wdrag

On the above: I'd rewrite 20% chance of less than 1" to 80% chance of greater than 1" Then go from there... Ate least I know to expect snow. The probs we derive are generated from collaborated 3 hourly or sometimes 1 hour snowfall information blended with the National Center. These tend to miss the high end of storms, and I think tend to be conservative but the latter is my opinion only. They are only as good as the modeling we chose to use... Note: I add the 08z NDFD graphic for snowfall. No wonder we are a little behind. Nada Philly area and LI. now the 17z... note big increases including 2"LI and 5" s NJ. I think we had some info at 08z that ddid not get into the NWS NDFD forecast. Hence the thread.

Added the criteria for 12 hour WATCH snowfall. It's verified as an average in the zone-county. THIS I NOT a NWS snowfall forecast map, only answering some of the base criteria for issuing a WATCH. Pleas make sure this is not mis interpreted as a snowfall forecast map. Color coded here you are. Also a link to the NWS snow probabilities and Winter Storm Severity Index is below, as of 10AM. https://www.weather.gov/phi/winter

Also, probably gone unnoticed GFS nothing for the 7th... GGEM snowstorm I95 nwwd. Mondays storm is first up. If the GFS and SREF fail too high or the NWS ensemble blend and NAM are too low. There modelers will argue sensitivity to the interactions...they are correct.

Criteria. My guess still 6 in 12 and 8 in 24. and/OR combined PUBLIC IMPACT. If I was in the drivers seat with more internal info and collaborating across the NWS borders, I'd argue for a watch = brief high impact potential in the 8A-4P time frame. It's a watch. Rush hour impact or residuals of and clearly there is big bust potential. Can't be afraid to be wrong. Preparation is critical for the infrastructure, already impacted by Covid. They can use the probs to help prep folks. If it misses south, the guidance is there to support the decision making. I add the possibly biased high SREF chc of 1"/hr. Use the legend for prob. I checked blizzard conditions and those are just 20 mi offshore of LI and the NJ coast at 18z Monday. By the way this graphic data is probably not used in NWS... i still it valuable for me from the old school days which for me still work well, with the exception of not having the improved details of modeled soundings and snow growth. Graphic added 1209P

I sort of do too... and NAM idea of dry layers near 850 MB looks good NYC, but this system is showing better 500MB separation and tending to go negative as it whips out to the se of Cape Cod. I do not like the SREF being so abundant this far north (especially SPC SREF plumes). It won't take much for big snow growth and I expect we will see 1-2"/hr snowfall rates for a couple of hours mid late morning somewhere very close to Toms River... may still be south of there but I think now is not the time to hold onto a snowfree forecast. Folks need to be aware of potential and if it misses south of NYC... excellent. I just don't think our modeling is that good to be so determinant that nothing will happen, in the face of the ensembles, GFS/ SPC SREF plumes etc. Mt Holly made the right move, 6 hours late but enough to prep their folks. Going to be quite a storm for 6-12 hours Baltimore area to ACY and probably a bit further nw.

Soooooo much variability. I think a watch will be needed for a portion of NYC subforum...up to and including Monmouth County to eastern LI. A watch is not a warning but it signifies potency and be alert. NWS can describe the options in the details. Watches should verify about 50% of the time, probably higher verification in shorter lead time. These graphics from the SPC SREF are surprising to me but not so for the GFS. Wow! Both the 03z and 09z have mean some where near 5" LGA. This is up from 0.2" 15z cycle yesterday and 2" in the 21z cycle yesterday. Big banding signal for for S NJ. NYC best time for a burst of snow seems 10A-1P.

SPC HREF from the 12z cycle... further north and heavier. Close call NYC.

GFS positive snow depth change: sure involves NYC and 1 foot amounts in the axis. Going to be an amazing GFS coup if this works out. NAM, ensembles, SPC HREF will be unbelievably defeated. Soon we will know. I still think lots of mixed precip DCA-Cape May or Dover DE. Thicknesses are still warm at the start and sounding still yet to be subfreezing. It will change rapidly shortly after precip begins. SPC HREF will be far more conservative than the GFS on the northern side of the storm.

Mt Holly finally issued a WSA for the southern part of their area. It will show up soon.

All this modeling needs to be published and allow reality to verify. I may not be posting 3P-8P. Will review at 930PM and possibly start an OBS thread at that time if we are looking at more than a trace LI central NJ. If these ensembles BUST now (thanks for hotdog), then NWS will need to review the mix. Seeing less than a 30% chance of 1" at Toms River is telling in the 14z/2 NWS ensembles. EPS amounts can be biased high because 10 to 1 ratios, even mixed wintry. Where I think ensembles tend to fail is along the gradient edge, (go either way) and in the core, not high enough probs. However, modelers will tell you it's a matter of dispersion of solutions. Warrants further conversation. In the meantime, I hope we have a better system than this for the rest of the winter.

