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NYC/PHL January 7-9 Potential Part Deux


NickD2011

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Yeah, we're all going to see a little something. I haven't a clue where the band will set up, but I find it interesting that the NAM and GFS have been pretty consistent over the last 12 hours depicting the axis of heaviest snow over NYC Metro.

In years gone past for NJ its the RGEM that has done the best with these norlun trof events (and its still not within its fcst range) and best is a relative term because fcstg the axis of heavy snow is almost the equivalent of fcstg where a line of tsras are going to dump the heaviest rain in summer.

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They will neve issue a watch with this much uncertainty. More likely you will see advisories upgraded to warnings as the event is already underway. Barring a big jump in QPF with the 12z suite.

If I was on today at PHI, I wouldn't and if I had to given the wide dispersal angle at this forecast range for a mesoscale event, it'd be quite a large watch area. This is my opinion and my opinion alone.

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Confidence is too low for a warning criteria event so I doubt watches and advisories usually don't come out until 12 hours prior in most cases. Unless all models converage that a watch is needed I think we'll just see advisories come out tomorrow afternoon/evening

I'm still sticking with:

PHL: 1 - 3"

ABE/RDG - 2 - 4"

MTP - 3 - 5"

NEPA + NYS - 5+

Do you think WWA could be issued as early as later today do you think?

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Confidence is too low for a warning criteria event so I doubt watches and advisories usually don't come out until 12 hours prior in most cases. Unless all models converage that a watch is needed I think we'll just see advisories come out tomorrow afternoon/evening

This event is a classic widespread WWA event with upgrades to warnings as the snow is already falling. Never quite understood the point then anyway as warnings are suppose to "warn" the public so they can prepare and if its already snowing outside people can clearly see the conditions. Even so...looks like this is a widespread high end advisory event. Let's not forget...watches/warnings are all based on probability...and when you take a look at the criteria below you can understand why watches would be hard to come by with this event.

12HourSnowWarningCriteria.gif

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Confidence is too low for a warning criteria event so I doubt watches and advisories usually don't come out until 12 hours prior in most cases. Unless all models converage that a watch is needed I think we'll just see advisories come out tomorrow afternoon/evening

There will probably be advisories for most and those would likely be issued tomorrow afternoon. If there are any watches, it'll be Central/North Jersey...probably not issued until the AM hours tomorrow at the earliest.

This is one of those situations that advisories may be bumped up into a warning for a number of counties and I'm sure there will be some sort of notation by the NWS to account for the potential of an advisory being bumped up.

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I agree with what you guys are saying and I somewhat take back what I said before, unless there is some surprise and ALL models agree on this, which is nearly impossible. I would probably wait until tomorrow morning also before issuing a Winter Storm Watch. I was probably a little ahead of myself. Good discussion though.

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Guest Patrick

Sounds reasonable...

But just to keep this in perspective, I am not sure that most of the posters on this board have ever actually experienced a Norlun event. Back in '93 the National Weather Service had one of the worst busted forecasts ever thanks to one of these Norlun troughs. The forecast was for 1-3 inches of snow for Cape Cod and they got 30 inches.

Taunton has since become the experts in identifying these little beasts, attempting to dissect the hows and whys. Regardless of what the NAM shows, keep in mind that moreso than usual, we are talking about a complex interaction between sea and land frictional differences that may result in snowfall rates of 2-4" per hour. If I was a gambling man, I would bet we see the inverted trough rotate just a bit so it is not completely perpendicular to the coastline. I would also bet that Mt. Holly, Upton, etc, are currently counseling with Taunton....

Just my two cents.

There will probably be advisories for most and those would likely be issued tomorrow afternoon. If there are any watches, it'll be Central/North Jersey...probably not issued until the AM hours tomorrow at the earliest.

This is one of those situations that advisories may be bumped up into a warning for a number of counties and I'm sure there will be some sort of notation by the NWS to account for the potential of an advisory being bumped up.

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Sounds reasonable...

But just to keep this in perspective, I am not sure that most of the posters on this board have ever actually experienced a Norlun event. Back in '93 the National Weather Service had one of the worst busted forecasts ever thanks to one of these Norlun troughs. The forecast was for 1-3 inches of snow for Cape Cod and they got 30 inches.

Taunton has since become the experts in identifying these little beasts, attempting to dissect the hows and whys. Regardless of what the NAM shows, keep in mind that moreso than usual, we are talking about a complex interaction between sea and land frictional differences that may result in snowfall rates of 2-4" per hour. If I was a gambling man, I would bet we see the inverted trough rotate just a bit so it is not completely perpendicular to the coastline. I would also bet that Mt. Holly, Upton, etc, are currently counseling with Taunton....

Just my two cents.

Walt Drag is here now. :scooter:

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gonna have to iron out the little facts under 48hrs with meso models and now casting.. the GFS lower res prob isnt the best choice for this event. Overall though, not a bad agreement this far out

Agreed, the gfs in the 120 - 156 timeframe will be interesting.

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Don't worry about total model QPF just worry about where the highest concentration of QPF is. If your under that band, you will get dumped on. Looks like NE NJ, and SE NY will cash in on this one.

Nam has NW NJ in bullseye so this will be nowcasting to see who gets highest totals..

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Guest Patrick

haha... oh yeah Tony.... the mind forgets the little things....

I assume Mr. Drag will not be sleeping for the next 48 hours. This is going to be a nailbiter

Walt Drag is here now. :scooter:

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haha... oh yeah Tony.... the mind forgets the little things....

I assume Mr. Drag will not be sleeping for the next 48 hours. This is going to be a nailbiter

We'll let him have some sleep time. ;)

BTW the gfs's solution is what one would expect from a global model trying to resolve a norlun trof. I was really impressed whether it would be geographically correct or not how much norlun detail its 00z run had. Tombo has me golfing for the snow this afternoon, so I got to get there before its too late.

See ya on the other side of the European.

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No one can count on anything more than a couple or few inches more than maybe 12 hours out with these things because of how narrow they are, and how perfect the conditions need to be for these bands to develop. Of course, where the band does develop gets more but it's so narrow that a lot of people get hosed.

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