RU848789

Agree those are very likely high, unless the HRRR scores a reverse NAM coup, lol

The updated NWS maps for snow/ice are below and show a bit of an increase in snowfall amounts for the NWS-Philly counties from Sussex down through EPA/CNJ vs. yesterday. Note that other media forecasts show more snow/sleet than the NWS (News12/TWC) and some have similar amounts (Channel 4/Channel 7; I could post them if people are interested, but I thought they were frowned upon here. Obviously a very tough forecast with 1" per hour snow (or the equivalent amount of sleet) falling over 5-6 hours, so when the changeover occurs (for those who change over) will hugely impact how much snow vs. sleet is observed; and most look to get maybe 0.1" of freezing rain at the end; also, the sleet/snow will all accumulate at night with temps generally at or below 32F for the storm. And there are models with mostly snow and little sleet vs models with mostly sleet with little snow and everything in-between so good luck to people who forecast for a living. No matter what, at the end of this storm for most in this forum, there will likely be 0.5-0.7" of frozen QPF on the ground (even the freezing rain will simply be absorbed into the snow/sleet pack) which is substantial, so impacts on driving will be significant regardless of how much snow vs. sleet and it'll be a heavy shoveling.

Changing the topic is a sure sign you have lost the argument. But for the record, at 1 am this morning on a model summary post I said "we're nearing consensus on a 3-5" event between 276/195 and 78" and was referring to model consensus, which was absolutely true based on last night's 0Z model runs where every single model most look at (GFS, CMC, Euro, UK, ICON, NAM and RGEM) had 3-5" for that area. It was not a forecast and I seriously questioned that model consensus this morning after seeing the 6Z and 12Z NAM showing a lot of sleet.

Ridiculous post since tomorrow's event hasn't started yet and its outcome is unknown. Could be a sleetfest but could also be significant snow for the City or somewhere in-between.

Gotcha - was just curious what you were referring to as it wasn't obvious. I was also surprised by the watch, which was pretty early.

That GFS run shows about 1.5-2" of sleet when comparing the Pivotal vs. TT maps.

More trolling. You do realize it'll be Saturday night when a ton of people will be out and about, with some probably drinking, so there will still be plenty of accidents, especially if people think it's a "non-event" plus how will roads magically be "fine" Sunday morning with ~6" snow equivalent on the roads (it will all accumulate at night with temps <32F) and temps not going above 32F until 9-10 am?

Are you just trolling, as is your habit, or are you going to really try to convince people that 1" of snow, 1-2" of sleet and 0.1-0.2" of ZR is a non-event? We saw significant impacts yesterday from 1/2" of sleet for most and this would be about 4x as much frozen QPF otg.

0.5-0.7" QPF otg won't be washing away any time soon...

So, you're saying 1" of snow then 1-2" of sleet (3-6" snow equivalent) and then maybe 0.2" ZR is a non-event? Sure, it's not a lot of pure snow, verbatim, but we're still talking about 0.5-0.7" frozen QPF on the ground (the ZR will be absorbed). Pretty sure your neighbors will disagree as would most posters here.

Huh? No obvious changes - care to fill us in?

Still no NWS-Philly AFD - wonder if they're reworking things to align better with Upton, which would mean bumping snowfall back up for most of the area...

Collaboration alert, lol. The updated regional NWS map is below and clearly, the NWS-NYC and NWS-Philly offices are not in sync. Look at the bondary between Sussex and Orange, where it goes from 3-4" to 6-8 by magically crossing into NY; similarly NE Morris is at 2-3" and is up against 4-6" amounts in adjacent Essex/Passaic. I would think maybe the NWS-Philly might bump amounts back up to align them better (or vice versa, but the NWS-NYC just issued their info).

Wow, NAM-ed in some ways by the 18Z NAM, with double the QPF and a lot more snow than the past few runs for most, plus a lot of sleet and a bit of ZR but very little rain. Will take. Verbatim, for my house in the Edison area, that's 1" of QPF consisting of about 4" of pure snow (0.4" QPF) on the front end, followed by 2" of sleet (5" of equivalent 10:1 snow or 0.5" QPF, as sleet comparing the TT/Pivotal maps) and maybe 0.1" of ZR, so ~10" of 10:1 snow condensed down to maybe 5" of 5:1 slush (the ZR will just be absorbed into the pack). While I'd love 10" of snow, where do I sign up for this. Funny having to use 4 graphics for a forecast...

