wdrag

Modeling is favoring the development of some sort of extensive precipitation event along the east coast, with either the first or second of two short waves carving a pretty deep, albeit temporary 500MB trough in the eastern USA between next Friday and Monday. At least until Tuesday the 18th when the results of the 16th-17th are in, lets hold off on single model solution hype. Three graphics added, two from the 08z/16 WPC issuance. Low prob 3+" of snow, and the third was the CPC D8-14 hazard graphic, it paints a small chance of heavy snow just north of I-80 again (just like this 16th-17th event). It also ,not shown here,has a high chance of very cold air here 22nd-28th. 7AM/18 Update: I've updated the thread title-no guarantees our NYC subforum will share in what is coming to the Demarva-Carolinas but it seems models are gravitating to a decent snowstorm for a portion of the mid Atlantic and possibly through southern NYS-southern New England. 718A/21: Changed thread title to add part one was about 150mi too far southeast (slightly less average error for a D5 forecast than NHC on tropical systems). Withdrew wind from the tag. Otherwise the overall intent of the thread remains the same.

Please follow National Weather Service warnings/statements. Starting from another 10 degree morning in NYC, a rapidly changing weather scenario will cause some power outages, accidents (despite a Holiday weekend) and slippery travel for a time in a fairly large portion of the forum, in part due to at least 42 consecutive hours of freezing temperatures on non snow covered ground, and beginning near sundown when the impact of solar insolation lessens. Exactly who gets how much of what is being determined by member observations with model and forecast contributions enhancing, but not hyping interest. Coastal flood threat as per OKX. Usually we like at least 12 hours of gale force onshore flow to build the water levels, but with the astronomically higher tide cycle, 980s MB pressure at Monday morning high tide, an inch of rain in the 6 hours up to high tide emptying from rivers-streams, there should be enough surge and incoming wave action to cause coastal flooding. Working a bit against the flooding NYC southward along the NJ shore is the onslaught of wind abating and turning southerly near the time of high tide. Certainly the early part of the morning high tide cycle looms larger. If you're in a tidal inundation area, follow NWS statements. I'd park my car with parking laws in mind where it can't get flooded. Wind damage: several 12z/16 HRRRX graphics are appended. Please use the legend. Midnight to 6AM is best chance for damaging wind , to occur in a 3hour period ranging from near 2A NYC to near 5A e LI. Gusts to 60 kt possible e LI with gusts 45 kt possible NYC metro airports. I could be too conservative. Have cell phones charged and be prepared for no internet early Monday. Many of our members, even to western LI will be reporting a bit of snow or sleet late today (some are from Ocean Effect already). mPing will be helpful especially for us inland folks just north of I78 where an hour or 2 error in the precip phase change from snow to sleet/freezing rain or rain can mean an inch or two of snow. The 12z HRRR, HRRRX, and 3K NAM seem to support slightly more snow than maybe some are anticipating. Whether that occurs is unknown. No matter, if you have heart problems and live north of I80, you may want some assistance removing slush laden with maybe 3/4" of rain (glop). And of course have your resources to clear it by 6PM Monday when temperatures falling below freezing start the solidifying process. {The HRRRX amounts may be too large by 2", so it is a slower to change model with 1/4-1/2" everywhere up through I84 by 06z, so that could bias the amounts high there. edited in at 1036AM} ICE: I think parts of the I84 corridor including Sussex County NJ may have pockets of damaging ice near 4AM Monday when the ice combined with wind gusts 45 MPH in the ridges could be enough to knock out some power. Monday afternoon-evening: The trough aloft passage and influx of colder air should wring out areas of 0.1-1" snowfall in the steep moist lapse rates associated with the cold pool aloft, including NYC-LI.

Will start Jan 21-23 open ended east coast storm thread-threat to likely (not categorically) followed by coldest weather of the season around the 24th. I think we're noticing each cold surge getting a little colder here in the northeast as the month proceeds. I see two more potentially big shots of cold air around here (24th), 27th)... dates fluid. 921A/16

Okay, I understand Moderators general hands off. Thank you all for your strong support. I have a couple of goals in mind when threads are started. To ensure an impact storm occurs or is real close (ACY 10" 1/3 but bust up here), and to highlight the accuracy (or inaccuracy) of the many different models physics up to 7 days in advance. Finally, that the impact will include NYC where snow and ice in winter is at a premium. If it's I84 only, I lay off. Believe me: It takes plenty of time to figure things out and my time is also precious and so I definitely do not want the membership to be torn away from family for just some weather, especially since so much can go wrong more than 60 hours in advance. I am confident that the 1 day forecast accuracy when I was growing up in nw NJ in 1960 is now valid as accurate to 5 days in 2022. To me, this is dedication of researchers and the financial support of platforms-computer power. Like it or not, there is valuable information well in advance that can prepare the interested consumer to mitigate adverse impact be it winter storms, firestorms, hurricanes, 10+" rains. Some of our posters are able to mine the gold and share some pretty cool stuff- we're fortunate to share these advance notice posts. ---- Will post Jan 21-23 open ended east coast storm thread-threat to likely (not categorically) followed by coldest weather of the season around the 24th. I think we're noticing each cold surge getting a little colder here in the northeast as the month proceeds. I see two more potentially big shots of cold air around here (24th), 27th)... dates fluid. 921A/16

The moderators should collaborate and let me know if they want me to change the thread strategy. If they feel this is not of detrimental value, then they will let me know. Moderators: all yours.

