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  1. The above hopefully encapsulates the likelihood of two upcoming significant east coast storms. Changes will occur from the some of the attached supporting graphics but we're in line for more significant weather and I'm sort of concerned about flood potential. This time maybe wet snowfall NYC.? Please consider limiting NYC snow enthusiasm with the stats attached from Don, at least until we get Jan 4-5 (if snow is still in the possibilities). It is hoped the Bluewave produced lack of 2" snowfall at CP can be put to bed, but it's possible that next Sundays probable wintry event will shift a little more inland with rain dominating along the coast. The event for the 10th could be brief snow or ice to heavy rain and snow melt, presuming we accumulate anywhere close to the attached 00z/31 EPS prob of 4" axis. Wind damage graphic via the EPS for the 10th... expectations are more of an e-ne wind (nor'easter we hope) for the 7th with gust potential 40-50 MPH along the coast and maybe minor coastal flooding (tide cycles are LOW for this storm). The event around the 10th "may" have stronger winds gusts vicinity 60MPH along the coast and a better chance of coastal flooding (tide cycles 10" higher to start). Power outages possible but impossible to predict without 24 hour confidence on wind gusts/qpf amounts/ptype/temp if and when it snows. This thread was started since I think there is general interest in snow, also flood potential for this weather interested forum. I may comment once/day but it's all yours. OBS for the 6th-7th will go in here. For whatever occurs the 10th...may have to separate out the OBS in a supplemental thread late 9th, but that's 10 days away and at least a portion of these ensemble expectations may be less than out looked through the 00z/31 cycle and therefore less impact and more routine. No guarantees here but definitely worth monitoring. Edited title 1156AM-Jan 6 to include obs and tags added obs and sleet. Edited title 645 AM Jan 8 iso include OBS for Jan 9-10 and removed the ? behind damaging wind.
  2. Added 12z/26 Blend of models rainfall, the WPC 22z/26 three day rainfall forecast, and a sample from the 18z/26 HRRRX ending 18z/Thursday, which in my mind shows the potential narrow axis of 2-3"+ of rain. If that ends up over the Passaic River Basin, then minor flooding would resume on parts of the Passaic. We'll have to wait for reality to know what will result. There should be an axis of 2-3" rainfall near I95 and it could result in moderate impact for travel Thursday morning. This in addition to the overnight-Wednesday morning dense fog impact will mean some difficulties for air and surface travel. An additional 0.2-0.6" could fall in the NYC subforum 1P Thu-7P Friday with bands of rain/drizzle in the convergent surface trough region west from the departing low pressure system off New England, and to the north of the weakening upper low moving eastward off the mid-Alantic coast. If 2 inches occurs in Central Park by Friday night, that would push December into the top 5 rainfall (7.12"), and the year to #11 (59.23"). Central Park rainfall seems to have a pretty good chance of exceeding 1.5" but there is always uncertainty on qpf. So, another significant rain event is on the way. The 48 hour qpf from the SPC HREF, HRRR, RRFS from 00z/27 and 12z/27 cycles could be helpful perspectives if and where the potential exists for 3" of rain from this event. This thread headline and/or tags may update if the NWS issues flood watches.
  3. Periods of rain, some of it heavy at times is destined for most of the NYC subforum Friday-Saturday as low pressure develops off the mid Atlantic coast into a vertically deep slow moving cyclone. PW increases at times to near 1.7" in warm advection along the inverted trough Friday then the pinwheeling PWAT circles back around our area Saturday. Gusty northeast-east winds Friday morning to 35 MPH and the constancy of northeast flow this week at the time of the highest tides in Sept should yield at least minor coastal Flooding within 2 hours of high tides Friday and possibly moderate coastal flooding at the highest tide cycle Saturday or Sunday as the backwash of the offshore storm shoots some 45 MPH north-northeast winds down the NJ coast by Sunday morning. The previous 3-4 day rains are attached, and the numbers for this coming one may exceed 6" again in parts of the NYC subforum. If so, where? It's possible, despite all this projected rain, that flooding might be imited to a few small areas. Too early to be sure as of 447PM/27. The EPS has been most aggressive with this system since 9/24 cycles and the 12z/27 EPS mean rainfall is attached. These values are quite high and much higher than the GEFS 12z/27 cycle with the GEPS midway between. If it causes fresh water flooding---where? Not sure this will be very much freshwater flooding except possibly NJ/CT/urban LI. This topic should serve also for the rainfall reports. at 505PM added the tag power outages. If this rainfall develops per the more aggressive 12z/27 EPS mean, rain softened ground from this past weekend combined with new 2+" rainfall may allow spotty power outages due to tree uproots of still fully leaved trees.
