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February 11 -12 Winter Storm Threat


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24 minutes ago, RU848789 said:

At the risk of being accused of beating and stomping on the neck of a dead horse, this is why I hate those "snow only" maps in a mixed precip events and prefer the TT style sleet+snow (all at 10:1, so I know the LE falling in frozen form) maps.  On the 12Z CMC, the storm doesn't look like much of a big deal for the 95 corridor, including NYC, but that's wrong.  Let's use the 12Z CMC and NYC just to illustrate (same holds true down to at least New Brunswick) what I'm talking about by analyzing what the model says at a deeper level (not a forecast).  

  • The sounding for NYC is clearly for snow at 7 am, with the whole column well below 32F down to the surface at 26F
  • The sounding for NYC is then just barely sleet at 1 pm with 700-850 mbar, just barely going above 32F, but with all of 850 mbar to the surface being well below 32F and the surface at 29F. 
  • The sounding for NYC at 7 pm is still for sleet, with 700-900 mbar above 32F, but with the column below that well below 32F until just at the surface, where it's 33F - sleet will certainly form falling through ~3000 feet of sub-32F column and shouldn't melt from the last 100 feet or so being above 32F to the surface at 33F, IMO.    
  • But the snow only map shows only 1/2" of snow falling in NYC (and Edison/NB) from 7 am to 7 pm, implying a change to sleet soon after 7 am (which is questionable, but irrelevant to my point).  But the model then is completely ignoring close to 12 hours of sleet and the precip map shows 0.5" LE falling in NYC between 7 am and 7 pm (and 0.7" in NB), plus it's likely that that sleet signature for NYC lasts another couple of hours to get NYC to maybe 0.7" LE as sleet, like NB. 
  • A storm with 1-2" of snow on the map, like the 12Z CMC, looks benign.  A storm with 1-2" of snow, followed by 0.7" of LE as sleet, which is about 2" of sleet (at a 3:1 ratio) is a far different and much more impactful storm, as that's a total of 0.8-0.9" LE in frozen form (8-9" worth of snow, even if it will only be 3-4" on the ground) and that mass is what's critical for shoveling, plowing, driving, etc.  Not as pretty as snow and much less of a visibility issue, but very impactful. 
  • Because of this, I think the NWS might issue watches, which are usually reserved for 6" of pure snow, for the 95 corridor and NW of there, since the frozen equivalent will likely be 6" of "snow equivalent" or more. The risk of 0.1" or more of freezing rain might also tip the scales towards watches (and warnings tomorrow morning if the models don't change much). We'll see soon.
  • One more thing.  If we get 0.6-1.0" of LE in frozen form for the Trenton-NYC corridor, as almost every model is showing, that amount of frozen precip will likely absorb much of the subsequent 0.5-1.0" of rain that likely falls after the changeover to all rain (especially if it's on the 0.5" side of things as rain), creating a slushy mess holding about 1.5-2.0" of LE - a bit of melting will obviously occur with temps in the mid/upper 30s and rain, but I'd guess <25% melting.  However, if the CMC is right and we hit 50F on Wednesday, lots of melting will occur (other models top out at 35-40F, so big variance there in melting rate/amount).  



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Post of the day. 

NYC will get at least 4" of snow/sleet.

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15 minutes ago, Snow88 said:

Tricky forecast for the NYC area just like it was for the November storm. The earlier the precip comes in the better.

The forecast changes if the models are wrong with the strength of the high and the placement

88 or anyone else ,,at this point in time does it pay to look at the Mesos or any other model or are we down to now casting and just looking at radar ? I mean given that this is a cad event at this time is there ANYTHING we should be looking at that could help determine what MIGHT actually happen ?

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Just now, Brasiluvsnow said:

88 or anyone else ,,at this point in time does it pay to look at the Mesos or any other model or are we down to now casting and just looking at radar ? I mean given that this is a cad event ,at this time is there ANYTHING we should be looking at that could help determine what MIGHT actually happen ?

The strength of the high and the placement.

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1 minute ago, Brian5671 said:

They've closed for less here-it's ridiculous.   I think though with snow/sleet falling from 6am-2pm, they close.

It's done by a secret cabal. Each super sits around to see who blinks first. Once one of em folds, the others in the immediate area usually follow. This is what one of em told me, at least in these kinds of events. Obviously when serious snow is called for there's no question.It's getting late in the winter, there haven't been any days in a lot of the area ( S Jersey and N Jersey have had some ) so my guess is they will close unless heavy rain is predicted early OR it starts after school opens. Also, if it doesn't start until 6 am, that is usually too late. They make the decision before that.

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4 minutes ago, Snow88 said:

Most likely early dismissals inland areas

Depends on the start time; if it starts after 6, we're going to school. If it isn't raging by 9 am, we're staying all day. Also depends on what you mean by inland; I wouldn't consider Most of Middlesex or parts of Union Co as really too far inland, but they will close if it is snowing heavy in the morning and sleet is expected later.

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1 minute ago, weatherpruf said:

It's done by a secret cabal. Each super sits around to see who blinks first. Once one of em folds, the others in the immediate area usually follow. This is what one of em told me, at least in these kinds of events. Obviously when serious snow is called for there's no question.It's getting late in the winter, there haven't been any days in a lot of the area ( S Jersey and N Jersey have had some ) so my guess is they will close unless heavy rain is predicted early OR it starts after school opens. Also, if it doesn't start until 6 am, that is usually too late. They make the decision before that.

your'e right on that.   Usually all the SW CT coastal towns go together.  2 hr delay?  Everyone has one....Closed-same deal.

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My kids go to Western CT State U in Danbury and a few of their professors have already decide they won't have school on Tuesday so they emailed out or posted assignments already. Granted there are 6k students and a ton of staff that commute so they, and most of the colleges around here, have very low standards for when they close.

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3 minutes ago, gravitylover said:

My kids go to Western CT State U in Danbury and a few of their professors have already decide they won't have school on Tuesday so they emailed out or posted assignments already. Granted there are 6k students and a ton of staff that commute so they, and most of the colleges around here, have very low standards for when they close.

Danbury is a lot snowier than down here in general, no?

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Winter Storm Watch

URGENT - WINTER WEATHER MESSAGE
National Weather Service New York NY
341 PM EST Sun Feb 10 2019

NJZ002-NYZ067-111000-
/O.NEW.KOKX.WS.A.0002.190212T0800Z-190213T1100Z/
Western Passaic-Orange-
341 PM EST Sun Feb 10 2019

...WINTER STORM WATCH IN EFFECT FROM LATE MONDAY NIGHT THROUGH
LATE TUESDAY NIGHT...

* WHAT...Heavy mixed precipitation possible. Total snow
  accumulations of 4 to 7 inches and ice accumulations of one
  tenth to two tenths of an inch possible.

* WHERE...In New Jersey, Western Passaic County. In New York,
  Orange County.

* WHEN...From late Monday night through late Tuesday night.
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