wdrag

Wantage snow and sleet mix east 722A and temp now 34.5. Tinge of white on the roofs.

You'll get there...first a mix of sleet and rain then wet snow and sleet. Not sure if you can accumulate more than an inch or 2 by 2P.

ice pellets at 644A in Wantage NJ

Few small flakes in Wantage NJ.. temps 34-36F around here.

From Topic headline at 6AM Monday 12/14/20. Please monitor NWS Watch-Warnings for this storm and associated statements and still uncertainty on where highest impact. There is/was some overall slight southward shift in the guidance in the past 24 hours and so my uncertainty for the forum is northern CT-Catskills, and LI/I95 southeastward. WPC still has 1.5"+ qpf just s of I80-LI and 3/4" into northern CT. Added the EPS 10 to 1 ratio graphic of both today and Wednesday nights storm. I think that serves as continued good starting point with the usual caveat on the northern and southern fringes. If you have travel plans Wednesday into Thursday I95 northwestward from VA through WV, PA, NJ, NYS and southern New England it's probably a good idea to consider changes, based on your NWS or other favorite media outlet forecasts. I think this will be a top 20 snow storm for a few parts of our NYC subforum (basically ~ 1 foot will prompt that review) but unsure where. For now between I95 to I84. Anticipating (not guaranteed) widespread closures or delays for all transportation systems I95 corridor northwestward Wednesday evening into Thursday morning,. For those who have access and wish to do so, you can calculate an experimental storm index to get an idea of what is probably coming. I don't want to presume more than Major yet (crippling is the next step up). Here is some information. https://www.ncdc.noaa.gov/snow-and-ice/rsi/?nesis Still variability in northward extent of heavy 1 foot snow ranging from the NAM Adirondacks to the GFS-RGEM I80-LI. UKMET is still quite far north. Ensembled r/s line looks to remain mostly south of I80-LI but awfully close, close enough to think sleet, rain or freezing rain mixes in for a time after the initial Wednesday evening thump for LI and s of I80. EPS continues almost unyielding on the widespread 8-18" snowstorm (isolated 2 feet possible in the banding somewhere north of I80-LI). Major power outages possible wherever the 6" of 32-33F wet snow accumulates along with wind gusts of 40-50 MPH. If this were to occur, it would most likely develop between 9 PM and midnight Wednesday evening per consistent modeling of snow onslaught and wind gusts increasing past 30 MPH. Am targeting LI south coast and NJ coast but this will require 6" wet snow (32-33f). Isolated wind gusts above 50 MPH possible on those coasts. Snowfall rates of 1-3"/hr possible in northward transiting bands Wednesday-evening/ night. Where these tend to park on the northern extent of the storm, will probably be the 2 feet of snow, especially with ratios drier than 10 to 1 (maybe 13 to 1). NWS has the multi model ratio blend tool and BUFKIT can assist for those who have that tool. There could be closing bands of moderate snowfall Thursday morning after sunrise into early afternoon as the comma head tends to fold southeastward behind the eastnortheastward departing storm. Clearing the first few inches of snow around 8-10PM Wednesday will make it easier to remove the additional snow Thursday morning. Where it's wet-caution for those with heart conditions., This strong easterly surface gradient (northeast wind) between the cold 1035MB high over Quebec and and the probable 995-1000MB low near Cape May early Thursday will produce minor to moderate coastal flooding, for the Thursday morning high tide cycle. Follow NWS statements. So the base EPS snowfall graphic is added. Also multiple locations of whatever is in their climate database (did not check for missing data). This gives us an idea of amount goals to reach top 20... No guarantee anywhere but I would think 1 or 2 of these would make top 20. May not comment in detail again til late today or this evening, shifting attention to today. Have a good day and fun debating. Am still uneasy about the northward extent of the 00z/14 EPS 1" qpf which is still near the MA Pike.

