wdrag

It could. I’m just worrying about the fact that primary jets split us. North and south so that WAA QPF is less than 1 inch in that ice period. I see 12z GFS still on track and the for some reason furnace RGEM this year does have some ice but less than USA models. For now I’m playing the lower end of icing but it is coming from what I can tell remotely

Wantage NJ: 0.1" snów shower 805-825A. Vsby briefly 1/2SW. 31.8F. wind blown. driveways and where covered elsewhere, slippery. Treated roads wet. 828A/29

Agreed: Maybe Pike too, and High Point SR 23 extreme northern Sussex County. Just difficult for me to see above freezing prior 9P Friday night at High Point, points n and w, at least based on modeling through the 06z/29 cycle. Enclosed map shows the defined subforum coverage area. Sometimes, I'll mention interior MA for those who might be interested in New England.

I edited the 1/1 event about 20 minutes after posting. The change: I'll begin a new topic for 1/3 late today if its still modeled by the GFS para and EC but prefer GGEM on board.That one would be very low confidence for what could be a grazing fast developing nor'easter w snow somewhere close to NYC??? Again low confidence but on recent GFS parallel and EC OP. My energy is focused on 1/1 since ensembles are not very enthusiastic for land impact on 1/3.

Good Tuesday morning everyone, Dec 29. Have concentrated the event to primarily 1/1. It may bleed into 1/2 morning, but for now trying to simplify. From the topic update; Decreased model qpf has dropped the impact level to what i think is a relatively routine 3/4" to 1.5" qpf event with sleet and glaze expected I84 corridor. I dropped the front end concern on the 31st since it's minor, maybe a bit of snow or ice mix in the higher Poconos with the CFP. I'll begin a new topic for 1/3 late today if it's still on the EC and GFS para but prefer GGEM on board That one is very low confidence for what could be a grazing fast developing nor'easter w snow somewhere close to NYC??? Again low confidence but on recent GFS parallel and EC OP. Timing for renewed precipitation seems to have delayed about 6 hours from prior modeling with 6-10 hours of ice anticipated for the I84 high terrain, beginning midday the first in the Poconos-far nw NJ-se NYS and late day CT/MA portion. Treated surfaces may be just wet during the daylight hours, but if it's several hours of sleet, then a bit of a different story. Glaze, probably 1/4" or less even if .75" freezing rain occurs. This will need much more refinement as we move into mesoscale-fram analysis. So I see this as an advisory hazard NY afternoon/evening for at least parts of I84. Unsure if temps can remain at or below freezing long enough to have glaze approach 1/2" in our I84 corridor high terrain. As of this time, would not favor that higher end impact but worthy of monitoring. Flooding rain is probably no longer a risk,due to less qpf. However, those who had sump pumps running for the 12/24 event, may see a resumption-not that this is a big deal, provided they are operational, but in our area of nw NJ, it's unusual for this to occur in December. No new graphics today. 537A/29

Saw the comments on GFSV16. I'm the outlier and you may be correct but I see it lagging on big events except on two occasions the past 6 weeks. I'll monitor temps etc the next 3 days vs GFS. On GEFS 2-3" snow still on the 18z/28 run, you probably already knew (old news?)... but from my perspective, that's probably the GEFS trying to treat sleet as 10 to 1 snow ratio. Therefore the GEFS implication that a bunch of sleet is coming Jan 1 to I84. I won't say what will be right, but noticed the 18z EC op has 27F in PHL 12z Friday..not precipitating yet. That's 7F colder than the 12z/28 GFS MOS. So, i know cold air can erode, especially since 850 flow is southwest, not aiding CAD, but yet, the max 850 jet cores are split... one to the Adirondacks and the other s of LI...leaving not quite so much scouring potential into I84. If models warm from here on out, then I'm wrong. However, if RGEM is not furnace and starts showing 9-12 hours sleet/freezing rain into parts of the I84 corridor, I won't be surprised. GGEM should start tipping us off soon, one way or the other. One other note: I saw the note on Jan 3 being included in a topic. On our NYC forum I did that so we can keep all the discussion of multiple coming events in one place. They know that this original topic was 1 day either side of 12/29 and 1/1, as originated 1/21. I'm letting the models vacillate for another 24 hours. By Wednesday morning it should be more defined whether there is a significant I84 ice event. Added the 00z/21 NAEFS averaged trough for 00z/2. Have to go...probably won't see the forum til 6A Tuesday.

