wdrag

Back tomorrow morning but adding one graphic that should alert everyone to potential for some heavy duty removal problems by the 20th. WPC7 day QPF.. most of this should be ice/snow I84 corridor and i doubt any big warmup next Friday. Too difficult to be sure of what will happen but I think I84 has a pretty good chance of 6+ by next Friday- tbd. Modeling continues the heavy snow axis similarly for the past 4+cycles, really back to the 00z/8 cycle. The question on our southern side of the axis, how much of that is erroneously high due to sleet 10 to 1 conversion. Finally: today was beautiful cloudy subfreezing mid 20s day here in nw NJ with deep snowpack. Wednesday the 17th may be the last such beaut before we return to warmer temps starting next weekend (and melting).

yes... I 84 itself looks rather light, the EC seemingly a little better than. Yes, they're in the OBS thread once we get it going.

Will begin the OBS-NOWcast for the 13th-14th advisory event (already a portion of NJ) at about 5A Saturday, gaining a little more confidence on timing the showery mixed precipitation heading our way. Maybe it will be more stratiform? Think it will begin as a bit of snow or sleet at the start NYC midday-afternoon with maybe a few tenths before any change to freezing rain at night, ending sometime Sunday. nw of I95 there's a small chance of an inch or so of snow-sleet, before any ice.

Agreed... and thank you.

72 hour is usually the demarcation for good UA sampling but with such a precarious balance of warm air aloft nearby, we may not know til 24-36 hours in advance. 12z/12 RGEM appears of on its on the 15th with an e lakes low while the V16 i think is correctly colder icy or snowy with a low s of LI. OP GFS in between but for now, I'd continue with a cold scenario with the only problem 875-750MB. Point is... at 72 hours, the models don't appear to have any decent consensus. so for the 18th-19th, ensemble solution is best.

Sorry about the initial attachment posting error.

Fixed the PPT attachment as a pdf and now accessible with hyperlinks making life easier. 1012A/12

