wdrag

A little late and after the fact, but here is the CoCoRAHS snowfall report for Thursday December 9, 2020, NYC forum.

Hi! A few different things... just to try to keep perspective. I need op GGEM on board... i see some of it's ensembles are there but I need GGEM op on board. I don't think it will be much of a snow storm for us, if it isn't. 12z NAEFS has slightly warmer thickness than it's 00z/10 version...5540 cutting thru LI now 00z/17. That increases risk of mix or rain LI, for at least a time. Caution on buying in on the ratios til till we know for sure the sounding is all snow, and that the 1000-500 thickness is preferably ~5400m Thereafter it's the DGZ and Banding. WAYYYY too far off for me to count on anything except decent snow I84 north (heart of the ensemble axis). For now we in the NYS forum seem to be close to the gradient of snow and no snow. Gradient error's can be very large. I've added the WPC D7 GEFS forecast for 3" or greater of snow Or 1/4" water equivalent glaze or combo thereof. The prob is 30-49% in dark green. Will revisit tomorrow morning...

I wasn't there, but did CP not have any cover on grassy surfaces yesterday? They had .05" of melted snowfall... and moderate snow at times. I would ave thought a slimy wet snow covering of 0.1?

Good Thursday morning all, My morning update on this thread. I probably won't comment again til Friday. My primary dates of interest for wintry precip elements in the NYC forum are Monday the 14th, Wednesday the 16th and Friday the 18th. All dates have possibilities and I suspect will have qpf. The jet stream will be just to our south throughout. In addition there will be 3 southern stream short waves to monitor which should have qpf impact here and a NEAR 50/50 500 MB low will be developing mid and late week (actually closer to 55N, 50W). Thinking the primary date of concern for snow here is Wednesday the 16th, but let me begin with this coming Monday the 14th. When you look at the models, It doesn't look much qpf with the front on the 13th, at the expense of a trailing short wave in the lower Mississippi Valley, that currently is modeled mostly to our south. However, if it trends a little north, wintry precip could easily occur on it's northern fringe-just north of NYC. This would be a minor event, at worst, if my impression of what will happen is correct. This Monday event is my lowest confidence, but the GEFS is flagging decent qpf just to our south. NAEFS image attached. The 16th event to me is clearly cold enough for snow and ice, even down to NYC. BUT, given that it's at D7 and that modeling could be too cold (sfc pressure too low on the presented ensemble for 00z/17), I have to leave open the door for all rain NYC-LI and s of I80 in NJ. I've added a number of NAEFS graphics including small qpf, cold enough 1000-500 thickness, Surface pressure. Later the 18th is flagged as well. I think that one in part depends on what happens the 16th- If the 16th ends up as strong as the 00z/10 ECMWF op run, then the 18th probably is delayed or suppressed- however if we end up with a 1000MB surface low just to the south of LI next Wednesday evening, then the next southern steamer has a chance. Regarding the 00z/10 ECMWF op... I'm recommending tempering the amounts seen (especially the whopping Kuchera). Just too early and how often do those huge values verify at D7? I have added the 10 to 1 ratio EPS which looks like a reasonable start to me, realizing the southern edge amounts could fall as rain and make snowfall nil. I do not expect the EPS amounts to disappear I84 northward but what I expect and reality could be wrong.. Still, I have above average confidence that a wintry event of some sort is coming to the northeast USA the middle of next week, whether NYC/LI are involved is the most uncertain and could end up just wet and windy. Let's monitor. 542A/10

Timing timing timing... I'm no long ranger - no skill. I do look at basic (non MJO) patterns and it seems like we're running a bit different than Dec 2019.

I don't think you need as much cold air with respect to normal anymore. I am definitely interested in the 14th (weak wave of precip) and something more substantive 16-17 (wintry mix)... and with blocking in Greenland modeled by both the GEFS-EPS for the foreseeable 16 days... rainstorms are not a constant lock.Even seasonable temps give us a bit of a chance.

I see OKX afternoon prelim CLI for CP as T snowfall today.

I just checked the 12z/9 NAEFS... it's favorable for a light wintry weather event here, around Thursday the 17th. Plentyyyyy of time for things to go wrong or, get heavier. I am always keeping in mind the mild base state for our winter and many long rangers conservative snow forecast for this winter. Nevertheless, still something to watch for during this 5 day period and make the most of the marginal opportunities.