Think I figured out the GEFS snow accumulations on the first. I think it's taking sleet and converting it as a 10 to 1 ratio. Therefore, I think the GEFS is offering quite bit of sleet to I84 on the first as the 18z/28 version continues with its 2-3"snowfall there. I kind of think that is correct (sleet, but total sleet less than 0.3"). Noticed the 18z EC op has 27F in PHL 12z Friday..not precipitating yet. That's 7F colder than the GFS MOS.

Patience on this coming event: I could be wrong and I see lots of folks are on the EC warm, very little ice. That could be right. However, the NAEFS is arguing considerably colder than the op cycle of the GGEM. The BL temp has dropped about 4-5C near I90 for 00z/2 and now sitting nr 0C with at least 1/4 qpf by that time. I'll add these NAEFS images and let this be, til tomorrow morning... maybe consensus by then will convince me that I'm wrong. I sure like the RRQ of the Maritimes Jet and LF quad of the Ohio Valley, and while thicknesses are warm, in the top of the ridge it can snow down to a 543-546 thickness. That will need individual checks of soundings. 12Z GEFS continues the 06z several inches I84. 12z NAEFS qpf by 00z/2, BL temp 00z/2, 500MB pattern 00z/2. Use with caution as I know many like the north, stronger and warmer. Until the NAEFS caves, it's just time to wait on outcomes with I think the 12z Wednesday cycle the potentially more reliable guidance and closing in on whatever. As far as GFS V16: seems like I'm an outlier on it's lack of reliably improving here in the northeast, but i only look at the big events. Coin flip for me. Go with your colleagues on it's improvement over V15 (hopefully improved BL temps).

It's D4 but here are the 06z/28 GEFS probs for more than a T of freezing rain and more than 0.2" The snow probs for more than 3" (10 to 1 ratio) look good just north of I90 (NNE and N NYS). Offline til 1 or 2 P. Hopefully Global models are not depressingly warm for I84.

New 15z/ WPC D4-5 qpf. As you see, slipping south on max axis. Usually I don't like to be in max axis of qpf for winter weather, UNLESS deep layer cold. The reason: MAX axis suggests warmer higher PWAT closer to the warm front 850MBJET and rain involvement. I like this portrayal for I84 north wintry. This is going to be interesting ... tho to me its front end snow-ice end as drizzle then see what late 2/3 brings, IF anything. 12z NAM looks good to me to at least give us ice and possibly snow on the front side - mid lvl FGEN WELL ahead of the primary low heading into the OH Valley.

Yep: Would be a bit odd for the EPS to miss this 1/1-3 event so I temper myself. Still, what the GEFS and multiple models are telling us... lookout for at a minimum, a significant ice event 1/1-2.

Wantage NJ ..snow pellets... well times 30-60 minute was band moving east. Trace at 845A/28 33.8F Ending as RW- at 9A. Trace and slippery underfoot. Cant tell if its icing but air temp 33.8, dew point 32.2.

Looking pretty good to me for a long duration wintry wx event on I84... starting time on 1/1 uncertain and if you look at the trend, biggest part of the event could be late 1/2-3. For now going with 1/1 solid afternoon in CT but this is not yet completely resolved. What seems to be well resolved now, is no big low into the eastern Great Lakes. Possible yes, but not likely, due to the closed low initially into the Ohio Valley is too far west of us to negate wintry weather, and it weakens out across the top of the ridge awaiting what might be a better positive tilt short wave late 1/2-early 1/3. Interesting for sure.

06z/28 GEFS trends continue ever more wintry with several inches accumulation of snow I84 region on the first-second... even early 3rd looking interesting. EC 06z run through 90 hours looks interesting. Strongly suggests at a minimum, a 12 hr winter weather event is coming for I84 on 1/1... even sleet to NYC possible early on. Start time uncertain but should be going in earnest during the afternoon. Probably going good in the morning Poconos. Ever more looking more like a snow to ice situation, 12+ hours duration at the top of the 500MB ridge with primary upper low too far west to inflict major early on warmup to our area, provided we get the subfreezing temps here by 12z/1.

