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A moderate to major 6-12 hour snowstorm will occur Monday, mainly from somewhere within the I95 corridor southward. Snow, sleet, rain or freezing rain should begin between 3 and 6AM in NJ and NYC-LI-s CT around 6A-8A. Any mixed precip will change to all snow soon after beginning. Temperatures may be still be just above freezing at the start, but drop into the mid 20s by 10AM with wind chill down into teens and north-northeast winds gusting 20 to possibly 30 MPH. Drifting snow should develop wherever amounts exceed 4". 12z/2 NAM 900-500MB and 800-600MB banding suggests 1-2"/hour snowfall for a couple of hours during the height of the storm across central NJ and southern-eastern LI. Details of how much and where the sharp cutoff on the northern fringe (NYC), NNJ/s CT/se NYS still to be determined but too many models have slowly shifted northward the past day of cycles to prompt concerns for a significant impact storm. 03z and 09z/2 SPC SREF modeling has broad range of solutions but suggest close to 5" LGA with the blizzard conditions remaining just offshore. Let's keep the modeling-storm discussion in the January thread til after the 9PM (00z/3 NAM cycle has posted through Monday). MPing may be helpful. The 12z/2 ECMWF Kuchera snowfall map has been added per our thanks and appreciation to the ECMWF-Weather.US. This is a single operational member of all the modeling but represents potential... This could shift a bit either direction with time and amounts might end up significantly less in some areas but overall, it seems to have the axis of high impact travel concern fairly well outlined.

637AM Sunday: : headline updated to Major near blizzard and added power outages. Major near blizzard Nor'easter coming. I would not plan on driving anywhere on Monday in northern NJ, ne PA, se NYS and ditto CT Monday afternoon-night, MA Monday night. NYC my guess is a foot, possibly more before mixed Monday night. Otherwise, amounts between 1-2 feet from I78 northward with lesser 8-18 inches CT and MA where rain/sleet invades later Monday night. Isolated 30" possible nw NJ, or ne PA into the Catskills by the time this storm ends early Wednesday.. Drifts 3-4 feet. Power outages possible Monday afternoon and night from northern NJ northeastward to CT and Boston from a combination of heavy wetter (heart attack for the hear tcondition vulnerable) snow and northeast wind gusts of 40-55 MPH. Snow starts central NJ around 3 PM, northern NJ-ne PA 6-10P, CT around dawn Monday. Worst of the storm NJ/PA sunrise Monday-midnight Monday night, CT Monday afternoon-night. Coastal flooding may be major near the midnight Monday high tide cycle? Follow NWS. ---- 615AM Saturday: Imperfect probably messy big snowstorm is coming, imperfect in that modeling the past 24 hours is drifting north and suggesting a dry slot late Monday will allow enough warming for sleet (rain LI) to I80 including all of I95 Monday night so that the stratiform burst of 1-2"/hr Heavy snow during Monday, especially afternoon, becomes bands of snow in the interior late Monday night-Tuesday, some areas probably recovering Tuesday with several hours of no precip. So, my own single forecaster point of failure but use of ensembles could be too pessimistic about the sleet/rain intrusion. For NYC... I'll start with 6" with possibly as much 1/2" late 31. Hope that its mostly snow after 00z/2 but even if, snow ratios may be down to 7 or 8 to 1?? I dont' want to cap NYC since am uncertain about dry slot. Sleet/rain/freezing rain may be getting involved Philly to Toms River during Monday morning. There may be a period of near blizzard conditions on LI centered Monday afternoon? BUT, I don't want to call it a blizzard for fear of easily missing criteria. The point of this paragraph, is that I think Monday, especially afternoon should be the worst period of travel and if models continue this, in future cycles through Sunday morning, then I think it would be a recommended no travel for that 6-12 hour period to limit accidents and allow plows to maintain passable-less slippery conditions for first responders. Snow may be wet on LI/Monmouth-northern Ocean Counties in NJ if 6" at 32-33F, we would have power outages... still too early to be sure. CT I84... continue to notice some multimodeled lesser snowfall there, so while I think a big snow there, cautioning myself. Coastal flooding: see NWS statements/flood watches already posted and no change from yesterday with the late Monday evening high tide cycle most favored for flooding (within 2 hours either side of the time of high tide) Graphics are the 00z/30 EPS as a base amount, the 00z/30 EC IR prediction for 06z/Tue showing the dry slot penetration, and the NWS 09z/30 prob for 6" or more of snow by 12z Tues. That's the reasoning basis for this update.