Wantage NJ, last band on its way in now for us out here. 0.8" solid. Thanks for adding your data. Will be curious what OKX does for CLI tonight--- 430CLI is prelim. The 130A Thursday will be the official. CP ASOS had moderate snow at a temp I think around 33F. Looks to me like first measurable snow must have occurred. Also note the moderate snow around 1P and the early morning NAM 3K image post on the DGZ lift. It doesn't take a lot of lift in the DGZ to make good sized flakes. NAM was pretty good for this event, I think. KNYC 091951Z AUTO VRB04KT 6SM HZ BKN016 BKN037 OVC070 01/M02 A2976 RMK AO2 SNE20 SLP070 P0000 T00111017 $ KNYC 091943Z AUTO 7SM SCT014 BKN037 OVC070 01/M02 A2976 RMK AO2 SNE20 P0000 T00111017 $ KNYC 091921Z AUTO 23007G15KT 200V270 3SM BR FEW010 BKN014 OVC034 01/M02 A2976 RMK AO2 SNE20 P0000 T00061017 $ KNYC 091915Z AUTO 22006G21KT 1 3/4SM -SN BR SCT010 BKN015 OVC036 01/M02 A2976 RMK AO2 P0000 T00061017 $ KNYC 091907Z AUTO 26007G16KT 210V010 1SM -SN BR BKN010 BKN015 OVC021 01/M02 A2976 RMK AO2 P0000 T00061017 $ KNYC 091851Z AUTO 24009G15KT 1/2SM -SN FG BKN009 OVC015 00/M02 A2977 RMK AO2 SLP074 P0004 T00001017 $ KNYC 091808Z AUTO VRB03G15KT 1/4SM SN FG BKN009 OVC016 01/M02 A2979 RMK AO2 P0001 T00061017 $ KNYC 091751Z AUTO VRB05KT 1/2SM -SN FG SCT008 OVC016 01/M02 A2979 RMK AO2 SNB09 SLP080 P0001 60001 T00061017 10033 20006 56021 $ KNYC 091731Z AUTO VRB06G15KT 1/2SM SN FEW009 BKN023 OVC031 01/M02 A2980 RMK AO2 SNB09 P0000 T00111022 $ KNYC 091723Z AUTO VRB06G18KT 1 1/4SM -SN FEW012 BKN031 OVC041 01/M03 A2980 RMK AO2 SNB09 P0000 T00111028 $ KNYC 091716Z AUTO 24011G18KT 2SM -SN BKN029 BKN043 OVC055 02/M03 A2980 RMK AO2 SNB09 P0000 T00171028 $ Snow reports so far by the NWS.

The 2" report just east of Scranton its probably closer to 3.5" .. solid event there. Here's some snow reports that are posted by the NWS.

Yea...NYC First trace of the season- unmistakeable at the KNYC ASOS!!

Wantage NJ (8 s High Point) 0.5" so far. Roads wet. Driveway mostly wet but some slight accumulation. Concrete and pavers accumulating. Nice small flake snow continues. 30.2F

Wantage 0.2" down to 30.4. TD 29.8 3/4-1mi S-. small flake but densely filled air. Hope the main precip clusters don't miss CP (splis right-left)

Sometimes this stuff acts like summer convection. Once it gets going, it lasts longer-further downstream than expected. Hope CP gets it's trace today and we can get that out of the way. I have followed up with the OKX web team.

Impact NYC metro probably nil except folks exclaiming 'It's snowing' (maybe mixed with sprinkles at the start). It could still fade, but i am pretty sure NYC will see some snow at CP sometime between 1230-2P. Doubt if it can measure... just too warm .. melt on contact except some of the roofs/carts/grass nearby the city. My daytime 1030AM ish greeting card - wish it were deeper. Soon it will be.

Mt Cobb on exit 8 I84 just east of Scranton with ~2" in less than 2 hours. Doing. We here in Wantage are down to 3/4mi or so. Ground whitening...still T. pavement wet. 32.2.

MPIng'd snow for Wantage NJ. It's just flurries but flake size decent. 32.7/25.3

Here's what you saw... May have more info in a few hours. It was their 442PM report. Thanks...

Helpful... Let's call it zero for now, OKX has to validate one way or the other. I'm not even 100% sure NYC will see snow today- i still think so. It's crossing the Delaware now and I expect to mPING here in Wantage by 1015A.

