes ago, MJO812 said:

Precip and cold shifted south.

Ukie is a miss 

Cmc is also flatter

I agree, the GFS is trending to the Ukie and Euro and now the CMC, I expect the ICON will follow later. You were right about the fast flow shearing it. 

 

[SnoSki14]

9 minutes ago, MJO812 said:

With the fast flow , a miss is more likely.

A rare time when an unfavorable pattern could help us out. But it could also get sheared out.

[MJO812]

5 minutes ago, SnoSki14 said:

A rare time when an unfavorable pattern could help us out. But it could also get sheared out.

Yep agree

[MJO812]

Cmc and Ukie 

[NEG NAO]

12Z Euro - looking better

[winterwx21]

6 minutes ago, NEG NAO said:

12Z Euro - looking better

Looking better if you like the colder but much weaker scenario. Right now most models are painting a picture of light snow with a coating to an inch or so. We'll see if this continues to change.

[MJO812]

6 minutes ago, winterwx21 said:

Looking better if you like the colder but much weaker scenario. Right now most models are painting a picture of light snow with a coating to an inch or so. We'll see if this continues to change.

Eps is also cold enough for snow