Winter Storm Warning - Wednesday Dec 16 into Thursday Dec 17
drummerboy said:
ugh. snow AND wind?
I'm tired of losing power.
For fear of hyping this one too much, I won't use the B word. But there's been a pretty consistent signal for some strong wind with this one.
drummerboy said:
ugh. snow AND wind?
I'm tired of losing power.
Time to buy a generator. In advance of Superstorm Sandy, I drove to Ohio to buy a generator. Didn't need it then, haven't needed it since. It's insurance that I'll never lose power.
First call for this week's weather:
1. Bury the lede department. There is a strong probability of snow and rain during the day tomorrow, Monday 12/14/20. While a little accumulation of snow may occur, temperatures will be steady in the high 30's and I do not expect anything to linger. While icing is unlikely, some road slickness should be expected during the day.
2. Wednesday, 12/16/20.
Expect a significant nor'easter, with blowing and accumulating snow.
Still a couple of moving parts to this storm, particularly the behavior of a high pressure to our north that could have significant effect on how long precipitation lasts.That said, the models are coming into better agreement that there will be a significant to major storm starting midday Wednesday and lasting 8 - 12 hours. Lighter snow may bracket on either side of that. The temperature profile for our area makes a snow event likely.
The amount of precipitated water (what would be rain if it were warmer) is one of the larger disagreements in the models right now, with a range of 1 - 2" of water. With temps at or below freezing near the ground and various profiles of the upper air between the models, it is still hard to project what this will translate to in terms of snow depth, but 6" - 18" is a reasonable guestimate right now. Snow may be heavy at times. Right now, expect this to be a denser, heavier snow rather than powder, but that could change. Most responsible meteorologists are hedging toward the lower end of maybe 6 - 10 as of this morning. This could change significantly in the next couple of days, though, as the storm comes into better focus.
Wind becomes a factor overnight Wed into Thurs with gusts in the 30s. If the snow is powder (not as likely here as to our north) then drifting could become an issue.
TL/DR: At this time, we expect a significant winter storm Wed afternoon into Thurs morning. At this time, it is prudent to plan for accumulating snow of at least 6" or more.
One other note. If you use the Shadow app, delete it. Their post yesterday was an alarmist clickbait application of the available data. While it is just within the realm of the possible, it is within the 'even a broken clock is right twice a day' margin of error at 96 hours out.
I have shoots growing under the leaf blanket that I left covering the flower bed, and forsythia blooming. And my strange little rose stalk that always seems to have late flowers bloomed the first week of December.
ETA: I'm not ready for a big snow... but at least my kids' snowboots should arrive tomorrow. Then they can shovel. 
(Please fit.... please fit...)
I've heard that just before a snowstorm starts is a good time to throw down some grass seed if you're trying to overseed your lawn. I may try it Tuesday night.
Also I guess it's time to set up the bird feeders.
Tomorrow -- Not super impressed with snow prospects. It's simply not cold enough for anything noteworthy. Could see a couple shots of heavy snow with some enhancement from evaporational cooling, but this is a non-event with regards to accumulations IMO.
Wednesday -- I'd like to preface this by saying that I'm still fairly bullish on snow totals for this storm. I think that there's a decent chance we end up with at least 6-12 inches of snow when it's all said and done. That said, these "early season" snow storms come with quite a few caveats and this one is no exception. My greatest concern here is that the snowfall forecasts -- and the associated hype therein -- that are coming straight from the models are overdone, as some of the atmospheric profiles (vertical view of the wind/temp/moisture in the atmospheric column) are making me a bit hesitant to say that this is anywhere close to a slam dunk. I think that areas north of the area are, as of right now, more likely to be in that 12 inch range given the more favorable thermodynamic profiles.
As a quick reminder, snowfall totals spit out by models are calculated by applying a "ratio" of liquid water to snow. Canonically, we tend towards a 10:1 ratio (10 inches of snow to every one inch of liquid water), however that ratio is at best an educated guess and at worst total nonsense. Applying a 10:1 ratio everywhere in a model domain when there are going to be large temperature and moisture gradients both in the vertical and horizontal is a pretty big leap to make IMO. In contrast, there are also "dynamic" ratios such as "Kuchera" that try to better approximate small differences in spatial temperature and moisture distributions that may offer a slightly better approximation, but even Kuchera has its limitations. One other issue to consider is that many model snowfall algorithms count sleet and other frozen precip as snow, possibly inflating snowfall totals in transitional zones.
