wdrag

550AM sunday: This is mostly a Tuesday-Tuesday night event. Periods of mostly light snow, at times changing to sleet, freezing rain (rain where above 32F along the coasts) or freezing drizzle up to I80, NYC, LI. Snow amounts trimmed a bit and I sure hope NYC can muster 1/2-3" depending on precip type and intensity for this event. I pushed the start time back to 7P Monday but it could be delayed NYC-LI-CT til as late as 9AM Tuesday. Also took MODERATE event out of the headline. Banding signature suggests snow should break out across PA/NJ between 7P and midnight Monday. The primary event is the 26th, ending sometime Wednesday morning. While amounts are light, suspect there will could be a period or two of 3/4mi light snow - bordering 1/2S for an hour or two, from northern NJ into ne PA/se NYS and western CT. 06z/24 NAM banding signature and also seen in the 06z/24 GFSv16 qpf, that the heaviest snow may occur early Wednesday near NYC. This may be associated with a trowel/inverted trough/ departing shortwave with the weak seaward moving low pressure. Something to monitor but not get hopes overly high. So, manageable delays sometime during this event due to plowable snow northwest of I95, except snow-ice I80 southward in NJ to Baltimore and snow/ice/rain NYC-LI southward along the NJ coast southeast of I95. Amount expectations lowered to range from an uncertain 1-4" CT with the least in eastern Connecticut and a less than certain forecast there, to between 3-5" se NYS, ne PA and 2-4" nw NJ north of I80. Temps will generally be subfreezing throughout the event except NYC/LI/NJ coast which are in the margins of ice-snow at the start, changing to periods of rain then ending as snow, so amounts of each element will depend on duration but it will probable get slippery there on untreated surfaces for a time as well-especially if and when precipitation occurs during the nighttime hours. Check others herein and other resources for other opinions. Added some graphics which are probabilistic. use read the graphic and probability legend. I did not add the NWS regional snowfall forecast because it ends at 7P Tuesday.

Good Sunday morning everyone, Jan 24. I dropped the rain out of this Thursday 28th topic. Otherwise I leave with two WPC graphics from their overnight shift (chance of 3+" of snow --see legend-chance is in the 10-29% category for the southeast part of our NYC forum, and their QPF forecast). I see this as a grazer, at worst ,between LI-I80 and I195 (TTN east). There could be a period of snow or flurries up to I80/LI Thursday morning midday- but otherwise so far, guidance suggests mostly a miss to our southeast- development just a little too late. However, do monitor future guidance. There still is a chance of a track that is a little closer.

I think so. It really is nice, despite the degneral lack of snow. If we had more days like this we could skate here in nw NJ.

Low pressure in the Virginia's late Wednesday will get picked up by an intensifying short wave moving east across the Mid Atlantic states Thursday and become a pretty good sized nor'easter as it departs the mid Atlantic coast Thursday afternoon. Does development occur fast enough to bring significant wind driven snow to a part of the NYC forum (rain or snow LI/NJ coast?)? 12z/23 GEFS is fairly robust on qpf, but further south than it's 00z/23 version, while 12z/23 EPS and GEPS are indicating too little too late. One small caveat: the low levels should remain fairly moist after the Tuesday - Tuesday night ( 26th) event (whatever it is) and there may be some advance snow or snow grains/freezing drizzle/drizzle late Wednesday or Wednesday night, in part related to leftover moisture and some sfc convergence. That too is an unknown. Added the WPC day shift forecast qpf and chance of 3+" of snow (darker green). Will update Monday the 25th, when some of the nor'easter threat to our area has resolved itself. Also added the NAEFS qpf... seems a little high near and north of I80 but it could happen. Also added the 12z/23 GEFS 500MB spaghetti for 12z/Thursday.

No confidence on downgrading changes to thread thinking on the coming event, despite a number of models too dry to support. I could be wrong but what I see is a good cold BL to overrun...(850MB initial sw flow lift Monday night becoming light s-se for a time Tuesday) I also see the 'potential' for some nearly stationary subtle banding somewhere between I80 north to maybe as far I90 Tuesday-Tuesday night, along and north of the mid level vort stretching eastward. There is very small potential that this will become an inverted trough northwestward by early Wednesday to near KMPO or KABE, as the surface low redevelops eastward out to sea. Then its dendrite growth etc. Too far out for me to be confident in a marginal situation but frozen ground (even if above freezing Monday) and the good chance that ice will be mixed in almost up to I80 argues for a probable manageable advisory situation. Even if 'isolated' all snow 6+ occurs north of I80 in far nw NJ/ne PA/se NYS, since it's stretched out over 24+ hours, criteria won't be met for a warning event. No matter... snow and ice is coming with I think the deepest accumulation north of I80 but debatable and so I will maintain close to the 6a update and reevaluate tomorrow morning. By then we should know if the NAM is going to start developing qpf of .3 to 5" over a 36 hour period I80 north, and if the GEPS is going to lose it's 1/2". Added two ensemble plumes for KLGA. Both are a little interesting. For now, I'd discard everything above the mean,.and think an inch less then the mean presented. Later, Walt