So, 12z NAM, HRRR, HRRRX matches more conservative forecast as only flurries or no snow NYC N and W, but e LI and central NJ Toms River south near the sharp cutoff. Also, some modeling is showing heavy snow near DC-Baltimore. Caution---sleet mixed in may but back amounts but still result in treacherous travel there. I think the further s you go in the axis, the greater the chance of mixed qpf. Added a few graphics: 1) 09z/2 SREF too abundant too far north and not enough mix south to limit amounts. 2) 12z HRRRX amount through 2PM. 3) NWS 14z /2 ensemble chance of 4" Note how conservative - that is because I think it models mixed types better. 4) NWS 14z/2 prob for 1" VERY difficult for NYC to see an inch, maybe all of LI too. I do not know but I lean drier and lower amounts in our area. That does not mean I'm correct but NWS conservative posture, barring 12z GGEM/EC probably works for our subforum with advisory conditions possible e LI snd central NJ. Further it's a mess where being on the road in the morning is not where I'd want to be.

Will add the following: Potential 6-12 hour snowstorm even close to NYC 4A-4P Monday... here is some guidance that is conflicting but warrants concern for a potential 6+" event for parts of e LI, central NJ titrating down to flurries I84. Exactly what modeling is best... your call. We won't know for sure til Monday night which modeling has been most accurate in the longer and shorter range. NWS ensemble at 09z for >1" is still quite conservative NYC as is the SPC SREF. The HRRRX is also conservative but the normal SREF, last image is bullish. Click for more detail including legend for amounts. There may be a little melting at the start, otherwise, where it snows, it should become quite slippery on all surfaces. Driving possible e LI and central NJ coast if the heavier amounts occur.

No thread for Monday. The sounding provided by eduggs is helpful to illustrate a potential GFS problem. Nevertheless, keeping an eye upon. 18z EC is a touch north as is GGEM (both shown below). However NDFD (NWS forecast digital database) is basically nil, as is the prob for >1" (shown below). Will rereview at 7AM Sunday but no thread, at least for now. 22z/1 WPC chance of >1" of snow continues receding southward Monday. I know a lot of folks are talking big hit in mid Atlantic but this does not imply that at all. It defies GFS, GGEM and EC. So unless it's mixed precip and or melting at 33-34F, it seems that some of these stronger hitting models are going to be too heavy on snow, or the WPC ensemble is far far too conservative.

Okay, The following are multiple cycles of the EC OP Kuchera for our area. Consistent that something will happen in the northeast. Where it rains and snows, definitely uncertain and I've not yet looked at EPS. But regarding what the modeling has shown... whether it's important? To me it is of value and validates expressing some interest. The time of the cycle and it all ends at 12z/8 except I think inadvertently ended one cycle at 00z/8. There is one cycle missing since it as basically a null event down here se of Ithaca. Also again: My thanks to the ECMWF and Weather.US for these graphics.

I checked all the runs back to 29/12. 29/12 had 5-6" up at i84, 00z/30 and 00z/31 10"+ just inside I95. Recent runs that did not were big in upstate NY. This is not a D6 perfect prog... could still be an inside runner with a rain shower CFP. Pattern is in the process of evolving away from west coast winter focus into the central and eastern USA.

Grain of salt yes, but basically it's been big event in a part of the Northeast USA every cycle since 12z/29, with 29/12z, 00z/30, 00z/31 all big in a part of our forum (5+")

!2z EC is back for a snowstorm in much of our area from I95 inland. Am not threading til tomorrow morning, at the earliest. I'd like the 00z/2 GGEM and GFS to be a little more in agreement with the 12z/1 EC, Not posting any more 12z/1 EC graphics and will probably lay low for another 18z hours. The 29/12, 00z/30 and 00z/31 all had sizable snowsrtorms in part of our forum. The more recent others were to our northwest. Now the 12z/1 is back over us.

Forgot to add but most importantly-thank you for your AFD complements. Those days are long gone. Ensembles-improved modeling have changed the game. Not being an MJO specialist leaves me kind of behind on the flow interactions. I just pattern recognize. I still think LR is very-very difficult to be constantly reliably accurate, especially timing the embedded 2-3 week periods of extreme weather. Since my understanding is that the NAM goes away sometime in 2023--- am unsure what replaces but I'd like to see the SPC HREF extended to 84 hours. However, am not sure if that will be useful. I always like the NAEFS 8-14 days and it might not hurt to start looking at NAEFS 15-21 Day. Again, there may not be any predictability? And here is the 12z/1 EC at 54 hours. Slightly further north... but still south of us. No thread for me as yet for Sunday night-Monday morning. Thanks to the ECMWF and Weather.US for this graphic.