12/28 535 AM copied from topic update: 5 days in advance so I may be too detailed and too cold in my thinking-therefore uncertainty. Also the overnight WPC guidance does not support my concern. So caution on the following: Don't bet on it, but if you wish, keep it in mind. As everyone can see via the modeling the big warm windy event days ago modeled for 1/1 is gone and snow/sleet/freezing rain has increasingly been added to the mix near I80 northward ,with what I think is a likely hazardous advisory situation for the I84 corridor, especially Poconos-se NYS NY Day morning-midday. For now I left HIGH impact in the headline because I've seen these situations with sw 850MB WAA flow-not scour out whatever 32F airmass creeps into the interior, and the supposed change to non freezing rain does not occur or is delayed 6-12 hours. This whole event may become a routine 1-3" qpf event with an advisory event for the interior and if it becomes completely evident, I'll withdraw HIGH impact. This situation doesn't mean the temp cannot burst into the 40s /low 50s early on January 2, but I'm cautioning on literally believing an above freezing forecast, especially from MOS guidance, IF and only IF, the subfreezing airmass does sift back down into our area NY eve. QPF as per WPC--still outlooking 1-2" and I think there is potential for 3", wherever the max qpf axis, which seems to have slipped south to PA/NJ/LI. Whether this causes any flooding of rivers is unknown, but it does not look major and it's possible that the icing will lock up or delay-spread out runoff a bit in the interior, so the river response is contained within the river banks. It is good to know that that qpf in DEC has been 150% of normal with about 2" in 24 hours, threatening to cause some river flooding, and renew sump pump action in homes where sump pumps were still active yesterday. Big wind is no longer a threat. So the questions: how much sleet and freezing rain for the interior, inclusive of nw NJ, ne PA, on up the I84 corridor to Worcester, MA. The precip comes in waves, with the primary event NY Day. I am expecting a slippery-hazardous morning across ne PA/nw NJ developing northeastward into interior CT/MA but particularly ne PA/nw NJ on all untreated surfaces. Roads during the daylight hours, after initial treatment probably just wet but this ever changing situation should be monitored. Glaze amounts of 1 tench inch foreseen for parts of the interior high terrain, maybe ~1/4" if my concern is correct about temps not warming above freezing until the primary burst of heavier qpf has passed out to sea late on the first or early Jan 2. I didn't speak of snow amounts but there could be some coatings of snow included on NY Day morning at the beginning of the primary event, if an even colder scenario evolves. Again, remember, WPC has no outlook for 1/4" of frozen water equivalent here (but which I dont think includes glaze). 00z/28 GEFS has an over 50% chance of glaze in the interior n of I80. Then there's the trailer short wave for later the 2nd into the 3rd....I think it needs to be monitored for an eventual colder wintry impact here...probably light, IF ANYTHING at all this far north. Finally: for NY eve celebrants and pandemic considerations do not recommend , but if you're outside on the lawn for some reason, there could be an interlude of no precipitation near midnight (between the earlier in the afternoon cold frontal passage and onset of the NY morning qpf). Please be aware that I saw the 00z/28 GFS para which finally has 1+ qpf here (delayed a few cycles from the GFS) but it's temps are warm with no ice threat here in our area- It's a warm option but I think highly unlikely. Graphics are the NAEFS 52 member sfc pattern (NO EPS in this mix, just GGEM ens and GEFS), the GEFS prob of icing, the FFG for 6 hour amounts and our Dec 2020 % above normal qpf.

Thank you very much - many times just a little lucky to get close and I learn from our posters. Helps me incorporate multiple thinking. In any case Happy New Year all! Let's hope it is as good or better than the soon to be exiting 2020. Walt

At 120 hours... I think we have time to see a weaker low in the eastern Great Lakes, more of a development on wfront near or s of I80 for ice I-84. I will say this, it appears to me the GGEM is slightly colder...ever so, and it and the GFS are on board with 1-3" of rain. Additionally, the GFS is a bit colder. Does not take much to keep colder air in for ice, high terrain I84. Right now, I'll go with the preponderance of guidance-forum sentiment but I think, unless the EC reverts to it's previous days of 12/24-25 scenario, that the more wintry options have opened up for I84, certainly more than we had yesterday and prior. I am not discounting the northern stream weakening eastward out of the Ohio Valley forcing the occlusion s of LI. It is winter and not every storm is going to be wet. You'll have more info prior to me as I've got to go offline for a while. From my perspective, the fact that the GFS has some ice along I84 is significant since the GFS BL is not very good as compared to the eventual NAM and RGEM incorporations tomorrow and beyond. Noting WPC is waiting on on it's D4-6 winter weather, which means they too are a little more concerned than previously for the interior ne. Here is their updated D4-6 QPF from 14z, with no input from the 12z cycle. So not gospel but I think a decent idea.