Good Sunday morning everyone, it is a cold January 16 and likely to be even colder for a day or two between the 23rd and 30th. What follows is my own expectation. Please follow updates on all NWS warnings-statements-forecasts for todays storm. Uncertainty on when the snow mixes with or changes to sleet/ freezing rain or plain rain. Two hours error can mean a snowfall forecast error of 1-4". Baltimore-Philly-NYC: an hour or two of snow begins 4P-8P changing briefly to sleet-freezing rain, then to heavy rain by 10 PM with 3 hours of 45-55 MPH easterly wind gusts sometime sometime between 11PM and 4 AM . Untreated surfaces possibly slippery for a couple of hours late today-this evening. Power outages possible because of the wind later tonight. Snowfall probably a trace to around an inch. The rain washes it away overnight. However, there could be a half inch of snow showers between 11A-11P Monday, probably minor impact at worst. Yes I can see 60 MPH gusts NYC, but I think the 60-70 is better reserved for where the NWS has the warnings. It is definitely a short wind of opportunity. I84 corridor from the Poconos-northwest NJ through interior northeast MA. Snow begins 630PM-10PM, probably accumulating an inch an hour, for an hour or two before changing to sleet and freezing rain by 4 AM Monday, and then to a bit of rain Monday morning daylight hours. It goes back over to snow showers Monday afternoon - evening where slippery conditions might redevelop on untreated surfaces with an additional inch of snow possible. Significant travel problems tonight, especially Poconos extreme northwest NJ (Sussex County) into the hills west of Hartford between 830PM this evening and 6AM Monday with delays or cancels for Monday morning activities, especially the Poconos. Minimum snowfall 1.5" with generally 2-5" in the I84 corridor, possibly 8" parts of the Poconos, Catskills, Litchfield Hills. Scattered wind gusts of 45-50 MPH between midnight and 4 AM may cause power outages. SNOW REMOVAL: those with heart issues, be alert for the heavy wet soaked snow tomorrow morning. Even if only 2" of slush, it might effectively be 1" of rain soaked weight. Get some help to remove by 6PM Monday as the slush starts to refreeze. Attached: The National Weather Service 5AM snowfall map. Please use the legend for your area of interest. Big snow western NYS down the Appalachian rim. Remember: it's not perfect but gives a good idea of what is coming. Posted 657AM/16

For what it is worth: Will begin the 21st-22nd thread around 8AM pending more review. No guarantees on that one for us but certainly potential in a strong baroclinic zone. Maybe ATL-ILM will get 4+"? and we miss? or..... not another LaNina inside runner?

No change to this thread. Will replace with an OBS-NOWCAST thread around 11A. I think the thread title suffices and 38+ pages of discussion notes all the elements, disappointments but I'm sure you'll be busy by 8PM with winter obs and then early Monday with the damaging wind e LI and wind advisory power outages elsewhere, heart attack snow-slush removal I84; then back side 0.1-1" snow showers 11A-11P Monday. Something like that. Follow NWS statements-warnings (despite what I might suggest in my expectations). Il'l also begin the 21-22 thread around 8AM pending more review. No guarantees on that one but certainly potential in a strong baroclinic zone. Maybe ATL-ILM will get 4+"? and we miss?

I dont see wind advisory criteria NYC til the 2A-5A time frame. seems like gusts below 40 knots thru 1A. I could be wrong. I checked HRRRX 80 meter winds and they don't reach 40 kt til 1A and the window of opportunity is about 3 hours, best around 2 or 3A. I can see G 50KT NYC but I would not forecast this. I think pressure falls will help concentrate the action as the storm occludes in e PA Monday morning. Soundings don't look unstable to me for transfer. E LI I think best chance gust 50-55kt.

I can understand... Wind advisory may suffice. Not clear cut to me about warning level, and where tho I agree e LI looks best.

