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wdrag

Sunday-Monday Jan 3-4 potential rapidly intensifying ene moving nor'easter along the mid Atlantic coast with rain to snow mainly I84 to near I95 north through west of NYC

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January 2, 2021 605AM Update: Am probably not commenting for our NYC forum on anything beyond 9AM January 4, which is about the still possible extension for eastern New England. That part of our oncoming light to moderate Nor'Easter snow event for the entire I84 corridor, will not happen for us. The remainder of the NY Day comments below seem reasonable. My anticipation is a widespread plowable 2-6" elevation dependent snow event from I95 northward through the I84 corridor and probably I90 eastern NYS and northern NJ/ne PA eastward through southern New England.  I-84 valleys will manage this better because of marginal melting temps (32-34F)  and the southeast edge near I95 will also be manageable, in part because a little rain/freezing rain/sleet is possible there. as well as the daytime temps near 33F.  So, it's a mixed bag but the I84 corridor should enjoy this, with the primary event mainly Noon Sunday-6AM Monday. This storm will probably affect some of the return home holiday travel and also may force some Monday morning 2 hr cleanup delays, especially CT-MA portion where it still may be snowing a bit. NYC-LI should see a touch of snow/sleet but whether it measures or not and where, i don't know. My guess is eastern LI may do a little better and thats where there will probably be some wind gusts to 35 MPH but NYC might also see less than an inch??  There will be 1 or 2 brief periods of moderate snow with this event, but I'm not thinking of more than 10 to 1 snow ratios, possibly only 7 or 8 to 1 near I95. Will begin the OBS/NOWcast thread later tonight. Earliest part of snow/sleet/very brief ice arrival is around 8A-10AM Sunday for our NJ eastern PA membership. I don't anticipate adding any further potentially helpful information until maybe this evening. Noting the WPC ensembles for more than 2" are not very enthusiastic for this event, so we need to keep in mind failure. They also weren't as enthusiastic as they should have been for glaze this past night and the SPc SREF did much better. It already has 2-4" in ne PA by 7PM tomorrow night. Keep an eye on the SPC HREF MEAN snowfall after the 12z/2 cycle completes around 1030AM.  The HRRRX was all over the place for this freezing rain/sleet/snow event that is wrapping up now and am not referencing it today. I as others here , like consistency in the modeling.  One event at a time. 

 

NY Day 2021 558AM quick update: Extended the date to Jan 4.  Ensembles suggesting a pretty good chance of 3+ inches for some the I84 corridor high terrain in possibly two long duration episodes. A short wave diving into the back side of the initial short wave trough may prolong the event considerably for the New England portion of the forum by forming a a very slow moving upper low along the New England coast. So it's complex but potent, especially if the 850-500 MB lows form in a favorable position for banding on the northwest side of this storm near I84. Just too early to overcommit but this could be a nice snow event for the I84 corridor and as previously proposed (modeled), can't rule out a touch of wet snow on the back side for NYC and especially eastern LI on the 4th.  Just too early, especially with marginal thermal profiles and absolutely do not want to buy into any 8"  amounts seen on some of the single member operational models for New England, at least not this early with so many differing solutions. If it's progressive and mainly afternoon of the 3rd into early 4th, then the 8" amounts won't happen and this would be an interior I84 standard climo modest event.  Graphics is the 00z/1 GEFS prob of 2+ inches for this coming storm-- 10 to 1 ratio.  Just an idea of primary risk area. 

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Uncertainties exist including how much deepening and track for NYC subforum qpf, timing thermal profiles for phase change to wet snow.  Looks like it will happen despite GFSV16 dropping it in recent cycles. EC has been on it for 3 successive cycles (prior to the 00z/30 cycle) and EPS now throwing out decent qpf  (still does with the 00z/30 cycle) and a bit of snowfall all the way down to LI (questionable but could occur late in the storm and not be much...but??).  12z/29 NAEFS has it a little and the fact that the 12z/29 GGEM lit into it, also the 12z/29 UK, should be enough for us to give it a good chance to produce snow down to at least the I84 corridor. 