553P/12: South of I80 and also all of LI: probably no snow except possibly a short period of wet snow, melting on contact Friday. For the interior suburbs, especially elevations nw to ne of NYC, this could become a problem wet snow impacting power, and for those with heart conditions - safe removal of the water loaded accumulations. Shovels and plows may be of value in the hilly areas Friday morning,. Banding is likely to occur Thursday night-Friday in the northwest sector of the upper low that will enhance precipitation rates in some areas. EPS 850MB easterly inflow as of the 12z/12 cycle was twice that of the GEFS, Therefore, the ensemble snowfall yield from the GEFS is minimal - under 1" while the attached EPS is considerably more. It's too early to be overly confident of 6+" of wet snow, in parts of the extreme nw part of the forum, but certainly possible. IF 6" were to occur at 33F, I'd be thinking of power outages by 9AM Friday. Snow water ratio's may be less than the 10 to 1 used by the ensembles. It should be noted that the WPC Monday outlook for 3+" of snow is only spotty 10% chance in the Catskills. I think this is largely based on the GEFS. Still marginal temps and a breakdown in the 850MB inflow to a weaker GEFS solution would nix the risk of heavier snow. The bulk of any snow should accumulate during Thursday night, lingering into Friday with possibly a second batch of trailer heavier snowfall in the wraparound band Friday evening, especially CT/MA high terrain. As the snowfall rates lessen during midday Friday and afternoon, it could change back to rain. It is an interesting situation and not unheard of. Even last May 9 we had accumulative snow in some of the suburbs, so I don't think of this as a new normal. In summary: Looks interesting for the hilly areas northwest to northeast of NYC. How much and is it worthy of a thread, we'll know in 5 days. I'll be following the NAM/GFS positive snow depth change... that to me becomes the minimum to look for, once it is consistently established from cycle to cycle. And of course, Kuchera and NWS products. Small chance gusty winds 40-45KT e LI Friday?. Meanwhile, LI/CT/se NYS, ne PA should pick up a general melted combined rain/snow of 1-2", iso 3"?

Snow begins in spurts this afternoon-evening NJ and ne PA and reaches NY and se NYS LI 9PM -3AM and CT 4A-8A Monday. Heaviest continuous snowfall Monday LI/NJ/nePA, but the heaviest delays til Monday afternoon-night in CT. Power outages should become numerous Monday afternoon-evening ne NJ/se NYS/southern CT and all of LI. Coastal flooding for 3 successive high tide cycles beginning late morning-midday Monday with the worst moderate to major flooding possible with the late Monday night high tide cycle. Starter graphic is the snow depth as of Sunday morning 7AM.

Good Wednesday morning everyone, I've followed a recent example on the New England forum and offer this topic as a start over at 1PM with obs-nowcasts. The tags included hopefully cover the gamut of potential amounts. If we are certain about daily records being exceeded please add and ditto if we get top 20 at any xmacis climate site. Thank you all for contributing to the excitement-anticipation of a pretty good nor'easter.

