RU848789
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Everything posted by RU848789
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And the 18Z GFS Op is juicy (3-6" generally), but the 12Z was only 1-2" so we're seeing the high uncertainty express itself. Might be pretty late in the game that we get a good handle on this one (think the main energy comes ashore from the Pacific Weds night).
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NAM and RGEM have consistently shown that freezing rain risk after about 9 am or so, but the globals either have all snow for 95 or a later changover to sleet or freezing rain. Freezing rain sucks, as it's dangerous and aesthetically unpleasing. Saving grace could be that it'll mostly be falling on top of snow, forming a crust and not falling on bare ground forming ice rinks. It also could rob many of us along 95 and even a bit NW/SE of 95 of 0.1-0.2" QPF (or 1-2" of snow), which would also suck. Hopefully the Euro is right on this. Thoughts on how this might play out?
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A little surprised nobody posted the NWS snowfall maps, which show a general 2-4" snowfall with the higher end amounts (3-4") generally N of 276/195 and the lower end (2-3") south of there, although the lesser 2-3" amounts are also forecast from NYC eastward, presumably due to less precip. The NWS is a little more bullish than the NBM, also below, although most of the 6Z models are showing 2-4". The most important message for most people, IMO, is that it will be all snow for the region through about sunrise on Tuesday with temps below 32F (in the mid/upper 20s except near the coast where temps will be closer to 32F), meaning snow will easily accumulate at night with cold temps, leading to very slippery roads everywhere for the Tues am rush hour, as all but treated/heavily traveled roads will likely be snow covered and visibility will be reduced; even the treated major roads will likely be a bit slushy with temps below 32F. Also, people should shovel by sunset on Thursday, especially if they get above 32F and/or get some rain/ZR, since the wet snowpack would then freeze solid after sunset and it's not forecast to go above 32F for most through at least Sunday.
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Will be interesting if we see advisories for the areas north of 195/276, roughly, that have a 3" criterion over 12 hours for an advisory, since the NWS isn't really predicting 3" or more for most - but, it's likely to be more impactful than a typical 2-3" snowfall, with snow easily accumulating with sub-32F temps right around the morning rush hour and the NWS often takes impact into account when issuing WWAs. The counties with 2" advisory criteria would likely require WWAs and it would also look odd if only those counties had WWAs. Don't want to confuse the public.
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When was the last time we saw a model with NYC as the absolute bullseye. I know it's the HRRR late in its run, but damn, would be nice to see this verify.
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There still is along and SE of 95, but it only comes in near the end of the precip at least for me in the edison area (shows some sleet after 10 am then ending as a little zr)... didn't check other soundings...
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Unusually good agreement on snowfall, especially for Philly-NJ-NYC, from the three main ensemble forecasts~36 hours in advance of the precip. I'm sure this helps forecasters' confidence level...
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I'm missing something on the UK, since snowfall is 1-2" generally for Philly-NJ-NYC area, but the QPF is 0.3-0.4" and temps never really go above 32F except near the coast and soundings show the whole column under 32F for Edison and NYC, at least. It's almost like they forgot to calculate the snowfall, lol, as 0.3-0.4" QPF should be at least 3-4" of snow with <32F temps through the column. Anyone?
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A friend of mine who is a former NWS met said on a sports message board I frequent that, "The NBM is the starting pt for all NWS fcsts." You can tell he used to write AFDs by his abbreviations, lol. Anyway here's the regional NWS forecast (which I like better than the separate Philly and NYC office maps) and the NBM 19Z forecast which are nearly identical. Would be nice for these to verify and break those friggin' <1" streaks and it would also be nice to get at least 1-2" or more of snow and have it be around all week, given temps will struggle to get above 32F through next weekend. And it would be awesome to get more snow then...
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If you're disappointed in the dwindling snowfall amounts for this storm, go over to the January thread (GFS is huge for 1/19-1/20, which of course is still a week away).
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Yes it is...
