wdrag

Just a note: This thread will serve as the obs thread for this afternoon-Sunday obs and also continue comments on the Tuesday-Wednesday event.  A new OBS thread for Tuesday-Wednesday will issue 7A Tuesday.

fwiw--- I think NYC-LI is going to see some wet sloppy slushy snow acc on cars/grass 4P-10P and whether it is observed at CP I'm not sure but I expect 1/4-2" because of bursts of moderate snowfall 1/2MI vsby.  That despite temps above freezing, which I think will have to cool to 33 in snow after sunset.  Too much modeling is showing snow NYC...but temps will determine whether we can measure there. Am noting dewpoints not very far from freezing through this entire event for NYC north.  So--I may be very wrong but it's not worth the risk of a nil call being wrong for travelers.

I myself will continue commenting on this event in the original NY eve, two storm thread for consistency as the two storms = feed each other the results by Jan 10. It will also demonstrate how effective (or not) use of consensus modeling (ensemble blends) can be for preparation purposes out to 10-days in advance and how CPC hazard tools are probably underutilized.  Others may post here but I will post in the original thread with only a new obs thread for that storm issued at 7AM this coming Tuesday when we've exhausted model discussion. 

fwiw... 4PM NWS collaborated snow forecasting experimental impact.

For me, looks half an inch or so conservative I95 where I think an inch will fall but melt quite bit on initial contact 2-4PM. AFTER the initial thump goes by around 9P, it warms aloft for a few hours.  Matter of temp during snow. If 33 CP Will get some whitening on the snow board.  NBM and most models pretty conservative so that's the prevailing forecast.  None of em are easy.

fwiw.... T sections for NYC (LGA) when large dendritic growth shortly after onset arrives NYC on the GFS and 3K NAM.  Temp lowest 25 MB in question and if its snowing...wont be more than 33-34 at 7PM Sat evening.  00z/7 CP ob may have some snow acc? 

Anyway, this is another way to look at a specific location vertical profile. On sample.  Can do moisture, R#, wind profiles etc. 

4 minutes ago, allgame830 said:

You guys waffle back n forth wayyyy to much with every model suite…. It’s not a trend until the same solution verifies in multiple model suites!

agreed...

RGEM NAM HRRR cyclic repeatable trends may be helpful. 06z/5  HRDPS is too heavy but its colder.   

Elizabeth warehouse fire right now ... on TEWR radar...particulate matter blowoff. 1/5/24 628AM post

NWS 4AM snowfall forecast and resultant impact expectations if and when many of these forecasts verify Saturday night-Sunday. 

As you know I';ve become a fan of the base amount forecast to limit expectations, worst case double 

8 hours ago, psv88 said:

Thanks Walt. It’s very informative to read your analysis

reality-- lets see what happens.  I'm still with it as attempted to predict via these posts last eve. 

8 hours ago, RU848789 said:

I assume you've seen the latest WPC graphic on QPF from now through Wednesday.  3-6" for most of the EPA-NJ-SENY region would likely put many streams and river basins into major flood stage.  

Yes... this combo event - I can't rank it historically but no doubt the runoff next Wednesday should have rocket rises of small streams with slower rises of large rivers I95 corridor NJ/PA.  My concern if sump pump and power outages..then what. Detours and I think some evacuations in vulnerable flood zones may be necessary but we need to see how this plays closer to Tuesday. All I know, preparations as best as possible next few days which means cleaning storm drains today or Monday-Tues morning and just making it easier to mitigate what is coming in a 9 hour dump of 2-3" of rain, compounded in NJ by snowmelt. 

7 hours ago, jm1220 said:

Although @wdrag does give me hope there could be a surprise here. But definitely not banking on it. It could be easily the other direction-some slush to rain. 

It will almost definitely start as snow or r/s mix, but pavement probably won't accumulate... and over to all rain by 11PM but back to r/s mix Sunday morning.  Again... no one expected big snow I95 east but take what we can get. Am sure lots of reports will be coming in around 4-5PM Sat. 

am done for the night... flushing it for now. 