Edit topic: 525A Wednesday 12/16: No change in thinking including uncertainties along I95. I just cannot shake the basics: S+ axis is usually 90 miles left of the 850 low and the northern half of the 700MB low and the deformation zone near 500 MB with contribution from the nose of the 850MB 50-65 kt easterly jet (moisture transport). This favors I84 and banding casts northwest to a central PA - east central NY area (roughly IPT-ALB) where 20-25" seem probable within 60 miles of that axis - at least in the high terrain, but must consider mountain shadow lesser amounts in the leeward valleys. There a multiple models showing that axis. In our forum, I think most everyone will see a period of sleet near or after midnight and that the bulk of the snow occurs in a 6-10 hour period prior ~ midnight, but that there will be a tail of moderate to heavy snow toward dawn with still 1-4" after sunrise Thursday on top of whatever occurs before sunrise---the heavier 4" potential ne PA, extreme nw NJ, se NYS and CT {where 5" may occur in 2-3 hours after sunrise Thursday}. Drifts to 4 feet possible ne PA, se NYS and northern CT where 18" accumulates since winds will gust 30-40 Mph at times overnight. NYC CP still 6-10" in my mind but shakey and may be too high because of only 10-1 snow ratios at best, sleet and possibly rain compacting as well as temps near 33F at times during the night. The power outage concerns continue near I95 with 45-50 MPH gusts (9P-6A). Coastal flooding - please see NWS offices for minor or moderate near the time of high tide Thursday morning. Finally, even if it rains or is above freezing w LI and Monmouth/northern Ocean County NJ tonight--- there could be sudden icing near sunrise Thursday when the wind switches from northeast to north and drops temps 5-10F in an hour, and iceing the residue and make travel very hazardous again in leftover new snowfall. Otherwise temps in the I84 corridor ~20-25F throughout the event. Will add some graphics by 6AM on wherever the last page of the thread. NOT a top 20 for NYC...best chance is MPO-POU axis in our forum. This is my last topic update for this event. Edit Topic: 445 AM Tuesday 12/15: NO change in thinking. Except for the outlier south GFS/GEFS, all systems appear go for a major snowstorm as outlined below in the 6AM Monday topic update. Will detail in the latest page by 545AM. 00z/15 EC/NAM/RGEM/UKMET/GGEM/UKMET operationals on board! There will be multiple (~12 graphics of supporting model documentation-most probabilistic and 2 day top 20 snowfalls in the available period of record). --- Edit Topic headline at 6AM Monday 12/14/20. Please monitor NWS Watch-Warnings for this storm and associated statements and still uncertainty on where highest impact. There is/was some overall slight southward shift in the guidance in the past 24 hours and so my uncertainty for the forum is northern CT-Catskills, and LI/I95 southeastward. WPC still has 1.5"+ qpf just s of I80-LI and 3/4" into northern CT. If you have travel plans Wednesday into Thursday I95 northwestward from VA through WV, PA, NJ, NYS and southern New England it's probably a good idea to consider changes, based on your NWS or other favorite media outlet forecasts. I think this will be a top 20 snow storm for a few parts of our NYC subforum (basically ~ 1 foot will prompt that review) but unsure where. For now between I95 to I84. Anticipating (not guaranteed) widespread closures or delays for all transportation systems I95 corridor northwestward Wednesday evening into Thursday morning,. For those who have access and wish to do so, you can calculate an experimental storm index to get an idea of what is probably coming. I don't want to presume more than Major yet (crippling is the next step up). Here is some information. https://www.ncdc.noaa.gov/snow-and-ice/rsi/?nesis Still variability in northward extent of heavy 1 foot snow ranging from the NAM Adirondacks to the GFS-RGEM I80-LI. UKMET is still quite far north. Ensembled r/s line looks to remain mostly south of I80-LI but awfully close, close enough to think sleet, rain or freezing rain mixes in for a time after the initial Wednesday evening thump for LI and s of I80. EPS continues almost unyielding on the widespread 8-18" snowstorm (isolated 2 feet possible in the banding somewhere north of I80-LI). Major power outages possible wherever the 6" of 32-33F wet snow accumulates along with wind gusts of 40-50 MPH. If this were to occur, it would most likely develop between 9 PM and midnight Wednesday evening per consistent modeling of snow onslaught and wind gusts