Will begin a topic for Thursday - the 28th (r bleed Wednesday afternoon into Thursday night) for a rapidly deepening storm off the mid Atlantic coast but; will this miss the forum, at least the region along and north of I80? My gut tells me on too late for much up here n of i195 but bears watching for the mid level deformation zone well north -northwest of the storm center. I know this is a topic that needs concentrated forum discussion energy separate from the coming minor to yes, still moderate potential event for late 12/25-early 12/27. Drafted by 4P and very loosely. I think we need to pin our hopes for plowable snow I80 north, on the 26th, but I could be VERY wrong about the 28th. Therefore, keeping it loosely developed. Let me add; I know lots of folks here don't like the GGEM/GEPS, so thats our hope for the 28th (GEPS very very modest), and fairly warm up to I195. .

I added (not to this graphic) but the snow from 7A yesterday to 7A today, total 5.2" at MPO this week. Fabulous day to walk in real cold and wind up here in nw NJ at midday. Temp in the mid 20s and wind chill who knows, w a few flurries.

A quick note: Have seen some f the modeling for a big storm VA's/Delmarva se NJ/e LI. No topic-thread from me yet, until at least 4P today pending review of multiple 12z/23 ensembles and WPC outlook. This is the overnight outlook for the 28th into early 29th... we're on the fringe of the outlook, which looks reasonable to me in light of all the other guidance so far.

Good morning again, go for it! 12zNAM should be the start of some useful guidance on whether or not we can muster 1/4" or greater qpf and associated snow/ice/rain. I''ll revisit at 330PM. Third topic edits 626A/23: Delayed the start in the forum 3 more hours and that may not be enough due to the dry air in place, but sometimes the snow-sleet breaks out faster than modeled. I've had to admit a slower departure, especially because of the GFSv16 and EC. The following may be too high on amounts but it's just my opinion of the boiled down (in my mind) consensus of the 00z-06z/23 model suite. A colder week is now here with hazardous winter weather potential late Monday-late Thursday Late Monday the 25th-early Wed the 27th: Manageable. Still uncertainty on evolution. There is general model consenses for slower arrival and later departure, and less precip amounts. I am guarded about decreasing the wintry element amounts (low level pressure pattern, 500MB vort max track, GFSv16) but this update below may be an inch or 2 on the high side? Manageable delays sometime in this event due to plowable snow northwest of I95, except snow-ice I78 southward in NJ to Baltimore and snow/ice/rain NYC-LI southward along the NJ coast southeast of I95). The main event for I84 should Tuesday-Tuesday night. Expecting amounts to range from an uncertain 1-5" CT with the least in eastern Connecticut and a less than certain forecast there, to between 4- isolated 7" se NYS, ne PA and nw NJ. LI NYC/NJ coast 1" to possibly as much as 4" by the time all is said and done with the best chance for a POSSIBLE 4" NYC (possible, not probable). I expect plowing will be needed sometime for most of our area northwest of I95, except maybe east of the CT River. Temps will generally be subfreezing throughout the event except NYC/LI/NJ coast which are in the margins of ice-snow at the start, changing to periods of rain then ending as snow, so amounts of each element will depend on duration but it will probable get slippery there on untreated surfaces for a time as well-especially if and when precipitation occurs during the nighttime hours. Check others herein and other resources for other opinions. This graphic attached was issued by WPC at noon yesterday, but I think still applies.

Note; The GFS para is running again, tho not n tidbits yet. Found on Pivatol. It is more robust than the GFS and many other models north and west of NYC. I'm not sure what to think of it.

Heres' the 3 day CoCoRAHS totals as reported for the daily tally.