One event at a time: Today... as per the attached graphics. 1-4" of wet snow ne PA/nw NJ into all of CT. Heaviest probably hills of nw NJ and into ne PA south of I84. It may begin as rain and may end as sprinkles. Intermediate late morning-early afternoon brief periods of 1/2mile moderate snow with accumulation of 1/2"/hr for a couple of hours. Pavements wet except hilly areas above ~ 700 feet. Even NYC could Trace or measure 0.1" this afternoon after 1PM. EC came up quite a bit the past two cycles, the HRRRX went down quite and the SPC HREF stayed steady. Attached the 00z/14 SPC HREF (8 member ensemble) and the 06z 3k NAM 10 to 1 ratio =which may be a bit high on the se edge but it states where I think the potential is best. mPING will be helpful. 35/31 here in Wantage at 505A

Well researched. Thank you... I plan (if it still applies) to reference daily records at CP of 5.3" for the 16th - 1948, and 17th 6.7 in 1932. No promises we'll get either. Gotta rest. Walt

My terrible mistake! I was reading mo to date. Here's what I have for the 17th. Can this work? Just let me know. MY ERROR on the 19.8. Great catch!! Hmmmm... small chance we could break two successive daily records. Almanac for New York-Central Park Area, NY (ThreadEx) December 17, 2020 Daily Data Observed Normal Record Highest Record Lowest Max Temperature M 42 62 in 2000 15 in 1876 Min Temperature M 32 50 in 2015 1 in 1919 Avg Temperature M 36.9 54.5 in 2015 10.5 in 1876 Precipitation M 0.13 2.28 in 1888 0.00 in 2017 Snowfall M 0.1 6.7 in 1932 0.0 in 2019

Closing would help but maybe toss too much warming up to I80 to shave amounts by 6+ inches due to rain-sleet. SST's are a bit of above normal so lapse rates will be enhanced slightly. It seems to me this storm maxes intensity along the s NJ coast Thursday morning and then occludes east or east northeast, with a subsequent weakening of the short wave. This one is digging far enough south into the southern states before turning northeast that it's yanking moisture newd aloft, and the big high in Quebec adds an easterly low level jet flow and lift over the ene-wsw oriented thickness to yield the qpf modeled. I'm good without a stall... this will be very big and may satisfy the daily record snowfall at CP by midnight Wednesday night? (front end thump). Virtually no chance of exceeding the Thursday daily record of 2003 -19.8

I've been out of the forum for 7 hours and coming back to the still south GFS op is a little disconcerting but as many have posted... basically other models north and 12+. Maybe it's somewhere in between...blend and shift south 30 miles? Just can't add anything useful beyond this. By the way, I hope we all have something to post on the Monday thread. It's looking pretty good to me for a swath of wet snow. Will try and update both threads, Monday around 630A. PHI---bold and I think a very smart Watch move. We don't often get 1-2 footers... and even if some of the watch fails, it's a watch. The idea is get public attention with official product and steady the uncertainty a bit. There are multiple facets to this storm... damaging wind and wet snow accumulation with potential for considerable power outages LI and just se of I95, along with moderate coastal flood threat Thursday morning, airline impact and basic travel impacts are potentially very high I95 corridor on up through at least the I84 corridor, and probably up to near I90. Have a good night.

WPC D4 prob 3"+.

Here's some guidance...not gospel. Lets see if this guidance is too cold and less snow occurs NYC area down to I-195 in NJ than shown here. Please use the legends for your area. I definitely think there will be a period or two of 1/2mile moderate snow and 1/2" accumulation/hr in the region near and west of NYC. Decent banding will occur and there is some lift centered in the ideal DGZ. Have a look at the 12z/13 NAM 3k profile for LGA lift and temp. Later, Walt

Fwiw: WPC's first take late this morning on QPF for Wednesday evening into Thu, but does not include prior to 7P Wednesday. This will update early this afternoon.

Absolutely! The questions continue going forward, will it hold? I took a look at the 500MB pattern at 84 hours...modeling a 140 kt jet up over Quebec Wednesday evening and plenty of sw flow back to OHIO at 500MB. I'm pretty sure this says northern solution.

I like hanging out and tryin to provide some insight above and beyond straight model use... but it's still the models. back in the 1970s we could outguess the models 'sometimes', because they only ran 2x/day, fewer models and so we knew the biases. Not so today..,many models updated yearly. For this storm, soon we have to frame actions.. No pressure: I remember my shifts in the office... daytime phones ring off the hook with how much this and that, - that's why it's important to have a venue such as this to sound off and discuss, but also I think there has to be a public product framing these event, to keep things in perspective. I still worry, even on this one, hanging too far out. So far (including 06z EC) we're on track excepting the GFS op and GEFS south.