Looks like the NWS-Philly is going with the sleetier/icier forecast for almost everyone, given the advisories below with snow amounts decreased due to sleet and with freezing rain of 0.1-0.2" for most. For most of CNJ, where I live, 2" of sleet/snow with 0.2" of ice would have the equivalent frozen mass (the freezing rain will be absorbed by the sleet/snow, not melt it) of ~6" of 10:1 snow on all surfaces. This could be a shitstorm if places get 1/4" of ice accretion as per the NWS and some models which show even more. I think everyone would rather have all snow, but it's looking like a mix for anyone south of 78 and probably even south of 80 if these advisories are correct; wonder if Upton will follow suit. Also, nothing will melt overnight with temps at or below 32F for most until 9-10 am, so conditions in the morning will likely still be treacherous with 2" or so of snow/sleet then maybe 0.2" of ice on top of that. But who knows, maybe the snow will do better this time than yesterday. Edit: added in the newly updated NWS-Philly snow/ice maps, showing the significant deceases in snowfall forecasts for everyone, but people should know that the decreased snow will be replaced by sleet, not rain, so the frozen mass on the ground will be about the same and the amount of freezing rain forecast hasn't changed much (and that will add to the frozen mass on the ground). https://forecast.weather.gov/wwamap/wwatxtget.php?cwa=PHI&wwa=winter weather advisory URGENT - WINTER WEATHER MESSAGE National Weather Service Mount Holly NJ 101 PM EST Fri Feb 7 2025 NJZ009-010-012-015-PAZ054-061-062-105-106-080715- /O.NEW.KPHI.WW.Y.0007.250208T2000Z-250209T1100Z/ Hunterdon-Somerset-Middlesex-Mercer-Carbon-Lehigh-Northampton- Upper Bucks-Lower Bucks- Including the cities of Doylestown, Trenton, Bethlehem, Somerville, New Brunswick, Flemington, Jim Thorpe, Perkasie, Chalfont, Allentown, Morrisville, and Easton 101 PM EST Fri Feb 7 2025 ...WINTER WEATHER ADVISORY IN EFFECT FROM 3 PM SATURDAY TO 6 AM EST SUNDAY... * WHAT...Mixed precipitation expected. Total snow and sleet accumulations up to two inches and ice accumulations up to two tenths of an inch. URGENT - WINTER WEATHER MESSAGE National Weather Service Mount Holly NJ 101 PM EST Fri Feb 7 2025 NJZ013-020-022-027-080715- /O.NEW.KPHI.WW.Y.0007.250208T1700Z-250209T0700Z/ Western Monmouth-Ocean-Atlantic-Southeastern Burlington- Including the cities of Jackson, Wharton State Forest, Freehold, and Hammonton 101 PM EST Fri Feb 7 2025 ...WINTER WEATHER ADVISORY IN EFFECT FROM NOON SATURDAY TO 2 AM EST SUNDAY... * WHAT...Mixed precipitation expected. Total snow and sleet accumulations up to two inches and ice accumulations around one tenth of an inch. URGENT - WINTER WEATHER MESSAGE National Weather Service Mount Holly NJ 101 PM EST Fri Feb 7 2025 NJZ001-007-008-PAZ055-080715- /O.NEW.KPHI.WW.Y.0007.250208T2000Z-250209T1100Z/ Sussex-Warren-Morris-Monroe- Including the cities of Morristown, Washington, Newton, and Stroudsburg 101 PM EST Fri Feb 7 2025 ...WINTER WEATHER ADVISORY IN EFFECT FROM 3 PM SATURDAY TO 6 AM EST SUNDAY... * WHAT...Mixed precipitation expected. Total snow and sleet accumulations between 2 and 4 inches and ice accumulations up to one tenth of an inch. URGENT - WINTER WEATHER MESSAGE National Weather Service Mount Holly NJ 101 PM EST Fri Feb 7 2025 DEZ001-NJZ016>019-PAZ060-070-071-101>104-080715- /O.NEW.KPHI.WW.Y.0007.250208T1700Z-250209T1100Z/ New Castle-Salem-Gloucester-Camden-Northwestern Burlington-Berks- Delaware-Philadelphia-Western Chester-Eastern Chester-Western Montgomery-Eastern Montgomery- Including the cities of Honey Brook, Moorestown, West Chester, Oxford, Pottstown, Norristown, Wilmington, Camden, Mount Holly, Collegeville, Reading, Media, Glassboro, Lansdale, Pennsville, Kennett Square, Cherry Hill, and Philadelphia 101 PM EST Fri Feb 7 2025 ...WINTER WEATHER ADVISORY IN EFFECT FROM NOON SATURDAY TO 6 AM EST SUNDAY... * WHAT...Mixed precipitation expected. Total snow and sleet accumulations up to one inch and ice accumulations between one tenth and two tenths of an inch.