I would say advantage meteorologists who KNOW post-processed data known errors. Also, a slight advantage meteorologists who study the models, almost every cycle, learning biases, which may change every model iteration. Meteorologists may rely too heavily on pattern recognition, not study the model detail or just too easily toss guidance that doesn't fit their expectations (disadvantage consumer-wishcasting). That's where self control-realization that models are only as good as the data and the understanding of the model capability. (GFS handling of boundary layer temps or the NAM ability to sense warm layers aloft better than some other models) We have a whole lifetime to learn our own biases and make an effort to reduce those biases and see the primary guidance. I also think some meteorologists may not understand FGEN-banding, and what drives the big precip (jet cores), or favorable patterns aloft for Cold Air Damming. Also some meteorologists are probably not using all the available tools... TSections, Soundings to the forecast advantage, or hourly data platform information. Fortunately the models steady improvement raises the performance of all ships-forecasters Humility is a best practice and knowing in advance that our attempts at forecasting reality will be in error, at least to some extent.

Considerations: I84 corridor, hope HRRR and HRRX are too cold. Otherwise quite a snow/ice problem with power outages That's what Im getting hints of in the 18Z cycle...and the HRRRX is consistent with its 12z cycle. So, the bias is probably too cold and am looking for warmer cycles, especially the 00z. I am thinking the warming above 32F-scouring at the surface high valleys I84 corridor may not complete til after sunrise. If that happens, combined snow/ice will be a warning impact for at least some of this area. Pressure falls inflow will tend to turn the surface wind ne-or ene despite se isobars, at least in the interior. As of this mornings WPC cycles: am thinking the freezing rain risk is being underplayed n off I78 and w of I287 (ne NJ/se NYS and ne PA) Modeling is weakening the coastal flood threat NJ/NYC... onshore 40-50kt winds too short and pass by, by 12z..however low pressure in the 985 MB range gives a decent surge. So flooding possible but more than minor?? Have my doubts but reserve the opportunity to rereview tomorrow morning. Modeling also seems to trending to run a little east with the storm in the Carolinas then turns due north to DC-CXY to co-locate with the 850-500MB closed lows. Modeling also tending to offer only a 6-12 hr period of too warm for snow, suggesting any back side showers will fall as wet snow Monday, certainly the interior hills of w NJ and ne PA (closed low and colder thicknesses with the cold pool moving ne from DCA-CXY-which will make for steep moist lapse rates it crosses our area). No thread title adjustments now, but will re-review in the morning. I think it continues yes to serve reasonably well.

I looked at 12z NAM/3K. The wind windowg45-60 MPH is about 3 hours. I'm not changing anything on the thread headline yet. It's been left open to a host of possibilities. Coastal flooding is not a lock for anything more than minor in our area. Why? Because max inflow has departed to the east by the time of high tide. Only the low pressure in the 980's is the reason for continued big positive surge. Also EKMAN transport onshore ie better on east-northeast surface winds than southerly for our shores. Need further scrutiny but timing is critical.

What I am projecting based on modeling through 6AM. I've added 3 graphics. Note yet changing the headline. May lower the snow impact to interior and hype the wind a bit more but for now, until certitude, I'm staying with the headline. NYC: seems like an hour of snow begins 7P-830P Sunday changing to sleet-for a little while, then to heavy rain by midnight Sunday with 3 hours of 45-55 MPH easterly wind gusts sometime sometime between 1AM and 7AM Monday. Untreated surfaces possibly slippery for a couple of hours Sunday evening. Power outages possible because of the wind early Monday. Snowfall probably a trace to an an inch. NYC might see a slight accumulation of snow Monday evening with the trough aloft passage and temperatures falling back below freezing. That Monday evening backside may be a small travel problem. I84 corridor from the Poconos-northwest NJ-southeast NYS-W CT. Snow Sunday night should begin 7PM-10PM, probably briefly heavy changing to sleet and freezing rain by 5 AM Monday and then to a bit of rain Monday morning daylight hours. It goes back over to snow showers Monday afternoon or evening where slippery conditions might redevelop on untreated surfaces. I see significant travel problems, especially Poconos extreme northwest NJ (Sussex County) into the hills west of Hartford between 10PM Sunday and 7AM Monday with delays or cancels for Monday morning activities, especially the Poconos. Snow amounts uncertain due to how fast the snow changes to ice. I lowered the minimum snowfall 1.5" because of my concerns for snow to change to tick-tick-tick (sleet) about 3-5 hours after it starts snowing. My guess is generally 2-5" before the change. There might be another 1/2-1" of snow late Monday on the backside of the storm, but that is manageable by exercising a little caution. The main problem is midnight to 6AM Monday morning when snow-ice should be heavy for a time, and scattered wind gusts to 45 MPH could cause a few power outages. Appended the NWS snowfall forecast as of 5AM; the NWS ensemblechance of 4+" and the experimental winter storm severity index. I may work on that thread headline as early as 2PM. Have a day.