My 3P/22 impressions: have looked at everything that's available via 12z/22 modeling except no GFSv16. In any case, I may be 6 hours too fast on the start and 1-2" too high on the high end of the ranges provided this morning. Advisory or low end warning most of forum except n of POU-DXR-HVN (drying out?). Shorter duration with primary impact Tuesday morning commute. snow ratios should 10 to 12 to 1 north of I80 tho no guarantee. Understand the concern about dry air eating up snow near I84 se NYS and especially CT/MA where greatest doubts. QPF is not impressive but NAEFS holding it's own...maybe south by 20 MI at most. I like the 500MB vort max translating east or east southeast across northern PA Tuesday. Unsure whether we can get a deep saturated layer up here between I80 and the NYS border? so the I80 axis should do well with at least WAA snow Mon night and east then sewd movin rh from southern NYS and northern PA midday Tuesday. My end time still close to 6P Tue but may lag a little per EC. Waiting this out a little longer. I think the NAM will become more helpful with 12z/23 cycle...still a little out of range and 84 hr NAM not known to me as the best of its output.

Good morning this Friday Jan 22: Think consensus is developing that most here will enjoy a significant plowable snow event late Monday-Tuesday. My take below based on 00z/22 ops and EPS/GEFS/NAEFS, and 06z GFS op. Travelers into the northeast USA Noon Monday- 6PM Tuesday the 25th-26th: While still some uncertainty, if you have travel plans into the I84-I80 corridors or I95 Baltimore to NYC-New Haven Monday Night-Tuesday morning, prepare for delays due to snow, except snow-ice I78 southward in NJ to Baltimore. Expecting amounts to range from ~1" or less I90 in Mass (could be zero if the storm stays south), to an uncertain 1-5" CT with the least in northeast Connecticut (Ashford) and a less than certain forecast there, to between 4-7" se NYS, and 5-9" ne PA, nw NJ. The high side 9" amount is no guarantee but it's in some of the modeling. Best chance of 9" in ne PA is along I80. LI/NYC my expectation this early is 1 to maybe as much as 6"??? with the best chance of 3"+ western LI/NYC. I expect plowing will be needed most of our area except maybe n CT/MA/ and the region along or just southeast of I95 BWI-NYC. Temps will be subfreezing throughout the event except if it starts Monday afternoon when it will take an hour or two to drop below freezing. Baltimore-Philly is in the ice-snow zone so amounts of each element will depend on duration but it will get slippery there for a time, possibly as early as Noon Monday. Finally: the end of this event should be Tuesday afternoon, but it's possible that it could linger into the wee predawn hours of Wednesday? Attached a NWS graphic ensemble 30+% chance of 3+" of snow Monday into early Tuesday. Blue is 50+%. This gives an idea of the focus only through 7AM Tuesday and it will snow beyond 7AM Tuesday- so this is conservative. Also the 00z/22 NAEFS qpf for the 24 hr period ending 00z/27 with .4" = to the 10MM line, and also the sfc temp for near 00z./27 which shows 0C along I95.

I agree on the above 2 by Bluewave et al 5th-Feb 2. Snowfall that I see on the 12zEPS is about 8" NYC and 10-12" central PA through Feb 5. fwiw and am ot intent on threading for a couple of days til we see more consensus for the 25th-26th, 12z/21 NAEFS for the 28th has a nice 12-18 hour snow event NJ-down to central VA. Pretty impressive on the NAEFS.

12z NAEFS continues to offer sleet/ice s of I80 for the 25th-26th, about .2 QPF to I84 and about .4 or so I195. I like that for starters. 12z/21 version slightly further n than the 00z and so despite the rather paltry GEFS, the GEPS compromised up and it sort of matches the 12z/21 EPS...the concern being how much snow can occur in n CT or does the modeled confluence slip south with time? Right now the EPS and GEFS have flip flopped from 3 days ago with the EPS much more favorable for a widespread snow-ice event in the forum. Therefore, I've no changes to prior topic threads, including rushing the first snow in NJ during the day Monday (not that it will be correct but i cant confidently way one way or the other)... a light to moderate advisory event with a possible small swath of low end warning. Best I can do. Taking down the Christmas tree... something I'm reluctant to do. Later,

You did real good... if ever lose my County job, i'd look at USPS PT. No matter the internal complaints... I know most of these jobs are highly desired, and all respected. Regards,

I just get a little concerned when our NWS (Federal Public) services, which i know are provided by dedicated intelligent science friendly people are compared to the private sector, especially when NWS-DOC is dedicated to sharing-expanding the weather industry. The comps can be done private to private, but I think for an estimated $8/year tax payer dollars... the Federal return is pretty good. The NWS will work together with all sectors, no matter the situation. Civil Servants. I could have ignored this, and had I been a NWS manager, would have. But in retiree mode just thought it might be good to voice.