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It still is the 2nd best model after the ECMWF (for 5-day 500 mbar pressure anomalies)... https://opensnow.com/news/post/weather-forecast-models-explained Edit: that graph is from 2019; currntly, UK and CMC are essentially tied for 2nd after the Euro, with the GFS, sadly, 4th as per the link below for the past month. https://www.emc.ncep.noaa.gov/users/verification/global/gfs/ops/grid2grid_all_models/acc/
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I know the NAM is probably beyond its useful range when the precip hits, but it is interesting that the NAM and ICON have the surface low in similar positions Tuesday morning into the afternoon, when most of the precip falls, yet the NAM is much warmer/rainier for 95/coast (and even a fair amount NW of 95). And the RGEM is between the two. Any insight on why that is? TIA.
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Actually, not true, as they have plenty of precip (large areas of 0.6-1.2" of QPF) 150+ miles SE of the coast. Just need to move it NW...
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For me, this summarizes the surface trends well, showing the entire precip field moving NW about 150 miles vs. 0Z, bringing the 0.1-0.2" of precip to 95/coast and moving the 1" QPF line NW by ~150 miles, also. Still a ways to go, but the movement weneeded to see. 12Z also looks a little juicier, overall, too. And not that far off from the 12Z GFS precip field. Just need it to move another 150 miles NW...
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UK good hit just NW of 95 and decent hit for 95 (with some sleet/rain probably), but mostly rain for the coast, as temps start out below 32F, quickly go over freezing and don't go below 32F again for 95 and SE of there until after the precip shuts off. Most of the precip is done by 1 pm Tues. Still a decent winter storm signal.
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Walt - great post from someone who has actually had to make NWS forecasts with conflicting/limited data. The one thing I think many of us don't always think about is that the Euro is the best model - at predicting 500 mbar pressure anomalies globally (that's what the verification scores are based on - and not that that isn't important, but I've never seen "verification scores" for the various models, including the Euro on east coast winter cyclones. And that's where I think input like yours is really important based on experience and history. Doesn't mean the Euro can't be right, but one can't automatically think it is just because it's the "best" model. On the flip side, I think we've seen a bit of "confirmation bias" (wishcasting just a bit?) over the past 24 hours, where at 0Z 1/11, the Euro was somewhat of a snowy outlier and some were saying it was "leading the pack" and other models would move towards it, somewhat discounting the other 3 globals, but with regard to last night's 0Z runs, with the Euro being a non-snowy outlier, very few are saying the Euro is "leading the pack" and other models will move towards it. I'm no expert at all on synoptics, but I've done a lifetime of science where myself and my group had to evaluate scientific models and experimental results (chemical process development in pharma in R&D) and it was always difficult to not give in to confirmation bias, discarding or at least somewhat discounting data one "didn't like." Just some observations from the cheap seats - will be interesting to see how this one evolves and we're still 4+ days out with the main energy still way out in the Pacific and not sampled well (no ashore until Sat night/early Sun), plus how today's storm evolves will certainly influence how Tuesday's storm evolves. One thing for sure: the models will change, especially over the next 24-48 hours, but hopefully not much after that. That's why tracking is so fascinating.
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Impossible to know what's going to happen, but I'd rather be in the camp with 3 of the 4 major global models than one, even if that one is the Euro - the best model by a bit, not by an overwhelming amount (and that accuracy is not measure on performance with east coast cyclones - I'd love to see that though).
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While CMC is a hugger with lots of mixed precip after the initial snow thump and much faster than the GFS...
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GFS classic Miller A with great track and temps in the mid/upper 20s for the whole storm, so this is one storm where we might get >10:1 ratios - see 10:1 and Kuchera maps...
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The 18Z Euro Ensemble Mean snowfall axis moved back NW a decent amount vs. 12Z, perhaps indicating that the suppressed 12Z Op run was a bit of an outlier. It's possible. Hopefully we see a bit more consensus tonight, although as many pros have said, we might not get a great handle on Tuesday's event until we know the outcome of Friday's big storm and get the energy for Tuesday into the RAOB network so we can start with better initial conditions.