17 minutes ago, donsutherland1 said:

Latest EPS and NBE information:

Be wary of snow maps e.g., the 18z NAM's depictions below:

A significant share of the precipitation is rain or mixed precipitation, not snow. For example, at 75 hours when the NAM is piling on the digital snow, the sounding shows the above freezing layer extending almost to 975 mb with above-freezing surface temperatures. Over New York City's urban heat island, that's not accumulating snow. The precipitation ends as snow, but accumulations will likely be limited. Outlier models for heavy snowfall that lack support should be disregarded given the marginal air mass and historic experience with snowfall at above freezing temperatures in New York City.

 

 

 

 

 

 

 

the 18z NAM looked off... something not right about it. It's companion 3KM looked better.  Your stats seem to me to  indicate 1" categorical NYC (not 100%).  I have great respect for Cliff Mass (NBM) as I do for Lance.  In the case of of the NBM, its at 0.6" as I interpret.  That is splitting hairs. 1 hr dump at 33F and measuring at 05z could make it 1.5.  The idea though... NYC from your stats should at least see a r/s mix for a while at the start and I think the bulk of Sunday, if not all snow at the start and end. and some sort of whitening of the CP ground. 

Now that we're at 48 hours away... from 2"- 8PM in Wantage NJ... I'm thankful that so far, that which makes forecasters queazy because of a sudden warm wet, or goodbye out to sea "probably" won't be happening. 

I'll be keeping this thread active through about 12z Tuesday, with obs for whatever happens this first storm embedded. 

At about 12z Tuesday, I'll get the OBS thread specific to the 9th-10th started as it is going probably be many pages (flooding rain, damaging wind, maybe front end snow west of I950. This storm as you're probably aware has potential for 2-3" in 12 hours (rain) and melting whatever water equivalent in NJ (mainly I80 south) is going to result in very rapid rises of rivers on the 10th. Looks to me like considerable river flooding of varying magnitude, awaiting reality. 

Passaic Pine Brook, IF 3" occurs total from these two storms, it goes to MDT flood on the 10th. Some our BOM guidance has 3.5-4" for basins.  Not sure if it will be that much but if your sump pump dont work because of power outages... 

Worthy to monitor. Not Sandy etc but pretty significant.

2 minutes ago, HVSnowLover said:

This is likely an oversimplification but last year the RGEM never got in board with basically anything. Every winter is different but the fact it doesn't look that horrible I think might be a good sign.

That in my opinion is correct.  Canadian has to be on board for synoptic scale snow. 

Lets look at the 00z-06z/5 NAM thermal profiles for NYC.  My guess is there will be steady snow much of Sunday NYC-northern Li but melt on pavement and have difficulty accumulating on grass during midday bit its all sub the about temps 32-34 and precip rate.  For now I think odds are under 3" CP-northern LI and mostly likely 1/2-2" but I've been wrong before.

I dont know if anyone has noticed the cyclic steadiness of EC and GGEM. 

Now I'm switching down to the HRRR, NAM RGEM.

49 minutes ago, HVSnowLover said:

I certainly don't take the nam seriously but the euro, gfs, and rgem are not that bad for most of the subforum away from the immediate coast. Only the CMC seems like a complete whiff SE of I287.

Watch CMC trends... it tends to run warmer than NAM. HRRR ag 48 hours tends to run warm and then as we trend close toT0 it should cool.  Those two models are my overall operational experiences. 

Stats are helpful...they temper enthusiasm but sample size can also have new contributions that are not in the more plentiful solutions.  

NBM has been steady through all the recent dailies.

 Even 18z EC has only 33F NYC Sat night... good VV and timing with the midnight ob might yield an inch Manhattan.  Think its going to be interesting NYC and northern LI.  Nothing off the table yet...in my mind.  I want to see if the 00z/5 12KM can settle on something more reasonable than its 18z predecessor. I'll  be sleeping when it comes in. 

44 minutes ago, Dark Star said:

and where is the cold air coming from?  

western USA looks like it wants to seep east.  Seems like we have an interesting two months in progress. 