Others have been wanting a topic to track the models etc for this increasingly likely Sunday January 3 potential nor'easter.  The initial precipitation (rain) from this initially weak Virginias low pressure system could begin after sundown Saturday Jan 2, as rain. As it intensifies and 500 MB heights lower, the combined lift, cooling thicknesses plus north-northeast wind advection of somewhat colder boundary layer temps southward, should change precipitation to snow along the I84 corridor by early Sunday, and possibly down to I95 west and north of NYC by nightfall Sunday? Rain over NYC and LI possibly ends as a bit of snow later Sunday or Monday morning? Probably too early for all this scenario detail but it's based on the 12z/29 NAEFS, EPS, GGEM, UKMET.   No snow amount forecast though it appears that elevations should have highest accumulations, presuming it does snow.  Snow looks to be slushy during the daytime and generally controllable for road crews, especially valleys,  since daytime melting of any snowfall would occur during periods of lighter precipitation rates with marginal temps of 31-34F.  

LOW chance paragraph but reserve the option to increase IMPACTs of wet snow, add a small chance of gust 50MPH LI and minor flooding for a couple of NJ/PA rivers based upon the already anomalously wet December, plus future unknown qpf's from Jan 1 and 3...IF qpf up to I84 increases to 3/4" and mostly snow along I84?  This is unlikely for now, but could happen, especially in the deformation zone if a closed low to 700MB develops near LI in this positive tilt trough.  

After review of the 00z/30 and 00z/31 cycle-no changes. Best to keep options open and look to the I84 corridor as most likely area to see some snow. Marginal thermal profiles the continuing concern. 00z/31 ensembles are growing qpf... but surface and upper lows may be too close to LI/se MA for much snow in the NYC subforum.  This looks to me to be mainly an elevation I84 corridor wet snow concern.  Definitely cannot commit any further details - just too uncertain and that uncertainty may continue another day or 2. Far from an ideal snow event, but also the typical winter uncertainties for our area. 

Screen Shot 2021-01-01 at 5.12.17 AM.png

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As these systems for 1/1 and 1/3 head our way with variable solutions, at least they are wintry for the interior part of the forum.  Here's maybe an eye opener ensemble look  the 18z/29 GEFS 500MB for 18z/3.  With above normal SST just s and e of LI... I now like our chances for an equally sizable event compared to 1/1 and bit colder... how much is snow (wet snow-elevation dependent?) is a question. I did see the 18z GEFS QPF ens come up similar to the 12z EPS.  Unless the modeling fritters on this trough, I see this system as likely looking more robust in future ensembles and probably one of our routine late developing nor'easters, strongest winds e tipLI.  

Screen Shot 2020-12-29 at 7.06.57 PM.png

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A GFS CMC compromise solution for Sunday might look interesting for most of the area. In fact you could throw the EC, UK, and even ICON in there for good measure and the inter-model average is intriguing. Still plenty of spread on the ensembles.

The initial mid-level low track might be fairly far north.  But a late developing coastal low could crash the column at the last moment. Not a perfect snow setup. Maybe that's why this one feels like it's sliding under the radar.

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17 minutes ago, eduggs said:

A GFS CMC compromise solution for Sunday might look interesting for most of the area. In fact you could throw the EC, UK, and even ICON in there for good measure and the inter-model average is intriguing. Still plenty of spread on the ensembles.

The initial mid-level low track might be fairly far north.  But a late developing coastal low could crash the column at the last moment. Not a perfect snow setup. Maybe that's why this one feels like it's sliding under the radar.

I like a cmc/Euro/ukie blend. The GFS is out to lunch and is once again playing catch up. Right now not enough cold air for large portions of the forum. ATM it looks like you have to be north of 84 for a chance of accumulating snow. 

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5 minutes ago, HeadInTheClouds said:

I like a cmc/Euro/ukie blend. The GFS is out to lunch and is once again playing catch up. 

The op GFS is definitely on its own a little bit.  But I don't think it's as far off as it appears at the surface. I expect the GFS to shift slightly closer to the coast with the surface low in future cycles. I just hope the mid-level low doesn't track too far north. I'd like to see it a little further south before - hopefully - closing off several isobars. I think you're in a pretty decent spot up there in Dutchess if this thing does develop. 

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After review of the 00z/30 cycle-no changes to the topic. Best to keep options open and look to the I84 corridor as most likely area to see some snow.  Agreed with the prior member posts... I too am concerned about the latitude of the closed low aloft.  One thought--- as many have probably noticed...models are trending a bit further south and slower for 1/1. Suggests to me blocking is playing a role. That should occur again 1/3 and force a slightly further south track of the 850-700 low than what we're seeing through the 06z/30 cycle.  Lows aloft might develop too late to be significant for our subforum. However,  for now, I do think the vertical 850-700 low development will occur in time, and if you use the 90L of 850MB low rule for max snowfall, I'm looking at I84 or even MA Pike (presuming thermal profiles allow for snow soon enough).  I prefer not to reassess - comment on this storm again until Thursday morning, since models will have differing solutions and just want make small adjustments this far in advance.  Plus 1/1 is the first order of concern. 