increasing past 30 MPH. Am targeting LI south coast and NJ coast but this will require 6" wet snow (32-33f). Isolated wind gusts above 50 MPH possible on those coasts. Snowfall rates of 1-3"/hr possible in northward transiting bands Wednesday-evening/ night. Where these tend to park on the northern extent of the storm, will probably be the 2 feet of snow, especially with ratios drier than 10 to 1 (maybe 13 to 1). NWS has the multi model ratio blend tool and BUFKIT can assist for those who have that tool. There could be closing bands of moderate snowfall Thursday morning after sunrise into early afternoon as the comma head tends to fold southeastward behind the eastnortheastward departing storm. Clearing the first few inches of snow around 8-10PM Wednesday will make it easier to remove the additional snow Thursday morning. Where it's wet-caution for those with heart conditions., This strong easterly surface gradient (northeast wind) between the cold 1035MB high over Quebec and and the probable 995-1000MB low near Cape May early Thursday will produce minor to moderate coastal flooding, for the Thursday morning high tide cycle. Follow NWS statements. No graphics update with this topic edit. --- Edit Topic time at 506AM Sunday... otherwise an 18-24 hour nor'easter coming with the uncertainties continuing as previously listed below. HIGH impact late Wednesday afternoon into Thursday morning with many cancellations probable of whatever activities in this Pandemic. It's 5-6 days away but taking my cue from our participants, have separated Wednesday-Thursday (16-17) from the prior 5 day (14-18) topic. Modeling is showing the potential for a 6"+ snowfall for a large part of the NYC forum area, somewhere between the I95 corridor and I90. There is model uncertainty regarding the intensity of the upper air and surface systems but enough information in the models to monitor this storm for possible high impact in parts of the NYC subforum. Some potential exists for nearly a foot of snow in a small portion of the forum area, IF everything comes together correctly... but it's too early to be sure and it's best not to focus on the higher amounts yet. Banding in the DGZ could make for as much snow along and north of I84 as may occur closer to the storm center in NNJ where the snow could be a lot wetter. Usually it takes -3 to -5C at 850MB this early in the season with wind off the 40's SST, for snow not to change to rain. So LI and the NJ coast are presently in the modeled greatest uncertainty region whether it's mostly rain or snow. Astronomically high tides Wednesday and Thursday mornings seem destined to allow some coastal flooding within 2 hours of high tide, but this is going to be driven by storm intensity and wind direction. Just too early have a good handle on flood potential but I would think minor at a minimum. Not posting a topic for late Friday-Saturday Dec 18-19 as that storm could easily pass to our south. Just good enough to know that appears to be a highly unusual week, potentially, for the NYC forum to have up 3 different snow events of varying magnitude in a 6 day period. Added this afternoons NWS ensemble driven D6 chance of more than 3" of snow, which has increased considerably over the past 24 hours. I also added the GEFS probability of half a foot of snow or more... use the legend color (greens-yellows edging past 65%) for your area of interest. The Dec snowfall's in NYC since 2010, 2nd column from the right. and The daily almanac for NYC CP-Wednesday Dec 16...the 5.3 " is the daily snowfall record. Small chance of daily record snowfall??

The models have been extremely consistent with this and have taken it from 240-252 hours out to now 126 hours out until the Western forum begins feeling the effects. Tonight's model suite features heavy snow for a large portion of the forum on all models. The GFS brings this per the 1-28 00Z. The GFS has been consistent with heavier snow north of 40 on nearly every run for 5 days in a row. Quite a few of these runs sees a nice bit of accumulation well south of 40 as well. The Canadian was late to the party and is still waffling around. It painted the entire region almost with heavy snow during it's 1-27 runs. Today it moved the snow axis very far north at 12z, the 00z quickly brought it back, this time west of the Plateau and north of 40. The Euro has been pretty consistent with this as well. It actually moved towards the GFS a few days ago and for the most part has held to it's solution for several days as well. Tonight's 00z run was it's most robust into Tennessee in several runs.