9 hours ago, WestBabylonWeather said:

Such a nail biter for LI 

No more nail biting there, I don't think.  Northern LI-NYC have a hard time with my expectation T-2" due to above freezing temps. You still have hope at the onset 5-9P Sat and Sunday departure 9A-3P.   Just have to be realistic. Here's the Blend of models from 2AM today. 

18z EPS is within a tenth of an inch on its new qpf for the Sat night -Sunday morning snow storm. I've added an 18z EPS graphic 10 to 1 ratio chance of 4+.  While I do not like using 10 to 1 ratio as a first guess... in the all snow region 10 to 1-Kuchera should work but always keeping in mind the base Positive snow depth change. I'll keep pounding this since it's the easiest way to reduce disappointment.  For NYC... EPS Positive snow depth change is 2" now...so within there 1-4 bracket. We're still about 72 hour from the start... so I can't say its a lock yet but hope exists for northern and Western LI to break the less than 2" curse. 

6 minutes ago, Tatamy said:

Snow amounts on here are a lot greater than those shown on its ensemble mean.  

That's because many are using 10 to 1.  That doesn't work well with melting processes. Everyone in the longer range should start with a base of POSITIVE snow depth change. Then you can look at top end of the range with the 10 to 1, if no sleet/rain. Sleet is converted the same way as snow in the 10 to 1 so it biases amounts high along the warmer edge of the snowfall forecast.

There will be banding and we can look at that more closely Friday, with greater confidence.  

I think we'll see clusters of power outages from wet snow and gusty northeast winds 30-40 MPH early Sunday somewhere near I78 if the snowfall there is 4" or more and falling at temps of 32-33F. 

Otherwise, I kind of think the original plan thread plan still looks reasonable.  Impacts will be much more substantial 9th-11th with I think widespread river-small stream flooding up and down the east coast along the I95 corridor from NNJ southward to Philly and down to NC. Some rivers may go into the low end of the major flood category, provided two storm rainfalls exceed 3". This and wind damage potential looks pretty significant across the eastern third of the country for 9th-10th, plus of course 1/2-3" wet snow I95 west to start that second storm.

Temps into the 50s on Wednesday the 10th I84 southward will add the snowmelt contribution up here in NJ southeast PA. 

You're welcome to chatter here about he 10th, but for sure after the 7th all that belongs in the current two storm thread.

I have no plans to start a snow thread for the 13th-15th, until the 10th when we are solely posting damage combo 3" water equivalent snowmelt-rainfall/wind reports in the obs thread for the 9th-10th,  that one I'll start the morning of the 9th.

For now I'm now seldom commenting on modeling for both these next two storms in the primary 6-7 9-10 thread. 

Hi!  Haven read anything since last eve... I'm sure there was consternation with the 00z/06z GEFS-GFS. Fortunately the EPS is back up as is the CMCE. No change to my own overall thinking since the thread inception, NYC 1-4" to be further adjusted if needed. Just caught Don's post about rations.  Good post.

Won't be back to post til sometime this eve. Was on call First Aid driver overnight with two calls.  

Enjoy as you can what's coming 6-7 (split short waves makes this a 24 hour event instead of one bombing 12 hour storm), 9-10 and now looks more and more 13-14. I know if you dont get 4" of snow, unhappiness.  s LI looks worst chance 1". At least this was a tracker.  It's coming but exact details of snowfall etc tbd.  

12 minutes ago, RU848789 said:

Correct.  Here it is if interested.  Also, the link below has a very nice summary of what the model consists of, especially with regard to the various model inputs which get "blended" in the BOM (they're not all equal).  

https://luckgrib.com/models/nbm_conus/

well done on the link explaining.  Its a good start and should be paid attention to. Available via Pivatol Wx and probably other sources.

For the record nationally:  inclusive of our own top 10 wettest Dec, some climate sites top 5.  Top 3 warmest.  snapshot via CP, EWR, ABE for both temp/qpf vs yearly reality.

2 minutes ago, wdrag said:

Can’t hope.  Just have to work the ensemble pattern and negate smoothing out the cyclic changes.  No one has promised more than 1 NYC 

Negate should read.  Gently