So, without the 12z/1 EC op in hand... I agree with the very recent post about GFS repeatedly too much snow into drying air nw fringe. IF the GFS is correct, it will have scalded the GGEM/EC, with only the ensembles prevailing for the minority of amounts (less than 1" in our area) and virtually always a dusting in the ensembles due to climo in our area in winter. So the WPC morning ensembles are out (14-16z ish) and they have slightly lowered the threat of 1" in NYC Monday, and decidedly lowered the chance of 3" just n of I84 Thu night-Fri. I did not add these graphics but if you do not trust, please go to the WPC Winter Weather page and check. Always uncertainty but for now, I take my chances on Friday morning being more productive in our area than Monday morning for one reason: Barring a 12z/1 EC northward shift, all the other primary modeling has a null event NYC Monday. Friday is still 6 days out and we know there are going to be changes in the modeling since confident lead-time in this pattern around here seems to be less than 84 hours. Examples below from the 06z/1 GEFS. Note the confluence zone is to our south for Monday morning. But Friday morning: note the confluence zone is in se Canada. The Friday event could still run inside and be mainly rain... but at least my confidence in an event is much higher than what is indicated to me by the 06z/1 500MB pattern for early Monday. Am not 100% null on Monday but still not excited til l i see the GGEM and EC come north. For now, continue Trace flurries at worst NYC Monday morning through the 16z/1 modeling guidance.

Agree... it's about timing. NOT a certain oscillation configuration. Preferred oscillations are valued as more lead time but even those fail, frequently. Thought this was worded I84 and particularly the Poconos and elsewhere just too far away in this overall pattern as described by others previously to this post. I do note quite bit of NO it won't happen, so that pattern recognized thinking-experience is considered. Think I want to wait it all out. Even 12z/1 GFS refuses to leave I95 dry, opting for a period of snow 4A-10A Monday.

Welcome to 2022 everyone along the broad hilly I84 corridor (40 miles N and S of I84)! Thursday night-Friday (6th-7th): A snowstorm looks possible for the Adirondacks with rain to accumulative snow I84 corridor, especially Poconos. If you have travel plans you may want to monitor future forecasts. Track can still vary. Windy cold weather follows Friday into Saturday. Added are two ensemble graphics: please reference the legend chances for your area of interest and click each for greater clarity. These ensembles tend to be conservative but try to show the axis of greatest concern with the gradient edges most uncertain. The first is the chance for more than 1" of snow Sunday night-Monday ( a miss of I84 except a few flurries). The second is the chance for 3" or more of snow late Thursday into Friday. Happy New Year everyone.

Happy New Year to every member that posts here! Am not threading anything yet for Jan 2-3, Jan 6-7 The reasons are in the graphics below. The uncertainties are largest in the gradients. If interested, click each for greater clarity. The 06z/1 raw 10 to 1 snow ratio'd operational EC and GDPS (Canadian). Both are nada and as is the NAM (not attached). My guess is a few ensemble members of the EPS/GEFS have a touch of snow in our forum but overwhelmingly it's unlikely. Saw the 06z GFS northern fringe but my guess on that is that not enough dry air is infused to dry out the northern fringe to virga. So, until the Canadian and NAM move north, I just cant get excited. Jan 6-7 is of more interest to me, at least I95 itself northwestward. Anything can happen at this point but it does look like a sizable wintery qpf event is coming to the northeast. How close it gets to NYC... unknown but I've alerted my I84 friends to monitor future forecasts for travel Friday morning. Click the graphics if interested for greater clarity. 06z/1 EC OP, 06z /1 GGEM=GDPS OP, NWS 09z/1 Ensemble prob of 1"---all these focused on Sunday night-Monday morning, and then the late Thu-Fri ensemble chance of 3" of snow.

No, no word missing. Typically nice to wish all a good day, but I know some might not like that. What I do know, is that I want to be back tomorrow... to do that, I have to have some sort of day. Most days are very good...we are blessed. Happy New Year to all! Walt

Jan 7-8: Euro likes it best but when looking at last 4 cycles, varying latitude and certainly too early for me to highlight-thread, given the less than reliable wintry modeling beyond 3 days. WPC 10z/31 ensemble probs less than 30% for 3" in our I84 area D7; and WPC ensemble probs for 1" NC to s NJ for this Sunday night are very low except NC Mountains. I think we need something in the southern stream out of Texas to NC to give me some hope (850 low developing to our south). Models can inspire me..maybe that will happen soon?

Anyway, this snowless early winter is good for my work which is bridge and guide rail inspection for Sussex County in extreme nw NJ. No snow on the ground is best, for easier access/viewing/documenting conditions bridge and guiderails. This coming week, barring the unforeseen, I should be able to complete one project- the inspection of 492 County bridges and adding guide rail to the GIS database where it's not already documented. Once complete (I hope this week- good 4-5G WIFI helps complete the work rapidly for on-line access), then I move on to updating all the inventory where GuideRail was replaced in 2021 (taking it out of the red = need to done, to green = this is undamaged). In our County, it costs about $31/foot of Guiderail and when you hit those ends with the nice yellow-black object markers, its about $3500. (Costs can vary depending on market). Those guide rails, no one thinks about, but they are constantly saving lives via embankment tumbles, returning vehicles to the highway When folks spin out-bounce off and go merrily on their way with some damage their vehicle, little do they think--- thanks for the guide rail. So there is benefit for a few of us. Have a day! Walt 1020A/31