554A/17: Topic headlines adjusted from the original late last week to the snowier wintry solution. A burst of moderate to briefly heavy snow Thursday, begins lightly between midnight and 6AM (OBS-NOWCAST thread will be started this evening) Thursday much of the area, though it may delay a bit to the daylight hours north of I84. QPF etc has decreased since originally threaded. Modeling allows sleet/freezing rain to get involved near the Thursday evening rush hour and eventually back to manageable, possibly intermittent snow on Friday. Some modeling has a decent burst of snow Friday. ~Half a foot or more seems likely for much of the area with sleet/freezing rain (even maybe eventually even a bit of rain e LI) limiting the risk of 6" south of I78 and possibly LI as well. Graphics added are WPC 09z ensemble chance of 8"+, chance of .01 freezing rain for the periods indicated (note ensemble chance of 8+ has higher chances southwest of Harrisburg but that includes time not shown in this depiction) and the NWS regional snow forecast. 517A/16: A nice solution coming (overall colder and snowier than what modeling was generally offering Friday the 12th) with a range of accumulations of 1" to possibly as much as a foot in the upper high end scenario. Thursday's evenings commute should be snowy for much of the area and see delays, as it readies for a possible change to ice Near I78-LI (rain far south part of the subforum) and then ends Friday, most of it done by sunrise Friday (but with early morning delays/cancels). Too early for me to be sure for the NYC/LI/NNJ membership but plenty of modeling close to half a foot. A watch/warnable snow-ice event seems to be coming for a portion of NYC subforum,. IFFFFF NYC were to report half a foot, that would place NYC in the top 5 snowiest February's. This coming snow-sleet, whatever, should rejuvenate snow depth , and maybe allow half a foot or more for much of the area into Monday Feb 22. One WPC graphic added: the 24 hour prob of 2" of snow by 7P Thursday. --- 625A/15: Adding the ~5z/15 NWS prob of 3+" snow graphic. Otherwise, variable modeling with it appears to me a slightly colder trend, but still any snow should change to sleet/freezing rain for a time, and maybe just rain LI s of I78. Very uncertain but NWS probs are very high just north and west of NYC for 3"+. We'll see how it works out. 525AM Sunday the 14th- Valentines Day! This event still looks interesting for snow lovers, despite the warm GFS OP. This is a prelim update for an event 5 days away. Definitely Advisory minimum potential, especially interior and possible Watch-Warning material interior part of the forum north of I78. Early guess on modeling...a range of 1/2-5" of snow-sleet Thursday before a change to ice North of I78 and just rain LI and south of I78 Thursday evening with rain most of the area for a short time Friday morning. Snow and ice ne PA/nw NJ se NYS/n CT. How much of each phase unknown. May add another graphic or two by the 915AM full update of this topic. Here's the NWS ensemble prob of 3+" of snow Thursday...that light blue is 70% up there by I84. 520PM Saturday: EPS drifting north for Friday morning so front end snow/ice goes to rain, possibly north of I84 Fri AM? Still... with all the modeled qpf, the 806AM water snow equivalent weight concerns, and definitely gutter ice water damming/roof leakage possibilities. Five to 6 days away. 806AM Saturday the 13th update: Ensembles differ (GEFS far northwest with a primary into the e Great Lakes), while the 00z/13 EPS further southeast with a coastal and therefore colder. NAEFS is in the middle and says snow or ice to start the 18th, changing to rain before ending on the 19th. I won't add many graphics since its similar to yesterday. My concern is another ice storm for the I84 high terrain corridor and snow pack water equivalent weight increasing as well as jammed snow and ice laden gutters. 00z/13 EPS-EC not to worry so much as it likes less qpf and more snow down at least to I84. What I think we all know... delays and cancels coming for Thursday, at least the region close to the nw side of I95 and northward. I added the Thursday-Friday 12/8-19 total qpf graphic generated by the NWS early this morning. It might be a bit heavy and too far north but uncertainty. As of this starter thread it appears the region along and south of I80 including LI-NYC would have mostly rain but possibly a front end burst of snow or ice. Presuming the cold source over New England remains intact at the time of late next weeks arrival of this large amplitude central USA trough, there exists potential of around 1/4" of glaze or more, for at least the I84 corridor high terrain (especially northeast-east slopes), IF there is only a little sleet or snow to start. Longer duration of any snow or sleet (ice pellets) at the start, would reduce the risk of advisory or even warnable amounts of icing. There is even some modeling suggesting enough cooling toward the departure of storm that precip might end as snow. Finally the long shot (low probability-wishcast?) this far in advance is that this system comes out in two pieces, one ~the 18th...colder and bit snowier, and a second delayed piece of energy late 19-20, possibly redeveloping a little further south than now modeled with a colder solution. For now, it looks like a period or two of heavy rain LI/NJ coast and a period or two of mixed heavy precipitation nw of I-95, especially the I-84 corridor. EPS modeling of snowfall has been emphasizing PA-NYS central-northern New England for heavy snowfall (or ice) with the gradient edge in our NYC subforum meaning greater chances of snowfall ice accumulation error. This could become a major storm of one sort or another for our subforum. It will be of interest to monitor the water equivalent in the remaining snowpack the morning of the Feb 20. If that snowpack is with 4" of water equivalent on some widespan flat roofs and or ice/snow clogged gutters, we might be seeing some associated damage developing? No science from myself on this.

Close to final two day CoCoRaHs reports as of 830AM/12.

Have not looked at that very closely. Probably won't. Difficult to beat the models but always look for the edge. Its' trying hard to close off over Texas but then merges with northern stream by the time it gets here.

854AM Friday the 12th: Have no changes to the Thursday 11th updated post. Added the WPC overnight prob for 3"+ of snow which favors north of LI and lots of zr/ip/r for LI and the NJ coast.

NO one inch snow probs for our subforum from WPC this morning but it's possible there is a bit of snow accumulation along the I84 corridor spotty 1-2?. Whatever it is, is light and I think only advisory where the eventual ice encroachment. Graphics added from 09z/12 for probs of 0.01 freezing rain. Remarkable I think to see a freezing rain bullseye for LI on Valentines Day. Treated roads would probably be just wet, but untreated surfaces, bridges and overpasses... caution. Probably not enough glaze for power outages unless someone slides into a pole.

Agreed 100% . depends in part on the strength of each WAA pulse and whether we can ever close off something at 850MB s of LI which looks doubtful but I am interested in the eventual progress of these systems. The little ones add up. We'll need to track water equivalent in the remains snowpack on the morning o the 20th.

This thread is basically closed. I took a look at the week in advance post (5th) with the Sunday followup (7th). We got our 1-2" but not 10's; with the heaviest axis SOUTH of our forum instead of northern edge of the forum and while it was foreseen that this could come in pieces, the 12th as named, was wrong. I'm glad we got the 1-2" with 3-6" BWI to s NJ. SOUTH not north of I80.

Not over, til it's over. Today is the 11th, the last event in this coming series is 7-8 days away that may change in its outlook. There could be others the very end of Feb or March. Just in the series, we're living on the edge of decent snow, rather than the heart of there axis.

