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December 4th-5th, 2020 Nor'easter

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This topic for Friday-Sunday dual event is posted with much lower issuing confidence than the topics of 11/11-15, and 11/30-12/01.  

There may be several verifiable flood (not flash flood) warnings for rivers-small stream in northern NJ-northwest of I95  by Sunday morning from a widespread 1-2" rainfall, isolated 3" possible.  There is a small chance for 45+ MPH gusts. It appears the best chance of verifiable hazards will be along the I84 higher terrain where ice or snow can occur.  The ice or snow amounts 3-4 days in the future cannot be counted on to be more than 1 tenth inch glaze or more than 3" of snow, though the option exists for heavier snowfall north of I84. 

Lead precipitation Friday afternoon and night is associated with a reinforcing cold front. Rain NYC.  However the I84 corridor may see some wet snow Friday night?  mPING.

Saturday: Chilly rain most of the NYC forum, heavy at times with 1-2" general, isolated 3". I84-best chance that there could be some ice Saturday before cooling thicknesses and the rapidly developing low change precipitation to some snow before it ends Saturday night or Sunday morning.  mPING may be quite helpful. 

Winds: Depends how fast the storm develops. If a 998MB low is south of Islip Saturday-then brief northeasterly gusts 40-50 MPH Saturday would be possible on LI and the NJ coast, otherwise I think there may be a better chance of northwest wind gusts 45-50 MPH Saturday night or Sunday morning as the storm moves rapidly past Boston.

After further review, I don't think tidal flooding will be a significant threat Saturday. 

Starter graphics: 6 hr FFG..shows the vulnerable areas.  Once yesterdays wave off rising river waters passes Wednesday night, I'll add some small stream guidance-if it applies. 

Added the 12z/1 GEFS prob of 1".  Yellow is up around 75-80% chance. The 12z/1 EPS also has 1-1.5" as does the 12z/1 NAEFS.

Final starter graphic is a 52 member NAEFS blend of where the sfc low will be and it's intensity Saturday evening.  You'll note the yellow color northeast of the  center... that implies greater variability of the pressures there..and could mean that the surface low will be further northeast by Saturday evening.  

Good luck with this... I hope this topic will produce some verifiable NWS hazards. 521P/1

Screen Shot 2020-12-01 at 5.02.09 PM.png

Screen Shot 2020-12-01 at 4.22.26 PM.png

Screen Shot 2020-12-01 at 4.08.43 PM.png

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Good Wednesday morning,  I've no changes to this topic.  

EC-EPS are far different than the GFS-GEFS.  NAEFS leans EPS and that is without the ECMWF members.  That tells me the EC needs to weighted heavier than all the models.  I still don't want to believe it's that strong when it comse through our area but potent for heavy wet snow it is, for northern PA-central and eastern NYS (except extreme se), and northwestern New England.  So, everything stated in the topic is reasonable, I think.  Will rereview late today.  WPC has some pretty large rainfall for our area (widespread 1.5"-2"). Some of modeling is continuing or adding potential for strong easterly flow ahead of low. Needs to be monitored for the midday Saturday night tide, especially if surface pressure dips below 990MB s of ISP. 

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06z euro crushes NW Jersey and gets flakes down to LI 

 

This is a perfect track for snow all the way to the coast but the airmass is putrid. Look like we will crack the cutter/hugger tracks with this one @bluewave

E94C8FAB-E8AD-45BD-B31E-CAF2FB9C4E02.png

715147C7-1B6F-46D1-B164-813E94838746.png

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GFS progressive bias on show now with getting the first system out of the way and trying to make the second one a thing. Don’t fall for it 

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29 minutes ago, Allsnow said:

06z euro crushes NW Jersey and gets flakes down to LI 

 

This is a perfect track for snow all the way to the coast but the airmass is putrid. Look like we will crack the cutter/hugger tracks with this one @bluewave

E94C8FAB-E8AD-45BD-B31E-CAF2FB9C4E02.png

715147C7-1B6F-46D1-B164-813E94838746.png

If only we had more cold air. Great track . Models have been shifting east with this. 

Like you said , looks like we finally broke the cutter trend.

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45 minutes ago, Allsnow said:

 

 

This is a perfect track for snow all the way to the coast but the airmass is putrid. Look like we will crack the cutter/hugger tracks with this one @bluewave

 

It’s a variation on the same theme. Last December 2nd had the low track just south of Long Island also. But there was more cold available to start last December than this year near the coast. It’s interesting that we are seeing a similar track almost a year to the day.

939A0555-D209-4F9C-9642-206032971DB5.gif.1f79b7bd08365c9b0c3a9751d9100878.gif

 

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3 minutes ago, Allsnow said:

Lots of model chaos going on with this storm. The American guidance is now showing its progressive bias. 