  4. Record daily rainfall values in the POR at POU 2.51-1972 and NYC CP 4.09-1972. Add on as deemed useful Above normal small stream flows from ne NJ into extreme se NYS and w CT, plus multiple small scale modeling of 3-5" and worst case maximum 7+ prompts this topic. WPC has marginal to slight risk excessive and a watch was just issued for the primary concern area at 312PM. It's possible the small scale models have gone overboard, especially the attached FV3 HRW but the SPC MAX amount axis of over 7" and other 12z/6 max axis modeling suggests the primary area of Turn around Don't Drown concern Saturday, if any roads are inundated. Support from PW near 1.6", a 12 hour nearly stationary inflow axis Saturday morning and modeled embedded lightning. The NYC-vicinity max axis may already be forming mid afternoon Friday (monitor radar). Awareness of potential assists mitigating unexpected impacts, planning your day. Again, we'll see what the tallies are but we should not expect as an expansive area of 5+ rainfall as last Friday, though isolated amounts of 5" seem to be within reach somewhere in a 20 miles radius of NYS northward to about 30 miles either side of CT-NYS border. Axis may vary. but multi cycle modeling suggests this is one of primary areas of concern. Self explanatory 12z/6 modeling amounts by 00z/Sunday 8 Oct 2023. There we(RE NO-corrected 10/8) SPC HREF Probs of 1,2,3" in this 12z/6 cycle which suggests modeling errors. Caution but worthy of monitoring.
  5. Topic Edit 508AM: Added HIGH IMPACT and the time back in to the topic and extended 4 hours. Strongest winds in NJ/ne PA/se NYS roughly 10PM-4A, NYC/se NYS 1A-6A, LI/CT 2A-to possibly as late as 9A/25 e tip of LI. Minimum wind gust on LI 55 MPH with max 75MPH, NYC-se NYS minimum wind 50 MPH isolated max 70 MPH. Please follow NWS on all warnings/statements. I'll leave it yourselves to add graphics etc as need be. I'll begin an OBS-NOWCAST thread by 6A. Have not looked at soundings but everything else discussed in yesterdays 518AM topic edit below including HSLC SVR's continues. We may reach within 2F of the record 66F-2015 max temp for Christmas Day at CP. Flooding of some of the larger rivers, if it is to occur, may be delayed 24 hours or more after after the rain quits Christmas morning, Max rainfall axis in our forum looks to me to be CT, isolated 4", not including snowmelt runoff. If anything is missed, please let me know. Thank you. Topic Edit 518AM Wednesday 12/23: No significant changes. The prime threat period might by 2 hours too fast but not enough evidence to change the primary initialization period of weather related issues. My assessment tells me to prepare, without science, for many many thousands without power starting 9PM to midnight Christmas Eve evening, and then across se NYS, LI, CT, MA beginning midnight to 6AM Christmas morning. Gusts NYC airports should be 45-55kt, with potential for isolated 65KT LI/CT/MA. I expect SVR's for the HSLC lines of heavy showers to help focus the primary short-fuse threats. Lower chance of any damage northeast PA but ridges there will be most vulnerable there to ~ 55 MPH gusts. There is limited science on power outage wind damage with leaved trees, without, softer unfrozen ground versus frozen but I don't have this information nor any private services predictive algorithms. I still think that wind damage will prevail as the most important aspect of this storm, but please follow NWS flood watches, warnings as issued, due to the combined snowmelt and new widespread NYC subforum rainfall of 1-2", with isolated 4" potential inland-most of this in a 9 hour period during Thursday night, Any snow on the backside is exceedingly minor on the I84 high terrain. There actually might be a little better chance for a slight coating of snow Christmas night with the weakening trough aloft passage. --- Topic edit at 526AM Tuesday the 22nd: Changed the title to WILL be accompanied by damaging wind LI, and restricted the period of accumulative snow to the interior. I think the wind damage potential is the largest threat from this rapidly deepening 980s surface low moving northward up the front into NYS predawn Christmas. SVR's possible (in my mind