Tomorrow morning what watches will post, will be out and and then i can make any headline adjustment at that time. Have a good night. Walt

Might see gusts around 45 MPH near sundown.

Added 10z/14 ensemble chance of 1" and 4+" of snow: both by 7AM Monday. More careful details and graphics post this evening. The NWS GIS snowfall was only thru 7PM Sunday as of this writing so useless to post.

Basic thread headline looks acceptable to me still well in advance of the Sunday night-Monday morning storm. I'll rereview everything this event and possibly improve the headline but I just don't want to lock out possibilities yet. I know it says Noon Sunday start. I'm protecting at a slightly faster forward motion. And it looks like very little snow LI/coasts (less than 2", if that but it still could be messy for an hour or two, especially if cold air damming even holds sway along the coast for a little while. Have a good day: will revisit this evening.

on SREF reliability, I don't think it would to exist in NCEP USA model suite, if it wasn't a helpful tool. It can be stellar, and sometimes miss completely but wherever the core axis... it's pretty darn good.

SREF too early. 09z run is conservative on snowfall w NC and I like that. As multi above - wait to refine and cant rule out an ene turn once the storm gets near BWI. Out to sea, think the chance of that is less than 5%. Better chance of a miss all wet than out to sea no qpf.

My own view having reviewed most of the modeling through 06z/13. The Sunday-Monday morning storm, still has track uncertainty. The USA model is more snowy-icy than the European. Solutions below lean a little to the warmer less snowy scenario but not with high confidence of being correct. If you need to travel Sunday-Monday morning, please follow later forecasts from your reliable sources. Baltimore-Philly-NYC: seems like a short period of snow near or just after sundown Sunday changing to sleet-freezing rain for a little while, then to heavy rain overnight Sunday with gusty east winds, possibly to 45 MPH near or after midnight. Untreated surfaces possibly slippery for a few hours. I84 corridor from the Poconos-northwest NJ through interior northeast MA. Snow Sunday night, should be heavy for a time changing to sleet and freezing rain by dawn Monday and either ends as rain or snow midday Monday. I see significant travel problems, especially Poconos extreme northwest NJ (Sussex County) into the hills west of Hartford. Snow amounts uncertain due to how fast the snow changes to ice. Also, wind gusts in the ridges may reach 45 mph near sunrise Monday and if trees iced, that's a power problem=uncertainty on ice amounts. Graphics: The ensemble chance of 3" of snow or a significant combo of snow-sleet Sunday 7am through only 7am Monday. An incomplete first glance at potential impact from this storm, only through 7AM Monday. The orange area is a start. The new 06z EC OP (rather gross 10 to 1 snow-sleet conversion) for snowfall ending 7PM Sunday - slightly faster and a bit further east than the previous 00z/13 op for comparison. Sleet is high bias problem with these 10 to 1 ratio's, and I think too for the positive snow depth change products.

My only comment on all that is posted. Think ensembles mxd precip & sleet is counted as snow 10 to 1 ratio. Therefore be cautious where mixed precip can occur and think se EDGE might be way too high??? Gradients are always a problem. All modeling has se 850 inflow till late Monday morning= Cold Air Damming for the interior. In the meantime, I will probably wait til 6 hours before the period of snow (and possibly rain) that I think is going to occur LI/CT/MA, especially east sections of all, with small accumulation possible Friday. Not enough members covered for a thread except possibly OBS-NOWCAST. Will reevaluate all by 720AM Thursday.

Sort of agree but, I don't think we have another way, unless we look at clustering. ?? I thought this appended site would cease, but alas we still have it. GEFS... plume clustering if you will. I've taken a look back and the GEFS has been having LGA at 3-4" the last 4 cycles. Does not imply it's correct. Like all here, I could see it much less, but I think we need to think about a turn-redevelopment to the ENE off NJ. Just my thinking based on 06z ensembles. I could be wrong but I just dont see this storm up to ALB... the upper air I do not think supports that track. Again I could be wrong so I dont want to provide useless hope, but this is why I'm waiting another 24 hours before any further commitment one way or the other. Probably my last post til this evening or tomorrow morning. By the way, I see the NAM is coming west with qpf on FRI morning. Watching that carefully for E LI to BOS.

06z GEFS of interest on 2" snowfall: it cuts w of BWI-PHL, then turns ene across LI. What I'm seeing via the 06 GEFS is a tendency to close off the 500 short shortwave as it crosses LI Monday. I think interest in snowfall NYC north and west should be continued til future modeling closes the door. 5 days to go.

Good morning again, No thread e LI/e CT/E MA this morning for Fri morning of 1/14. Models basically dry. Still not convinced there won't be a band of snow in the FGEN zone, as added below. Also, I keep looking at the GEFS and impressive attempt at cold shot after the 22nd and continues cold looking through at least the 28th.