Just a note from a retired NWS forecaster this is not NWS supported, especially since the NWS is part of the Department of Commerce, developing the weather industry. These are my own words and I know would never be supported by anyone in NWS management. So, the following probably is of no bother to anyone who was not in the NWS. I am slightly irritated by TV mets comparing their accuracy to the NWS. You can bet the NWS lays out the ground work for all media through it's extensive quality controlled data gathering, model productions-international availability, and forecast/watch-warning-advisory-statement production, 24x7 365. While it may be true at times that the private sector is superior, I do know the NWS is a group collaboration, forecasts constrained at times by differing opinions (forecaster biases) and attempts to produce a useful product via the ONE VOICE method, to the benefit of not only metro regions but the rural sectors (ALL of our USA). Their must be another way to display competitive superiority. This certainly differs from the private sector which often can offer a differing (probabilistic?) opinion using whatever resources, such as we do here on this forum. Overall, this is small potatoes but I thought it good to voice my small concern. ps...1/22 7A: noted an improvement in advertising this morning. Thank you.

Good Morning--- wasn't sure where to place this... I'd like a little immediate visibility for this written conversation with the ECMWF yesterday - January 20, 2021 - and then you take and run with it as you wish---just strongly recommend that we are are realistic about limitations of snowfall-snow depth on the EC model. This speaks only of the ECMWF and EPS. As some of us know there has been discussion about various vendor depictions of snowfall. My recommendation is to take the lower value of EC snowfall. Snow depth on the EC is a good lower end check and may in some ways if initing at zero depth, represents a total positive snow depth change as seen via tropical tidbits, which I like to use as a baseline for accumulations. However, I'm still unsure how sleet is treated in some of the vendor depictions but if it's 10 to 1...its wrong, probably ~70% inflated. Here is how the ECMWF group handles snow/rain/ice pellets (PL or sleet in the USA-) Note the UK calls a rain-snow mix as sleet, a different approach there. I'll place this in the Model Thread as well so it's there as a reference for the future. Ice pellets are not stored as such in the model but reach the ground as a mixture of rain and snow, and it is the proportions of those that are present, and the type of surface onto which the ice pellets are falling, that will determine how the accumulation on the ground works. Similarly if there is already snow on the surface, then it depends on how deep the snow there is modelled to be, what it's density is, and what the air and snow temperatures are. In short there is a lot of scope for forecast snow depth on the ground to go wrong, and this is particularly true if you have ice pellets or (UK style) sleet falling, or if there is already a lot of snow on the ground. And known (extraneous) systematic errors in the handling of snow depth on the ground, relating mainly to there being only 1 snow layer currently in the IFS, do not help at all. So unfortunately there really is no rule of thumb (like 10:1), and this evidently stems from many issues. Ordinarily ice pellets would, I think, change snow depth on the ground via a ratio that is rather less than 10:1, but that is about all I can say. The deterministic ECMWF model (HRES) and the ensemble (ENS) both behave as described above. So I doubt this is the answer you were hoping for, but anyway please feel free to read further on such topics in either the Forecast User Guide (e.g. here: https://confluence.ecmwf.int/display/FUG/9.7+Precipitation+Types - second sub-section in particular), or in our listing of known model issues (here: https://confluence.ecmwf.int/display/FCST/Known+IFS+forecasting+issues)

Good Morning--- wasn't sure where to place this... I'd like a little immediate visibility for this written conversation with the ECMWF yesterday and then you take and run with it as you wish---just strongly recommend that we are are realistic about limitations of snowfall-snow depth on the EC model. This speaks only of the ECMWF and EPS. As some of us know there has been discussion about various vendor depictions of snowfall. My recommendation is to take the lower value of EC snowfall. Snow depth on the EC is a good lower end check and may in some ways if initing at zero depth, represents a total positive snow depth change as seen via tropical tidbits, which I like to use as a baseline for accumulations. However, I'm still unsure how sleet is treated in some of the vendor depictions but if it's 10 to 1...its wrong, probably ~70% inflated. Here is how the ECMWF group handles snow/rain/ice pellets (PL or sleet in the USA-) Note the UK calls a rain-snow mix as sleet, a different approach there. I'll place this in the Model Thread as well so it's there as a reference for the future. Ice pellets are not stored as such in the model but reach the ground as a mixture of rain and snow, and it is the proportions of those that are present, and the type of surface onto which the ice pellets are falling, that will determine how the accumulation on the ground works. Similarly if there is already snow on the surface, then it depends on how deep the snow there is modelled to be, what it's density is, and what the air and snow temperatures are. In short there is a lot of scope for forecast snow depth on the ground to go wrong, and this is particularly true if you have ice pellets or (UK style) sleet falling, or if there is already a lot of snow on the ground. And known (extraneous) systematic errors in the handling of snow depth on the ground, relating mainly to there being only 1 snow layer currently in the IFS, do not help at all. So unfortunately there really is no rule of thumb (like 10:1), and this evidently stems from many issues. Ordinarily ice pellets would, I think, change snow depth on the ground via a ratio that is rather less than 10:1, but that is about all I can say. The deterministic ECMWF model (HRES) and the ensemble (ENS) both behave as described above. So I doubt this is the answer you were hoping for, but anyway please feel free to read further on such topics in either the Forecast User Guide (e.g. here: https://confluence.ecmwf.int/display/FUG/9.7+Precipitation+Types - second sub-section in particular), or in our listing of known model issues (here: https://confluence.ecmwf.int/display/FCST/Known+IFS+forecasting+issues)