likely, even if no lightning) for High Shear Low Cape (HSLC) heavy showers.The Richardson (R)#/wind profile combo on the NAM and even GFS tells me 45kt+ gusts all the major airports in NYC sometime between 10P/24 and 5A/25 . This is further supported by multiple models 80KT+ 850MB winds over LI, in some cases around 90-95kt. From my looking at R# and wind grab, this has the most favorable potential in my past 3 months of examining to realize downward transfer 50-65KT from the lowest 25 to 50 MB of the boundary layer. Whether an isothermal sounding in the lowest part of the boundary layer, or even a slightly inverted sounding can diminish-mute the potential, I don't know. What I do think, is that a lot of folks could wake up with lights out Christmas morning across LI, and possibly NJ/CT. Flooding potential to me looks the same as it did yesterday-previous days, all a matter of qpf, snowmelt combo to prompt a few rivers into minor or eventually moderate flood stage, even as temps plummet from 60ish near midnight Christmas morning, to near freezing by ~ Noon Friday. Please follow NWS closely on flood potential-they have more tools than I. Snowfall, accumulation less than 1 inch probably restricted in our forum counties only I84 high terrain northwestward. I'll copy this to the last page of this topic and add a couple of wind profiles there. The future posts will look at FOUS BL winds, which I think will exceed 34kt at LGA and BOS around 06z and 12z/25 respectively. IF not, then I'm a little too severe on my wind expectations. Also, I'll be adding shorter term wind gust potential graphics, especially Wednesday onward. (corrected many typos 826A) --- Below from the origination date of Friday evening the 18th. This topic is started primarily because of the recent operational model cycles at one time or another offering a more than ordinary 12-18 hour period of weather here near Christmas, on top of melting snow. Always uncertainty. Uncertainties abound, including how far inland can a couple of hours of 60 degree temperatures penetrate to melt the snowpack, and will there be any hazardous snow accumulation closer than the hilly western and northern suburbs? Add to that, is there an inversion thats prevent excessive low level winds from reaching the ground.? Snowpack will be melting a bit the next few days,, til a sudden brief surge of 60 degree warmth Thursday evening or very early Friday morning, associated with a strong cold front. That front is embedded within a high amplitude trough. It's slowed by a strong 1030-35MB high anchored near the Maritimes, and there is potential for northward moving low pressure along the front, as it traverses across the NYC forum. Max rainfall should be concentrated just inland (se or sse surface wind) and combined with remaining snow, may? be enough to promote some small stream flooding? Flooding will be dependent on how much snow melts on the 24th/early 25th combining with around 1" to possibly 2" of rain, prior to the sharp cool down to near freezing by midday the 25th. Current 12/18 river response models to multiple ensembles are not alarmed at this point so I don't want to make this look worse than it will be. Of greater concern is the ECMWF cyclic offering of 60+ MPH gusts to LI (50 inland) which may cause some damage. Recent experience with the storm of the 16th-17th suggests to me, that we will need at least 60 MPH gusts to see significant damage along the coasts and ridges. It's possible - IF the 850MB southerly jet can exceed 75 knots, preferably 85 knots. The 18z/18 GFS has 80 knots for e LI and the 12z/18 EC has near 100 knots for all of LI. IF the ECMWF were to verify, it would be lights out for many and not a pleasant Christmas morning. Timing of the event probably sometime at night (6P/24-6A/25 EST) Snow: Backside snow doesn't often accumulate significantly with temperatures falling rapidly from the 60s to near freezing. Thinking best chance I84 corridor high terrain sometime Friday morning the 25th. Graphics: 1) 12z/18 EC 850 wind. EC surface gusts, GEFS chance of 60 MPH wind gusts early Christmas and finally, the WPC qpf forecast from ~18z/18. 608P/18
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