From a purely meteorological perspective, this storm is beautiful. It has all the makings of a textbook northeast snow event complete with a classic double jet streak above a nice (near-)surface temperature gradient just off the coast. The antecedent airmass being relatively cold will help keep ratios high and theres a chance this thing is fairly long duration event -- both of which in consequence should inflate snow totals. The latter point is aided by the fact that the upper-level wave inducing this thing is not super amplified, which should keep the low from flying off to the north super fast. But as usual, the track of the low and the location of mesoscale banding will make all the difference. The GFS is doing some funky stuff with the main low, fracturing it into two separate centers and weakening the overall pressure gradient/wind. The NAM is a little more bullish on a compact, single low. The ECMWF ensemble has 90%+ probabilities for at least 6 inches of snow in Maplewood. But as we saw in January 2015, there's always a failure mode for big snowfall.
Considering the above caveat regarding model snowfall output I'll say this: the ECMWF ensemble snowfall signal at Newark Airport is robust. A 50 member ensemble spitting out this type of agreement can't be ignored. The average is ~14 inches.
Rain on Wednesday, turning to snow into Thursday morning? So the bulk of the snow will fall on Thursday morning? Probably 8 inches of snow. Wet heavy snow?
Jaytee said:
Rain on Wednesday, turning to snow into Thursday morning? So the bulk of the snow will fall on Thursday morning? Probably 8 inches of snow. Wet heavy snow?
Hard to give an estimate for timing yet. It will change a lot between now and Wednesday. Wetness/heaviness will depend on how cold it gets.
Edited to add: could very well be more than 8. I’d stick that at the median right now.
Don't look for me to post on Tuesday. I'll be charging up the batteries on my snow blower.
Expected Major Snowstorm Wed 12/16 - Thur 12/17
Monday 12/14/20 update
The models are still in relative agreement in indicating the likelihood a significant winter storm Wednesday afternoon through Thursday morning, with possible snowfall accumulations of 6" - 18" in the MAPSO area.
There is also a strong signal for high winds during this storm, with steady winds of 20 - 25mph and overnight gusts up to possibly 50mph. These winds could cause blowing and drifting conditions that would make travel even more treacherous.
Some details: a strong coastal low will develop off the southeastern US Wednesday morning and is likely to trace up the coast just offshore. A high pressure area to our northeast will provide ample cold air and will also serve to slow the storms progress as it passes our area, allowing a longer duration event to occur. A relatively warm ocean will feel lots of moist air into the system. Total precipitation (liquid water) over the entire storm period is pretty consistent from model to model and run to run right now in the 1" - 1.8" range with the Euro being a bit wetter than the GFS and NAM. Temperature profiles are also consistent with the entire event being below freezing near the surface and through the lower atmosphere. This is a good thing -- it makes freezing rain and ice less likely. Snowfall rates could at times exceed 1"/hour, especially if banding develops.
Caveats: This storm is still over 48 hours away. Small changes in track can have large perceived effects -- the band of deepest snowfall is likely to be about 40 - 60 miles wide with fairly steep gradients on either side so a shift of 20 - 30 miles one way or the other could mean a difference of more than a foot of accumulation. That is why I am still not comfortable with a forecast snow range narrower than 6" - 18"
Images below are snow maps from recent runs of the Euro and GFS. These maps are highly speculative and change with every run -- they are not forecasts, they are raw data output, and should be taken with are large bucket of salt. But the colors are pretty and they both seem to confirm the midrange of my forecast so here they are.
I think the image below exaggerates the snow a bit so don't look at the numbers but I do think the graphic gives a good idea of how narrow the band of maximum snow depth will be
max_weisenfeld said:
Some details: a strong coastal low will develop off the southeastern US Wednesday morning and is likely to trace up the coast just offshore. A high pressure area to our northeast will provide ample cold air and will also serve to slow the storms progress as it passes our area, allowing a longer duration event to occur. A relatively warm ocean will feel lots of moist air into the system. Total precipitation (liquid water) over the entire storm period is pretty consistent from model to model and run to run right now in the 1" - 1.8" range with the Euro being a bit wetter than the GFS and NAM. Temperature profiles are also consistent with the entire event being below freezing near the surface and through the lower atmosphere. This is a good thing -- it makes freezing rain and ice less likely. Snowfall rates could at times exceed 1"/hour, especially if banding develops.