Good Wednesday morning everyone, No change for me in this 5 day period. I think we could see a change develop in the way the GFS is modeling the 14th (a b luging weak wave of qpf. Ditto the 16th-17th which looks to me cold enough for snow or ice, even down to NNJ/NYC- BUT, I'm not jumping the gun on this since the NAEFS isn't showing much qpf-development. If....and when its does, the snow-rain thickness fields will adjust a bit tighter-warmer. Still... to me it's a 5 day period of interest. Take whatever we can get. Am not looking beyond the 18th, until we know wintery weather does not occur as topic'd.

Hi! I just checked CP Climate data and I dont see any snow...did I misread the CLI for CP? Also, is NKNYC CP...kind of looks like it but I might be mistaken. Thanks for your further clarifications and previous alerts. I'll look for your replies. And so for today: Still uncertainty... my guess is CP will have a hard time measuring 0.1" unless it comes down hard, because of above freezing temps. I added the 06z/9 NAM profile for LGA... see the temps above freezing BUT a dip to nearr freezing around 2PM, co-located the the highest rh descending to the surface (Blue-purple-see legend) and also co-located with looks like to be a minor shot of lift through the vaunted DGZ (dendritic growth zone). We'll see how this plays out. I still could see a few sprinkles mixed at onset in NYC but a swift change to all snow, presuming the precipitation arrives. Last graphic is the hrrrX variable density snowfall map...conservative so this is sent to try to keep things in perspective. 603A/9

This posts due to forum interest in wintry weather, but with uncertainty on evolution of precipitation events and how far south ice or snow can develop (even a low chance NYC). Marginal thermal profiles may limit snow or ice to I84 northward but may be worth monitoring for a minor or moderate wintry weather event I84. The NAEFS pattern along with various models, though cyclically inconsistent, suggest the possibility that the latter part of the Mondays(14th) precipitation could be a little ice or even end as snow along the I84 corridor. A wintry event possibility. Evolution thereafter is uncertain but it appears there will be some sort of decent storm system heading into the northeast USA which has a chance to involve snow-ice, at least along the I84 corridor. It's possible short wave interactions will force a northward buckle of the thicknesses and result in all rain but for now, I think there is enough model guidance to open the door for some wintry weather, mainly I84, sometime between 16th-18th. Confidence for one or two precipitation events in that 5 day period is above average, and a good sign is the constancy of a decently strong upper level jet just to our south (LF quad= exit region), frequently with the jet core near VA. Normal High Low at CP next week is ~43-32. Added two graphics: the WPC midday Tuesday (8th) chance of of more than 1/4" frozen water equivalent Monday the 14th. and the CPC D6-10 outlook for the 14th-18th. As we draw closer, it may be that we'll delete some of this and refocus the topic title- for now, this should hold us. Let's see if we can get a little winter in our area next week.

First snow of the year at CP? Snow showers are likely to dust the NY forum suburbs between 9A and 5P Wednesday 12/9/20. Does CP ASOS see snow and then is it the first Trace or tenth of the 2020-21 season? The sooner the snow showers arrive (presuming they arrive), the better the chance of measuring on the snow board. Most roads just wet but the northern and western hilly suburbs could have up to 1/2 or 3/4" on the snow board-grass-roofs-even a bit on some untreated pavement?", with I84 high terrain possibly an inch in PA NYS, lesser amounts you proceed east across the Hudson into I84 CT. No guarantees of precipitation in NYC (small chance its a mix of rain/snow in NYC) but a pretty good short wave passage along with NAM/RGEM/RDPS support all have it to the city (not necessarily measurable but snow in the air). Central Park climate data base (entire back to 1869), the mean first date of measurable there is December 7. mPING reports will assist what we see on radar Wednesday morning.

Will post two topics by 815 PM. Both shakey but there is so much interest in winter that I think there is enough model evidence to get something out there.

I just checked for myself. I don't want to waste forum time on a 1 inch gust 45 MPH routine event. However... I or yourselves can post a thread topic. I just need to build some confidence. It's been on my radar but I'm not willing to commit a thread this far out.... looking at marginality for the NYC forum-mainly I84 corridor, but certainly potential, any, date 16,18. My first interest lies in a possible (12z/8 GEFS 50% chance) first T snow (if ASOS sees it as snow), lower prob measurable (0.1") CP sometime between 10A-2P Wednesday 12/9. Normal first date of measurable in the entire CP (thread X) database is around 12/7. With hope... but not necessarily science yet.