For the benefit of my friends in the NWS, I tend not comment on WHEN watch-warning issuance, instead focusing on my impressions-considerations. Help me out: GFSv16 - is that the parallel? I saw what you saw. I can tell already that WPC is leaning heavier and I think many of us on the forum are in favor. That said, NWS has Monday problem to deal with that may result in an advisory hazard for a portion of NJ (please see Monday topic). If I was working, most folks know I tried to push (collaborate) the lead time successfully. Watches are meant to verify 50% of the time (that's the purpose-a defined heads up with potential for failure, whereas the warning needs 80% success according to the NWS criteria, which sometimes limits warning issuance since impact is personal perception). I think my prior colleagues tend to issue with more certitude- more conservative and not wanting to hype. IFFFF this scenario continues as as consistently outlined... That would be a 24 hour Watch from Noon Wed-Noon Thu... usually max watch lead time up to 60 hours (5 twelve hour forecast periods, today, tonight etc) is pushing it but for a 1 footer...and potential airport closures. My guess is a Monday morning issuance but with less staff, maybe it will be late today-depending on the 12z cycle and WPC-NWS collaboration. I don't know what the social scientists say, but I'm all for lead time on high probability large events, similar to NHC. I could see an issuance late today that this process will be collaborated between WPC Winter Wx Desk and multiple impacted offices from The Virginias-PA-NYS-New England. These calls can take 30 minutes or more for every office to have a voice, around 130A and 130P. And this with not all the latest cycle guidance available. Thereafter, it's a push to get a good clearly useable product out and with Covid staffing, not sure how they handle. Think I'd like to leave this as is and let the NWS processes work as their guidance directs.

Good Sunday morning everyone with probably small interest in Monday as compared to Wednesday-Thursday, Added the 00z/13 SPC HREF 8 member ensemble for snowfall Monday, and the 06z/13 HRRX variable density snowfall. A period of snow is expected between 8AM and 4PM Monday across most of the forum, mostly melting on pavement due to daylight hours (except possible hazardous plowable 2-3 inches in the hilly areas of western-nw NJ and ne PA south of I84). Snow should eventually accumulate on all untreated non paved surfaces. Range of accumulation in our forum area 1/2-~4". I think the heaviest will be hilly terrain of nw NJ and ne PA s of I84. The I95 corridor may start as rain or a rain/snow mix but eventually go over to snow before ending. It's possible that many areas in the northern third of NJ across LI and maybe s coastal CT will see a short period or two of half mile moderate snow with 1/2" accumulation in an hour.

Good Sunday morning everyone (Dec 13), still 3-4 days away from a big one-the largest since March 2018?. Follow NWS statements/watches and warnings for snow, wind damage and coastal flooding. EC and GFS models differ on track and intensity of the 850 Low/500 MB short wave (slight neg tilt or not?) and so... while I adjusted the topic headline and first two lines of the topic... no overcommitment for me on how severe. 00z/13 GFS MOS is a bit weak on POPS - is that a sign of a southward trend? I like closed lows at 500MB e of Cape MAY NJ and then out to sea s of ACK to bury NYC in snow... others may see it different but since the EC track continues consistently closer to LI than the GFS through the 06z/13 cycle, I leave my downside options open. Have added graphics the ~0724z/13 WPC QPF which if occurs implies a major snow storm, with 1 foot amounts fairly widespread in our forum north of LI-I80. So, overall, I have no change to the topic considerations. From my perspective, a widespread 6" or greater snowstorm is coming (including NYC and much of LI), even if sleet-rain mix in over NYC/LI up to I80 in NJ, which is a distinct possibility if little banded dry slots develop Wednesday night. Max amount axis to me favors near I84 (snow ratios and 700MB frontogenesis) but that is said since I'm leaning with the consistently stronger, more northern EC/EPS solution. I could be choosing the wrong solution. One note on the EC... IF it's too strong at 700MB trying to close off a low over NNJ-LI, then the GFS will prevail. I think the NAM will help us tomorrow morning and my guess is the NAM will favor a more robust northern solution, but no guarantee. In the meantime: I think it's time to think about getting all Wednesday activities complete by around Noon, and plan to resumé after the Thursday cleanup (sometime Thursday afternoon or Friday). I expect considerable closures for Wednesday evening and Thursday morning activities in our forum (safety purposes). Also, while powder is expected n of I80 with temps only in the 20s, I can see power outages from 6" of wet snow somewhere LI, I95 corridor eastward in NJ, presuming the warmer EPS is correct. Drifting snow can occur during the height of the storm and shortly after it's departure. Snow measuring may be difficult-snow boards cleaned every 6 hours and then add those 6 hourly totals. Graphics are: WPC qpf forecast issued 0724z/13, the 00z/13 EPS snowfall (10 to 1 ratio) - not the heavier Kuchera yet for the the powder area, the 00z/13 GEFS chance for 8+" of snow which is LI-I95 for the rooters of the GEFS and probs quite for high for this. 538A/13