On Polar Vortex: wikipedia and then some government definitions. Myself, I prefer not to use Polar Vortex in winter til we get down to a 500MB 498 or 504 DM (corrected 540 to 504 at 419P) height-something more common n of the arctic circle (60N). Use as appropriate with respect to NOAA etc definitions. A strong polar vortex configuration in November 2013 A more typical weak polar vortex on January 5, 2014 A polar vortex is a persistent, large-scale, upper-level low-pressure area, less than 1,000 kilometers (620 miles) in diameter, that rotates counter-clockwise at the North Pole and clockwise at the South Pole (called a cyclone in both cases), i.e., both polar vortices rotate eastward around the poles. The vortices weaken and strengthen from year to year. As with other cyclones, their rotation is driven by the Coriolis effect. The polar vortex was first described as early as 1853.[1] The phenomenon's sudden stratospheric warming (SSW) develops during the winter in the Northern Hemisphere and was discovered in 1952 with radiosonde observations at altitudes higher than 20 km.[2] The phenomenon was mentioned frequently in the news and weather media in the cold North American winter of 2013–2014, popularizing the term as an explanation of very cold temperatures.[3] Ozone depletion occurs within the polar vortices – particularly over the Southern Hemisphere – reaching a maximum depletion in the spring. Polar vortices are weakest during summer and strong

Will try to remember for 1030A... basically it's always been around but along with much of the drama of weather life (I definitely am apprehensive about overuse of extremes, especially if the issuers do not consistently verify). Later... ping me this eve, if I forget to comment with documentation (unless others do so).

Now that we have a day or two of relative downtime, I've started a new topic in MET 101- a concern of mine is bleeding/muting the appropriate use of weather terminology. We have by and large, my guess, is at least 80% routine weather days. Then there are the High Impact events. One of these are arctic outbreaks. It is my opinion, that we tend to apply the term arctic too frequently, reducing it's valued application in truly very cold, wind chill warning (not advisory) criteria situations. If you're interested, it's all in MET 101. Have a day!

Good Sunday morning everyone, Dec 27. I won't repeat it here, but if you're interested..I've posted a topic in Met 101: My own concern about the overuse of the term Arctic Air. Have a good holiday season. Walt

Good morning this 2020 holiday season. Weather tends to highlight dramatic events. I find the term - use of ARCTIC air far too often here in the northeast USA. I have provided the American Meteorological Society definition of arctic air, and the NWS lesson source regions. I think it would be good for us to review the source region of many of these air masses (and if we know how, use trajectories to locate the source). In essence, I am concerned about the overuse of this term. I myself would probably reserve the use of the term to something like wind driven 20 degrees below normal (and only in winter in the USA). Here in the I84 corridor, i don't think of arctic air til we get wind driven near zero airmass in DJF or maybe the NWS definition of Wind Chill WARNING as it is applied in the USA.. There is no specific definition as I've written in this paragraph but I'd like to see the use of ARCTIC reduced, to where it can be of more value (VERY cold). Your approach and counter concern with this topic- let em rip. arctic air A type of air mass with characteristics developed mostly in winter over arctic surfaces of ice and snow. Arctic air is cold aloft and extends to great heights, but the surface temperatures are often higher than those of polar air. For two or three months in summer arctic air masses are shallow and rapidly lose their characteristics as they move southward.

On the 27th, at 703A..have added the tail end CoCoRAHS snowfall for the I84 area on Christmas evening. , also the CoCoRAHS two day totals for the rainfall of 12/24-25 and the radar - platform analyzed rainfall for this event. This should close it for me.

Just a note: Unsure if anyone noticed the river stage forecasts for the snowmelt-rainfall combo on 12.24-25 appeared to be too high- less impact.