wdrag

Good morning everyone...just a note on threads. Will begin the OBS thread at 8 or 9P tonight. Am looking at threads for Sunday the 9th which is trending colder - ice and or snow along or just northwest of the I95 corridor westward (too warm Long Island I think but time to change), and then the following weekend (15-16) but absolutely nothing from me til Friday or Saturday on those. Am off line til at least 6PM. Have a great day!

Good Thursday morning everyone, I'll start an OBS-NOWCAST thread at 8PM tonight. In the meantime--it's coming. What do I think from looking at op models and ensembles? 2-4" nw NJ and 3-6" elsewhere with nuances. You all will be on top of model guidance and your own sense of what will happen. I'll get into the banding with the NOWCAST thread this evening and haven't examined that nor snow growth but it seems to me NYC should receive 3". I could be wrong, as usual. The storm continues to be a 5-10 hour event (midnight-Noon) with ending time most of our area 9A-11A, though a few flurries should be scattered about through the afternoon as the sharp cold 500MB trough passes through. Added the NWS 5AM regional snow forecast and the Winter Storm Severity Index. Use the legends. Delays and/or at least some morning activities cancels anticipated in my opinion. Am looking at threads for Sunday the 9th which is trending colder, and the following weekend (15-16) but absolutely nothing from me til Friday or Saturday on those. Am off line til at least 6PM. Have a great day!

Seems like we've evolved into a seasonable January around here with snow and ice opportunities and possibly some consensus on western ridge,eastern trough for at least the next two weeks. Both GEFS/EPS have been showing low pressure off the coast in the northeast Jan 14-16 for the past two days. That may also be an opportunity for a fairly decent ne USA system as the 500MB trough tends to deepen westward with short waves dropping down the western NAM ridge into the eastern USA.

NWS 5AM deterministic forecast.

I'm a little cautious. Checked some 00z guidance, banding, DGZ... I just wish we had more 850 low development further south. Seems to me like a 5-10 hour event.. Good short wave, but little inflow and certainly no easterly inflow at 850MB, at least not yet. Banding possible could enhance snowfall. Too early for me to be sure where. EPS-GEFS from 12z/4 and 00z/5 were timid. There is time... and NYC-LI you should get your first solid inch. Here's my take for the forum not reviewing 06z 3KNAM Banding. Midnight-Noon Friday: A 5 to 10 hour period of snow occurs from northern VA through Baltimore, PA/NJ/NYC and the I84 corridor to Boston. Amounts should be in the range of 1-5". Uncertain where the heaviest occurs, though tending to favor coastal NJ through NYC and especially CT/MA but this could be wrong. All untreated surfaces will be snow covered and slippery for a few hours near dawn Friday, so prepare for some delays in snowy conditions. Snow ends Baltimore around sunrise, ends NYC/nw NJ/ne PA 9-11A but for Boston it may linger til mid afternoon. Added three graphics generated around 4am today: showing the chance of 1" and 4+" and the Winter Storm Severity Index. We can add the regional snowfall forecast by the NWS when it updates at 530AM. Adjustments in amounts and ultimate heaviest axis will need to be further reviewed-changed. We'll have the SPC HREF at 11AM for a first crack up to 7AM Friday. Added NWS snowfall forecast as collaborated through 5A today.

Showers are moving northward into our area and with frozen ground and subfreezing conditions, it could become quite slippery on untreated surfaces in some spots along the I95 corridor just southwest to north of NYC. The National Weather Service has advisories posted. Added NYC 550AM as well per obs below. Also some snow mixed at the start nw NJ thru se NYs, W CT, WMA.

If the banding is there for 6 hours, you get as yesterday 1-2 inches/ hour and thunder snow. I have not looked at any 12z guidance. I guess fast moving will cap max amount at whatever value but if this times with the morning, there will be big impact. Note yesterday Fredericksburg. Also this argues my own bias to prep early and that all of us understand in advance the consequences of eliminating the broader range of possibilities. Off line now through 5p. Have a day.

I know there isn’t much stat support but these Day before near record warmth followed a day later by a snow storm, in my opinion are not uncommon, and associated with leftover Large PW near the front and an oncoming intensifying short wave.

Modeling is tending to try for a neg tilt intensifying nor'easter. Best snowfall north of our area since ensembled 850 LOW is still north of us. Added 00z/4 GEFS spaghetti and NWS ensemble chance of 6". THIS DOES NOT INCLUDE guidance after 12z/Friday. The idea Is I95 could serve as a mix boundary? Something wintry is coming, especially interior.

Also, Correct me if I'm wrong: Atlantic City calendar day snowfall yesterday was their 7th highest in their period of record.

Adding on: I saw a gradient of 8" over 32 miles: between Brick 2" and Barnegat 10... or 1" every 4 miles traveled south/north along the NJ coast. That's an approximation but does indicate the sharp cut off south of I78.

This will have to suffice til CoCoRaHS post Tuesday. NOHRSC snowfall analysis. Think this pretty much captures it...maybe has measurable 10 miles too far north?

No model consensus and lots of possibilities that this could be less because of the track and stage of development. It's out there... we know it is of interest but when you see the NOHRSC snowfall analysis on the OBS page, you can feel the disappointment. Might happen again.

