wdrag

Wow... TOUGH forecast. I do think they will see sleet and rain after maybe 2" of snow to start. This based on 00z and 06z guidance. Could be wrong but thats a quick guess.

Good Tuesday morning, Dec 15. I have no change in my previously expressed opinions regarding what I think is coming. Not the worst ever, by far, but this will alter pandemic normal lives. If you have plans Wednesday and Thursday across parts of WV, western VA, PA, NJ along and northwest of I95 as well as NYS and all of southern New England, I would think twice (and probably change plans) about traveling there (especially 4PM Wednesday to 10AM Thursday). Follow local NWS Warnings/Statements/ forecasts and that of local government officials. Other than e LI and portions of coastal NJ near and s of Toms River, where an uncertain less than 6" of snow-sleet should occur, this will be a widespread 6"+ snow storm with a period of sleet possible in the overnight hours up to I80. The 45-50 MPH wind gusts are still expected on the coasts 9P Wednesday to 6A Thursday, This with the periods of heavy wet snow changing to sleet and/or rain should result in extensive power outages, somewhere near or just east of the NJT, or on LI. Moderate coastal flooding is probable along the coasts-inlets for the Thursday morning high tide (follow local NWS guidance). With a likely 10-20" of powdery snow from I80 (or I78?) northward through the I84 corridor, it will be time to sit back and sip hot cocoa and get into the Holiday Spirit. Those with heart conditions, be careful...the snow will be wetter and heavier as you get close to NYC. Otherwise removing a batch of snow around 9PM Wednesday will make it easier not to break overwhelmed with snow removal Thursday morning. My guess for CP is 6-10"--it will be wetter snow there and I think sleet mixes in and I could see 2-4" of snow on the ground there by 7PM. Top 20 snowfall potential exists for MPO, POU, BDR. Banding will be big and may overcome some slightly above freezing layers aloft to keep snow going over w LI and I80. The banding could yield isolated 2 foot snowfall somewhere near I84. These storms have suppressed areas and enhanced areas of snowfall and I've no way to predict where. So while you see the base snow amounts in the EC ensemble graphic... snow ratios will possibly add 10" to this in a few spots of ne PA or NYS, CT? Then there are snow measuring guidelines, and the 30 MPH gusty wind fracture of dendrites overnight Wednesday as well as drifting that will make it a bit more difficult to figure out the amounts. You may want to regionalize your post-storm assessment (the mean of multiple snowfall abs within a 15 mile radius?) Graphics are: NWS office collaborated impact product-please use as an experimental guidance. WPC 304AM QPF assessment. The EC EPS ensemble baseline 10 to 1 snow ratio snowfall (be careful southeast edge where sleet is treated as snow), the WPC probability of 6"+ and 18+". This gives a feel for confidence by the NWS and axis of concern. Added SPC Short Range Ensemble Forecast (SREF) plumes for snowfall amounts at LGA, AVP, POU, IJD. We see the spread in the members and mean (Bold line). Then close with the two day top 20 snow accumulations - Note the shorter Period Of Record (POR) at some stations. Sussex is in there to show that we have quite a hurdle to exceed here, but MPO, POU (valley shadow lower amounts??) and BDR are vulnerable for top 20. Follow local NWS products and the advice of officials. My posts do not represent the NWS, only utilizing all the available models-tools to the public including NWS generated products. I may be off-line many hours today and probably won't have a comment on whether I overdid this, until about 6PM tonight or 6AM Wednesday. Have at it and do the downside checks to help keep perception of future reality, realistic, with hopefully few disappointments Thursday. 533A/15 I'