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It looks like the latest GFS still brings some wet snow to elevated areas N&W of the City, but I still don't like the ULL track heading up into NNY. The primary surface low holds on a little too long, keeping a southerly component to the flow through the low and mid-levels until late in the game. So the area appears to get dryslotted with backside precipitation limited to upstate NY and NE.

I'm glad there are at least a few wintry threats to track, and this event could still be salvaged, but it needs some work.

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4 minutes ago, HVSnowLover said:

Starting to get real interesting for the northern parts of the sub forum

 

18 minutes ago, MJO812 said:

Nice hit for inland areas on the para gfs

5fed522706a45.png

Northern and western NJ too also the pattern is obviously changing again after this storm passes.............

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I agree with prior posts but also limiting my enthusiasm due to marginal thermal profiles. Sort of want to clear the interest for 1/1 night event. 

After review of the 00z/30 and 00z/31 cycle-no changes. Best to keep options open and look to the I84 corridor as most likely area to see some snow. Marginal thermal profiles the continuing concern. 00z/31 ensembles are growing qpf... but surface and upper lows may be too close to LI/se MA for much snow in the NYC subforum.  This looks to me to be mainly an elevation I84 corridor wet snow concern.  I cannot commit any further details - just too uncertain and that uncertainty may continue another day or 2. Far from an ideal snow event, but also the typical winter uncertainties for our area.  Forward we go... worthy of monitoring. 515A/31.

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2 hours ago, wdrag said:

I agree with prior posts but also limiting my enthusiasm due to marginal thermal profiles. Sort of want to clear the interest for 1/1 night event. 

After review of the 00z/30 and 00z/31 cycle-no changes. Best to keep options open and look to the I84 corridor as most likely area to see some snow. Marginal thermal profiles the continuing concern. 00z/31 ensembles are growing qpf... but surface and upper lows may be too close to LI/se MA for much snow in the NYC subforum.  This looks to me to be mainly an elevation I84 corridor wet snow concern.  I cannot commit any further details - just too uncertain and that uncertainty may continue another day or 2. Far from an ideal snow event, but also the typical winter uncertainties for our area.  Forward we go... worthy of monitoring. 515A/31.

Agree still time for changes but right now I’d say rain for nyc metro and immediate suburbs and white rain for interior lower elevations  with accumulating snow in the higher elevations. If it bombed out a bit earlier or further south it could be a different scenario but unlikely. 

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Two back to back ULLs are forecast to take basically the same track from northern Mexico/west Texas to near Chicago, separated by just over 24 hours. That's kind of funky. The second tracks slightly east of the first on most guidance, but the trough axis and airmass are little improved after the first. There is a forecasted weak high pressure center in eastern Quebec/Maine early Sunday and a slight hint of damning, but once again cold is really marginal until you get into interior SNE. Still I think any slug of heavy precipitation could bring the parachutes because the forecast soundings show mostly a boundary layer issue. Let's hike to our highest local hills and hunt for the snow line.

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5 minutes ago, MJO812 said:

12z GFS

Mid 30s on the coast

5fedf3ffd1401.png

IF the precip is heavy enough it could snow all the way to the coast but a a big IF could have an effect on both NFC playoff spot games in NJ and PA Sunday afternoon

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3 hours ago, HVSnowLover said:

Agree still time for changes but right now I’d say rain for nyc metro and immediate suburbs and white rain for interior lower elevations  with accumulating snow in the higher elevations. If it bombed out a bit earlier or further south it could be a different scenario but unlikely. 

It's going to be precarious even for us I84 peeps. Elevation and precip intensity will certainly help overcome marginal temps but  its going to be close for us in the valley. 

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5 minutes ago, NEG NAO said:

IF the precip is heavy enough it could snow all the way to the coast but a a big IF

Gfs is the coldest out of the bunch

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The GFS has a really nice looking sounding for near interior areas. Really steep lapse rate in the lower boudary layer. That would probably be rain at 200ft and a winter wonderland at 500ft in NENJ and the Hudson Highlands. The NAM has an above freezing layer near 800 or 850mb that would probably mean mostly rain until you got near the Poconos, far northern NJ or western Orange County.

I still don't like the primary cutting off our "cold" air supply. This could be rain to pounding snow, ending as light rain or drizzle.

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