I'll add the CoCoRAHS snowfall on here as a wrap late Tuesday. Clearly this thread was biased too far north and inaccurate for our area. 1/2/22 EC OP, SREF were not helpful. 12z/2 EC OP was my greater disappointment...SREF we know it can have issues at the edges and then the GFS not drying out north fringe qpf. The gradient from 1" to 12" in coastal s NJ will be very large when all is evaluated. I think it went from a Trace of melted w.e. to 1.26" at Atlantic City over a 60 mile distance. The gradient may have been even tighter. The good news is the mid Atlantic did get hit hard as others were pointing out and now a pseudo warm frontal boundary may be set up to our south (snow depth s NJ through VA).

I agree. I'm not in direct conversation with NWS colleagues. So they may be more aware than I of this problem... no question it was a serious issue with GFS on this event. Sometimes you fix one thing and something else goes bad.

Cyclic modeling of the EC/GGEM and ensemble portion of the GFS since this weekend has been developing a fast moving late developing coastal low, resulting in a period of precipitation occurring mainly between midnight and 6PM Friday. Tracking and therefore precipitation type are uncertain but recent ensembles were offering at least 2" of snow to portions of our area, the EPS furthest west and the GEFS/GEPS a bit further east. The GFS op model has been generally offshore. If the low develops further north or further east, very little snow will occur here. Right now 850MB Low development looks too far north for a moderate event but probably worthy of monitoring and trying to figure it out. Based on the model performance for the 1/3/21 grazer snow, we may not know much til we see the NAM consistently give us 1/4" qpf in frozen form with more than 2" of event Total Positive Snow Depth as shown on the Tropical Tidbits web site. 12z/3 500MB ensemble plots below serve as a baseline to witness future modeling departures, GEFS top and EPS next. IF this approaching short wave ends up weaker or further north, it will be difficult to receive meaningful snow here. At 321PM added the 16z/3 WPC D4-5 probs of 1/4" frozen W.E. (lower 2 graphics) which bridges Friday morning 12z/7. The darker green is greater than 30% chance.

So, what do the EPS and GEFS ensembles look like 12 hours into a forecast. The 12z/3 cycle attached ending 00z this evening. This is only 1 vendor. So the EPS looks more throughly available... but notice how much light snow it put into the dry air nw of I95. Ditto the less spatially complete GEFS, but there as well, too much snow into the dry air and these are only 12 hours into the forecast. So there were still a variety of solutions with the 12z init. This tries to demonstrate some limitations in the ensemble utility... the core axis should usually should be reasonable in big systems, presuming it's consistent, not wind shield wiper = back and forth.

9.5" in ACY as of 1P...makes it top 14 snowiest January on record and I think Bluewave indicated we might get top 10 snowiest day. Right now #16 snowiest 24 hour snowfall in a climate calendar day. All this means (for me): it was a big one for that area.

NW edge obviously dried out and SREF in particular was too far nw while the multiple model ensemble axis S+ did well (GEFS/EPS/SREF)...many reports 8-12" just south of DCA to near or just south of ACY. GFS obviously has a problem drying out snow, despite its decent soundings. Even the drier NAM was too robust on the NW side. Am thinking similar drying out problem with the EC. Which leaves the SPC HREF best of the short range groups with its 00z/2, 12z/2 and 00z/3 cycles attached. It was a grazer as initially threaded by Forky. As a planner-preparer for minimizing impacts, even though essentially nada occurred NYC, I would prepare similarly again. The downside is far larger problem than the successful zero accumulation forecast. It's a matter of all of us realizing that the gradient edges of ensembled, or operational cycles can be wrong and keeping that in mind as we anticipate. I'm sure we're in a far better place with the modeling than 10 or 20 years ago, let alone 50 years ago.

Definitely a concern that dry air ingest cuts back snow accums I95w itself...NYC could escape with NIL and PHL less than currently modeled-forecast?? Just need to wait til 1030AM to be sure (for me). The storm is still near Hatteras so we should see a northward push by Noon... I added the HRRRX which looks reasonable to me. At 830A widespread 1/4S+ to 1/2S DCA-BWI-ACY. Now awaiting some northward advance in NJ around 10A. You can see the scalloped edges of northern snow boundary as dry air evaporates the falling snow LI-PHL.

Seaside in Ocean County is the southern fringe of our area. Thanks for your report.

No thread on Friday but GEFS-EPS ensembles have decent interior snowfall for 96+ hours away. Euro and GGEM continue steady for the event and 06z GFS working its way west. Waiting on results for today before looking ahead.

Out of area but to illustrate the potency..Asheville NC just had a nw wind gust to 51 knot at 506A and of course snowing there... maybe more than here in NYC.

NYC-LI on the edge. The SPC SREF came down NYC to around 2-3" and that may be too high. Think best chance NYC to transfer from virga storm to a brief period of steady snow is Noon-3P. Follow the models and the we'll check the results around 7PM. Graphics below are the SPC HREF--- looks good to me and NWS ensemble probs for 1" and a foot. NAM banding page suggests 1-2"/hr snowfall rate potential s NJ 10A-3P. We'll see if that encroaches into Monmouth-Ocean counties midday?

All good... as of 520A... the forecast posted by the NWS looks good. Dry air eats us up along the northwest edge with T-2" NYC. When it does descend through the dry layers below 700MB, it could come down at 1/2MI vsby for a short time JFK eastward sometime Noon-3P. As of 5AM I like TDWR EWR as the northern edge edging north now and snowing extreme southern Monmouth back through PHL/DCA areas. From this point forward am on the nowcast thread.