Hi! More action possible. Three storm opportunities 28-30, 31-Feb 1, Feb 4-5 -- this last may be more rain, then any snow as 500MB heights try to warm above normal along the east coast. May be good for one of our leaders to start a Feb thread pretty soon? I'm pretty sure members will be commenting on the potential as we always look to the next.

I'll do a wrap up snow amounts for the week either Friday or Saturday at 10AM as a second episode occurs midday today - Friday, just north of I84 where a few of our members live. Dustings to possibly as much 1" possible by Noon Friday, with the Litchfield Hills and Catskills most favored. (I'll toss in the prelim week summary CoCoRAHS graphic by Noon today).

The modeling variability continues. Topic update is as follows, subject to considerable debater I'm sure. Go for it. I'll check back at 4P. Fingers crossed. Topic reedits 630A/2: Added widespread to the topic title. Uncertainty continues, especially northern extent of 2+" with I84 somewhat in doubt because of the last 24 hours of GFS depressed cycles. However, the GGEM/GEPS, and especially the EC/EPS have come back north since the 00z/20 cycles. NAEFS is still south, and one can debate if the event lasts into Tuesday night but overall, the topic stands as is, with considerable debate on what happens. I've added the latest WPC probability of 1/4" melted w.e. frozen which you can see has trended higher and more expansive and i think that is correct. It does not match some of the WPC prior to 08z/21 qpf which looks slightly lighter but going with the WPC frozen prob, because of the GEPS and EPS. My take at 6A/21 Travelers into the northeast USA Monday-Tuesday the 25th-26th: Still considerable uncertainty on how this all transpires but we should be aware that an extensive hazardous wintry episode is expected for all untreated surfaces, especially the I84-I80-I95 corridors from Baltimore to I80, with less certainty I84. The front end Monday start time is uncertain. It could start for a couple of hours Monday morning then stop for 12 hours. The bulk of this event probably occurs Monday night into Tuesday the 26th. Odds favor a change to rain or ice along the I95 corridor Tuesday morning the 26th, but mostly snow northwest of I95, especially the I80 corridor northward. There is considerable uncertainty on where the primary snow or ice event will occur in the northeast so its good to be aware of the possibilities but no action recommended yet, unless you're headed to Baltimore-Philly where messy slippery wintry elements develop by Noon Monday. Have a day!

Hi! 12z/20 NAEFS still south with qpf everywhere but I think thats' due to the GEFS not being robust. Maybe tomorrow it will all mesh a little better. I'm not into any 10+" amounts at all for this event (just dont think that is a high probability) but i can see widespread advisory conditions I95 corridor northwest to I84, maybe an embedded swath of lower end warning amounts. Have to keep moving and will reevaluate Thursday morning and at that time include some info from the EC.

Early but encouraged that the 12z/20 GGEM has come back... whether that's correct I don't know, but I think it's correct. As noted earlier in the thread... the 12z/20 UK is on board big time, but for the UK, thats past 96 hours...not so reliable and just previous-now, the 12z/20 EC is back where it was and so... waiting it out. Will comment around 4P but I'm encouraged we continue on track for a widespread wintry event. Thank you to the 12z/20 GGEM, EC and UK op's. Unsure what is going on with the GFS the past two cycles and no para to check. Have to move on with the NAEFS and EPS as best we can. Won't tidy up the topic til tomorrow morning but everything originated looks good to me. Also, later today, or tomorrow morning I will present information on the EC and how it handles snow accumulation. Not so cut and dried. Later, Walt