Progressive ?

 

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1 minute ago, Allsnow said:

Lots of model chaos going on with this storm. The American guidance is now showing its progressive bias. 

The parallel GFS is actually closer to the Euro. But it’s not quite as amped yet. 

25234360-3A22-4C17-ABCB-9DAA1CF9EB99.thumb.png.e83eb20d228473d84446192be253fbf7.png

 

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13 minutes ago, MJO812 said:

Progressive ?

 

 

12 minutes ago, bluewave said:

The parallel GFS is actually closer to the Euro. But it’s not quite as amped yet. 

25234360-3A22-4C17-ABCB-9DAA1CF9EB99.thumb.png.e83eb20d228473d84446192be253fbf7.png

 

It’s happens with the American guidance inside 100 hours with S/W energy. It becomes progressive and weak because it’s focusing on the next vort coming 

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19 minutes ago, Allsnow said:

Lots of model chaos going on with this storm. The American guidance is now showing its progressive bias. 

True, but we still can’t discount the idea of a weak wave since it has support and the EUROs medium skill just seems crappy anymore. 

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14 minutes ago, Allsnow said:

 

It’s happens with the American guidance inside 100 hours with S/W energy. It becomes progressive and weak because it’s focusing on the next vort coming 

All models have their individual biases. That why I pointed out the other day that the Euro was leaving too much energy back to the SW. So it’s now more phased for the 5th instead of squashing the low off the SE Coast.

New run

6D37601F-70DA-4EC7-9073-8448E7830FAB.thumb.png.8000b0598bb05f8e6f054c18fc16d7c3.png
 

Old run

 

D8697DE7-AD7E-4A24-865D-7BB358E7FEF6.thumb.png.771b41e381b3374dc5fe8b8c9b3270fc.png

 

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56 minutes ago, Allsnow said:

 

It’s happens with the American guidance inside 100 hours with S/W energy. It becomes progressive and weak because it’s focusing on the next vort coming 

Looks like the Nam is starting to correct

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The 12z NAM is a quick hitting wet snow bomb north of the City with a little snow in elevated NNJ.  Compared to most other guidance, the NAM has a relatively compact precip. field.  This is still evolving with every cycle so it's conceivable things could shift more widespread wintry with time.  But without much cold air it seems like a lot more can go wrong than right.

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4 minutes ago, MJO812 said:

I'm shocked people are quiet over the Nam's output especially for people north and west of the city.

It's the 84 hr NAM, that's why....

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11 minutes ago, eduggs said:

The impact in our area is towards the end of its run, but the stage is set by hrs 60 or 66.

Exactly and the rgem just came in off the coast and colder.  I think the coast will see a cold rain with maybe some flakes at the end but interior areas should keep an eye on it.

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7 minutes ago, MJO812 said:

Have you checked the Euro ? Come on.

it's a wind driven rainstorm for 98% of the board on a weekend day no less, why would anyone get excited over that?   

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5 minutes ago, Brian5671 said:

it's a wind driven rainstorm for 98% of the board on a weekend day no less, why would anyone get excited over that?   

6z Euro ? Check again 

There are many people who are getting excited for interior areas. Trends have been east. All im saying is interior areas should watch. 

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3 minutes ago, Brian5671 said:

GFS and CMC show a suppressed solution with almost no precip north and west of NYC.    With no cold high to the north, I'd doubt such solutions

There is a high but really weak. These suppressed solutions are most likely due to the - NAO and no northern stream influence.

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2 hours ago, MJO812 said:

Exactly and the rgem just came in off the coast and colder.  I think the coast will see a cold rain with maybe some flakes at the end but interior areas should keep an eye on it.

I'm at 2000 ft NW of the city through Monday so I'm excited about the storm but I'm also excited about when I get back because it looks like we'll have about a 10 day window between Dec 10 and 20 when it could get quite wintry at the coast.

 

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2 minutes ago, Brian5671 said:

Euro has been slowly moving the precip max east last 3 runs.  NE PA and Catskills get close to nothing now where the big rains and snows are now over New England.

I can’t remember the last time the Euro jumped around this much from run to run. Maybe one of the recent upgrades threw the model off?

38F1235F-6981-4BFE-8B1A-BB0ED7DF8E05.thumb.png.53f08ae525a37551d87ef2198a3d1fc3.png

0959301E-CAB1-4476-A8A7-D5A77993795E.thumb.png.6f4c42cd84e751e8dba25689abc7eef4.png

B22D5AB2-5284-4E19-8253-64F161B8A59B.thumb.png.bf886e98fdc106880bdb4f44747c47ee.png

 

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