eduggs

Wintry 5 days on the GFS! Might even squeeze in some flakes or ZR on Xmas day in the weak wave in between the Tue and Fri night events.

Both GFS and GFS-AI ticked slightly further north vs. 18z. Still snowy (some ice SW) for most areas. Kind of the sweet spot right now.

HRRR (01z), RRFS, and ICON are a little juicier than the NAM: 0.2 - 0.3 liquid for NYC. Heaviest band could be fairly narrow. Snow accumulations along coastal plain likely intensity dependent. So far no obvious change at 0z.

Some flakes reported on mPING in northern MD near Hagerstown with the initial finger of overrunning. Latest HRRR and current radar look decent. Hoping for a good burst of snow in the 5am - 11am timeframe. If moderate or better rates materialize, it should accumulate for most.

I'd feel more comfortable too with colder temperatures but this airmass should support accumulating snow in most areas away from the coastline. Yeah should drop a few degrees when the lower levels fully saturate. Before then the temps are likely to rise as clouds move in and then stabilize or fluctuate slightly. Should be approx. 30-36 until precip. starts and then 30-34 (elevation and location dependent) with mostly snow late tonight.

Maybe this misses south. But I say, let's get to the modeled cold side first to avoid rain and then hope it nudges north in the short range when model changes tend to be smaller.

This could be either a great local NWS forecast or a terrible one. With multiple days of 0.1 - 0.3" liquid model forecasts with a snow-supporting model profile across the interior... forecasting <1" of snow accumulation is ballsy. I respect the conservative approach. And there are reasons to be cautions with an unfavorable angle of precip. approach, non-uniform precip. shield, and possibly above freezing surface temperatures. But if it turns into a messy morning commute, many will be unprepared.

0z and especially 06z EPS mean and members show some serious CAD on Friday. Love the thermal gradient even on the means, with mid teens in ENY and 50s in SWPA. If this stays south or shifts further south we're likely to lose some of the QPF too, which is a fair tradeoff I think. We could also see a snap back north today after a major shift south. Fun times when there are multiple threats inside 5 days to track!

Don't even look at the GFS "clown" maps for Friday. You will not be able to unsee them.

That's a big shift from the GFS. It represents the southern edge of its ensemble spread from 12z and 18z as well as several of the ECM ens members. We pray! If it's real we would expect to see movement from other models over the next day or two. I'm doubtful for now but the ECM has been hinting at this possibility...

0z GFS has a significant snowstorm for Friday.

I don't put too much stock in the GFS-AI, but it's showing snow and ice for Friday 12/26: >0.5 liquid with surface temps at or below freezing NYC north throughout the event. It has hinted at this wintry outcome for several cycles. There is a little support amongst the ensembles, particularly the ECM suite, but the majority of mid-range guidance takes the boundary well north of us, favoring NNE for wintry precip.

The WPC maps have <10% probability for 2" of snow in the far northern reaches of the OKX forecast area, including elevations above 1000ft. That should have nothing to do with "white rain." Those areas might not get 2" of snow. But I would like to know what the basis is for assigning a probability of less than 1 in 10 chance.

Other than the usual weird jump by the NAM, so far 0z looks similar to previous cycles. Changes look like noise to me... Still looks like a coating to 3" or so from the south coasts to far northern suburbs with a ragged and unpredictable gradient... The variable and inconsistent geographic distribution of snowfall between models suggests a low probability forecast. Model changes are being driven by very minor differences in vorticity and micro-short-waves. The WRF-NSSL is the weenie model of 0z with 3-5" right through the NYC metro. Unlikely but probably not impossible.

I'm thinking 2" as the average across I-84 - not the upper limit - but with a wide range and maybe a funky regional distribution. I wouldn't expect uniform and consistent precipitation. I would guess the precip. shield is more banded and variable with winners and losers. But it's just a guess really.

Considering just about all guidance has 0.2" liquid or more across NNJ and SENY and a snow-supporting model profile, those WPC snow maps look low. You would seemingly have to go against model consensus to come up with those probabilities. Or maybe they are heavily skewed towards the GEFS. Either way, the lack of granularity across our region makes it only modestly useful.

I think Friday still bears some watching. A few ECM runs and GFS-AI run the precipitation into a wall of CAD. Lots of northerly low level drain. It's a much better threat for New England, but there's still enough time and enough ensemble spread... Pretty low likelihood however outside of some ice across the northern interior or maybe flakes to end.

Warm advection precip especially with a parent low significantly separated from the overrunning can be locally unpredictable. It can be banded with distinct maxes and mins that defy typical geographical snowfall distributions. The inter- and intra-model variability supports this. As usual, this will be an interesting nowcast. With surface temperatures near or just above freezing, snow could accumulate pretty much anywhere. Can't really count anyone out for a coating to about 3". I don't think this event will reveal its character until the last moment. Hopefully when it does early Tue it appears wintry and festive.

The RGEM wasn't further north. The shortwave was actually a hair south. But lighter precipitation and different distribution of precipitation screwed the impression. ICON and RRFS highlighting the potential for a narrow area of heavier banding. Some indications of possible 0.1" liquid per hour. It probably wouldn't last too long as it shifts east, but it could put down a quick couple of inches if we're lucky.

We haven't had any particularly good setups for snow this late fall and early winter and yet there have been several accumulating snow events, particularly for NW areas. It's a little frustrating to not have any bigger events to track, but I must admit December has felt pretty wintry compared to recent years. Maybe that continues early Tue... There are some indications of a pretty good burst of snow with cold antecedent conditions. That would continue the trend of sneaking accumulating snow out of a marginally favorable setup.

The RRFS actually has additional snow showers for the area (esp N) Tue night. Doubtful since there's not much support and the RRFS isn't reliable at the end of its run. But if the tight thermal boundary stays close to our area and we remain on the cold side, there will be chances for snow. Different models at different times have shown snow chances every day from Tue through Fri. It depends on the track of the very minor shortwaves in the longwave flow and how they interact with the thermal boundary. At some point next week I suspect we'll switch to warmth... but it's not certain yet.

RRFS is even further south than 12z. Precip is not quite as robust as 12z but it's basically all snow for our area except maybe ELI. Quick burst then the forcing quickly fizzles. Not much snow for SNE. Good sign to see the south shift but we don't want to lose the signal for heavier banding.

Model guidance brewing some big warmth for late next week. GEFS, GEPS, EPS all have it. Most of the country is modeled to be above freezing on Xmas. Our warmest day might come right after. Still waiting for a positive surprise in the mid-range...

All of the mid-range guidance through day 7 has the thermal boundary too far northeast for us to have much of a shot at snow. Out to day 10 isn't much better. I hope it changes. It's a pretty ugly and repetitive looking longwave setup that would seem to favor New England for snow chances. But it doesn't exactly look warm either after Friday and the real cold is not too far off. But it's sure no fun looking at a huge stagnant ridge over the central US.

Cool to see several reports around or even over an inch of snow from yesterday's snow showers in Morris, Warren, and Sussex counties. That made two days in a row of accumulating snow for the higher elevations. https://forecast.weather.gov/product.php?site=NWS&product=PNS&issuedby=PHI This was pretty well modeled.