What am i to make of the continuously decreasing negative 3.4 Dec anomaly? and from what I can tell MJO influences may be weakening toward the end of the month? Any implications of both changes on winter snow here? GEFS seems to attempt a +PNA toward the end of the month and continues some sort of Greenland + anomaly. Just seems like wintry options may still be on the table? Is there a different read? Thank you very much for any reply, Walt

Yes, 18z NAM continues at 42-54 hours... probably going to happen. NAEFS came north and a sharp cutoff nil near AVP-BAF. Melting beneath should suppress amounts a bit, especially lower elevations but ground should be white near NYC by 4PM Monday... the 12z/12 EC op was the least interested.

Hi... I see some posts on the 12z EPS.All these op model members are part of the entire group. I want to think that the 12z EC op for the northeast is a lower end member. Checking the 12z/12 EPS ens... the qpf is just about as robust as the GEFS and basically close to the WPC 1750z solution. Snow maps (10 to 1 ratios), about the same or an inch higher than the 00z/12 cycle and both cycles are higher than yesterdays 12z. Very steady. So, banding, IF a 700MB closed low is across LI or passing by 44025 will make up for lower qpf I84 region. In essence, I want to see the following cycles not decrease too much. The 850 low on the EPS is quite quite nice (see the 06z and 12z projections with excellent near 50 knot ensemble inflow). Because of 40s sst, have to think sleet rain mixed at times LI/I80 or I78 southward, (during lower precip rates) after the probable initial burst (1/2S) of snow Wed afternoon I95 corridor. Also, if it does go over... that spells trouble on further snow accumulations rates til the column cools significantly. Attached successive cycles of the EPS storm snow, plus the 850 MB wind 06z and 12z/17, plus the 850 anomaly gradient near LI and finally the NORMAL 850 temps for OKX. To me the suggestion is 850 zero is very close to the south shore of LI. None of this is gospel...just brings up things I try to remember to consider. I don't haven an answer but do have cautions I80 south but rossi could be right.

WPC 1750z updated graphics... awfully wet NYC... I hope it's right, because oof the GEFS which has a pretty darn good 500 low at 12z/17. Still want to see the EPS. They've slightly tempered confidence in PA.

For sure no KU mention in any topic. Could be one cycle, especially since the GEFS has neg tilt close off going here... early Thu, but an EC op southward slide noted. Not going to comment on whether this is correct but it is possible if the 500 short wave shatters too quickly. Still big but at 96 hrs+... just good to let things sit and stew for a couple of model cycles and allow the ensembles to guide.

More spread and some slight nw trend... track is good...

Just scanned the abstract and closing remarks, including the caveats. I myself am not sure how to account for this in a forecast, except to keep it in mind. I use the variable density snow forecast from the HRRRX, sometimes good, and other times not so. I'll presume surface wind above 18 knots shatters dendrites a bit, making the layer more densely packed. Here's my concern... minor as in the closing pgh. I cant even pinpoint snow ratio itself, or exactly where best banding (in advance)... then I need to use model winds... for the near surface, and the winds we see are generally 8-10 meters... need face level wind, not commonly available. Snow measuring every 6 hours will reduce this problem, especially in events where wind is primarily at the tail end. Later, Walt The surface wind speed plays a minor role by decreasing snow ratio with increasing wind speed. Although previous research has shown simple relationships to determine the snow ratio are difficult to obtain, this note helps to clarify some situations where such relationships are possible.