Issues are discussed with ptype and numerous free links-tools to assist the forecast process without the benefit of NWS data resolution, BUKIT, snow ratios etc This is designed to ball park winter event expectations (lower wish casting) and be prepared well in advance for possible hazardous winter weather. This is only part of the arsenal of internet links that can be of value. NWJO Feb 2021 forum.pdf

Will check the CoCoRaHs two day at 10am. Don't know.

Probably an example of why we can't buy into one model that shows what we want, but just ride out all the variations and try to smooth out to a reasonable expectation of reality. I don't think that EC cycle will be mirrored on it's 12z/12 run. If it shows consistency, there will be lots of chatter but for now, conservative is best, imo.

Added to this thread (a copy of my private FB post earlier this morning) as a hold for the main threads. Focuses on the I84 corridor. Good Friday morning everyone - Feb 12! Lots of wintry elements coming from Baltimore to the Canadian border late Saturday the 13th-Friday the 19th. Then after Friday the 19th, it warms up a bit and this spate of frequent ice and snow events should relax to the more normal 3-4 day separation. I84 corridor sometime late Saturday -Vaelntines Day: periods of light snow, sleet and maybe even freezing rain. Minor but because of ice, it may be advised? Late Monday the 15th-Tue the 16th: a significant advisable-warnable extensive ice event coming. Could turn into snow for the I84 corridor? Modeling all over the place for this. Recently thought 6+ there but have to back down because off possible warming aloft? I just don't know. Thursday the 18th into Friday the 19th: A potentially warnable dangerous ice event coming to the I84 corridor. May even be warm enough for rain to eventually get involved for a short time, but this could end as snow later Friday the 19th. NWS ensemble graphics. Best chance of icing 7AM Saturday-7AM Sunday (see I-95 Baltimore area toward NYC), then the best chance of icing Valentines Sunday itself which is close to LI; finally the chance of 3+" of snow on the 16th, also the 18th = both with highest chance I84 northward. Just use the legend for the chance.

Good morning everyone, I'll get to the thread updates by 9AM ish. If i had to do over again... I'd lump the 13th-19th as one messy wintry period with a a wide ranging spread of solutions every day. I do think NJ/E PA will see wintry precip every day (13,14,15,16, 18, and maybe 19). At least 5 of the 7 days with 17th being mostly likely the driest day and the 19th the least certain for wintry). NYC/CT/se NYS might escape the 13th.. Precip on the 13th,14th should be just light. late 15-16 much more important, and the biggest scoop probably on the18th-19th. Snow axis for every ensemble cycles on the EPS has focused PA-NYS-Central and northern New England with amounts breathing up and down with each cycle. That means the subforum is on the southern edge where leaning on snowfall for more than a couple inches s of I84 could be a big mistake. However the southern edge of that axis should be a lot of ice with rain reserved mainly for a part of the 19th. The EC take on 18th-19th could be a one cycle aberration. I'm being careful by not buying into this, until I see two or three successive cycles of similar snowy scenario. Right now the NAEFS does not support the EC. 539A/12

May come in two pieces 18 and 19... instead of one stronger system. If that happens, going to be colder surface, at least inland. Precip rates may be too heavy for heavier FRAM glaze but I have to think at pretty good chance of a quarter inch of glaze coming this 5 day period, interior east-northeast slope high terrain. Worthy of monitoring. I'm not convinced by current modeling that it cant snow the first 6-12 hours on the 18th along I84. If it further warms aloft, then that snow won't happen.

I've no confident change to the topic as updated at 830AM and reassess tomorrow morning. The 14th event is light, 15th?, the 16th might not be as heavy as some of the models which may leave it colder and more snow? 18th-19th... think heaviest qpf since our Feb 1 event. It looks pretty cold at the surface with generally primary low pressures, so far, along our coasts for this entire period per 12z/11 NAEFS. Probably not much snow along I80-Li, especially 18th-19th (replaced by sleet, freezing rain and on LI and coastal NJ.. rain).

Will recheck tomorrow morning ~7A; for now now change to the 8AM updated thinking. Ice has to be in the mix and snowfall limited to the I84 corridor. Max amount 4" and quite possibly only 1-2" there with ice south of that in the subforum. Light, probably mixed sleet/freezing rain, snow event.

Good point... I just ignore those numbers. NWS when it publishes a map of actual snowfall, usually filters out erroneous reports. These go into Watch, Warning, Advisory verification.

My guess is typos, OR combined several days-events? Probably typos. I hope CoCoRaHs has a filbert check or someone who checks these. I don't know.