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Dec 8th - 9th (2nd wave/winter storm discussion)


Zelocita Weather

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It's odd to see the GFS so dry compared to the rest of the guidance. I've been worried about suppression from the beginning.

 

If you look at the 12Z GFS ensemble members out of the 12...10 had precip north of the Op run at 84 hours (00Z Sun Eve)....about 3-4 had it WAY north of the Op...the op run had the northern precip extent through 84 hours near ACY, there were some ensemble members up near POU/SWF with precip by 00Z....I'm leaning Euro/Canadian til I see them cave...its also a major red flag to see the always slow NAM have precip north of the GFS at 78-84 hours.

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There continues to be some hope on the CIPS analogs, as was discussed 12/28/90 still showing up, its not going to be that good because the wave is much stronger with more WAA...an interesting one showing now is 12/09/86...its actually a very good hit at 500mb, not so much at the surface, the high positioning was not as good as this event and we had more of a SE flow vs. this event where the flow may be more ENE...even in that event LGA had about a 3-4 hour period of snow to start...here is the link...as you can see very similar at 500mb, surface setup not quite as good as high was already more into its departing stage and more NW which enabled the SE flow.

 

http://www.meteo.psu.edu/~fxg1/NARR/1986/us1209.php

 

12/9/86 was in the coating to an inch range for just about everyone from LI to the Catskills.  The uniformity of the snowfall is strange given that it was a change over situation.  The highest snowfall totals I found in this region were on LI and at Slide Mountain, an odd pair to be sure (totals in the 1 - 2" range).  NYC/NNJ/Westchester/Putnam <1"

 

Rain amounts were relatively light too. 

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12/9/86 was in the coating to an inch range for just about everyone from LI to the Catskills.  The uniformity of the snowfall is strange given that it was a change over situation.  The highest snowfall totals I found in this region were on LI and at Slide Mountain, an odd pair to be sure (totals in the 1 - 2" range).  NYC/NNJ/Westchester/Putnam <1"

 

Rain amounts were relatively light too. 

12/9/09 was a surprise over-performer around here and even in the NYC burbs in which the ML warming was overdone. Looking on NARR though it's pretty clear that set-up was much different with a strong primary went over Chicago and a secondary formed over eastern VA.

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12/9/09 was a surprise over-performer around here and even in the NYC burbs in which the ML warming was overdone. Looking on NARR though it's pretty clear that set-up was much different with a strong primary went over Chicago and a secondary formed over eastern VA.

 

Only 1.2" IMBY from that one, but it looks like it was much better to the north (contrast with 12/86).

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12z NAM looks very nice for both systems....coldest run so far with the 1st wave, and another nice 2-4" type front end deal for the 2nd.

The NAM doesn't have the first wave getting eaten alive. The 4k radar shows snow all the way to the coast by 00z Sunday night. Long Island is too warm though. It would have you believe that the subsidence sets up near KSWF.

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12z NAM looks very nice for both systems....coldest run so far with the 1st wave, and another nice 2-4" type front end deal for the 2nd.

It actually shows an appreciable period of snow throughout the area. The snow map from the E-wall site shows maybe 1-3" even for the city. The NAM overdoing precip though makes me doubt it. Later in the run it warms up fast, and even way inland switches to plain rain eventually and gets well above freezing.

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It actually shows an appreciable period of snow throughout the area. The snow map from the E-wall site shows maybe 1-3" even for the city. The NAM overdoing precip though makes me doubt it. Later in the run it warms up fast, and even way inland switches to plain rain eventually and gets well above freezing.

I thought the NAM was underplaying precip amounts compared to its normal bullish Qpf predictions lol.. But it looks like it's making up for that with the past few runs

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Winter weather advisory posted for my area

... Winter Weather Advisory in effect from 7 PM this evening to

7 am EST Saturday...

The National Weather Service in New York has issued a Winter

Weather Advisory for Orange and Putnam counties... which is in effect from

7 PM this evening to 7 am EST Saturday.

* Locations... Orange and Putnam counties

* hazard types... sleet... snow and possible some light freezing

rain or drizzle.

* Accumulations... 1-2 inches of sleet and snow... thought higher

elevation over 1000 ft may see 3-5 inches. Along with around a

trace of ice.

* Winds... north 5 to 10 mph.

* Temperatures... falling into the upper 20s. .

* visibilities... 1/2sm or less in snow from 11 PM through 4 am.

* Timing... sleet this evening... mixing with and changing to snow

by midnight. The precipitation may end as light freezing rain

or drizzle towards daybreak.

* Impacts... hazardous travel.

Precautionary/preparedness actions...

A Winter Weather Advisory means that periods of snow... sleet... or

freezing rain will cause travel difficulties. Be prepared for

slippery roads and limited visibilities... and use caution while

driving.

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  •  gfs_6hr_snow_acc_east_7.png

Why is it really dry? Usually with these types of events the precip comes in either earlier than expected or a better precip shield than what the models show.

 Thats wave 1 for the city and coast , Wave 2 isnt going to look much better for the same areas .

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I really wouldn't stress too much about the GFS. The 06z GEFS ensembles were all wetter than the op. Sometimes the models can have trouble when they are dealing with more than one event in the short-medium range. In other words I think we'll need to wait for the 12z runs tomorrow to know for sure, once the current event is out of here.

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