NAM FGEN plots are impressive with regards to banding. Indicating 3"/hr rates are possible over the area. I'm worried about this thing tracking further south at the moment, which is why I'm waiting for the 12z EC before making any guesses.
12z model analysis in a quick snapshot:
NAM shot north. ECMWF went south. GFS ticked north a bit. Looks to me like we're still very much under the gun here, but I'm really not thrilled by the lack of major model agreement. Makes for yet another tough forecast.
Winter Storm Watch
URGENT - WINTER WEATHER MESSAGE National Weather Service New York NY 400 PM EST Mon Dec 14 2020 CTZ005>012-NJZ002-004-006-103>108-NYZ067>071-151000- /O.NEW.KOKX.WS.A.0001.201216T1900Z-201217T1800Z/ Northern Fairfield-Northern New Haven-Northern Middlesex- Northern New London-Southern Fairfield-Southern New Haven- Southern Middlesex-Southern New London-Western Passaic- Eastern Passaic-Hudson-Western Bergen-Eastern Bergen- Western Essex-Eastern Essex-Western Union-Eastern Union-Orange- Putnam-Rockland-Northern Westchester-Southern Westchester- 400 PM EST Mon Dec 14 2020 ...WINTER STORM WATCH IN EFFECT FROM WEDNESDAY AFTERNOON THROUGH THURSDAY AFTERNOON... * WHAT...Heavy snow possible. Total snow accumulations of 12 to 17 inches possible. Winds could gust as high as 45 mph, especially along the coast. * WHERE...Portions of northeast New Jersey, southern Connecticut and southeast New York. * WHEN...From Wednesday afternoon through Thursday afternoon. * IMPACTS...Travel could be very difficult to impossible. Hazardous conditions could impact the Wednesday evening and Thursday morning commute. PRECAUTIONARY/PREPAREDNESS ACTIONS... Monitor the latest forecasts for updates on this situation.
Tuesday morning update
Forecast remains on track for a major winter storm Wednesday 12/16 - Thursday 12/17
Likely snow will overspread the area Wednesday becoming heavier after 4 pm and continuing through the morning Thursday. Winds 15 - 20mph increasing to 20 - 25 overnight with 30 mph gusts are also likely.
Total snow accumulation on 8 - 18" possible depending on where the heaviest bands set up. We are not likely to have a better idea of total accumulation than that until the storm actually happens, though.
Snow tapers off Thursday by noon although some snow showers may persist.
Temps will remain below freezing throughout the event..
The NWS has issued a Winter Storm Watch for our area from 1:00pm Wed until 1:00pm Thurs
Welp, here's the first big potential failure mode: mid-level drying. Could we get dry slotted? It's entirely possible. While this isn't to say I think it'll happen, but it's possible for sure.
Actually now that I'm taking a closer look, theres a couple of failure modes. In addition to the mid-level drying, the NAM is hinting at a more amplified pattern. This could deflect everything to the north and leave us on the southern fringes. Last night's ECMWF/GFS still clobbered us with a foot+, but this morning's NAM solution is pretty interesting. Will wait and see what the 12z globals do, but can not rule out this thing getting shunted to the north.
Now that I take a closer look, the big brown splotch looks like a vulture.
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Details are coming into focus a bit better now regarding the potential for a relatively stout snow event on Wednesday and Thursday. I'm always weary of posting snow maps or basing my forecasts off of them, but there are some pretty impressive numbers popping out of the global models. While the usual caveats apply, the upper-atmospheric pattern looks to be pretty textbook for a heavy mid-Atlantic snowstorm.
A potent upper-level trough will move toward the area Wednesday and phase with a developing surface low off the Carolina coast late in the day/overnight. With the enhanced upper-level support associated with this trough, the low will deepen and translate north, bringing snow and strong wind to our area. Both the GFS and ECMWF are in good agreement on this, and there is some pretty strong ensemble support for this solution as well. Given that we're still a few days out, I'm not quite ready to start posting accumulation forecasts as (of course) the track of the low pressure center is still somewhat in question. That said, the potential certainly exists for a substantial snow event impacting our area.