Finally found this, which really shows well the amounts of snow, sleet, freezing rain and rain for the 12Z NAM for selected locations. For Newark, it has 0.54" total precip, which includes 1.7" of snow (assumes 10:1 ratio), about 1.1" of sleet (from 0.37" of sleet as liquid and using a 3:1 ratio) and no freezing rain or plain rain. For Philly, it has 0.69" total precip, which includes 1.4" of snow, about 0.3" of sleet (from 0.11" of sleet as liquid and using a 3:1 ratio), but it also shows 0.42" of freezing rain (and no plain rain), which would be just terrible. Rule of thumb is maybe 1/2 to 2/3 of freezing rain precip actually accretes on sub-32F surfaces (some runs off, especially if precip is moderate to heavy; drizzle accumulates much better), meaning maybe 0.25" of ice accretion, which is close to the 0.17" of accumulated freezing rain from the NWS forecast. Biggest take home message is no plain rain, so this will be quite impactful even for areas south of 78 which might get a lot less pure snow, as sleet and freezing rain are as bad or worse. Even AC is only showing half of the 0.6" of total precip as plain rain. Of course, this is just the NAM model verbatim and the actual outcome might be much different as per the NWS with more snow and less sleet/freezing rain for most. https://coolwx.com/cgi-bin/getbufr.cgi?region=NJ&stn=KACY&model=nam&time=current&field=prec

GFS also showing more sleet where the sleet amount = (TT "snow" (which includes 10:1 sleet) - Pivotal pure snow)/3; when they show the same amount of "snow" that means no sleet. Would be nice to have a sleet map and a pure snow map, lol...

Huh? NAM has 0.5-0.7" QPF like most of the other models; it's just that most of it is sleet...

See my post above. TT counts sleet as 10:1 snow in their "snowfall" maps, meaning 2" of sleet would be about 6" of snow, so the NAM is spitting out about 2" of sleet and a little snow on TT. But Pivotal doesn't count sleet toward the snow total at all, which is why their NAM maps are only showing 1-2" of pure snow for most, at least south of 80. 2" of sleet has the same mass as 6" of snow, so the impact on driving/removal is the same - there just aren't visibility issues and it's not as pretty. It's above my pay grade to speculate on whether the NAM or the other models will be right, lol.

Remember even if the NAM is right (it's not always in these mix situations), it would still be very impactful to have 1-2" of sleet (same mass as 3-6" of snow at 3:1 sleet to liquid ratio vs. standard 10:1 snow to liquid ratios) and some ice on top of that instead of 3-6" of snow (for areas N of 78 currently forecast to get 3-6" of snow), but it certainly won't be as pretty or fun. The Pivotal vs. TT maps show that most of the "snow" on TT is sleet (Pivotal doesn't count sleet); would be nice to have a sleet map...

0Z Euro is nice...a bit more for folks south of 78 and south of 276/195, but a little less for folks north of 80 (but still 5-6")...

I think something is wrong with the Kuchera calculation for that CMC map. The algorithm is liquid equivalent ratio (RAT) is 12.0 + 2.0*(271.16-MaxT) and looking at Philly, for example, the 10:1 ratio is 4.0", whereas the Kuchera for Philly is essentially 0.0, which makes no physical sense at all, especially given the algorithm. For the SLR to be 0 means that the max column temp in the column would have to be 277.16K (6C or 42.8F), so the equation would be SLR = 12.0 + 2.0(271.16-277.16) = 0. It just makes no sense. It's another reason I almost always use 10:1 ratio maps, so I know how much QPF is falling as 10:1 snow and then one can still adjust. https://www.facebook.com/hopwrf/posts/562550350492139

0Z GFS zoomed in; nice improvements over 18Z for most, although those weird cutoffs/discontinuities persist - there's just no way Allentown gets 0.8" and Easton gets 3+".

0Z NAM and ICON, fwiw...still think the NAM map with the "hole" in CNJ is improbable (I get a bigger early thump SW of CNJ and more N of CNJ with the later coastal, but not sure I've ever seen this before). Also, kind of curious if folks in this forum like seeing the zoomed in Pivotal maps or the regional mid-Atlantic or NEUS maps.

The demonization of good science, from climate/weather to vaccines to public health, in general, by this Administration (among other things) is unconscionable and will set this country back in many ways and make it less safe and less healthy.