Forgive me if this is a repeat... I haven't been following for 5 hours. WPC heavy snow discussion from ~430P. ...Appalachians/Mid-Atlantic to New York and Southern New England... The latest forecast continues to advertise a significant winter storm for portions of the central Appalachians, the Piedmont area of the Mid-Atlantic, and much of south-central/southeast NY and southern New England, as a nor'easter develops and lifts up along the East Coast Wednesday into Thursday. The wave that crosses the southern Plains Tuesday will eject through the Mid-South Tuesday night and is forecast to take on a negative tilt as it arrives across the Appalachians on Wednesday. This will promote cyclogenesis off the Southeast coast with low pressure then lifting north and strengthening along the Mid-Atlantic coast and then arriving offshore of southeast New England by early Thursday. Meanwhile, a cold, 1036+mb high will be focused over Quebec and will be nosing south down across the interior of the Northeast and the Mid-Atlantic with a rather classic cold air-damming event expected to be in place as the low center moves up the coast. As strong warm-air advection/isentropic ascent occurs ahead of the upstream trough along with increasingly moist Atlantic inflow over the cold air, a large swath of moderate to heavy snow is expected to develop for portions of the central Appalachians and the adjacent Piedmont areas of WV/VA/MD and PA on Wednesday with the focus west of the I-95 urban corridor, and the bigger cities of Washington D.C., Baltimore and Philadelphia. By Wednesday night and early Thursday the focus of heavy snow will overspread areas of southeast NY and southern New England including the New York City and Boston metropolitan areas. The latest model guidance favors a rather strong comma-head/deformation zone impacting especially areas of eastern PA, southeast NY, northern NJ and southeast New England on Thursday as the low center further deepens and then begins to edge east-northeast and farther offshore. Meanwhile, down across areas of northwest SC, western NC, southwest VA, and southern WV, the cold air will be much more shallow by comparison, and it appears likely that there will be a period of freezing rain and locally some sleet as the event ensues on Wednesday. Some of this may sneak up near or just west of I-95 as well from Washington D.C. to Philadelphia. But the threat of ice farther north closer to New York City and certainly Boston will be notably lower. WPC favored a a multi-model blend approach for the precipitation forecast with a tad more weighting to the ECMWF, and lesser weighting to the NAM and GFS. The NAM is farther west and warmer with the evolution of this system, with the GFS a bit colder and farther east. While not totally dismissing the NAM and GFS, a model consensus somewhat closer to the ECMWF and ECENS mean was favored for QPF and was applied to the thermal profiles. Based on the latest forecast, the expectation is for storm total snowfall to be as much as 12 to 18 inches for the interior of especially the northern Mid-Atlantic, far southeast NY and southern New England. Where freezing rain occurs, the greatest ice accretions are expected over northwest NC, southwest to central VA and over parts of southern WV where locally as much as a tenth to quarter inch of ice will be possible. Added the collaborated snow range from the mid afternoon NWS forecast cycle. And , an example of the primary band of lift for ~4AM Thursday (18z/14 NAM)...in an arc fro nw NJ to SNE. IF this is reliable, a band of S+ should be occurring near or just north of the arc.

Wow... not sure when that changed? I do think this will suppress amounts do to settling, drifting. Up through March 2018, it was clear the board every 6. Anyway, you're saying 24 hrs... that's what it is. Thanks! Walt

Hi! I don't have any big changes for our forum... My thinking is we have a 6-12 hour blitz of with lingering lighter snows extending this to 20-24 hours. The EPS continues solid 1" to just s of the MA Pike and I agree with posters about sharp cutoff near or just n of I90. I also have concerns about the I95-LI stretch (PHl-NYC ) sleet/cold rain/junk mix after the first few hours off thump that will need traveler behavior modifications (S+ for 1-4 hours?) . Still the EC EPS continues steadfast on a nose of max snowfall from near HAR to somewhere along or just s of I84 to near BOS? I don't have enough time to study the 12z cycle (Xmas cards). This is the NWS collaboration. I do think this will be high impact nor'easter. Not the severity that it could be because it's shorter duration and not quite the gradient but folks are going to be shoveling and my thinking, they don't want to be out traveling in our forum roughly 6P-3A. I have to think a slew of watches will post by 4PM...then we just have to do what the NWS does... be patient, head for a reasonable blended solution and emphasize their points via social media. I think our topic is good... probably a touch overdone on top 20 snow event. Will NYC set a daily record snow tomorrow. I don't know. Can we get to 20" (several 20" reports) in our interior hilly forum... maybe but it's not my emphasis. If we see a widespread 6"+ snowstorm with a band of 12-15" ne PA/extreme nW NJ far se NYS into CT... I am satisfied, particularly since this has been modeled very consistently for days. LI/coastal NJ i our forum... no confidence yet on inches. 311P/14 One additional note: You may be noticing strange pockets of heavier and lighter qpf, ditto RH dry and wet fields at 700 and 500 MB. That's model signs of banding..modulation of the qpf fields. I'd look at the srn edge of the 700-400 moisture for potential banding,. 313P/14

Typically CO-OP stations and CoCoRAHS sites measure 1x/day...max depth on the board since the prior morning ob. However, more accurate snowfall that limits settling-drifting etc is taken every 6 hours with a snowboard wipe. Snowfall: Measure and record the greatest amount of snowfall that has accumulated on your snowboard (wooden deck or ground if board is not available) since the previous snowfall observation. This measurement should be taken minimally once-a-day but can be taken up to four times a day, (every 6 hours) and should reflect the greatest accumulation of new snow observed (in inches and tenths, for example, 3.9 inches) since the last snowfall observation. Here's the link. https://www.weather.gov/gsp/snow Hope this helps. Walt

Wantage NJ ... final 0.9" at our Wantage location - 740' MSL. Snow after 1P melted on contact. 34.0F at 237P.

Ditto this part of Wantage Nj ~740'MSL 1PM 6 hourly...deck cleared for new snow after the first 6 hr total was 0.9" Pavement 1/3rd" wet slushy. 33.4F gentle 1 to 1.5Mi s-.

WOW... 25mm light orange is 1" melted in 12 hrs. still big. my experience, often the big qpf has sleet and rain. In this case... i dont have much to look at but I'm wary of ALL snow in 1.5" qpf unless clearly the soundings support. You all are on top of this. Hang on... even if we don't get top 20 snow, some folks on LI and NJ are probably going to wish it was powder. It just looks a little dangerous to me with sleet slashing through the air on gusty winds or wet snow pasting on the NJ coast and parts of LI. 6" 32-33F wet snow is my threshold for widespread power outages. It first begins with 4" wet snow. Talk after 4p.

I think everyone up to I80 will mix but this is yet to be determined. It's going to be a mess I95 in Nj and LI after the initial thump. Maybe UVV will overcome but whenever, the dry slot arrives, then I think thereafter we look at sleet and small flake snow...if indeed the dry slot arrives with maybe a chance of a little bigger flakes on the swan song Thursday sunrise or after. Again, this presumes a sNJ coast hugger overnight Wednesday before shifting eastward. Let's see the EC, and really some more model cycles. Future NAM has to backdown too if we go with the CMC/RGEM/GFS. Plenty of unknowns. Patience

watch for sleet LI and s of I80 which is treated like 10 to 1 in the snow ratios...bad news for southern edge if sleet develops. Those 10 to 1 ratios won't work with sleet involved... slash by ~2/3rds once the sleet develops.

Euro EPS has been very very steady through 06z..just ever so slight southward drift. If the GFS is to win this southward track, the UK and NAM need to come south, and then the EC will join. 12z UK may have some precursor trend soon?? For now...stay the course on everything... allow NWS office and WPC collaborative processes work up the 330PM updated graphics. Ensembles can steady the model disparity. A snow storm is coming to the northeast an impressive 6 hour thump Wednesday evening-night.

Wantage NJ. Almost 5/8 mi. coming down pretty good ... small to moderate sized wet flakes. 33.3F at 1115A

Wantage NJ 0.5" total now and 0.1-0.2 slush on pavement..some pavement starting to get slightly slippery. If this keeps up thru 1P, they'll need a little salt on the rural roads above 700 feet.

Wantage NJ 0.3" at 10A - continuing 3/4s- 3.3. acscums on trees/roofs, grass but only sketchy on some untreated pavement.

Wantage: 3/4S- decent flakes. I see that nice bright band on the backside of this event just se of BGM... Some of that has to be pretty decent snowflake size.

Wantage NJ 4sw: Had mostly r- and some ip- for about 90 minutes but all snow (2mi) now. 0.2" total so far...its wet snow out there but didn't clear. we'll see what we have at 1P. 33.1F. pave wet. 942A

Don't give up on snow in NYC this afternoon. Could get interesting for an hour two around 1-3P.

Let's wait this out... I need to NAM to be more realistically south and closer to EC or GFS. It cant keep trying to drill big snow into the southern Adirondacks.

Hi! Gradient collaborated grids that see adjacent offices and work with together with WPC. So qpf, whether its all snow and the associated mixing ratios dictate snow amounts. These are put together sometimes before new guidance that you and i see and sometimes hastily because of the eastern time zone and 330-4PM/AM deadlines (deadline office dependent). I'd take the lower numbers of the range as a start, and focus on the axis. I want to reserve comment on anything beyond what we see here, til 430 or 5P. Too many models and interps...

Mostly rain here since around 810A in Wantage. at least 0.2" snowfall so far. 33.1F. roads wet.

Need to wait til 4P....thanks

NWS collaborated snow amounts in case this hasn't posted yet... only thru 7A Thursday. Temps will probably be generally 20-25F during the entire snowstorm across nw NJ/seNYS/ne PA and CT.

Tables for JFK/LGA I think attached. Have looked at two day (crossover with the midnight climate... tougher for top 20 depending on where all snow but, MPO seems a best fit... others may too-dependent on track and mix potential. Won't post the two day til late today or tomorrow if that still applies.